The fermentation of lactic acid by a Gram-negative coccus

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Abstract
The relative specific activities and distribution of label within the products of (2-C14) lactate fermentation by washed cells of the rumen organism LC were measured. The CO2 produced is unlabelled. The acetate formed is carboxyl-labelled and the propionate is labelled exclusively in the methylene position. The specific activity of the butyrate is twice that of the butyrate carboxyl group; the specific activity of valerate is twice that of the valerate carboxyl group and the specific activity of caproate is 3 times that of the caproate carboxyl group. The distribution of label within propionate and acetate formed from (2-C14) lactate was confirmed with cell-free extracts. The specific activity of propionate formed by the fermentation of lactate in the presence of C14O2 by washed cells of LC, is only 6% of that of the final CO2- The propionate formed from acrylate under similar conditions is not significantly labelled. Cell-free extracts of LC catalyze an exchange reaction between the pyruvate carboxyl group and CO2- The mechanism of formation of fatty acids from lactate by LC are discussed.