Studies on Diacetyl Biosynthesis by Streptococcus Diacetilactis

Resting cell and cell-free extract experiments demonstrated the presence of citritase, oxaloacetic acid decarboxylase, α-acetolactic acid decarboxylase, and pyruvic acid decarboxylase in Streptococcus diacelilactis. Results indicated that citric acid or pyruvic acid was converted to diacetyl and acetylmethylcarbinol with intermediate synthesis of α-acetolactic acid. Acetylmethylcarbinol also was synthesized by condensation of active and free acetaldehyde. Evidence was obtained for the presence of diacetyl reductase and a reversible 2,3-butanediol dehydrogenase in cell-free extracts of S. diacetilactis. The data suggested that S. diacetilactis produced diacetyl from citrate with the intermediate production of oxaloacetate, pyruvate, and α-acetolactate in that order.