Engineered salt-tolerant yeast to improve the physicochemical properties and volatiles of sweet flour paste

Abstract

Sweet flour paste is a traditional condiment and fermented in high brine solution (14∼18%). Aroma-producing yeast plays a crucial role in the flavor and taste of sweet flour paste, but high salt concentrations often inhibit the action of the yeast. In this study, yeast Zygosaccharomyces rouxii AS2.18 was used as the parent strain to breed a salt-tolerant aroma-producing yeast strain by a combination of atmospheric and room temperature plasma (ARTP) mutagenesis and adaptive laboratory evolution (ALE). The engineered strain AMS79 showed the good growth and fermentation capacity at 18% NaCl concentration. The salt tolerance was closely related to intracellular glycerol production, Na+K+-ATPase activity enhancement and cell wall integrity improvement of the strain. During sweet flour paste fermentation, the maximum amino nitrogen content of the AMS79 group was 1.07- and 1.11-fold higher than that of the AS2.18 group and blank group, respectively. Compared to Blank group, the inoculation of AS2.18 enhanced the relative contents of alcohols, acids, ketones and furan(one)s, and the content of all 7 volatile compound types increased when AMS79 was inoculated for fermentation. In particular, the contents of 2-methyl-butanoic acid, benzeneacetaldehyde, 5-methyl-2-phenyl-2-hexenal and furfural were significantly enhanced by the salt-tolerant strain AMS79 compared to the parent strain AS2.18.