FRUCTOSE DISSIMILATION BY LACTOBACILLUS BREVIS

Abstract

Sonic extracts of fructose grown cells of L. brevis contained the enzymes of the heterofermentative pathway. The extracts contain mannitol dehydrogenase, fructokinase, hexosephosphate isomerase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase which effect the over-all oxidation of fructose to CO2 and ribulose phosphate. The extracts actively dissimilated ribose-5-phosphate to acetyl phosphate and triose phosphate, suggesting the presence of phosphoriboisomerase, phospho-ketopentoepimerase, and phosphoketolase. The demonstration of triosephosphate dehydrogenase, phosphoglycerate kinase, and lactic acid dehydrogenase in the extracts and the earlier evidence in the literature for the presence of enolase implicate the classical route of lactate formation from glyceraldehyde-3-phosphate. Fructose-1,6-diphosphate aldolase, transketolase, 6-phosphogluconate dehydrase, and 2-keto-3-deoxy-6-phosphogluconate aldolase activities were negligible or absent in the cell extracts. These data are discussed in accordance with known pathways of hexose and pentose fermentation among both the homofermentative and heterofermentative lactic acid bacteria.