EFFECTS OF CYSTEINE AND OTHER THIOLS ON THE GROWTH OF A BREWER'S YEAST

Abstract

L‐Cysteine at low concentrations (up to 25 mg. cysteine‐S per litre) in an other wise sulphur‐deficient medium will support limited growth of the brewer's yeast under study. At higher concentrations (25–250 mg. cysteine‐S per litre) cysteine is toxic and produces diminished growth. This effect is also observed when the yeast is grown in presence of sulphate, glutathione or L‐methionine as sources of sulphur. Cysteine acts by prolonging the lag phase of growth without affecting cell size. Mercaptoacetate is also growth‐inhibitory, but DL‐homocysteine considerably less so. Cysteamine inhibits growth only when the sulphate concentration is suboptimal. Reduced glutathione, mercaptosuccinate and DL‐penicillamine are not growth‐inhibitory. Cysteine and to a lesser extent mercaptoacetate also depress the respiration of the yeast. 1961 The Institute of Brewing & Distilling