Selection of Enzyme-Producing Microorganisms from Jiuqu and Their Influence on the Quality of Fermented Rice Wine

Generally, commercial rice wine has stable quality with bland flavor, while traditional rice wine has a mellow taste but is unstable in quality. In order to solve this problem, the influence of mixed culture fermentation with monocultures of culturable fungi producing amylase, protease and esterase isolated from Jiuqu from different regions in China and commercial sweet wine koji on the quality of rice wine was assessed. According to the enzyme-producing characteristics and 18S rDNA gene sequence analysis, the five obtained strains were identified as Rhizopus oryzae, Mucor circinelloides, M. lanceolatus, and two strains of Saccharomycopsis fibuligera (XG and HB). The addition of S. fibuligera HB increased the contents of ethanol and amino nitrogen, enriched the types and contents of organic acids, reduced the contents and percentage of bitter amino acids, and increased the contents of volatile compounds when compared with the control group (commercial sweet wine koji alone). More importantly, the contents of phenethyl alcohol and ethyl acetate were significantly higher than those in the other groups. Therefore, S. fibuligera HB can significantly improve the quality of rice wine, suggesting its application potential in multi-strain Qu for rice wine.