Clostridium acetobutylicum
Clostridium acetobutylicum ( unstained, phase contrast method, 1000x magnification in oil immersion light microscope)
Clostridium acetobutylicum is a bacterium of the genus Clostridium, which has special biotechnological importance due to its ability to produce butanol and acetone by fermentation.
Features
Clostridium acetobutylicum is a gram -positive bacterium. Like other clostridia can also actively move this to the on the entire bacterial surface peritrich arranged flagella.
The genome of the bacterium ( strain ATCC 824 ) was completely sequenced using the shotgun sequencing and elucidated. It consists of a circular chromosome of 3940880 bp and a likewise circular plasmid.
Occurrence
The bacteria live mainly in soils and sediments from water, but may also occur in many other habitats. They are also inhabitants of the intestine ( intestinal flora ) a series of organisms. Like most clostridia they are classified as ubiquitous.
Ecology
C. acetobutylicum lives obligate anaerobes, that is required for the formation of reproductive cells, an oxygen- free substrate. Under aerobic conditions, it is after a few hours endospores that survive for several years as resting stages in oxygen-rich substrates and under anaerobic conditions back to vegetative bacteria.
Metabolism
Within the clostridia C. acetobutylicum is ecologically associated with the saccharolytic clostridia, which are characterized by the ability of digestion of carbohydrates (sugar, starch, whey ). Primary fermentation products are ethanol, butyric acid, acetone, butanol, carbon dioxide, and molecular hydrogen (H2). The carbohydrates are converted into glucose and this first below by glycolysis to pyruvate. About a pyruvate ferredoxin oxidoreductase, the pyruvate is subsequently decarboxylated to acetyl -CoA, with a hydrogenase hydrogen is formed. The acetyl-CoA is degraded by reducing the steps to different metabolites, including ethanol as well as use of an acetoacetyl-CoA thiolase over acetone, propanol, butanol, and butyric acid ( butyrate).
Technical Meaning and History
Clostridium acetobutylicum is able to ferment sugar to the solvents acetone, 1-butanol, ethanol, and to the organic acids, acetic and butyric acid. Because of these properties, there is a great interest to use the bacteria in industrial biotechnology for the production of these products.
The first time was described in the biotechnological importance of the chemist Charles Weizmann and patented. Weizmann was the first president after the founding of Israel, under its new name Chaim Weizmann.
The bacterium has been used on an industrial scale for the biotic production of said organic solvent until the mid 20th century, after which production was replaced by the more economical petrochemical synthesis from propene fraction of petroleum.
Due to decreasing oil reserves and related strongly fluctuating oil prices, with highlights to the oil crisis of 1973 and 2007/2008 the fermentative production of butanol is mainly ( biobutanol as a biofuel ) again discussed and implemented by some companies for several years. In addition to agricultural commodities (sugar, starch) while the use of synthesis gas for synthesis gas fermentation is increasingly scientifically researched. The focus is on the connection of the metabolic characteristics of C. acetobutylicum with the viability of carbon dioxide and carbon monoxide as a carbon source. These metabolic properties as they exist in some other clostridia ( acetogenic bacteria) are used via metabolic engineering.