Biochemistry and Genetics of Citrate Utilization in Streptococcus lactis ssp. diacetylactis

Abstract

A review of current literature regards Streptococcus lactis ssp. diacetylactis and its ability to utilize citrate to produce the flavor compound diacetyl. Plating media to isolate organisms capable of citrate utilization are reviewed, as are biochemical mechanisms of citrate utilization and diacetyl synthesis. In addition, historical aspects of the organism are discussed with particular emphasis on reports of instability of citrate utilization and its relevance to taxonomic classification of S. lactis ssp. diacetylactis. Finally, the relationship between plasmid deoxyribonucleic acid and citrate metabolism and future applications of genetic research are discussed. Because citrate permease activity appeared to be linked to a 5.5 megadalton (Mdal) plasmid in all strains of S. lactis ssp. diacetylactis examined, studies determined the relationship between the 5.5 Mdal plasmids. By restriction endonuclease digestion, evidence is provided that the 5.5 Mdal plasmids in all strains examined are identical. © 1981, American Dairy Science Association. All rights reserved.