The production of extracellular and intracellular free amino acids during aerated fermentation of glucose by Baker’s yeast (Saccharomyces cerevisiae)

Abstract

During a study of the effects of a high level of NaCl on the content of free intracellular amino acids in baker's yeast grown in aerated fermentation of glucose it was found (Malaney et al. 1988, 1989; Malaney and Tanner 1988) that 0.6 mol/L exogenous NaCl significantly increased the content of free intracellular citrulline, glutamine, ornithine, arginine and lysine (all basic amino acids) over that observed at zero mol/L exogenous NaCl. (Exogenous is defined as salt added beyond that present in the mineral salts in the culture medium.) This paper describes the production and relative relationships of both extracellular and free intracellular amino acids by S. cerevisiae under conditions of high NaCl content in the growth medium at pH 5 and 32 degrees C. For early culture times (6 h), the production of glutamine, citrulline, valine, isoleucine, ornithine, lysine and histidine were all enhanced by the addition of NaCl. For late times (24 h), except for ornithine, the early-time-enhanced amino acids continued to be enhanced by the addition of NaCl. In addition, the yields of several other amino acids also were increased by exogenous salt at this late time. These include aspartic acid, threonine, glutamic acid, cystine, methionine, tyrosine, phenylalanine and arginine.