The Efficient Conversion of Paper Sludge to Ethanol by Simultaneous Saccharification and Cofermentation Using Co-Culture

Abstract

Simultaneous saccharification and cofermentation (SSCF) experiments were conducted to optimize the conversion of paper sludge to ethanol using co-culture of Saccharomyces cerevisiae and Escherichia coli KO11. The fermentation parameters were optimized at 5 wt.% substrate via orthogonal experiments: 25 FPU/g cellulase, 38 • C, 6 wt.% inoculums, and 1:1 S. cerevisiae/E. coli KO11. The ethanol conversion efficiency of co-culture was higher than that of single culture of S. cerevisiae or E. coli KO11 in 72 h fermentation. The maximum ethanol yield achieved by co-culture was 5.69 g/L, which corresponds to a theoretical conversion rate of 63.06 wt.%. The consumption of total reducing sugars reached 90.8%, with higher glucose utilization relative to xylose.