Effects of rice husk on the tolerance of Saccharomyces cerevisiae to high temperature and ethanol concentration

In recent years, growing attention has been devoted to improving stress resistance of yeast to temperature and ethanol concentration as it affects fermentation productivity in biofuel ethanol industry. Rice husk was found to increase the resistance of yeast to high temperature and high ethanol concentration, which can be attributed to yeast cell adsorption on rice husk. Compared with no addition of rice husk, the ethanol yield of brown rice fermented at 32 degrees C and 39 degrees C with 1.0 % rice husk increased by 9.4 % and 5.1 %. The fermentation kinetics of cell growth and ethanol formation could be described by the improved Logistic model and Luedeking-Piret model, respectively. Based on the effect of rice husk, the higher ethanol concentration (106.7 g/L at 32 degrees C) and complete substrate utilization could be achieved by using a mixed substrate at dry mass ratio of whole rice to brown rice of 3:1.