Screening for Quality Strains of Yeast from Yellow Rice Wine and Stress Resistance Analysis
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Abstract:
Four strains of yeast, namely BR 20, BR 25, BR 26 and BR 30, with preferable values for initial fermentation capacity, alcohol-producing ability, and fermentation performance were isolated from the main fermentation broth, yeast starter culture as well as from industrial units in the Shanghai area producing yellow rice wine. These four strains were identified as Saccharomyces cerevisiae by 5.8S rDNA-ITS sequence analysis. These four strains were analyzed in terms of tolerance to high concentrations of ethanol, sugar, and lactic acid as well as high osmotic pressure. The results showed that not only could the BR 20 and BR 30 strains withstand 18% alcohol concentration, but they could also adapt to high osmotic pressures of up to 1.6 mol/L. On the other hand, BR 20 and BR 26 stains had preferable growth capacity in the presence of high content of lactic acid, up to 54 g/L, while BR 30 strain showed highest tolerance to sugar, at 40% concentration. Thus, BR 20 and BR 30 strains showed highest resistance to stress and were chosen for further experiments. Comparison of the fermentation efficiency of BR 20 and BR 30 strains showed that the average substrate utilization rate of BR 20 strain was 1.67% higher than that of the BR 30 strain, and the average ethanol yield of BR 20 strain was 6.76% higher than that of the BR 30 strain. Thus, the use of the BR 20 and BR 30 strains as hybrid strains for wine fermentation from yellow rice will reduce fermentation time, improve the utilization of raw materials, and increase alcohol yield.
