Products of Glucose Metabolism by Homofermentative

It is well recognized that products other than lactic acid may be produced by homofermentative lactic acid-producing streptococci. Small quantities of formic, acetic, propionic, and butyric acids, ethanol, carbon dioxide, 2,3-butanediol, acetoin, and biacetyl have been reported as metabolic products of these organisms (Hammer, 1920; Foster, 1921; Langwill, 1924; Long and Hammer, 1936). Of these, however, only ethanol and lactic, acetic, and formic acids have been taken into account in quantitative studies of glucose fermentation (Friedemann, 1938, 1939; Gunsalus and Niven, 1942; White et al., 1955). Carbon recoveries in such experiments were usually 85 to 95 per cent, and equimolar quantities of oneand two-carbon products were found. Oxidation-reduction (O/R) indices, however, varied considerably from the theoretical 1.0, indicating that the products reported, particularly those other than lactate, were not the only ones formed. It was believed that complete fermentation balances, especially in regard to O/R indices, would clarify and extend the knowledge of the metabolic processes of these bacteria. This paper reports a quantitative study of the products formed by several homofermentative lactic acid streptococci in their anaerobic fermentation of glucose.