Tyrosols retrieved from traditionally brewed yeasts assist in tolerance against heavy metals and promote growth of cells

Abstract

Abstract Heavy metals act as co-factors for several microbial enzymes and are required in low concentrations for proper biological functioning of yeasts. Since concentrations beyond permitted threshold can damage cell's functionality and viability, metal tolerance in yeasts towards such heavy metals is therefore desirable during fermentation. Tyrosol, a quorum sensing molecule in yeasts, protects yeasts from oxidative stress induced by various factors, but the performance of the molecule under heavy metal induced stress is not known. In this investigation, metal tolerance of four species of endemic yeasts from northeast India, viz Wickerhamomyces anomalus, Candida tropicalis, Saccharomyces cerevisiae and Candida glabrata, isolated from traditional starter culture cakes were tested towards zinc (Zn+2), manganese (Mn+2), cobalt (Co+2) and copper (Cu+2) in presence and absence of tyrosols retrieved from these isolates. The decreasing order of tolerance of isolates were found to be Mn+2 > Zn+2 > Co+2 > Cu+2. Under the influence of tyrosols, isolates showed enhanced growth in their upper metal tolerance limit. C. tropicalis showed enhanced growth (2−48 fold, p<0.0001) in all the tested metal consisting medium (2 mM Zn+2, 5 mM Mn+2, 2 mM Co+2 and 1 mM Cu+2) whilst W. anomalus, C. glabrata, S. cerevisiae showed increased growth (3−17 fold, p<0.0001) in Zn+2 (2 mM), Mn+2 (5 mM) and Cu+2 (1 mM) augmented medium. Overall result suggests that tyrosol exert protective effect under heavy metal induced stress, which could be useful in enhancing the quality of fermented products.