produce fewer acids but considerable amounts of butanediol, and also carbon dioxide. This difference is the basis for the diagnostic key used to differentiate Escherichia coli and Enterobacter aerogenes. In the mixed acid fermentation glucose is converted by way of glycolysis. The fate of pyruvate is a reduction to lactate by the action of lactate dehydrogenase, a reduction to succinate after carboxylation to oxaloacetate, and a cleavage to acetyl-CoA and formate by pyruvate:formate