Acetone-butanol-ethanol fermentation
| Main products of fermentation (structural formulas) |
|---|
 n -butanol |
 acetone |
 Ethanol |
The acetone-butanol-ethanol fermentation or acetone-butanol-ethanol fermentation (abbreviation: ABE fermentation or ABE fermentation ) is a form of anaerobic fermentation in which n- butanol (≈60%), acetone, is made from carbohydrates as the main product (≈30%) and ethanol (≈10%) arise. The conversion is usually done by Clostridia , especially Clostridium acetobutylicum . In many ways it is similar to alcoholic fermentation .
The process is mainly used for the production of biobutanol , a promising biofuel .
The optimization of the process is the subject of current research.
history
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In 1861, Louis Pasteur discovered for the first time a fermentation that also produced butanol.
In 1905 the first microbiological production of acetone was described by Franz Schardinger.
The commercialization of these processes began with the patenting of the formation of alcohol and acids by microorganisms by Auguste Fernbach and Edward Strange in 1912. The manufacture of acetone in particular was of great importance at the time, as it was needed to manufacture cordite during the First World War .
The next development step was achieved in 1919 by Chaim Weizmann , who later became Israel's first president. He was the first to isolate Clostridium acetobutylicum and patented both the bacterium and the manufacturing process of acetone and butanol with this bacterium. The new method enabled a higher product yield and starchy substrates to be used. There are some inconsistencies with a possibly earlier patent.
After the war, the demand for butanol for paint production increased due to the emerging auto industry, so that production was expanded on a large scale, initially in the USA and Canada and later in many other nations. After the Second World War , the fermentative production of butanol was gradually pushed back, as a cheaper, petrochemical synthesis of butanol was discovered in the 1950s. In the following two decades, industrial ABE fermentation was completely stopped in Europe and the USA. Only a few countries (including China) continued to produce until the end of the 20th century .
Due to rising oil prices and the plan to use biobutanol as a regenerative fuel, ABE fermentation has re-established itself in many parts of the world.
Procedure
During the conversion, depending on the substrate and the bacterial strain used, the substances n- butanol, acetone and ethanol are produced in a ratio of 6: 3: 1. There are also numerous by-products, including carbon dioxide , hydrogen , butyric acid , and acetic acid .
The classic procedure
In the classic industrial process, diluted molasses or maize mash are converted as substrates for Clostridium acetobutylicum in a static batch process. The product ratio of butanol to acetone to ethanol in this process is 6: 3: 1 and the product concentration is 12–22 g / L. The solvent yield amounts to 25-33 percent by weight of the substrate used. The product mixture is then separated by distillation . In addition, the by-products hydrogen and carbon dioxide can be used, as can the cell mass, which can be used as animal feed .
The process had its peak before World War II and is no longer used today.
More modern procedures
The process can now also run as a fed-batch process or as a continuous process , with the optimal process control depending on the size of the system. Various in situ processing methods , such as gas stripping and liquid-liquid extraction, are also used to keep the butanol concentration in the reactor low.
Substrates
Classically, in ABE fermentation, hexoses are fermented, which are obtained from starchy plants such as corn , wheat , and rice .
In order to avoid competition for land and to reduce costs, numerous lignocellulose- based waste products such as wheat straw or rice bran were successfully tested. The fermentation of algae , which has many ecological advantages, was also carried out successfully. However, such projects are not yet implemented on a large scale. Reducing raw material costs is an important aspect in order to make the process economical, as a large part of the costs depends on the raw materials (2007: 45%).
Organisms
Clostridial strains are mainly used for ABE fermentation. In addition to the most widely used and best studied Clostridium acetobutylicum , Clostridium beijerinckii , Clostridium saccharobutylicum and Clostridium saccharoperbutylacetonicum were also used industrially. In the meantime, genetic engineering has made it possible to carry out fermentation with bacteria from other strains, such as Escherichia coli . The aim of the research is to increase the efficiency of fermentation and to increase the tolerance of bacteria to butanol.
Problems and Perspectives
There are currently still problems with ABE fermentation that prevent a breakthrough:
- n -Butanol is toxic to the cells, so the concentration must not exceed 20 g / L.
- The n -butanol yield is low (0.28-0.33 mass percent).
- The work-up processes are expensive.
- In industry, only the classic substrates can currently be used, which are expensive and compete for space for the production of food and feed .
There have been many technical innovations in recent years to solve the problems. However, more research is needed to make the process more economical.
Research is currently being conducted into using the entire acetone-butanol-ethanol mixture as a biofuel in addition to biobutanol . In this way the expensive separation could be avoided.
Individual evidence
- ^ Mark Anthony Benvenuto: Industrial Biotechnology . De Gruyter, Berlin, 2019, ISBN 978-3-11-053639-3 , pp. 31–35.
- ↑ a b c d e f g Yuqiang Li, Wei Tang, Yong Chen, Jiangwei Liu & Chia-fon F. Lee: Potential of Acetone-Butanol-Ethanol (ABE) as Biofuel In: Fuel, Volume 242, 2019, doi: 10.1016 / j.fuel.2019.01.063 .
- ↑ a b c d e f g Peter Durre, Hubert Bahl & Gerhard Gottschalk: The acetone-butanol fermentation: the basis for a modern biotechnological process? In: Chemie Ingenieur Technik , Volume 64, No. 6, 1992, pp. 491-498, doi: 10.1002 / cite.330640603 .
- ↑ Patent US1044368 : Fermentation process for the production of acetone and higher alcohols from strach, sugars, and other carbohydrate material. Registered on September 24, 1912 , published November 12, 1912 , inventors: Auguste Fernbach, Edward Halford Strange.
- ↑ Patent US1315585 : Production of acetone and alcohol by bacteriological processes. Registered September 9, 1919 , published December 26, 1916 , inventor: Charles Weizmann.
- ↑ a b c d e f B. Ndaba, I. Chiyancu & S. Marx: n-Butanol derived from biochemical and chemical routes: A review. In: Biotechnology Reports, Volume 8, 2015, pp. 1–9, doi: 10.1016 / j.btre.2015.08.001 .
- ↑ a b Ye Ni & Zhihao Sun: Recent progress on industrial fermentative production of acetone - butanol - ethanol by Clostridium acetobutylicum in China. In: Applied Microbiology and Biotechnology , Volume 83, 2009, pp. 415-423, doi: 10.1007 / s00253-009-2003-y
- ↑ a b c d e f Garabed Antranikian : Applied Microbiology , 1st edition, Springer-Verlag Berlin Heidelberg 2006, ISBN 3-540-24083-7 , pp. 316–321.
- ↑ Garabed Antranikian : Applied Microbiology , 1st edition, Springer-Verlag Berlin Heidelberg 2006, ISBN 3-540-24083-7 , p. 69.
- ↑ Stefan Nordhoff, Hans Höcker & Henrike Gebhard: Renewable raw materials in the chemical industry - away from oil? In: Chemie Ingenieur Technik , Volume 79, 2007, DOI: 10.1002 / cite.200700007 , pp. 551-560.