Salt tolerance and ester production mechanisms of Candida etchellsii in Chinese horse bean-chili-paste

Candida etchellsii is a predominant strain in Chinese horse bean-chili-paste, a famous and traditional condiment with high salt content. In this study, physiological properties, ester production capacity and gene expression of C. etchellsii under salt stress were investigated, and the results showed that the strain evoked miscellaneous regulations to resist high salt stress. Under salt stress, C. etchellsii would accumulate intracellular glycerol, Na+ and K+ to balance osmotic pressure. Interestingly, the strain showed much stronger capacity to yield ethyl hexanoate and hexyl acetate after 5% and 20% (w/v) NaCl treatment whether in esterification or alcoholysis system. Furthermore, transcriptome data indicated that the genes associated with carbohydrate metabolism and amino acid metabolism had significantly different expression, and their regulations were consistent with the results of physiological analysis. The results obtained in this study could contribute to understand the salt tolerance mechanism of C. etchellsii and provide a theoretical support for its application in traditional food fermentation.