Evolutionary enhanced acetic acid stress tolerance and induced glycerol biosynthesis of the probiotic S. cerevisiae var. boulardii

During the environmental stresses, high acid concentration has a negative effect on yeast cell growth and limits biochemical production. Improvement of yeast strains via evolution experiment is an approach to develop robust microorganisms. Here, we aimed to induce adaptive stress tolerance of Saccharomyces cerevisiae var. boulardii strain, grown under low pH and high temperature, to investigate inducibility of acetic acid stress tolerance. The evolved strains of S. boulardii was tolerated to high levels of acetic acid concentrations than the ancestral strain and the S. cerevisiae. Subsequently, using the evolutionary experiments, the evolved yeast strains showed increased survival under high concentration of acetic acid at 8 g/L, when compared with the ancestral strain. This indicated that the evolution strategy could improve the yeast tolerance to acids. Also, the evolved yeast S. boulardii strain showed enhanced capacity of glucose utilization and produced high glycerol level at approximately 6.2 g/L higher. The results suggested for reprogramming of stress response mechanism via induction of glycerol as a cellular protectant. Therefore, yeasts were evolved to enhance acetic acid tolerance and induced glycerol biosynthesis for cellular protection. These valuable strains could be employed as probiotics in food and beverage industries.