THE ROLE OF DIMETHYL SULPHOXIDE REDUCTASE IN THE FORMATION OF DIMETHYL SULPHIDE DURING FERMENTATIONS

The ability to produce dimethyl sulphide (DMS) during fermentation of wort is apparently a general characteristic of Saccheromyces cerevisiae and Saccharomyces uvarum. Washed suspensions of these yeasts reduce dimethyl sulphoxide (DMSO) but there is no correlation between DMS formation in fermentation and DMSO reduction in whole cells. Although different strains vary widely in their ability to reduce DMSO they all contain similar levels of NADPH—dependent DMSO reductase. This enzyme is a multi-protein system which closely resembles methionine sulphoxide reductase. Spoilage bacteria including Enterobacter cloacae can reduce DMSO more efficiently than can yeast probably because a different enzyme system is involved.