Ethanol production in simultaneous saccharification and fermentation of cellulose with temperature profiling

Abstract

The effects of temperature on enzymatic saccharification of cellulose and simulataneous saccharification and fermentation (SSF) were investigated with 100 g·l⁻¹ Solka Floc, 5g·l⁻¹Trichoderma reesei cellulase, and Zymomonas mobilis ATCC 29191. The following results were obtained: 1) Ethanol fermentation under glucose dificient conditions can proceed for more than 100 h at 30°C but gradually ceases after 50 h of operation at 40°C. 2) Equivalent glucose yield based on cellulose for SSF operated at its optimum temperature (37°C) is higher than that for enzymatic saccharification of cellulose at the same temperature by 32%. However, the same equivalent glucose yields were obtained for both processes if they were operated at their respective optimum temperature. 3) SSF with temperature cycling increased the ethanol productivity but gave similar ethanol yield to SSF at 37°C. 4) SSF with temperature profiling gave an ethanol yield of 0.32 g·g⁻¹ and cellulose use of 0.86 g·g⁻¹ which were increased by 39% and 34% over SSF with temperature cycling and at 37°C.