Acetic Acid Production from Bacteria-Based Processes

Acetic Acid Production from Bacteria-Based Processes 

A major decrease in the capacity to synthesize industrial acetic acid from methanol and CO or by other chemical processes may occur at the end of the next century due to depletion of natural gas and petroleum resources together with an increasing demand for these materials worldwide. With price increases accompanying this situation, bacteria-based processes can certainly become major players in the glacial acetic acid market. 

The early development of microbial processes for industrial production of ethanol or lactic acid occurred in Berfin at the Research Institute for Fermentation Industries, directed by Max Delbrfick. The major accomplishments of this institution were the preparation of pure cultures of bacteria or yeasts for industrial fermentations and the application of the principle of natural pure culturing. In natural pure culturing, the 

Organic Acid and Solvent Production Acetic, Lactic, Gluconic, Succinic, and Polyhydroxyalkanoic Acids 

In 1963, synthetic lactic acid production began on a commercial scale. The chemical synthesis route for synthetic lactic acid yields a racemic mixture of Di-isomers. The commercial process is based on lactonitrile (Holten et al. 1971). Lactonitrile is produced by the base-catalyzed addition of hydrogen cyanide to acetaldehyde. Lactonitrile is then hydrolyzed by strong acid to yield lactic acid, which is purified and recovered. Today, synthetic lactic acid is produced mostly in the United States and Japan, and it accounts for about 50 % of total worldwide production. Industrial fermentations also yield about half the world s lactic acid production and thus are very competitive. 

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Cocoa bean fermentation is a mixed-culture process, consisting initially of fermentations by yeast and lactic acid bacteria followed by oxidation of the fermentation products ethanol and lactic acid into acetic acid and acetoin by several Acetohacter strains, of which /I. pasteurianus is the prominent one (Moens et al. 2014). A C-based carbon flux analysis of Acetohacter during cocoa pulp fermentation-simulating conditions revealed a functionally separated metabolism during co-consumption of ethanol and lactate. Acetate was almost exclusively derived from ethanol, whereas lactate served for formation of acetoin and biomass building blocks. This switch was attributed to the lack of phosphoenolpyruvate carboxykinase and malic enzyme activities, which prevents conversion of oxalo-acetate and malate formed by acetate metabolism in the TCA cycle to PEP and pyruvate and subsequently to acetoin (Adler et al. 2014). Lactate, on the other hand, can be converted to pyruvate, which is then used for acetoin formation or, after conversion to PEP by pymvate phosphate dikinase, for gluconeogenesis. The inability of conversion of TCA cycle intermediates to PEP resembles the situation in G. oxydans, where in addition no enzyme for conversion of pyruvate to PEP is present. 

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