Abstract: The yeast which has &ggr;-glutamylcysteine-producing ability and is auxotrophic for pantothenic acid is proliferated in a medium containing a sufficient amount of pantothenic acid, and then it is cultured in a medium containing a limited amount of pantothenic acid to increase the &ggr;-glutamylcysteine content in its cells, whereby the yeast in which &ggr;-glutamylcysteine is accumulated is obtained.

Abstract: The present invention relates to a method for the manufacture of a food material containing high quantities of cysteine. In this method, a yeast extract is prepared from yeast cells that contains &ggr;-glutamylcysteine and the extract is concentrated by controlling the temperature to be not greater than 60° C. to prepare a food material in a liquid form, wherein the concentration of solids is at least 10% and the resulting food material is maintained at 70 to 130° C.

Abstract: A method of screening a yeast strain having a reduced glutathione activity and &ggr;-glutamylcysteine productivity comprising the steps of:

Abstract: Yeast extract is produced by using a strain of Saccharomyces cerevisiae, which can contain 1% by weight or more of &ggr;-glutamylcysteine and contains 0.004-0.1% by weight of glutathione during its logarithmic growth phase, when the strain is cultured in a medium in which a glutathione synthetase deficient strain shows a slower growth rate than a wild strain of Saccharomyces cerevisiae, for example, a strain of Saccharomyces cerevisiae, wherein glutathione synthetase encoded by a glutathione synthetase gene on a chromosome has deletion of a C-terminus region from the 370th arginine residue. There are provided yeast that can be used for production at industrial level and shows a high &ggr;-glutamylcysteine accumulation amount, and yeast extract produced by using the yeast.