Formation of dimethyl sulfide by Propionibacterium shermanii ATCC 9617

Abstract

As an extension of earlier observations on the ability of Propionibacterium shermanii ATCC 9617 to produce dimethyl sulfide, the quantitative production of this compound was investigated to determine the precursor(s) for dimethyl sulfide formation.Dimethyl sulfide was produced in milk culture at both 8 and 30 C. At 30 C maximum production was attained in 24 hours, further incubation decreased dimethyl sulfide, apparently due to metabolism by the organism.Although the test organism grew readily in sodium lactate broth, it did not produce dimethyl sulfide.Pyruvate as well as cell-free extracts of Streptococcus cremoris and Leuconostoc citro~orum stimulated growth but not allmethyl sulfide formation.Addition of methionine, cysteine, cystathionine or fldimethylpropiothetin chloride to the fermentation failed to enhance dimethyl sulfide accumulation.Upon rennet coagulation, the precursor fraction for dimethyl sulfide formation by the test organism was recovered mostly but not exclusively, in the whey fraction.After exhaustive dialysis of whey, the dlalysate and nondialyzable fractions supported allmethyl sulfide production.When the dialysate was fractionated by gel filtration, the ability of fractions to support dimethyl sulfide production paralleled the protein elution profile.Addition of precipitated whey protein or a-lactalbumin to milk cultures enhanced dimethyl sulfide production.We conclude that P. shermanii ATCC 9617 produces dimethyl sulfide from sulfurcontaining amino acids in peptide linkage.