Continuous ethanol production from sugarcane bagasse hydrolysate at high temperature with cell recycle and in-situ recovery of ethanol

Abstract

A continuous process with cell recycle was demonstrated on fermentation of sugarcane bagasse hydrolysate to ethanol having a facility of in-situ stripping of ethanol by air or nitrogen gas. The thermotolerant yeast Kluyveromyces sp. IIPE453, grown in xylose-rich hydrolysate, was used in this study for fermenting the glucose-rich hydrolysate at 50°C. The effect of dilution rate, cell mass concentration, and air or nitrogen gas stripping on ethanol production was evaluated. The maximum volumetric productivity of ethanol was 1.22gl−1h−1 on stripping the bioreactor with nitrogen at a dilution rate of 0.075h−1. An ethanol yield of 96% of its theoretical value and 95% sugar conversion efficiency could be obtained while the ethanol concentration in the condensate of the stripper was found to be 56.3gl−1, which was almost 3.4 times concentrated as compared to ethanol concentration in the broth without stripping. The specific ethanol productivity could be improved due to increase in sugar conversion efficiency and higher ethanol yield in a continuous cell recycle fermentation system applying gas stripping at high temperature.