Influence of growth medium and yeast species on the formation of γ-glutamyl peptides

Abstract

γ-Glutamyl peptides are known to impart a kokumi sensation and increase the palatability of food. To compare the γ-glutamyl peptides produced by different yeasts, Saccharomyces cerevisiae and Debaryomyces hansenii were cultured in a conventional medium (YPG) and a medium composed of porcine hemoglobin hydrolysates (YHG) for six days. Quantification of γ-glutamyl peptides as well as analysis of yeast growth and γ-glutamyltransferase (GGT) activity were carried out. Results showed that both strains could form a range of γ-glutamyl dipeptides and glutathione in either medium. The total concentration of dipeptides and the concentration of glutathione in each medium showed an upward trend over fermentation time. Compared with yeast species, medium composition had a greater impact on the formation of γ-glutamyl dipeptides. During most of the fermentation period, D. hansenii produced more γ-glutamyl dipeptides (reaching a maximum of 2.395 μM on day 6 in YHG), while S. cerevisiae generated more glutathione (reaching a maximum of 13.465 μM on day 5 in YHG). In addition, D. hansenii showed higher GGT activity than S. cerevisiae in the latter half of fermentation. This study illustrates the influence of growth medium and the crucial choice of yeast species for obtaining target γ-glutamyl peptides for kokumi sensation.