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{{Short description|Polymer of glucose and structural component of cell wall of plants and green algae}}
where is the e-number?[[Image:Cellulose-2D-skeletal.svg|thumb|right|260px|Cellulose, a linear polymer of <small>D</small>-[[glucose]] linked by β(1→4)-[[glycosidic bond]]s.]]
{{cs1 config|name-list-style=vanc|display-authors=6}}
[[Image:Cellulose-3D-balls.png|thumb|right|260px|Three-dimensional structure of cellulose, with four glucose units visible. (Black=carbon; red=oxygen; white=hydrogen.)]]
{{Use mdy dates|date=February 2024}}
[[Image:Cellulose-3D-vdW.png|thumb|right|260px|Space-filling model of cellulose, with four glucose units visible]]
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 457117700
| Name = Cellulose
| Reference = <ref>{{Cite journal |first1 = Yoshiharu |last1 = Nishiyama |first2 = Paul |last2 = Langan |first3 = Henri |last3 = Chanzy |title = Crystal Structure and Hydrogen-Bonding System in Cellulose Iβ from Synchrotron X-ray and Neutron Fiber Diffraction |journal = J. Am. Chem. Soc. |year = 2002 |volume = 124 |issue = 31 |pages = 9074–9082 |doi = 10.1021/ja0257319 |pmid = 12149011}}</ref>
| ImageFile = Cellulose Sessel.svg
| ImageSize = 260px
| ImageName = Cellulose, a linear polymer of D-glucose units (two are shown) linked by β(1→4)-glycosidic bonds
| ImageFile1 = Cellulose-Ibeta-from-xtal-2002-3D-balls.png
| ImageSize1 = 260px
| ImageName1 = Three-dimensional structure of cellulose
| IUPACName =
| OtherNames =
| SystematicName =
| Section1 = {{Chembox Identifiers
| CASNo = 9004-34-6
| ChEMBL_Ref = {{ebicite|changed|EBI}}
| ChEMBL = 2109009
| CASNo_Ref = {{cascite|correct|CAS}}
| EC_number = 232-674-9
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = SMD1X3XO9M
| KEGG = C00760
| PubChem = 14055602
| RTECS =
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID = None
}}
| Section2 = {{Chembox Properties
| Formula = ({{chem|C|12|H|20|O|10|)|''n''}}
| MolarMass = 162.1406 g/mol per glucose unit
| Appearance = white powder
| Density = 1.5 g/cm<sup>3</sup>
| Solubility = none
| MeltingPtF = 500-518
| MeltingPt_notes = Decomposes<ref name=PGCH/>
}}
| Section3 =
| Section4 = {{Chembox Thermochemistry
| DeltaHf = −963,000 kJ/mol{{clarify|reason=This huge number is surely not per unit. Providing the source would be nice too.|date=June 2021}}
| DeltaHc = −2828,000 kJ/mol{{clarify|reason=This huge number is surely not per unit. Providing the source would be nice too.|date=June 2021}}
}}
| Section5 =
| Section6 =
| Section7 = {{Chembox Hazards
| NFPA-H = 1
| NFPA-F = 1
| NFPA-R = 0
| ExternalSDS =
| AutoignitionPt =
| PEL = TWA 15 mg/m<sup>3</sup> (total) TWA 5 mg/m<sup>3</sup> (resp)<ref name=PGCH>{{PGCH|0110}}</ref>
| REL = TWA 10 mg/m<sup>3</sup> (total) TWA 5 mg/m<sup>3</sup> (resp)<ref name=PGCH/>
| IDLH = N.D.<ref name=PGCH/>
}}
| Section8 = {{Chembox Related
| OtherCompounds = [[Starch]]
}}
}}


'''Cellulose''' is an [[organic compound]] with the [[chemical formula|formula]] {{chem|([[carbon|C]]|6|[[hydrogen|H]]|10|[[oxygen|O]]|5|)|n}}, a [[polysaccharide]] consisting of a linear chain of several hundred to over ten thousand β(1→4) linked <small>D</small>-[[glucose]] units.<ref name=Crawford>{{cite book
'''Cellulose''' is an [[organic compound]] with the [[chemical formula|formula]] {{chem|([[carbon|C]]|6|[[hydrogen|H]]|10|[[oxygen|O]]|5|)|''n''|}}, a [[polysaccharide]] consisting of a linear chain of several hundred to many thousands of [[glycosidic bond|β(1→4) linked]] [[glucose|<small>D</small>-glucose]] units.<ref name=Crawford>{{cite book
| author=Crawford, R. L.
| author=Crawford, R. L.
| title=Lignin biodegradation and transformation
| title=Lignin biodegradation and transformation
| publisher=John Wiley and Sons
| publisher=John Wiley and Sons
| location = New York
| location=New York
| year=1981
| year=1981
| id=ISBN 0-471-05743-6
| isbn=978-0-471-05743-7
}}</ref><ref>{{cite journal
}}</ref><ref name="Updegraff_1969">{{cite journal
| author=Updegraff DM
| author=Updegraff D. M.
| title=Semimicro determination of cellulose in biological materials
| title=Semimicro determination of cellulose in biological materials
| journal=Analytical Biochemistry
| journal=Analytical Biochemistry
| year=1969 | volume=32 | pages=420 – 424
| year=1969 |volume=32 |pages=420–424
| doi=10.1016/S0003-2697(69)80009-6
| doi=10.1016/S0003-2697(69)80009-6
| pmid=5361396
}}</ref>
| issue=3
}}</ref> Cellulose is an important structural component of the primary [[cell wall]] of [[green plants]], many forms of [[algae]] and the [[oomycete]]s. Some species of [[bacteria]] secrete it to form [[biofilm]]s.<ref>{{cite book |last=Romeo |first=Tony |title=Bacterial biofilms |year=2008 |publisher=Springer |location=Berlin |isbn=978-3-540-75418-3 |pages=258–263}}</ref> Cellulose is the most abundant [[biopolymer|organic polymer]] on Earth.<ref name="Klemm">{{cite journal |last=Klemm |first=Dieter |author2=Heublein, Brigitte |author3=Fink, Hans-Peter |author4= Bohn, Andreas |title=Cellulose: Fascinating Biopolymer and Sustainable Raw Material |journal=Angew. Chem. Int. Ed. |date=2005 |volume=44 |issue=22 |doi=10.1002/anie.200460587 |pmid=15861454 |pages=3358–3393}}</ref> The cellulose content of [[cotton]] fiber is 90%, that of [[wood]] is 40–50%, and that of dried [[hemp]] is approximately 57%.<ref>Cellulose. (2008). In ''[[Encyclopædia Britannica]]''. Retrieved January 11, 2008, from Encyclopædia Britannica Online.</ref><ref>[http://www.ipst.gatech.edu/faculty/ragauskas_art/technical_reviews/Chemical%20Overview%20of%20Wood.pdf Chemical Composition of Wood]. {{Webarchive|url=https://web.archive.org/web/20181013004234/http://www.ipst.gatech.edu/faculty/ragauskas_art/technical_reviews/Chemical%20Overview%20of%20Wood.pdf |date=October 13, 2018 }}. ipst.gatech.edu.</ref><ref>Piotrowski, Stephan and Carus, Michael (May 2011) [http://www.biocore-europe.org/file/BIOCORE%20Multi-criteria%20evaluation%20of%20niche%20crops.pdf Multi-criteria evaluation of lignocellulosic niche crops for use in biorefinery processes] {{Webarchive|url=https://web.archive.org/web/20210403200802/http://www.biocore-europe.org/file/BIOCORE%20Multi-criteria%20evaluation%20of%20niche%20crops.pdf |date=April 3, 2021 }}. nova-Institut GmbH, Hürth, Germany.</ref>


Cellulose is mainly used to produce [[paperboard]] and [[paper]]. Smaller quantities are converted into a wide variety of derivative products such as [[cellophane]] and [[rayon]]. Conversion of cellulose from [[energy crop]]s into [[biofuel]]s such as [[cellulosic ethanol]] is under development as a [[renewable fuel]] source. Cellulose for industrial use is mainly obtained from [[wood pulp]] and [[cotton]].<ref name="Klemm"/> Cellulose is also greatly affected by direct interaction with several organic liquids.<ref>{{cite journal | last=Mantanis | first=G. I. | last2=Young | first2=R. A. | last3=Rowell | first3=R. M. | title=Swelling of compressed cellulose fiber webs in organic liquids | journal=Cellulose | volume=2 | issue=1 | date=1995 | issn=0969-0239 | doi=10.1007/BF00812768 | pages=1–22}}</ref>
Cellulose is the structural component of the primary [[cell wall]] of [[green plants]], many forms of [[algae]] and the [[oomycetes]]. Some species of [[bacteria]] secrete it to form [[biofilm]]s.
Cellulose is the most common organic compound on Earth. About 33 percent of all plant matter is cellulose (the cellulose content of [[cotton]] is 90 percent and that of wood is 50 percent).<ref>Cellulose. (2008). In ''[[Encyclopædia Britannica]]''. Retrieved January 11, 2008, from Encyclopædia Britannica Online.</ref>


Some animals, particularly [[ruminant]]s and [[termite]]s, can [[digestion|digest]] cellulose with the help of [[symbiosis|symbiotic]] micro-organisms that live in their guts, such as ''[[Trichonympha]]''. In [[human nutrition]], cellulose is a non-digestible constituent of [[insoluble]] [[dietary fiber]], acting as a [[hydrophilic]] [[bulking agent]] for [[human feces|feces]] and potentially aiding in [[defecation]].
For industrial use, cellulose is mainly obtained from [[wood pulp]] and [[cotton]]. It is mainly used to produce [[cardboard]] and [[paper]]; to a smaller extent it is converted into a wide variety of derivative products such as [[cellophane]] and [[rayon]].


== History ==
Some animals, particularly [[ruminant]]s and [[termite]]s, can [[digestion|digest]] cellulose with the help of [[symbiosis|symbiotic]] micro-organisms that live in their guts. Cellulose is not digestible by [[human]]s and is often referred to as '[[dietary fiber]]' or 'roughage', acting as a [[hydrophilic]] bulking agent for [[feces]].


Cellulose was discovered in 1838 by the French chemist [[Anselme Payen]], who isolated it from plant matter and determined its chemical formula.<ref name=Crawford /><ref>Payen, A. (1838) "Mémoire sur la composition du tissu propre des plantes et du ligneux" (Memoir on the composition of the tissue of plants and of woody [material]), ''Comptes rendus'', vol. 7, pp. 1052–1056. Payen added appendices to this paper on December 24, 1838 (see: ''Comptes rendus'', vol. 8, p. 169 (1839)) and on February 4, 1839 (see: ''Comptes rendus'', vol. 9, p. 149 (1839)). A committee of the French Academy of Sciences reviewed Payen's findings in : Jean-Baptiste Dumas (1839) "Rapport sur un mémoire de M. Payen, reltes rendus'', vol. 8, pp. 51–53. In this report, the word "cellulose" is coined and author points out the similarity between the empirical formula of cellulose and that of "dextrine" (starch). The above articles are reprinted in: Brongniart and Guillemin, eds., ''Annales des sciences naturelles'' ..., 2nd series, vol. 11 (Paris, France: Crochard et Cie., 1839), [ {{google books|plainurl=y|id=VDRsFWwgUo4C|page=21}}
==History==
pp. 21–31].</ref><ref name="Young">{{cite book
Cellulose was discovered in 1838 by the French chemist [[Anselme Payen]], who isolated it from plant matter and determined its chemical formula.<ref name=Crawford /><ref name="Young">{{cite book
| last = Young
| last = Young
| first = Raymond
| first = Raymond
Line 33: Line 93:
| location = New York
| location = New York
| year = 1986
| year = 1986
| isbn = 0471827614 }}</ref> Cellulose was used to produce the first successful [[thermoplastic|thermoplastic polymer]], [[celluloid]], by Hyatt Manufacturing Company in 1870. [[Hermann Staudinger]] determined the polymer structure of cellulose in 1920. The compound was first chemically synthesized (without the use of any biologically-derived [[enzyme]]s) in 1992, by Kobayashi and Shoda.<ref name=Klemm>{{Cite journal
| isbn = 978-0-471-82761-0}}</ref> Cellulose was used to produce the first successful [[thermoplastic|thermoplastic polymer]], [[celluloid]], by Hyatt Manufacturing Company in 1870. Production of [[rayon]] ("artificial [[silk]]") from cellulose began in the 1890s and [[cellophane]] was invented in 1912. [[Hermann Staudinger]] determined the polymer structure of cellulose in 1920. The compound was first chemically synthesized (without the use of any biologically derived [[enzyme]]s) in 1992, by Kobayashi and Shoda.<ref>{{cite journal|last=Kobayashi|first=Shiro|author2=Kashiwa, Keita |author3=Shimada, Junji |author4=Kawasaki, Tatsuya |author5= Shoda, Shin-ichiro |title=Enzymatic polymerization: The first in vitro synthesis of cellulose via nonbiosynthetic path catalyzed by cellulase|journal=Makromolekulare Chemie. Macromolecular Symposia|year=1992|volume=54–55|issue=1|pages=509–518|doi=10.1002/masy.19920540138}}</ref>
| volume = 36
| issue = 36
| last = Klemm
| first = Dieter
| coauthors = Brigitte Heublein, Hans-Peter Fink, Andreas Bohn
| title = Cellulose: Fascinating Biopolymer and Sustainable Raw Material
| journal = ChemInform
| date = 2005 | doi = 10.1002/chin.200536238 <!--Retrieved from url by DOI bot-->
}}</ref>


[[File:Plant cell wall diagram-en.svg|thumb|upright=1.3|The arrangement of cellulose and other [[polysaccharides]] in a plant [[cell wall]]]]
==Commercial products==
Cellulose is the major constituent of paper and cardboard and of textiles made from [[cotton]], [[linen]], and other plant fibers.


== Structure and properties ==
Cellulose can be converted into [[cellophane]], a thin transparent film, and into [[rayon]], an important fiber that has been used for textiles since the beginning of the 20th century. Both cellophane and rayon are known as "regenerated cellulose fibers"; they are identical to cellulose in chemical structure and are usually made from [[viscose]], a [[viscous]] solution made from cellulose. A more recent and environmentally friendly method to produce rayon is the [[Lyocell]] process.
[[File:Салфетка универсальная губчатая (вид сбоку).jpg|thumb|left|Cellulose under a microscope.]]
Cellulose has no taste, is odorless, is [[hydrophilic]] with the [[contact angle]] of 20–30 degrees,<ref>{{cite book|title=Vacuum deposition onto webs, films, and foils|editor=Bishop, Charles A. |year=2007|isbn=978-0-8155-1535-7|url={{google books|plainurl=y|id=vP9E3z7o6iIC|page=165}}|page=165|publisher=Elsevier Science }}</ref> is insoluble in [[water]] and most organic [[solvent]]s, is [[Chirality (chemistry)|chiral]] and is [[biodegradation|biodegradable]]. It was shown to melt at 467&nbsp;°C in pulse tests made by Dauenhauer ''et al.'' (2016).<ref name=Dauenhauer>{{cite journal|last1=Dauenhauer|first1=Paul|last2=Krumm|first2=Christoph|last3=Pfaendtner|first3=Jim|title=Millisecond Pulsed Films Unify the Mechanisms of Cellulose Fragmentation|journal=Chemistry of Materials|volume=28|page=0001|year=2016|doi=10.1021/acs.chemmater.6b00580|issue=1|osti=1865816 }}</ref> It can be broken down chemically into its glucose units by treating it with concentrated mineral acids at high temperature.<ref>{{cite journal|last1=Wymer|first1=Charles E.|title=Ethanol from lignocellulosic biomass: Technology, economics, and opportunities|journal=Bioresource Technology|date=1994|volume= 50|issue=1|page=5|doi=10.1016/0960-8524(94)90214-3|bibcode=1994BiTec..50....3W }}</ref>


Cellulose is derived from [[Glucose|<small>D</small>-glucose]] units, which [[condensation reaction|condense]] through β(1→4)-[[glycosidic bond]]s. This linkage motif contrasts with that for α(1→4)-glycosidic bonds present in [[starch]] and [[glycogen]]. Cellulose is a straight chain polymer. Unlike starch, no coiling or branching occurs and the molecule adopts an extended and rather stiff rod-like conformation, aided by the equatorial conformation of the glucose residues. The multiple [[hydroxyl|hydroxyl groups]] on the glucose from one chain form [[hydrogen bond]]s with oxygen atoms on the same or on a neighbor chain, holding the chains firmly together side-by-side and forming ''microfibrils'' with high [[tensile strength]]. This confers tensile strength in [[cell wall]]s where cellulose microfibrils are meshed into a polysaccharide ''matrix''. The high tensile strength of plant stems and of the tree wood also arises from the arrangement of cellulose fibers intimately distributed into the [[lignin]] matrix. The mechanical role of cellulose fibers in the wood matrix responsible for its strong structural resistance, can somewhat be compared to that of the [[reinforcement bar]]s in [[concrete]], [[lignin]] playing here the role of the [[cement|hardened cement paste]] acting as the "glue" in between the cellulose fibers. Mechanical properties of cellulose in primary plant cell wall are correlated with growth and expansion of plant cells.<ref name=Bidhendi2016>{{cite journal|last1=Bidhendi|first1=Amir J|last2=Geitmann|first2=Anja|title=Relating the mechanical properties of the primary plant cell wall. |url=https://academic.oup.com/jxb/article-pdf/67/2/449/9366354/erv535.pdf |archive-url=https://web.archive.org/web/20180113093611/https://academic.oup.com/jxb/article-pdf/67/2/449/9366354/erv535.pdf |archive-date=January 13, 2018 |url-status=live|journal=Journal of Experimental Botany|date=January 2016|volume=67|issue=2|pages=449–461|doi=10.1093/jxb/erv535|pmid=26689854|doi-access=free}}</ref> Live fluorescence microscopy techniques are promising in investigation of the role of cellulose in growing plant cells.<ref name=Bidhendi2020>{{cite journal|last1=Bidhendi|first1=AJ|last2=Chebli|first2=Y|last3=Geitmann|first3=A|title= Fluorescence Visualization of Cellulose and Pectin in the Primary Plant Cell Wall|journal=Journal of Microscopy|volume=278 |issue=3 |pages=164–181|date=May 2020|doi=10.1111/jmi.12895|pmid=32270489|s2cid=215619998}}</ref>
Cellulose is used in the laboratory as the stationary phase for [[Chromatography|thin layer chromatography]]. It is the raw material in the manufacture of [[nitrocellulose]] (cellulose nitrate) which was historically used in [[smokeless powder|smokeless gunpowder]] and as the base material for [[celluloid]] used for photographic and movie films until the mid 1930s.


[[File:Cellulose spacefilling model.jpg|thumb|A triple strand of cellulose showing the [[hydrogen bond]]s (cyan lines) between glucose strands]]
[[Cellulose insulation]] made from recycled newsprint is becoming popular as an environmentally preferable material for [[building insulation]].
[[File:Cotton.JPG|thumb|[[Cotton]] fibres represent the purest natural form of cellulose, containing more than 90% of this [[polysaccharide]].]]
Compared to starch, cellulose is also much more [[crystallinity|crystalline]]. Whereas starch undergoes a crystalline to [[amorphous solid|amorphous]] transition when heated beyond 60–70&nbsp;°C in water (as in cooking), cellulose requires a temperature of 320&nbsp;°C and pressure of 25 [[Pascal (unit)|MPa]] to become amorphous in water.<ref name=Deguchi>{{cite journal|last1=Deguchi|first1=Shigeru|last2=Tsujii|first2=Kaoru|last3=Horikoshi|first3=Koki|title=Cooking cellulose in hot and compressed water|journal=Chemical Communications|year=2006|doi=10.1039/b605812d|pmid=16883414|issue=31|pages=3293–5}}</ref>


Several types of cellulose are known. These forms are distinguished according to the location of hydrogen bonds between and within strands. Natural cellulose is cellulose I, with structures I<sub>α</sub> and I<sub>β</sub>. Cellulose produced by bacteria and algae is enriched in I<sub>α</sub> while cellulose of higher plants consists mainly of I<sub>β</sub>. Cellulose in [[regenerated cellulose]] fibers is cellulose II. The conversion of cellulose I to cellulose II is irreversible, suggesting that cellulose I is [[Metastability|metastable]] and cellulose II is stable. With various chemical treatments it is possible to produce the structures cellulose III and cellulose IV.<ref>[http://www.cermav.cnrs.fr/glyco3d/lessons/cellulose/index.html Structure and morphology of cellulose] {{webarchive |url=https://web.archive.org/web/20090426122947/http://www.cermav.cnrs.fr/glyco3d/lessons/cellulose/index.html |date=April 26, 2009 }} by Serge Pérez and William Mackie, CERMAV-[[CNRS]], 2001. Chapter IV.</ref>
Cellulose is used to make [[hydrophilic]] and highly absorbent sponges, as well as water-soluble [[adhesives]] and [[binder (material)|binders]] such as [[methyl cellulose]] and [[carboxymethyl cellulose]] which are used in [[wallpaper]] paste. [[Microcrystalline cellulose]] ([[E number|E460i]]) and powdered cellulose (E460ii) are used as inactive fillers in tablets and as thickeners and stabilizers in processed foods.


Many properties of cellulose depend on its chain length or [[degree of polymerization]], the number of glucose units that make up one polymer molecule. Cellulose from wood pulp has typical chain lengths between 300 and 1700 units; cotton and other plant fibers as well as bacterial cellulose have chain lengths ranging from 800 to 10,000 units.<ref name="Klemm"/> Molecules with very small chain length resulting from the breakdown of cellulose are known as [[cellodextrin]]s; in contrast to long-chain cellulose, cellodextrins are typically soluble in water and organic solvents.
=== Cellulose source and energy crops ===
{{Main|Energy crop}}
The major [[combustion|combustible]] component of non-food [[energy crop]]s is cellulose, with [[lignin]] second. Non-food energy crops are more efficient than edible energy crops (which have a large [[starch]] component), but still compete with food crops for agricultural land and water resources.<ref>Holt-Gimenez, Eric 2007. Biofuels: Myths of the Agrofuels Transition. ''Backgrounder.'' Institute for Food and Development Policy, Oakland, CA. 13:2</ref> Typical non-food energy crops include [[hemp|industrial hemp]], [[switchgrass]], ''[[Miscanthus]]'', ''Salix'' ([[willow]]), and ''Populus'' ([[poplar]]) species.


The chemical formula of cellulose is (C<sub>6</sub>H<sub>10</sub>O<sub>5</sub>)<sub>n</sub> where n is the degree of polymerization and represents the number of glucose groups.<ref>{{cite book |last1=Chen |first1=Hongzhang |title= Biotechnology of Lignocellulose: Theory and Practice |date=2014 |publisher=Springer |location=Dordrecht |isbn=978-94-007-6897-0 |pages=25–71 |chapter=Chemical Composition and Structure of Natural Lignocellulose|url= https://www.springer.com/cda/content/document/cda_downloaddocument/9789400768970-c2.pdf |archive-url=https://web.archive.org/web/20161213103751/http://www.springer.com/cda/content/document/cda_downloaddocument/9789400768970-c2.pdf |archive-date=December 13, 2016 |url-status=live}}</ref>
Some bacteria can convert cellulose into [[ethanol]] which can then be used as a fuel; see [[cellulosic ethanol]].


Plant-derived cellulose is usually found in a mixture with [[hemicellulose]], [[lignin]], [[pectin]] and other substances, while [[bacterial cellulose]] is quite pure, has a much higher water content and higher tensile strength due to higher chain lengths.<ref name="Klemm"/>{{rp|3384}}
[[Image:Cellulose strand.jpg|thumb|right|260px|A strand of cellulose, showing the [[hydrogen bond]]s (dashed) within and between cellulose molecules.]]


Cellulose consists of fibrils with [[crystalline]] and [[amorphous solid|amorphous]] regions. These cellulose fibrils may be individualized by mechanical treatment of cellulose pulp, often assisted by chemical [[oxidation]] or [[enzyme|enzymatic]] treatment, yielding semi-flexible [[nanocellulose|cellulose nanofibrils]] generally 200&nbsp;nm to 1 μm in length depending on the treatment intensity.<ref>{{cite journal |last1=Saito |first1=Tsuguyuki |last2=Kimura |first2=Satoshi |last3=Nishiyama |first3=Yoshiharu |last4=Isogai |first4=Akira |title=Cellulose Nanofibers Prepared by TEMPO-Mediated Oxidation of Native Cellulose |journal=Biomacromolecules |date=August 2007 |volume=8 |issue=8 |pages=2485–2491 |doi=10.1021/bm0703970 |pmid=17630692 |url=https://pubs.acs.org/doi/abs/10.1021/bm0497769 |access-date=April 7, 2020 |archive-date=April 7, 2020 |archive-url=https://web.archive.org/web/20200407120236/https://pubs.acs.org/doi/abs/10.1021/bm0497769 |url-status=live }}</ref> Cellulose pulp may also be treated with strong acid to [[hydrolization|hydrolyze]] the amorphous fibril regions, thereby producing short rigid [[nanocellulose|cellulose nanocrystals]] a few 100&nbsp;nm in length.<ref>{{cite journal|year=2011|title=Chemistry and applications of nanocrystalline cellulose and its derivatives: A nanotechnology perspective|journal=The Canadian Journal of Chemical Engineering|volume=89|issue=5|pages=1191–1206|url=http://www.arboranano.ca/pdfs/Chemistry%20and%20applications%20of%20nanocrystalline%20cellulose%20and%20its%20derivatives%20A%20nanotechnology%20perspective-2011.pdf|author1=Peng, B. L.|author2=Dhar, N.|author3=Liu, H. L.|author4=Tam, K. C.|doi=10.1002/cjce.20554|access-date=August 28, 2012|archive-url=https://web.archive.org/web/20161024021059/http://www.arboranano.ca/pdfs/Chemistry%20and%20applications%20of%20nanocrystalline%20cellulose%20and%20its%20derivatives%20A%20nanotechnology%20perspective-2011.pdf|archive-date=October 24, 2016|url-status=dead}}</ref> These [[nanocellulose]]s are of high technological interest due to their [[self-assembly]] into [[liquid crystal|cholesteric liquid crystals]],<ref>{{cite journal |last1=Revol |first1=J.-F. |last2=Bradford |first2=H. |last3=Giasson |first3=J. |last4=Marchessault |first4=R.H. |last5=Gray |first5=D.G. |title=Helicoidal self-ordering of cellulose microfibrils in aqueous suspension |journal=International Journal of Biological Macromolecules |date=June 1992 |volume=14 |issue=3 |pages=170–172 |doi=10.1016/S0141-8130(05)80008-X |pmid=1390450 |url=https://www.sciencedirect.com/science/article/pii/S014181300580008X |access-date=April 7, 2020 |archive-date=April 7, 2020 |archive-url=https://web.archive.org/web/20200407120239/https://www.sciencedirect.com/science/article/pii/S014181300580008X |url-status=live }}</ref> production of [[hydrogel]]s or [[aerogel]]s,<ref>{{cite journal |last1=De France |first1=Kevin J. |last2=Hoare |first2=Todd |last3=Cranston |first3=Emily D. |author-link3=Emily Cranston |date=April 26, 2017 |title=Review of Hydrogels and Aerogels Containing Nanocellulose |journal=Chemistry of Materials |volume=29 |issue=11 |pages=4609–4631 |doi=10.1021/acs.chemmater.7b00531 |doi-access=free}}</ref> use in [[nanocomposite]]s with superior thermal and mechanical properties,<ref>{{Cite journal | last1 = Pranger | first1 = L. | last2 = Tannenbaum | first2 = R. | doi = 10.1021/ma8020213 | title = Biobased Nanocomposites Prepared by in Situ Polymerization of Furfuryl Alcohol with Cellulose Whiskers or Montmorillonite Clay | journal = Macromolecules | volume = 41 | issue = 22 | pages = 8682–8687 | year = 2008 | bibcode = 2008MaMol..41.8682P | url = https://figshare.com/articles/journal_contribution/2897695 | access-date = June 19, 2023 | archive-date = December 30, 2023 | archive-url = https://web.archive.org/web/20231230132201/https://figshare.com/articles/journal_contribution/Biobased_Nanocomposites_Prepared_by_In_Situ_Polymerization_of_Furfuryl_Alcohol_with_Cellulose_Whiskers_or_Montmorillonite_Clay/2897695 | url-status = live }}</ref> and use as [[Pickering emulsion|Pickering]] stabilizers for [[emulsions]].<ref>{{cite journal |last1=Kalashnikova |first1=Irina |last2=Bizot |first2=Hervé |last3=Cathala |first3=Bernard |last4=Capron |first4=Isabelle |title=New Pickering Emulsions Stabilized by Bacterial Cellulose Nanocrystals |journal=Langmuir |date=June 21, 2011 |volume=27 |issue=12 |pages=7471–7479 |doi=10.1021/la200971f |pmid=21604688 }}</ref>
==Structure and properties==
Cellulose has no taste, is odourless, is [[hydrophilic]], is insoluble in [[water]] and most organic [[solvent]]s, is [[Chirality (chemistry)|chiral]] and it is biodegradable.


==Processing==
Cellulose is derived from <small>D</small>-glucose units, which [[condensation reaction|condense]] through β(1→4)-[[glycosidic bond]]s. This linkage motif contrasts with that for α(1→4)-glycosidic bonds present in [[starch]], [[glycogen]], and other carbohydrates. Cellulose is a straight chain polymer: unlike starch, no coiling occurs, and the molecule adopts an extended and rather stiff rod-like conformation. The multiple [[hydroxyl|hydroxyl groups]] on the glucose residues from one chain form [[hydrogen bond]]s with oxygen molecules on another chain, holding the chains firmly together side-by-side and forming ''microfibrils'' with high [[tensile strength]]. This strength is important in cell walls, where they are meshed into a carbohydrate ''matrix'', conferring rigidity to plant cells.


=== Biosynthesis ===
Compared to starch, cellulose is also much more [[crystallinity|crystalline]]. Whereas starch undergoes a crystalline to [[amorphous solid|amorphous]] transition when heated beyond 60-70 °C in water (as in cooking), cellulose requires a temperature of 320 °C and pressure of 25 [[Pascal (unit)|MPa]] to become amorphous in water.<ref name=Deguchi>''Cooking cellulose in hot and compressed water'' Shigeru Deguchi, Kaoru Tsujii and Koki Horikoshi [[Chem. Commun.]], '''2006''', 3293 - 3295, {{DOI|10.1039/b605812d}}</ref>


In [[Viridiplantae|plant]]s cellulose is synthesized at the [[plasma membrane]] by rosette terminal complexes (RTCs). The RTCs are [[oligomer|hexameric]] protein structures, approximately 25 [[nanometre|nm]] in diameter, that contain the [[cellulose synthase (UDP-forming)|cellulose synthase]] enzymes that synthesise the individual cellulose chains.<ref>{{cite journal|doi=10.2307/3871010|last1=Kimura|first1=S|last2=Laosinchai|first2=W|last3=Itoh|first3=T|last4=Cui|first4=X|last5=Linder|first5=CR|last6=Brown Jr|first6=RM|title=Immunogold labeling of rosette terminal cellulose-synthesizing complexes in the vascular plant vigna angularis|journal=The Plant Cell|volume=11|issue=11|pages=2075–86|year=1999|pmid=10559435|pmc=144118|jstor=3871010}}</ref> Each RTC floats in the cell's plasma membrane and "spins" a microfibril into the [[cell wall]].
Chemically, cellulose can be broken down into its glucose units by treating it with concentrated acids at high temperature.


RTCs contain at least three different [[cellulose synthase]]s, encoded by ''CesA'' (''Ces'' is short for "cellulose synthase") genes, in an unknown [[stoichiometry]].<ref>{{cite journal|last1=Taylor|first1=N. G.|title=Interactions among three distinct CesA proteins essential for cellulose synthesis|journal=Proceedings of the National Academy of Sciences|volume=100|pages=1450–1455|year=2003|doi=10.1073/pnas.0337628100|issue=3|pmid=12538856|pmc=298793|bibcode=2003PNAS..100.1450T|doi-access=free}}</ref> Separate sets of ''CesA'' genes are involved in primary and secondary cell wall biosynthesis. There are known to be about seven subfamilies in the plant ''CesA'' superfamily, some of which include the more cryptic, tentatively-named ''Csl'' (cellulose synthase-like) enzymes. These cellulose syntheses use UDP-glucose to form the β(1→4)-linked cellulose.<ref name=richmond2000>{{cite journal|last1=Richmond|first1=Todd A|last2=Somerville|first2=Chris R|title=The Cellulose Synthase Superfamily|journal=Plant Physiology|date=October 2000|volume=124|issue=2|pages=495–498|doi=10.1104/pp.124.2.495|pmid=11027699|pmc=1539280}}</ref>
Many properties of cellulose depend on its [[degree of polymerization]] or chain length, the number of glucose units that make up one polymer molecule. Cellulose from wood pulp has typical chain lengths between 300 and 1700 units; cotton and other plant fibers as well as bacterial celluloses have chain lengths ranging from 800 to 10,000 units.<ref name=Klemm/> Molecules with very small chain length resulting from the break down of cellulose are known as [[cellodextrin]]s; in contrast to long-chain cellulose, cellodextrins are typically soluble in water and organic solvents.


[[Bacterial cellulose]] is produced using the same family of proteins, although the gene is called ''BcsA'' for "bacterial cellulose synthase" or ''CelA'' for "cellulose" in many instances.<ref name="pmid24127606"/> In fact, plants acquired ''CesA'' from the endosymbiosis event that produced the [[chloroplast]].<ref name=popper>{{cite journal | vauthors = Popper ZA, Michel G, Hervé C, Domozych DS, Willats WG, Tuohy MG, Kloareg B, Stengel DB | s2cid = 11961888 | title = Evolution and diversity of plant cell walls: from algae to flowering plants | journal = Annual Review of Plant Biology | volume = 62 | pages = 567–90 | date = 2011 | pmid = 21351878 | doi = 10.1146/annurev-arplant-042110-103809 | hdl = 10379/6762 | hdl-access = free }}</ref> All cellulose synthases known belongs to [[glucosyltransferase]] family 2 (GT2).<ref name="pmid24127606">{{cite journal |last1=Omadjela |first1=O |last2=Narahari |first2=A |last3=Strumillo |first3=J |last4=Mélida |first4=H |last5=Mazur |first5=O |last6=Bulone |first6=V |last7=Zimmer |first7=J |title=BcsA and BcsB form the catalytically active core of bacterial cellulose synthase sufficient for in vitro cellulose synthesis. |journal=Proceedings of the National Academy of Sciences of the United States of America |date=October 29, 2013 |volume=110 |issue=44 |pages=17856–61 |doi=10.1073/pnas.1314063110 |pmid=24127606 |pmc=3816479 |doi-access=free|bibcode=2013PNAS..11017856O }}</ref>
Plant-derived cellulose is usually contaminated with [[hemicellulose]], [[lignin]], [[pectin]] and other substances, while [[microbial cellulose]] is quite pure, has a much higher water content, and consists of long chains.


Cellulose synthesis requires chain initiation and elongation, and the two processes are separate.
==Assaying cellulose==
Cellulose synthase (''CesA'') initiates cellulose polymerization using a [[steroid]] primer, [[beta-sitosterol|sitosterol]]-beta-[[glucoside]], and UDP-glucose. It then utilizes [[Uridine diphosphate|UDP]]-D-glucose precursors to elongate the growing cellulose chain. A [[cellulase]] may function to cleave the primer from the mature chain.<ref>{{cite journal|last1=Peng|first1=L|last2=Kawagoe|first2=Y|last3=Hogan|first3=P|last4=Delmer|first4=D|title=Sitosterol-beta-glucoside as primer for cellulose synthesis in plants|journal=Science|volume=295|issue=5552|pages=147–50|year=2002|pmid=11778054|doi=10.1126/science.1064281|bibcode=2002Sci...295..147P|s2cid=83564483}}</ref>
Given a cellulose-containing material, the portion that does not dissolve in a 17.5% solution of [[sodium hydroxide]] at 20 °C is ''α cellulose'', which is true cellulose. Acidification of the extract precipitates ''β cellulose''. The portion that dissolves in base but does not precipitate with acid is ''γ cellulose''.


Cellulose is also synthesised by [[tunicate]] animals, particularly in the [[test (biology)|test]]s of [[ascidian]]s (where the cellulose was historically termed "tunicine" (tunicin)).<ref>{{cite journal|author=Endean, R|url=http://jcs.biologists.org/content/s3-102/57/107.full.pdf |archive-url=https://web.archive.org/web/20141026222752/http://jcs.biologists.org/content/s3-102/57/107.full.pdf |archive-date=October 26, 2014 |url-status=live |title=The Test of the Ascidian, ''Phallusia mammillata''|journal= Quarterly Journal of Microscopical Science|volume=102|issue=1|pages=107–117|year= 1961}}</ref>
Cellulose can be assayed using a method described by Updegraff in [[1969]], where the fiber is dissolved in [[acetic acid|acetic]] and [[nitric acid]] to remove lignin, hemicellulose, and xylosans. The resulting cellulose is allowed to react with [[anthrone]] in [[sulfuric acid]]. The resulting coloured compound is assayed [[spectrophotometry|spectrophotometrically]] at a wavelength of approximately 635 [[1 E-9 m|nm]].


=== Breakdown (cellulolysis) ===
In addition, cellulose is represented by the difference between acid detergent fiber (ADF) and acid detergent lignin (ADL).


Cellulolysis is the process of breaking down cellulose into smaller polysaccharides called [[cellodextrin]]s or completely into [[glucose]] units; this is a [[hydrolysis]] reaction. Because cellulose molecules bind strongly to each other, cellulolysis is relatively difficult compared to the breakdown of other [[polysaccharide]]s.<ref>{{cite journal|year=2014|doi=10.1036/1097-8542.118200|author1=Barkalow, David G. |author2=Whistler, Roy L.|title=Cellulose|journal=AccessScience}}</ref> However, this process can be significantly intensified in a proper [[solvent]], e.g. in an [[ionic liquid]].<ref name="Synthesis of glucose esters from cellulose in ionic liquids">{{cite journal|last=Ignatyev|first=Igor|author2=Doorslaer, Charlie Van|author3=Mertens, Pascal G.N.|author4=Binnemans, Koen|author5=Vos, Dirk. E. de|s2cid=101737591|journal=Holzforschung|year=2011|volume=66|issue=4|pages=417–425|title=Synthesis of glucose esters from cellulose in ionic liquids|doi=10.1515/hf.2011.161|url=https://lirias.kuleuven.be/handle/123456789/321763|access-date=August 30, 2017|archive-date=August 30, 2017|archive-url=https://web.archive.org/web/20170830193820/https://lirias.kuleuven.be/handle/123456789/321763|url-status=live}}</ref>
== Biosynthesis ==
[[Image:Plant cell wall diagram.svg|thumb|250px|right|Location and arrangement of cellulose microfibrils in the plant [[cell wall]].]]
In [[vascular plant]]s cellulose is synthesized at the [[plasma membrane]] by rosette terminal complexes (RTC's). The RTC's are [[oligomer|hexameric]] protein structures, approximately 25 [[nanometre|nm]] in diameter, that contain the cellulose [[synthase]] enzymes that synthesise the individual cellulose chains.<ref>Kimura, Laosinchai, Itoh, Cui, Linder, Brown, ''Plant Cell'', 1999, 11, '''2075-2085</ref> Each RTC floats in the cell's plasma membrane and "spins" a microfibril into the cell wall.


Most mammals have limited ability to digest dietary fiber such as cellulose. Some [[ruminant]]s like cows and sheep contain certain [[symbiosis|symbiotic]] [[Anaerobic organism|anaerobic]] bacteria (such as ''[[Cellulomonas]]'' and ''[[Ruminococcus]]'' [[species|spp.]]) in the flora of the [[rumen]], and these bacteria produce [[enzyme]]s called [[cellulase]]s that hydrolyze cellulose. The breakdown products are then used by the bacteria for proliferation.<ref name="La Reau-2018">{{Cite journal|title = The Ruminococci: key symbionts of the gut ecosystem|journal = Journal of Microbiology|date = 2018|pages = 199–208| volume = 56 | issue = 3 |pmid =29492877|doi =10.1007/s12275-018-8024-4|first1 = A.J.|last1 = La Reau|first2 = G.|last2 = Suen|s2cid = 3578123}}</ref> The bacterial mass is later digested by the ruminant in its [[digestive system]] ([[stomach]] and [[small intestine]]). [[Horse]]s use cellulose in their diet by [[hindgut fermentation|fermentation in their hindgut]].<ref>{{cite web |last1=Bowen |first1=Richard |title=Digestive Function of Horses |url=http://www.vivo.colostate.edu/hbooks/pathphys/digestion/herbivores/horses.html |website=www.vivo.colostate.edu |access-date=September 25, 2020 |archive-date=November 12, 2020 |archive-url=https://web.archive.org/web/20201112015454/http://www.vivo.colostate.edu/hbooks/pathphys/digestion/herbivores/horses.html |url-status=live }}</ref> Some [[termite]]s contain in their [[hindgut]]s certain [[flagellate]] [[protozoa]] producing such enzymes, whereas others contain bacteria or may produce cellulase.<ref>{{Cite journal|title=Hidden cellulases in termites: revision of an old hypothesis|journal=Biology Letters|volume=3|pages=336–339|doi=10.1098/rsbl.2007.0073|date=June 22, 2007|author8=Tokuda, Gaku and Hirofumi Watanabe|issue=3|pmid=17374589|last1=Tokuda|first1=G|last2=Watanabe|first2=H|pmc=2464699}}</ref>
The RTC's contain at least three different cellulose synthases, encoded by ''CesA'' genes, in an unknown [[stoichiometry]].<ref>Taylor, Howells, Huttly, Vickers, Turner, ''PNAS'', 2003, '''100''', 1450-1455</ref> Separate sets of ''CesA'' genes are involved in primary and secondary [[cell wall]] biosynthesis. [[cellulose synthase (UDP-forming)|Cellulose synthase]] utilizes [[Uridine diphosphate|UDP]]-D-glucose precursors to generate microcrystalline cellulose. Cellulose synthesis requires chain initiation and elongation, and the two processes are separate. ''CesA'' [[glucosyltransferase]] initiates cellulose polymerization using a [[steroid]] primer, [[beta-sitosterol|sitosterol]]-beta-[[glucoside]], and UDP-glucose.<ref>Peng, Kawagoe, Hogan, Delmer, "Sitosterol-beta-glucoside as primer for cellulose synthesis in plants", ''Science'', 2002, '''295''', 147-150. PMID 11778054</ref> A [[cellulase]] may function to cleave the primer from the mature chain.


The enzymes used to [[wikt:cleave|cleave]] the [[glycosidic linkage]] in cellulose are [[glycoside hydrolase]]s including endo-acting [[cellulase]]s and exo-acting [[glucosidase]]s. Such enzymes are usually secreted as part of multienzyme complexes that may include [[dockerin]]s and [[carbohydrate-binding module]]s.<ref>{{Cite journal|doi=10.1021/cr500351c|title=Fungal Cellulases|year=2015|last1=Payne|first1=Christina M.|last2=Knott|first2=Brandon C.|last3=Mayes|first3=Heather B.|last4=Hansson|first4=Henrik|last5=Himmel|first5=Michael E.|last6=Sandgren|first6=Mats|last7=Ståhlberg|first7=Jerry|last8=Beckham|first8=Gregg T.|journal=Chemical Reviews|volume=115|issue=3|pages=1308–1448|pmid=25629559|doi-access=free}}</ref>
==Breakdown (cellulolysis)==
Cellulolysis is the process of breaking down cellulose into smaller polysaccharides called [[cellodextrins]] or completely into glucose units; this is a [[hydrolysis]] reaction. Because cellulose molecules bind strongly to each other, cellulolysis is relatively difficult compared to the break down of other polysaccharides.<ref>David G. Barkalow, Roy L. Whistler, "Cellulose", in AccessScience@McGraw-Hill, DOI 10.1036/1097-8542.118200. Retrieved 11 January 2008.</ref>


=== Breakdown (thermolysis) ===
Mammals do not have the ability to break down cellulose directly. Some [[ruminant]]s like cows and sheep contain certain [[symbiosis|symbiotic]] [[anaerobic]] bacteria (like ''[[Cellulomonas]]'') in the flora of the gut wall, and these bacteria produce [[enzyme]]s to break down cellulose; the break down products are then used by the mammal. Similarly, lower [[termite]]s contain in their [[hindgut]]s certain [[flagellate]] [[protozoa]] which produce such enzymes; higher termites contain bacteria for the job. [[Fungus|Fungi]], which in nature are responsible for recycling of nutrients, are also able to break down cellulose.
{{See also|Wood ash#Composition}}
At temperatures above 350&nbsp;°C, cellulose undergoes [[thermolysis]] (also called '[[pyrolysis]]'), decomposing into solid [[Char (chemistry)|char]], vapors, [[aerosols]], and gases such as [[carbon dioxide]].<ref>{{cite journal|author1=Mettler, Matthew S. |author2=Vlachos, Dionisios G. |author3=Dauenhauer, Paul J. |title=Top Ten Fundamental Challenges of Biomass Pyrolysis for Biofuels|journal=Energy & Environmental Science |volume=5 |issue=7 |pages=7797 |doi=10.1039/C2EE21679E |year=2012 }}</ref> Maximum yield of vapors which condense to a liquid called ''[[bio-oil]]'' is obtained at 500&nbsp;°C.<ref>{{Cite journal|title=Overview of Applications of Biomass Fast Pyrolysis Oil|journal=Energy & Fuels |volume=18 |issue=2 |pages=590–598 |publisher= Energy & Fuels, American Chemical Society|doi=10.1021/ef034067u |year=2004 |last1 = Czernik|first1 = S.|last2=Bridgwater |first2=A. V. |s2cid=49332510 }}</ref>


Semi-crystalline cellulose polymers react at pyrolysis temperatures (350–600&nbsp;°C) in a few seconds; this transformation has been shown to occur via a solid-to-liquid-to-vapor transition, with the liquid (called ''intermediate liquid cellulose'' or ''molten cellulose'') existing for only a fraction of a second.<ref>{{cite journal|doi=10.1039/B915068B |title=Reactive Boiling of Cellulose for Integrated Catalysis through an Intermediate Liquid|journal=Green Chemistry|volume=11|issue=10|pages=1555|year=2009|last1=Dauenhauer|first1=Paul J.|last2=Colby|first2=Joshua L.|last3=Balonek|first3=Christine M.|last4=Suszynski|first4=Wieslaw J.|last5=Schmidt|first5=Lanny D.|s2cid=96567659}}</ref> Glycosidic bond cleavage produces short cellulose chains of two-to-seven [[monomers]] comprising the melt. Vapor bubbling of intermediate liquid cellulose produces [[aerosols]], which consist of short chain anhydro-oligomers derived from the melt.<ref>{{cite journal|title= Aerosol Generation by Reactive Boiling Ejection of Molten Cellulose|journal= Energy & Environmental Science|volume= 4|issue= 10|pages= 4306|publisher= Energy & Environmental Science, Royal Society of Chemistry|doi= 10.1039/C1EE01876K|year= 2011|last1= Teixeira|first1= Andrew R.|last2= Mooney|first2= Kyle G.|last3= Kruger|first3= Jacob S.|last4= Williams|first4= C. Luke|last5= Suszynski|first5= Wieslaw J.|last6= Schmidt|first6= Lanny D.|last7= Schmidt|first7= David P.|last8= Dauenhauer|first8= Paul J.|url= http://works.bepress.com/paul_dauenhauer/5|access-date= August 30, 2017|archive-date= August 31, 2017|archive-url= https://web.archive.org/web/20170831130431/https://works.bepress.com/paul_dauenhauer/5/|url-status= live}}</ref>
The enzymes utilized to [[wikt:cleave|cleave]] the [[glycosidic linkage]] in cellulose are [[glycoside hydrolase]]s including endo-acting [[cellulase]]s and exo-acting [[glucosidase]]s. Such enzymes are usually secreted as part of multienzyme complexes that may include [[dockerin]]s and cellulose binding modules; these complexes are in some cases referred to as [[cellulosome]]s.


Continuing decomposition of molten cellulose produces volatile compounds including [[levoglucosan]], [[furan]]s, [[pyran]]s, light oxygenates, and gases via primary reactions.<ref>{{cite journal |title=Revealing pyrolysis chemistry for biofuels production: Conversion of cellulose to furans and small oxygenates |journal=Energy Environ. Sci. |volume=5 |pages=5414–5424 |doi=10.1039/C1EE02743C |year=2012 |last1=Mettler |first1=Matthew S. |last2=Mushrif |first2=Samir H. |last3=Paulsen |first3=Alex D. |last4=Javadekar |first4=Ashay D. |last5=Vlachos |first5=Dionisios G. |last6=Dauenhauer |first6=Paul J. |url=http://works.bepress.com/paul_dauenhauer/6 |access-date=August 30, 2017 |archive-date=August 31, 2017 |archive-url=https://web.archive.org/web/20170831083457/https://works.bepress.com/paul_dauenhauer/6/ |url-status=live }}</ref> Within thick cellulose samples, volatile compounds such as [[levoglucosan]] undergo 'secondary reactions' to volatile products including pyrans and light oxygenates such as [[glycolaldehyde]].<ref>{{cite journal |title=Pyrolytic Conversion of Cellulose to Fuels: Levoglucosan Deoxygenation via Elimination and Cyclization within Molten Biomass|journal=Energy & Environmental Science |volume=5 |issue=7 |pages=7864 |doi=10.1039/C2EE21305B |year=2012 |last1=Mettler |first1=Matthew S. |last2=Paulsen |first2=Alex D. |last3=Vlachos |first3=Dionisios G. |last4=Dauenhauer |first4=Paul J. }}</ref>
==Hemicellulose==
[[Hemicellulose]] is a polysaccharide related to cellulose that comprises ca. 20% of the biomass of most plants. In contrast to cellulose, hemicellulose is derived from several sugars in addition to glucose, including especially [[xylose]] but also [[mannose]], [[galactose]], [[rhamnose]], and [[arabinose]]. Hemicellulose consists of shorter chains - around 200 sugar units as opposed to 7,000 - 15,000 glucose molecules in the average cellulose polymer. Furthermore, hemicellulose is branched, whereas cellulose is unbranched.


==Derivatives==
== Hemicellulose ==
{{Main|Hemicellulose}}
The [[hydroxyl]] groups of cellulose can be partially or fully reacted with various [[reagent]]s to afford derivatives with useful properties. Cellulose [[ester]]s and cellulose [[ether]]s are the most important commercial materials. In principle, though not always in current industrial practice, cellulosic polymers are renewable resources.
[[Hemicellulose]]s are [[polysaccharide]]s related to cellulose that comprises about 20% of the biomass of [[embryophyte|land plants]]. In contrast to cellulose, hemicelluloses are derived from several sugars in addition to [[glucose]], especially [[xylose]] but also including [[mannose]], [[galactose]], [[rhamnose]], and [[arabinose]]. Hemicelluloses consist of shorter chains&nbsp;– between 500 and 3000 sugar units.<ref name="pmid22874093">{{cite journal | author=Gibson LJ | title=The hierarchical structure and mechanics of plant materials | journal= [[Journal of the Royal Society Interface]] | volume=9 | issue=76 | year=2013 | pages=2749–2766 | pmc=3479918 | pmid=22874093 | doi=10.1098/rsif.2012.0341}}</ref> Furthermore, hemicelluloses are branched, whereas cellulose is unbranched.


==Regenerated cellulose==
Among the esters are [[cellulose acetate]] and [[cellulose triacetate]], which are film- and fiber-forming materials that find a variety of uses. The inorganic ester [[nitrocellulose]] was initially used as an explosive and was an early film forming material.


Cellulose is soluble in several kinds of media, several of which are the basis of commercial technologies. These dissolution processes are reversible and are used in the production of '''regenerated celluloses''' (such as [[viscose]] and [[cellophane]]) from [[dissolving pulp]].
Ether derivatives include
* [[Ethylcellulose]], a water-insoluble commercial thermoplastic used in coatings, inks, binders, and controlled-release drug tablets;
* [[Methylcellulose]];
* [[Hydroxypropyl cellulose]];
* [[Carboxymethyl cellulose]];
* [[Hydroxypropyl methyl cellulose]], [[E number|E464]], used as a viscosity modifier, gelling agent, foaming agent and binding agent;
* Hydroxyethyl methyl cellulose, used in production of cellulose films.


The most important solubilizing agent is carbon disulfide in the presence of alkali. Other agents include [[Schweizer's reagent]], [[N-Methylmorpholine N-oxide|''N''-methylmorpholine ''N''-oxide]], and [[lithium chloride]] in [[dimethylacetamide]]. In general, these agents modify the cellulose, rendering it soluble. The agents are then removed concomitant with the formation of fibers.<ref>{{cite book |last1= Stenius |first1= Per |title= Forest Products Chemistry |series= Papermaking Science and Technology |volume=3 |year= 2000 |publisher= Fapet OY |location= Finland |isbn= 978-952-5216-03-5 |page= 35 |chapter=Ch. 1}}</ref> Cellulose is also soluble in many kinds of [[ionic liquids]].<ref>{{cite journal|title= Ionic liquid processing of cellulose|journal=Chemical Society Reviews |volume=41 |issue=4 |pages=1519–37 |doi=10.1039/C2CS15311D |pmid=22266483 |year=2012 |last1=Wang |first1=Hui |last2=Gurau |first2=Gabriela |last3=Rogers |first3=Robin D. }}</ref>
==References==
{{reflist}}


The history of regenerated cellulose is often cited as beginning with George Audemars, who first manufactured regenerated [[nitrocellulose]] fibers in 1855.<ref name="PolymerScienceandTechnology">{{cite book|last1=Abetz|first1=Volker|title=Encyclopedia of polymer science and technology|date=2005|publisher=Wiley-Interscience|location=[Hoboken, N.J.]|isbn=978-0-471-44026-0|edition=Wird aktualisiert.}}</ref> Although these fibers were soft and strong -resembling silk- they had the drawback of being highly flammable. [[Hilaire de Chardonnet]] perfected production of nitrocellulose fibers, but manufacturing of these fibers by his process was relatively uneconomical.<ref name=PolymerScienceandTechnology /> In 1890, L.H. Despeissis invented the [[Cuprammonium rayon|cuprammonium process]] – which uses a cuprammonium solution to solubilize cellulose – a method still used today for production of [[artificial silk]].<ref>{{cite book|last1=Woodings|first1=Calvin|title=Regenerated cellulose fibres|date=2001|publisher=The Textile Institute|location=[Manchester]|isbn=978-1-85573-459-3}}</ref> In 1891, it was discovered that treatment of cellulose with alkali and carbon disulfide generated a soluble cellulose derivative known as [[viscose]].<ref name=PolymerScienceandTechnology /> This process, patented by the founders of the Viscose Development Company, is the most widely used method for manufacturing regenerated cellulose products. [[Courtaulds]] purchased the patents for this process in 1904, leading to significant growth of viscose fiber production.<ref name="Borbely">{{cite journal|last1=Borbély|first1=Éva|title=Lyocell, the New Generation of Regenerated Cellulose|journal=Acta Polytechnica Hungarica|date=2008|volume=5|issue=3}}</ref> By 1931, expiration of patents for the viscose process led to its adoption worldwide. Global production of regenerated cellulose fiber peaked in 1973 at 3,856,000 tons.<ref name=PolymerScienceandTechnology />
==See also==
* [[Cell wall]]
* [[Cellulose insulation]]
* [[Cellulosic ethanol]]
* [[Cellulosic ethanol commercialization]]
* [[Hemicellulose]]
* [[Microbial cellulose]]


Regenerated cellulose can be used to manufacture a wide variety of products. While the first application of regenerated cellulose was as a clothing [[textile]], this class of materials is also used in the production of disposable medical devices as well as fabrication of [[Synthetic membrane|artificial membranes]].<ref name=Borbely />
==External links==
* [http://www.lsbu.ac.uk/water/hycel.html LSBU cellulose page]
* [http://msa.ars.usda.gov/la/srrc/fb/ca.html Clear description of a cellulose assay method] at the Cotton Fiber Biosciences unit of the [[United States Department of Agriculture|USDA]].
* [http://www.technologyreview.com/read_article.aspx?ch=infotech&sc=&id=17127&pg=1 Cellulose films could provide flapping wings and cheap artificial muscles for robots] - TechnologyReview.com
* [http://www1.eere.energy.gov/biomass/cellulase_enzyme.html Using cellulase enzymes in the bioethanol process].
* [http://www.wzw.tum.de/mbiotec/cellmo.htm A list of cellulolytic bacteria].


==Cellulose esters and ethers==
The [[hydroxyl]] groups (−OH) of cellulose can be partially or fully reacted with various [[reagent]]s to afford derivatives with useful properties like mainly cellulose [[ester]]s and cellulose [[ether]]s (−OR). In principle, although not always in current industrial practice, cellulosic polymers are renewable resources.

Ester derivatives include:

{| class="wikitable"
|-
! Cellulose ester !! Reagent !! Example !! Reagent !! Group R
|-
| rowspan=5 | Organic esters
| rowspan=5 | Organic acids
| [[Cellulose acetate]] || [[Acetic acid]] and [[acetic anhydride]] || H or −(C=O)CH<sub>3</sub>
|-
| [[Cellulose triacetate]] || Acetic acid and acetic anhydride || −(C=O)CH<sub>3</sub>
|-
| Cellulose propionate || [[Propionic acid]] || H or −(C=O)CH<sub>2</sub>CH<sub>3</sub>
|-
| Cellulose acetate propionate (CAP)|| Acetic acid and propanoic acid || H or −(C=O)CH<sub>3</sub> or −(C=O)CH<sub>2</sub>CH<sub>3</sub>
|-
| Cellulose acetate butyrate (CAB)|| Acetic acid and [[butyric acid]] || H or −(C=O)CH<sub>3</sub> or −(C=O)CH<sub>2</sub>CH<sub>2</sub>CH<sub>3</sub>
|-
| rowspan=2 | Inorganic esters
| rowspan=2 | Inorganic acids
| [[Nitrocellulose]] (cellulose nitrate) || [[Nitric acid]] or another powerful nitrating agent || H or −NO<sub>2</sub>
|-
| [[Cellulose sulfate]] || [[Sulfuric acid]] or another powerful sulfating agent || H or −SO<sub>3</sub>H
|}

Cellulose acetate and cellulose triacetate are film- and fiber-forming materials that find a variety of uses. Nitrocellulose was initially used as an explosive and was an early film forming material. When plasticized with [[camphor]], nitrocellulose gives [[celluloid]].

Cellulose Ether<ref>{{Cite web|title=Cellulose Ether|url=https://methylcellulose.net/cellulose-ether/|access-date=March 7, 2023|website=methylcellulose.net|date=March 5, 2023|archive-date=March 7, 2023|archive-url=https://web.archive.org/web/20230307132638/https://methylcellulose.net/cellulose-ether/|url-status=live}}</ref> derivatives include:

{| class="wikitable"
|-
! Cellulose ethers !! Reagent !! Example !! Reagent !! Group R = H or !! Water solubility !! Application !! [[E number]]
|-
| rowspan=3 | Alkyl
| rowspan=3 | [[Halogenoalkane]]s
| [[Methylcellulose]] || [[Chloromethane]] || −CH<sub>3</sub> || Cold/Hot water-soluble<ref>{{Cite web|title=Methyl Cellulose|url=https://www.kimacellulose.com/products/methyl-cellulose-mc-cas-9004-67-5/|access-date=April 15, 2023|website=kimacellulose.com|archive-date=April 15, 2023|archive-url=https://web.archive.org/web/20230415010711/https://www.kimacellulose.com/products/methyl-cellulose-mc-cas-9004-67-5/|url-status=live}}</ref> || || E461
|-
| [[Ethylcellulose]] (EC) || [[Chloroethane]] || −CH<sub>2</sub>CH<sub>3</sub> || Water-insoluble || A commercial thermoplastic used in coatings, inks, binders, and controlled-release drug tablets <ref>{{cite journal |last1=Maita |first1=Palmieri |title=Toward Sustainable Electronics: Exploiting the Potential of a Biodegradable Cellulose Blend for Photolithographic Processes and Eco-Friendly Devices |journal=Advanced Materials Technologies |date=2023 |volume=1 |issue=9 |doi=10.1002/admt.202301282|hdl=2108/345525 |hdl-access=free }}</ref> || E462
|-
| Ethyl methyl cellulose || Chloromethane and chloroethane || −CH<sub>3</sub> or −CH<sub>2</sub>CH<sub>3</sub> || || || E465
|-
| rowspan=5 | Hydroxyalkyl
| rowspan=5 | [[Epoxide]]s
| [[Hydroxyethyl cellulose]] || [[Ethylene oxide]] || −CH<sub>2</sub>CH<sub>2</sub>OH || Cold/hot water-soluble || Gelling and thickening agent <ref>{{cite journal |last1=Orlanducci |first1=Palmieri |title=Engineered surface for high performance electrodes on paper |journal=Applied Surface Science |date=2022 |volume=608 |doi=10.1016/j.apsusc.2022.155117}}</ref> ||
|-
| [[Hydroxypropyl cellulose]] (HPC) || [[Propylene oxide]] || −CH<sub>2</sub>CH(OH)CH<sub>3</sub> || Cold water-soluble || filming properties, coating properties, pharmaceuticals, cultural heritage restoration, electronic applications, cosmetic sector <ref>{{cite journal |last1=Maita |first1=Palmieri |title=Toward Sustainable Electronics: Exploiting the Potential of a Biodegradable Cellulose Blend for Photolithographic Processes and Eco-Friendly Devices |journal=Advanced Materials Technologies |date=2023 |volume=1 |issue=9 |doi=10.1002/admt.202301282|hdl=2108/345525 |hdl-access=free }}</ref> <ref>{{cite journal |last1=Orlanducci |first1=Palmieri |title=Engineered surface for high performance electrodes on paper |journal=Applied Surface Science |date=2022 |volume=608 |doi=10.1016/j.apsusc.2022.155117}}</ref> <ref>{{cite journal |last1=Orlanducci |first1=Palmieri |title=A Sustainable Hydroxypropyl Cellulose-Nanodiamond Composite for Flexible Electronic Applications |journal=Gels |date=2022 |volume=12 |issue=8 |page=783 |doi=10.3390/gels8120783 |doi-access=free |pmid=36547307 |pmc=9777684 }}</ref> <ref>{{cite journal |last1=Orlanducci |first1=Palmieri |title=Nanodiamond composites: A new material for the preservation of parchment |journal=Journal of Applied Polymer Science |date=2022 |volume=32 |issue=139 |doi=10.1002/app.52742|s2cid=249654979 }}</ref> <ref>{{cite journal |last1=Brunetti |first1=Polino |title=Nanodiamond-Based Separators for Supercapacitors Realized on Paper Substrates |journal=Energy Technology |date=2020 |volume=6 |issue=8 |doi=10.1002/ente.201901233}}</ref>|| || E463
|-
| [[Hydroxyethyl methyl cellulose]] || Chloromethane and ethylene oxide || −CH<sub>3</sub> or −CH<sub>2</sub>CH<sub>2</sub>OH || Cold water-soluble || Production of cellulose films ||
|-
| [[Hydroxypropyl methyl cellulose]] (HPMC) || Chloromethane and propylene oxide || −CH<sub>3</sub> or −CH<sub>2</sub>CH(OH)CH<sub>3</sub> || Cold water-soluble || Viscosity modifier, gelling, foaming and binding agent || E464
|-
| [[Ethyl hydroxyethyl cellulose]] || Chloroethane and ethylene oxide || −CH<sub>2</sub>CH<sub>3</sub> or −CH<sub>2</sub>CH<sub>2</sub>OH || || || E467
|-
| Carboxyalkyl || Halogenated carboxylic acids || [[Carboxymethyl cellulose]] (CMC) || [[Chloroacetic acid]] || −CH<sub>2</sub>COOH || Cold/Hot water-soluble || Often used as its [[sodium]] [[salt (chemistry)|salt]], sodium carboxymethyl cellulose (NaCMC) || E466
|}

The sodium carboxymethyl cellulose can be [[cross-linked]] to give the [[croscarmellose sodium]] (E468) for use as a [[Excipient|disintegrant]] in pharmaceutical formulations. Furthermore, by the covalent attachment of thiol groups to cellulose ethers such as sodium carboxymethyl cellulose, ethyl cellulose or hydroxyethyl cellulose [[Mucoadhesion|mucoadhesive]] and permeation enhancing properties can be introduced.<ref>{{cite journal|last1=Clausen|first1=A| last2=Bernkop-Schnürch|first2=A|title= Thiolated carboxymethylcellulose: in vitro evaluation of its permeation enhancing effect on peptide drugs |journal= Eur J Pharm Biopharm|date=2001|volume=51|issue=1|pages=25–32|doi=10.1016/s0939-6411(00)00130-2|pmid=11154900}}</ref><ref>{{cite journal|last1=Rahmat|first1=D|last2=Devina|first2=C|title= Synthesis and characterization of a cationic thiomer based on ethyl cellulose for realization of mucoadhesive tablets and nanoparticles |journal= International Journal of Nanomedicine|date=2022|volume=17|pages=2321–2334|doi=10.2147/IJN.S321467|pmid=35645561|pmc=9130100|s2cid=248952610|doi-access=free}}</ref><ref>{{cite journal|last1= Leonaviciute |first1=G|last2=Bonengel |first2=S | last3= Mahmood |first3=A|last4= Ahmad Idrees |first4=M|last5=Bernkop-Schnürch|first5=A|title= S-protected thiolated hydroxyethyl cellulose (HEC): Novel mucoadhesive excipient with improved stability |journal= Carbohydr Polym |date=2016|volume=144|pages=514–521|doi=10.1016/j.carbpol.2016.02.075|pmid=27083843}}</ref> Thiolated cellulose derivatives (see [[thiomer]]s) exhibit also high binding properties for metal ions.<ref>{{cite journal|last1=Leichner |first1=C|last2=Jelkmann|first2=M|last3=Bernkop-Schnürch|first3=A|title=Thiolated polymers: Bioinspired polymers utilizing one of the most important bridging structures in nature|journal= Advanced Drug Delivery Reviews|date=2019|volume=151-152|pages=191–221|doi=10.1016/j.addr.2019.04.007|pmid=31028759|s2cid=135464452}}</ref><ref>{{cite journal|last1=Seidi |first1=F|last2=Saeb|first2=MR|last3=Huang|first3=Y| last4=Akbari|first4=A|last5=Xiao|first5=H| title= Thiomers of chitosan and cellulose: Effective biosorbents for detection, removal and recovery of metal ions from aqueous medium |journal= The Chemical Records|date=2021|volume=21-152|issue=7|pages=1876–1896|doi=10.1002/tcr.202100068|pmid=34101343|s2cid=235368517}}</ref>

==Commercial applications ==
[[File:Cellulose strand.svg|thumb|A strand of cellulose (conformation I<sub>α</sub>), showing the [[hydrogen bond]]s (dashed) within and between cellulose molecules.]]
{{see also|dissolving pulp|pulp (paper)}}
Cellulose for industrial use is mainly obtained from [[wood pulp]] and from [[cotton]].<ref name="Klemm"/>

* Paper products: Cellulose is the major constituent of [[paper]], [[paperboard]], and [[card stock]]. [[Electrical insulation paper]]: Cellulose is used in diverse forms as insulation in transformers, cables, and other electrical equipment.<ref>{{cite journal |title=Cellulose as an insulating material |author=Kohman, GT |date=July 1939 |journal= Industrial and Engineering Chemistry |volume=31 |issue=7 |pages=807–817 |doi=10.1021/ie50355a005}}</ref>
* Fibers: Cellulose is the main ingredient of [[textile]]s. [[Cotton]] and synthetics (nylons) each have about 40% market by volume. Other [[plant fiber]]s (jute, sisal, hemp) represent about 20% of the market. [[Rayon]], [[cellophane]] and other "regenerated [[cellulose fiber]]s" are a small portion (5%).
* Consumables: [[Microcrystalline cellulose]] ([[E number|E460i]]) and powdered cellulose (E460ii) are used as inactive [[Excipient#Fillers and diluents|fillers]] in drug tablets<ref>
{{Cite book |isbn = 978-0-8247-8210-8
|page = [https://archive.org/details/excipienttoxicit103wein/page/210 210]
|last = Weiner
|first = Myra L.
|author2 = Kotkoskie, Lois A.
|title = Excipient Toxicity and Safety
|year = 2000
|place = New York
|publisher = Dekker
|url-access = registration
|url = https://archive.org/details/excipienttoxicit103wein/page/210
}}</ref> and a wide range of soluble cellulose derivatives, E numbers E461 to E469, are used as emulsifiers, thickeners and stabilizers in processed foods. Cellulose powder is, for example, used in processed cheese to prevent caking inside the package. Cellulose occurs naturally in some foods and is an additive in manufactured foods, contributing an indigestible component used for texture and bulk, potentially aiding in [[defecation]].<ref>{{cite journal|pmc=3614039|year=2011|last1=Dhingra|first1=D|title=Dietary fibre in foods: A review|journal=Journal of Food Science and Technology|volume=49|issue=3|pages=255–266|last2=Michael|first2=M|last3=Rajput|first3=H|last4=Patil|first4=R. T.|doi=10.1007/s13197-011-0365-5|pmid=23729846}}</ref>
* Building material: Hydroxyl bonding of cellulose in water produces a sprayable, moldable material as an alternative to the use of plastics and resins. The recyclable material can be made water- and fire-resistant. It provides sufficient strength for use as a building material.<ref>{{cite web |url=http://www.gizmag.com/zeoform-cellulose-water/28796 |title=Zeoform: The eco-friendly building material of the future? |publisher=Gizmag.com |access-date=August 30, 2013 |date=August 30, 2013 |archive-date=October 28, 2013 |archive-url=https://web.archive.org/web/20131028082032/http://www.gizmag.com/zeoform-cellulose-water/28796/ |url-status=live }}</ref> [[Cellulose insulation]] made from recycled paper is becoming popular as an environmentally preferable material for [[building insulation]]. It can be treated with [[boric acid]] as a [[fire retardant]].
* Miscellaneous: Cellulose can be converted into [[cellophane]], a thin transparent film. It is the base material for the [[celluloid]] that was used for photographic and movie films until the mid-1930s. Cellulose is used to make water-soluble [[adhesive]]s and [[binder (material)|binders]] such as [[methyl cellulose]] and [[carboxymethyl cellulose]] which are used in [[wallpaper paste]]. Cellulose is further used to make [[hydrophilic]] and highly absorbent [[sponge (tool)|sponges]]. Cellulose is the raw material in the manufacture of [[nitrocellulose]] (cellulose nitrate) which is used in [[smokeless powder|smokeless gunpowder]].
*Pharmaceuticals: Cellulose derivatives, such as [[microcrystalline cellulose]] (MCC), have the advantages of retaining water, being a [[stabilizer (chemistry)|stabilizer]] and [[thickening agent]], and in reinforcement of drug tablets.<ref>{{cite journal|pmid=24993785|year=2014|last1=Thoorens|first1=G|title=Microcrystalline cellulose, a direct compression binder in a quality by design environment--a review|journal=International Journal of Pharmaceutics|volume=473|issue=1–2|pages=64–72|last2=Krier|first2=F|last3=Leclercq|first3=B|last4=Carlin|first4=B|last5=Evrard|first5=B|doi=10.1016/j.ijpharm.2014.06.055|doi-access=free}}</ref>

===Aspirational===
Energy crops: {{Main|Energy crop}} The major [[combustion|combustible]] component of non-food [[energy crop]]s is cellulose, with [[lignin]] second. Non-food energy crops produce more usable energy than edible energy crops (which have a large [[starch]] component), but still compete with food crops for agricultural land and water resources.<ref>Holt-Gimenez, Eric (2007). ''Biofuels: Myths of the Agrofuels Transition''. ''Backgrounder''. [[Institute for Food and Development Policy]], Oakland, CA. 13:2 {{cite web |url=http://www.foodfirst.org/en/node/2638 |access-date=September 5, 2013 |title=Biofuels - Myths of the Agrofuels Transition: Parts I & II |archive-date=November 16, 2009 |archive-url=https://web.archive.org/web/20091116164308/http://www.foodfirst.org/en/node/2638 |url-status=dead|first=Eric|last=Holt-Giménez}} {{cite web |url=http://www.foodfirst.org/fr/node/1712 |title=Biofuels - Myths of the Agrofuels Transition: Parts I & II |access-date=September 5, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130906121836/http://www.foodfirst.org/fr/node/1712 |archive-date=September 6, 2013|first=Eric|last=Holt-Giménez |date=November 13, 2009}}</ref> Typical non-food energy crops include [[hemp|industrial hemp]], [[switchgrass]], ''[[Miscanthus]]'', ''Salix'' ([[willow]]), and ''Populus'' ([[Populus|poplar]]) species. A strain of ''[[Clostridium]]'' bacteria found in zebra dung, can convert nearly any form of cellulose into [[butanol fuel]].<ref>MullinD, Velankar H.2012.Isolated bacteria, methods for use, and methods for isolation.World patent WO 2012/021678 A2</ref><ref>{{cite journal|display-authors=etal|last1=Sampa Maiti |title=Quest for sustainable bio-production and recovery of butanol as a promising solution to fossil fuel |journal=Energy Research |date=December 10, 2015 |volume=40 |issue=4 |pages=411–438 |doi=10.1002/er.3458|s2cid=101240621 |doi-access=free }}</ref><ref>{{cite web |url=http://tulane.edu/news/releases/pr_082511.cfm |title=Cars Could Run on Recycled Newspaper, Tulane Scientists Say |author=Hobgood Ray, Kathryn |date=August 25, 2011 |work=Tulane University news webpage |publisher=[[Tulane University]] |access-date=March 14, 2012 |archive-url=https://web.archive.org/web/20141021085626/http://tulane.edu/news/releases/pr_082511.cfm |archive-date=October 21, 2014 |url-status=dead }}</ref><ref>{{cite web |url=http://www.greenprophet.com/2012/01/zebra-butanol-biofuel/ |title=Put a Zebra in Your Tank: A Chemical Crapshoot? |author=Balbo, Laurie |date=January 29, 2012 |publisher=Greenprophet.com |access-date=November 17, 2012 |archive-date=February 13, 2013 |archive-url=https://web.archive.org/web/20130213020525/http://www.greenprophet.com/2012/01/zebra-butanol-biofuel/ |url-status=live }}</ref>

Another possible application is as [[Insect repellent]]s.<ref>{{Cite news |last=Thompson |first=Bronwyn |date=April 13, 2023 |title=Natural treatment could make you almost invisible to mosquito bites |language=en-US |work=New Atlas |url=https://newatlas.com/science/cellulose-nanocrystals-invisible-mosquitos/ |access-date=April 17, 2023 |archive-date=April 17, 2023 |archive-url=https://web.archive.org/web/20230417154815/https://newatlas.com/science/cellulose-nanocrystals-invisible-mosquitos/?utm_source=New+Atlas+Subscribers&utm_campaign=f043af663f-EMAIL_CAMPAIGN_2023_04_13_01_37&utm_medium=email&utm_term=0_65b67362bd-f043af663f-%5BLIST_EMAIL_ID%5D |url-status=live }}</ref>

== See also ==
* [[Gluconic acid]]
* [[Isosaccharinic acid]], a degradation product of cellulose
* [[Lignin]]
* [[Zeoform]]

== References ==
{{reflist|30em}}

== External links ==
{{Commons cat|Cellulose}}
*{{cite EB1911|wstitle=Cellulose |volume=5 |short=x}}
* [https://web.archive.org/web/20090426122947/http://www.cermav.cnrs.fr/glyco3d/lessons/cellulose/index.html Structure and morphology of cellulose] by Serge Pérez and William Mackie, CERMAV-[[CNRS]]
* [https://web.archive.org/web/20051001072830/http://www.lsbu.ac.uk/water/hycel.html Cellulose], by Martin Chaplin, [[London South Bank University]]
* [https://web.archive.org/web/20050426105859/http://msa.ars.usda.gov/la/srrc/fb/ca.html Clear description of a cellulose assay method] at the Cotton Fiber Biosciences unit of the [[United States Department of Agriculture|USDA]].
* [http://www.technologyreview.com/read_article.aspx?ch=infotech&sc=&id=17127&pg=1 Cellulose films could provide flapping wings and cheap artificial muscles for robots] – TechnologyReview.com

{{Authority control}}
{{Portal bar|Plants|Fungi}}
{{carbohydrates}}
{{carbohydrates}}
{{Paper}}
{{Wood products}}


[[Category:Polysaccharides]]
[[Category:Cellulose| ]]
[[Category:Cellulose| ]]
[[Category:Excipients]]

[[Category:Papermaking]]
[[ar:سليولوز]]
[[Category:Polysaccharides]]
[[bs:Celuloza]]
[[Category:E-number additives]]
[[bg:Целулоза]]
[[ca:Cel·lulosa]]
[[cs:Celulóza]]
[[da:Cellulose]]
[[de:Cellulose]]
[[et:Tselluloos]]
[[es:Celulosa]]
[[eo:Celulozo]]
[[fa:سلولز]]
[[fr:Cellulose]]
[[hr:Celuloza]]
[[io:Celulozo]]
[[id:Selulosa]]
[[is:Sellulósi]]
[[it:Cellulosa]]
[[he:תאית]]
[[lt:Celiuliozė]]
[[hu:Cellulóz]]
[[mk:Целулоза]]
[[ms:Selulosa]]
[[nl:Cellulose]]
[[ja:セルロース]]
[[no:Cellulose]]
[[nn:Cellulose]]
[[oc:Cellulòsa]]
[[pl:Celuloza]]
[[pt:Celulose]]
[[qu:Silulusa]]
[[ru:Целлюлоза]]
[[sq:Celuloza]]
[[simple:Cellulose]]
[[sk:Celulóza (organická látka)]]
[[sl:Celuloza]]
[[sr:Целулоза]]
[[sh:Celuloza]]
[[su:Selulosa]]
[[fi:Selluloosa]]
[[sv:Cellulosa]]
[[ta:மாவியம்]]
[[th:เซลลูโลส]]
[[vi:Cellulose]]
[[tr:Selüloz]]
[[uk:Целюлоза]]
[[zh:纤维素]]

Latest revision as of 16:32, 11 March 2024

Cellulose[1]
Cellulose, a linear polymer of D-glucose units (two are shown) linked by β(1→4)-glycosidic bonds
Three-dimensional structure of cellulose
Identifiers
ChEMBL
ChemSpider
  • None
ECHA InfoCard 100.029.692 Edit this at Wikidata
EC Number
  • 232-674-9
E number E460 (thickeners, ...)
KEGG
UNII
Properties
(C
12H
20O
10)
n
Molar mass 162.1406 g/mol per glucose unit
Appearance white powder
Density 1.5 g/cm3
Melting point 260–270 °C; 500–518 °F; 533–543 K Decomposes[2]
none
Thermochemistry
−963,000 kJ/mol[clarification needed]
−2828,000 kJ/mol[clarification needed]
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
1
0
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp)[2]
REL (Recommended)
 TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)[2]
IDLH (Immediate danger)
 N.D.[2]
Related compounds
Related compounds
 Starch
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Cellulose is an organic compound with the formula (C
6H
10O
5)
n, a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units.[3][4] Cellulose is an important structural component of the primary cell wall of green plants, many forms of algae and the oomycetes. Some species of bacteria secrete it to form biofilms.[5] Cellulose is the most abundant organic polymer on Earth.[6] The cellulose content of cotton fiber is 90%, that of wood is 40–50%, and that of dried hemp is approximately 57%.[7][8][9]

Cellulose is mainly used to produce paperboard and paper. Smaller quantities are converted into a wide variety of derivative products such as cellophane and rayon. Conversion of cellulose from energy crops into biofuels such as cellulosic ethanol is under development as a renewable fuel source. Cellulose for industrial use is mainly obtained from wood pulp and cotton.[6] Cellulose is also greatly affected by direct interaction with several organic liquids.[10]

Some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts, such as Trichonympha. In human nutrition, cellulose is a non-digestible constituent of insoluble dietary fiber, acting as a hydrophilic bulking agent for feces and potentially aiding in defecation.

History[edit]

Cellulose was discovered in 1838 by the French chemist Anselme Payen, who isolated it from plant matter and determined its chemical formula.[3][11][12] Cellulose was used to produce the first successful thermoplastic polymer, celluloid, by Hyatt Manufacturing Company in 1870. Production of rayon ("artificial silk") from cellulose began in the 1890s and cellophane was invented in 1912. Hermann Staudinger determined the polymer structure of cellulose in 1920. The compound was first chemically synthesized (without the use of any biologically derived enzymes) in 1992, by Kobayashi and Shoda.[13]

The arrangement of cellulose and other polysaccharides in a plant cell wall

Structure and properties[edit]

Cellulose under a microscope.

Cellulose has no taste, is odorless, is hydrophilic with the contact angle of 20–30 degrees,[14] is insoluble in water and most organic solvents, is chiral and is biodegradable. It was shown to melt at 467 °C in pulse tests made by Dauenhauer et al. (2016).[15] It can be broken down chemically into its glucose units by treating it with concentrated mineral acids at high temperature.[16]

Cellulose is derived from D-glucose units, which condense through β(1→4)-glycosidic bonds. This linkage motif contrasts with that for α(1→4)-glycosidic bonds present in starch and glycogen. Cellulose is a straight chain polymer. Unlike starch, no coiling or branching occurs and the molecule adopts an extended and rather stiff rod-like conformation, aided by the equatorial conformation of the glucose residues. The multiple hydroxyl groups on the glucose from one chain form hydrogen bonds with oxygen atoms on the same or on a neighbor chain, holding the chains firmly together side-by-side and forming microfibrils with high tensile strength. This confers tensile strength in cell walls where cellulose microfibrils are meshed into a polysaccharide matrix. The high tensile strength of plant stems and of the tree wood also arises from the arrangement of cellulose fibers intimately distributed into the lignin matrix. The mechanical role of cellulose fibers in the wood matrix responsible for its strong structural resistance, can somewhat be compared to that of the reinforcement bars in concrete, lignin playing here the role of the hardened cement paste acting as the "glue" in between the cellulose fibers. Mechanical properties of cellulose in primary plant cell wall are correlated with growth and expansion of plant cells.[17] Live fluorescence microscopy techniques are promising in investigation of the role of cellulose in growing plant cells.[18]

A triple strand of cellulose showing the hydrogen bonds (cyan lines) between glucose strands
Cotton fibres represent the purest natural form of cellulose, containing more than 90% of this polysaccharide.

Compared to starch, cellulose is also much more crystalline. Whereas starch undergoes a crystalline to amorphous transition when heated beyond 60–70 °C in water (as in cooking), cellulose requires a temperature of 320 °C and pressure of 25 MPa to become amorphous in water.[19]

Several types of cellulose are known. These forms are distinguished according to the location of hydrogen bonds between and within strands. Natural cellulose is cellulose I, with structures Iα and Iβ. Cellulose produced by bacteria and algae is enriched in Iα while cellulose of higher plants consists mainly of Iβ. Cellulose in regenerated cellulose fibers is cellulose II. The conversion of cellulose I to cellulose II is irreversible, suggesting that cellulose I is metastable and cellulose II is stable. With various chemical treatments it is possible to produce the structures cellulose III and cellulose IV.[20]

Many properties of cellulose depend on its chain length or degree of polymerization, the number of glucose units that make up one polymer molecule. Cellulose from wood pulp has typical chain lengths between 300 and 1700 units; cotton and other plant fibers as well as bacterial cellulose have chain lengths ranging from 800 to 10,000 units.[6] Molecules with very small chain length resulting from the breakdown of cellulose are known as cellodextrins; in contrast to long-chain cellulose, cellodextrins are typically soluble in water and organic solvents.

The chemical formula of cellulose is (C6H10O5)n where n is the degree of polymerization and represents the number of glucose groups.[21]

Plant-derived cellulose is usually found in a mixture with hemicellulose, lignin, pectin and other substances, while bacterial cellulose is quite pure, has a much higher water content and higher tensile strength due to higher chain lengths.[6]: 3384 

Cellulose consists of fibrils with crystalline and amorphous regions. These cellulose fibrils may be individualized by mechanical treatment of cellulose pulp, often assisted by chemical oxidation or enzymatic treatment, yielding semi-flexible cellulose nanofibrils generally 200 nm to 1 μm in length depending on the treatment intensity.[22] Cellulose pulp may also be treated with strong acid to hydrolyze the amorphous fibril regions, thereby producing short rigid cellulose nanocrystals a few 100 nm in length.[23] These nanocelluloses are of high technological interest due to their self-assembly into cholesteric liquid crystals,[24] production of hydrogels or aerogels,[25] use in nanocomposites with superior thermal and mechanical properties,[26] and use as Pickering stabilizers for emulsions.[27]

Processing[edit]

Biosynthesis[edit]

In plants cellulose is synthesized at the plasma membrane by rosette terminal complexes (RTCs). The RTCs are hexameric protein structures, approximately 25 nm in diameter, that contain the cellulose synthase enzymes that synthesise the individual cellulose chains.[28] Each RTC floats in the cell's plasma membrane and "spins" a microfibril into the cell wall.

RTCs contain at least three different cellulose synthases, encoded by CesA (Ces is short for "cellulose synthase") genes, in an unknown stoichiometry.[29] Separate sets of CesA genes are involved in primary and secondary cell wall biosynthesis. There are known to be about seven subfamilies in the plant CesA superfamily, some of which include the more cryptic, tentatively-named Csl (cellulose synthase-like) enzymes. These cellulose syntheses use UDP-glucose to form the β(1→4)-linked cellulose.[30]

Bacterial cellulose is produced using the same family of proteins, although the gene is called BcsA for "bacterial cellulose synthase" or CelA for "cellulose" in many instances.[31] In fact, plants acquired CesA from the endosymbiosis event that produced the chloroplast.[32] All cellulose synthases known belongs to glucosyltransferase family 2 (GT2).[31]

Cellulose synthesis requires chain initiation and elongation, and the two processes are separate. Cellulose synthase (CesA) initiates cellulose polymerization using a steroid primer, sitosterol-beta-glucoside, and UDP-glucose. It then utilizes UDP-D-glucose precursors to elongate the growing cellulose chain. A cellulase may function to cleave the primer from the mature chain.[33]

Cellulose is also synthesised by tunicate animals, particularly in the tests of ascidians (where the cellulose was historically termed "tunicine" (tunicin)).[34]

Breakdown (cellulolysis)[edit]

Cellulolysis is the process of breaking down cellulose into smaller polysaccharides called cellodextrins or completely into glucose units; this is a hydrolysis reaction. Because cellulose molecules bind strongly to each other, cellulolysis is relatively difficult compared to the breakdown of other polysaccharides.[35] However, this process can be significantly intensified in a proper solvent, e.g. in an ionic liquid.[36]

Most mammals have limited ability to digest dietary fiber such as cellulose. Some ruminants like cows and sheep contain certain symbiotic anaerobic bacteria (such as Cellulomonas and Ruminococcus spp.) in the flora of the rumen, and these bacteria produce enzymes called cellulases that hydrolyze cellulose. The breakdown products are then used by the bacteria for proliferation.[37] The bacterial mass is later digested by the ruminant in its digestive system (stomach and small intestine). Horses use cellulose in their diet by fermentation in their hindgut.[38] Some termites contain in their hindguts certain flagellate protozoa producing such enzymes, whereas others contain bacteria or may produce cellulase.[39]

The enzymes used to cleave the glycosidic linkage in cellulose are glycoside hydrolases including endo-acting cellulases and exo-acting glucosidases. Such enzymes are usually secreted as part of multienzyme complexes that may include dockerins and carbohydrate-binding modules.[40]

Breakdown (thermolysis)[edit]

See also: Wood ash § Composition

At temperatures above 350 °C, cellulose undergoes thermolysis (also called 'pyrolysis'), decomposing into solid char, vapors, aerosols, and gases such as carbon dioxide.[41] Maximum yield of vapors which condense to a liquid called bio-oil is obtained at 500 °C.[42]

Semi-crystalline cellulose polymers react at pyrolysis temperatures (350–600 °C) in a few seconds; this transformation has been shown to occur via a solid-to-liquid-to-vapor transition, with the liquid (called intermediate liquid cellulose or molten cellulose) existing for only a fraction of a second.[43] Glycosidic bond cleavage produces short cellulose chains of two-to-seven monomers comprising the melt. Vapor bubbling of intermediate liquid cellulose produces aerosols, which consist of short chain anhydro-oligomers derived from the melt.[44]

Continuing decomposition of molten cellulose produces volatile compounds including levoglucosan, furans, pyrans, light oxygenates, and gases via primary reactions.[45] Within thick cellulose samples, volatile compounds such as levoglucosan undergo 'secondary reactions' to volatile products including pyrans and light oxygenates such as glycolaldehyde.[46]

Hemicellulose[edit]

Main article: Hemicellulose

Hemicelluloses are polysaccharides related to cellulose that comprises about 20% of the biomass of land plants. In contrast to cellulose, hemicelluloses are derived from several sugars in addition to glucose, especially xylose but also including mannose, galactose, rhamnose, and arabinose. Hemicelluloses consist of shorter chains – between 500 and 3000 sugar units.[47] Furthermore, hemicelluloses are branched, whereas cellulose is unbranched.

Regenerated cellulose[edit]

Cellulose is soluble in several kinds of media, several of which are the basis of commercial technologies. These dissolution processes are reversible and are used in the production of regenerated celluloses (such as viscose and cellophane) from dissolving pulp.

The most important solubilizing agent is carbon disulfide in the presence of alkali. Other agents include Schweizer's reagent, N-methylmorpholine N-oxide, and lithium chloride in dimethylacetamide. In general, these agents modify the cellulose, rendering it soluble. The agents are then removed concomitant with the formation of fibers.[48] Cellulose is also soluble in many kinds of ionic liquids.[49]

The history of regenerated cellulose is often cited as beginning with George Audemars, who first manufactured regenerated nitrocellulose fibers in 1855.[50] Although these fibers were soft and strong -resembling silk- they had the drawback of being highly flammable. Hilaire de Chardonnet perfected production of nitrocellulose fibers, but manufacturing of these fibers by his process was relatively uneconomical.[50] In 1890, L.H. Despeissis invented the cuprammonium process – which uses a cuprammonium solution to solubilize cellulose – a method still used today for production of artificial silk.[51] In 1891, it was discovered that treatment of cellulose with alkali and carbon disulfide generated a soluble cellulose derivative known as viscose.[50] This process, patented by the founders of the Viscose Development Company, is the most widely used method for manufacturing regenerated cellulose products. Courtaulds purchased the patents for this process in 1904, leading to significant growth of viscose fiber production.[52] By 1931, expiration of patents for the viscose process led to its adoption worldwide. Global production of regenerated cellulose fiber peaked in 1973 at 3,856,000 tons.[50]

Regenerated cellulose can be used to manufacture a wide variety of products. While the first application of regenerated cellulose was as a clothing textile, this class of materials is also used in the production of disposable medical devices as well as fabrication of artificial membranes.[52]

Cellulose esters and ethers[edit]

The hydroxyl groups (−OH) of cellulose can be partially or fully reacted with various reagents to afford derivatives with useful properties like mainly cellulose esters and cellulose ethers (−OR). In principle, although not always in current industrial practice, cellulosic polymers are renewable resources.

Ester derivatives include:

Cellulose ester Reagent Example Reagent Group R
Organic esters Organic acids Cellulose acetate Acetic acid and acetic anhydride H or −(C=O)CH3
Cellulose triacetate Acetic acid and acetic anhydride −(C=O)CH3
Cellulose propionate Propionic acid H or −(C=O)CH2CH3
Cellulose acetate propionate (CAP) Acetic acid and propanoic acid H or −(C=O)CH3 or −(C=O)CH2CH3
Cellulose acetate butyrate (CAB) Acetic acid and butyric acid H or −(C=O)CH3 or −(C=O)CH2CH2CH3
Inorganic esters Inorganic acids Nitrocellulose (cellulose nitrate) Nitric acid or another powerful nitrating agent H or −NO2
Cellulose sulfate Sulfuric acid or another powerful sulfating agent H or −SO3H

Cellulose acetate and cellulose triacetate are film- and fiber-forming materials that find a variety of uses. Nitrocellulose was initially used as an explosive and was an early film forming material. When plasticized with camphor, nitrocellulose gives celluloid.

Cellulose Ether[53] derivatives include:

Cellulose ethers Reagent Example Reagent Group R = H or Water solubility Application E number
Alkyl Halogenoalkanes Methylcellulose Chloromethane −CH3 Cold/Hot water-soluble[54] E461
Ethylcellulose (EC) Chloroethane −CH2CH3 Water-insoluble A commercial thermoplastic used in coatings, inks, binders, and controlled-release drug tablets [55] E462
Ethyl methyl cellulose Chloromethane and chloroethane −CH3 or −CH2CH3 E465
Hydroxyalkyl Epoxides Hydroxyethyl cellulose Ethylene oxide −CH2CH2OH Cold/hot water-soluble Gelling and thickening agent [56]
Hydroxypropyl cellulose (HPC) Propylene oxide −CH2CH(OH)CH3 Cold water-soluble filming properties, coating properties, pharmaceuticals, cultural heritage restoration, electronic applications, cosmetic sector [57] [58] [59] [60] [61] E463
Hydroxyethyl methyl cellulose Chloromethane and ethylene oxide −CH3 or −CH2CH2OH Cold water-soluble Production of cellulose films
Hydroxypropyl methyl cellulose (HPMC) Chloromethane and propylene oxide −CH3 or −CH2CH(OH)CH3 Cold water-soluble Viscosity modifier, gelling, foaming and binding agent E464
Ethyl hydroxyethyl cellulose Chloroethane and ethylene oxide −CH2CH3 or −CH2CH2OH E467
Carboxyalkyl Halogenated carboxylic acids Carboxymethyl cellulose (CMC) Chloroacetic acid −CH2COOH Cold/Hot water-soluble Often used as its sodium salt, sodium carboxymethyl cellulose (NaCMC) E466

The sodium carboxymethyl cellulose can be cross-linked to give the croscarmellose sodium (E468) for use as a disintegrant in pharmaceutical formulations. Furthermore, by the covalent attachment of thiol groups to cellulose ethers such as sodium carboxymethyl cellulose, ethyl cellulose or hydroxyethyl cellulose mucoadhesive and permeation enhancing properties can be introduced.[62][63][64] Thiolated cellulose derivatives (see thiomers) exhibit also high binding properties for metal ions.[65][66]

Commercial applications[edit]

A strand of cellulose (conformation Iα), showing the hydrogen bonds (dashed) within and between cellulose molecules.
See also: dissolving pulp and pulp (paper)

Cellulose for industrial use is mainly obtained from wood pulp and from cotton.[6]

  • Paper products: Cellulose is the major constituent of paper, paperboard, and card stock. Electrical insulation paper: Cellulose is used in diverse forms as insulation in transformers, cables, and other electrical equipment.[67]
  • Fibers: Cellulose is the main ingredient of textiles. Cotton and synthetics (nylons) each have about 40% market by volume. Other plant fibers (jute, sisal, hemp) represent about 20% of the market. Rayon, cellophane and other "regenerated cellulose fibers" are a small portion (5%).
  • Consumables: Microcrystalline cellulose (E460i) and powdered cellulose (E460ii) are used as inactive fillers in drug tablets[68] and a wide range of soluble cellulose derivatives, E numbers E461 to E469, are used as emulsifiers, thickeners and stabilizers in processed foods. Cellulose powder is, for example, used in processed cheese to prevent caking inside the package. Cellulose occurs naturally in some foods and is an additive in manufactured foods, contributing an indigestible component used for texture and bulk, potentially aiding in defecation.[69]
  • Building material: Hydroxyl bonding of cellulose in water produces a sprayable, moldable material as an alternative to the use of plastics and resins. The recyclable material can be made water- and fire-resistant. It provides sufficient strength for use as a building material.[70] Cellulose insulation made from recycled paper is becoming popular as an environmentally preferable material for building insulation. It can be treated with boric acid as a fire retardant.
  • Miscellaneous: Cellulose can be converted into cellophane, a thin transparent film. It is the base material for the celluloid that was used for photographic and movie films until the mid-1930s. Cellulose is used to make water-soluble adhesives and binders such as methyl cellulose and carboxymethyl cellulose which are used in wallpaper paste. Cellulose is further used to make hydrophilic and highly absorbent sponges. Cellulose is the raw material in the manufacture of nitrocellulose (cellulose nitrate) which is used in smokeless gunpowder.
  • Pharmaceuticals: Cellulose derivatives, such as microcrystalline cellulose (MCC), have the advantages of retaining water, being a stabilizer and thickening agent, and in reinforcement of drug tablets.[71]

Aspirational[edit]

Energy crops:

Main article: Energy crop

The major combustible component of non-food energy crops is cellulose, with lignin second. Non-food energy crops produce more usable energy than edible energy crops (which have a large starch component), but still compete with food crops for agricultural land and water resources.[72] Typical non-food energy crops include industrial hemp, switchgrass, Miscanthus, Salix (willow), and Populus (poplar) species. A strain of Clostridium bacteria found in zebra dung, can convert nearly any form of cellulose into butanol fuel.[73][74][75][76]

Another possible application is as Insect repellents.[77]

See also[edit]

References[edit]

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