Cyanophycin

Structural formula
General
Surname	Cyanophycin
other names	[ L -Asp (4- L -Arg)] n
CAS number	213250-52-3 (polymer) 2478-03-7 (monomer)
Monomers	L - aspartic acid and L - arginine
Molecular formula of the repeating unit	C 10 H 19 N 5 O 5
Molar mass of the repeating unit	289.29 g mol −1
PubChem	56928110
Type of polymer	Biopolymer
properties
Physical state	firmly
safety instructions
GHS labeling of hazardous substances no classification available H and P phrases H: see above P: see above
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Cyanophycin or cyanophycin granaprotein (CGP) is a biopolymer that is formed as a nitrogen storage molecule in a number of cyanobacteria and bacteria and stored in the cell. It was discovered by Antonino Borzì in 1887 and consists in equal proportions of the amino acids L - aspartic acid and L - arginine . This polymer has not yet been used, but it is conceivable due to its very similar properties to polyacrylate .

physiology

Cyanophycin is produced by a number of cyanobacteria and some bacteria (e.g. Acinetobacter calcoaceticus ) as a storage substance. Above all, it stores nitrogen and carbon and is formed in particular when the exponential bacterial growth changes to stationary, i.e. at the time of resource scarcity in the substrate.

Properties and Synthesis

Cyanophycin is formed by various types of cyanobacteria and can make up up to 18 percent of the dry cell mass. The polymer reaches a molar mass of up to 125,000 g · mol ⁻¹ and consists of a chain of repeating monomers of L -aspartic acid, which are linked to the α- amino group of one L - arginine molecule via their free β- carboxy groups . There are also variations in the amino acid composition.

The polymer is formed independently of the cell's ribosomes by the enzyme cyanophycin synthetase, which consists of two identical subunits of 90 to 130 kDa each. The enzyme needs a building block made up of at least three monomers as a starting polymer and, using energy, links the two amino acids to this chain by splitting one molecule of adenosine triphosphate (ATP). The polymer is first phosphorylated at the reactive end and the phosphate residue is then substituted by the amino acid . The activity of the enzyme is influenced by the concentration of Mg ²⁺ and potassium chloride .

Research and production

So far there has been no large-scale production of the biopolymer. For various reasons, cyanobacteria are unsuitable for large-scale approaches, since, on the one hand, they place demands on the substrate that are very difficult to maintain and, on the other hand, can only provide low yields of the polymer. Alternatives are the few bacteria that are able to produce cyanophycin, especially Acinetobacter calcoaceticus . A strain of this bacterium accumulates the polymer with proportions of up to 40% of the dry cell mass. In addition, the necessary for the formation of cyanophycin synthetase CPHA genes can in industrially relevant bacteria expressing be, especially in Escherichia coli , Corynebacterium glutamicum , Cupriavidus necator and Pseudomonas putida . These were a metabolic engineering brought production to a Cyanophycin optimized. The first processes for the isolation of cyanophycin on an industrial scale were also developed.

Another approach to the production of cyanophycin is the use of green genetic engineering , which is to be used to form cyanophycin in higher plants and thus make it available. In a project funded by the Federal Ministry of Food, Agriculture and Consumer Protection (BMELV), bsp. the cyanophycin potato developed. A gene from the cyanobacterium Thermosynechococcus elongatus was built into the potato, which enables the plant to produce a cyanophycin synthetase and thus cyanophycin from the amino acids aspartate and arginine. In other projects of the Federal Ministry of Education and Research (BMBF) the effects of field trials on potatoes were examined.

Dismantling

So far, only a few studies on the biodegradation of cyanophycin have been carried out. As part of his research, Alexander Steinbüchel was able to identify numerous Gram-negative and Gram-positive bacterial strains that break down the polymer. He also identified and isolated individual facultative and strictly (obligatory) anaerobic bacteria that are able to use cyanophycin as the sole source of carbon and nitrogen.

supporting documents

1. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
2. ↑ RD Simon: Cyanophycin Granules from the Blue-Green Alga Anabaena cylindrica: A Reserve Material Consisting of Copolymers of Aspartic Acid and Arginine . In: Proc Natl Acad Sci USA . 68, No. 2, 1971, pp. 265-267. PMID 16591901 .
3. ↑ Alexander Steinbüchel: Cyanophycin - Biosynthesis and Structure ( Memento from February 10, 2015 in the Internet Archive ). Westfälische Wilhelms-Universität Münster.
4. ↑ Cyanophycin potato: plastic from the tuber . biosicherheit.de, March 4, 2009.

literature

• Alexander Steinbüchel: Biopolymers and Precursors: Cyanophycin. In: Garabed Antranikian (Ed.): Applied Microbiology. Springer-Verlag Berlin and Heidelberg 2006; Pp. 387-388. ISBN 978-3-540-24083-9 .