Butanediol fermentation is carried out by members of the genera Enterobacter, Erwinia, Hafnia, Klebsiella, and Serratia. Most of these bacteria can be found in soil and water (Enterobacter and Serratia) and they can be plant pathogens
(Erwinia). Butanediol fermentation produces less acids than mixed-acid fermentation as two molecules of pyruvate are used to produce one molecule of 2,3-butanediol and are therefore not available for the production of acid compounds. Thus, the ratio of acidic to neutral products is 1:6. Moreover, the reactions that lead to the production of 2,3-butanediol involve a double decarboxylation step; thus, butanediol fermentation produces more gas than mixed-acid fermentation, with a ratio of carbon dioxide to hydrogen of 5:1.
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