| Effect of biomass concentration on high ethanol fermentation was investigated for feed batch and batch operations,respectively,with the flocculating yeast strain SPSC01 that has been used in non-carder immobilization technology.Fermentation performance of self-flocculating yeast of batch fermentation was better than that of feed batch fermentation, with higher final ethanol concentration and ethanol yield.Moreover,no significant change of the final ethanol concentration was found with the increase of initial biomass concentration for batch fermentations at 30℃.High ethanol fermentations with addition of broths obtained from fermentations at different string rates were carded out and compared.Fermentation performances were almost the same,which indicated that the yeast's metabolic pathway of the two different floc size was similar to each other.High ethanol fermentations at high temperature were investigated with a flocculating yeast strain SPSC01.Fermentation performance of self-flocculating yeast decreased with the increase of fermentation temperature.However,the tolerance of self-flocculating yeast was improved by elevating the temperature of culture process prior to fermentation.When the culture temperature was increased from 30℃to 36℃,the final concentration of ethanol and ethanol yield for the fermentation at 39℃were increased by 16%and 9.5%,to 133.3 g·L-1 and 0.46,respectively.Positive effect of biomass concentration on high ethanol fermentation at 39℃was also observed.By increasing the initial biomass concentration 5.7 g·L-1 to 55.1 g·L-1,the final concentration of ethanol was increased from 98 g·L-1to 133.3 g·L-1.Ethanol fermentation at 36℃was further investigated with repeated-batch fermentation technology.The whole fermentation process was lasted for 160h.The final ethanol concentration,residual glucose and ethanol yield were 122 g·L-1,0.46 g·L-1 and 0.46, respectively.The average ethanol productivity was calculated to be 5.33 g·L-1·h-1.
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