Preparation of a [gamma]-glutamylcysteine-enriched yeast extract from a newly developed GSH2-deficient strain

• Published in: Journal of bioscience and bioengineering 2013-01, Vol.115 (1), p.50-54
• Main Authors: Nishiuchi, Hiroaki, Suehiro, Mariko, Sugimoto, Reiko, Yamagishi, Kazuo
• Format: Article
• Language: English
• Subjects: Auxotrophy
• ISSN: 1389-1723

Gamma-glutamylcysteine ([gamma]-GC), the precursor of glutathione (GSH), may have significant health benefits as a dietary supplement, but there are few cost-effective methods available for its large-scale production. We developed an efficient method for producing [gamma]-GC in a mutant yeast strain using a three-step breeding procedure and a unique cultivation process. In the first breeding step, we prepared a glutathione synthetase (GSH2)-deficient yeast mutant. In the second step, selenate (Se O 4 2 -) sensitivity was introduced by crossing the GSH2-deficient mutant with a strain harboring the met30 mutation. In the final step, pantothenic acid auxotrophy was introduced by ethyl methanesulfonate mutagenesis. The isolated strain displayed significantly enhanced cellular [gamma]-GC when cultivated in synthetic medium without pantothenic acid, reaching a maximum level of 4.39% of dry cell weight. Using this strain, we were able to prepare a yeast extract containing approximately 13% [gamma]-GC (w/w), which is markedly higher than the reported value (0.3%) of commercially available yeast extracts. The present method may facilitate large-scale [gamma]-GC production for investigating the nutritive value and other benefits of dietary [gamma]-GC.