Promoted bioethanol production through fed-batch semisimultaneous saccharification and fermentation at a high biomass load of sodium carbonate-pretreated rice straw

Abstract

A study on the fed-batch semi-simultaneous saccharification and fermentation (FB-S-SSF) of sodium carbonate-pretreated rice straw at biomass loads between 10.0 and 30.0% (m/v) was conducted. Three different feeding modes, i.e., enzyme feeding (E feeding), substrate feeding (SR feeding) and the combination of both E feeding and SR feeding as well as batch mode were conducted for comparison under identical biomass loads. High ethanol concentrations above 90 g/L were obtained in all modes at a biomass load ≥25.0%. The SR feeding modes achieved higher final ethanol concentrations than those of the E feeding mode and batch mode. At biomass loads of 25.0%, 116.8 ± 3.3 and 118.9 ± 3.6 g/L ethanol was obtained for the SR feeding mode and the combination of E feeding and SR feeding modes, respectively. For batch mode and E feeding mode, the ethanol concentrations were 112.3 ± 3.6 and 108.6 ± 3.0 g/L, respectively. The present study shows that the production cost of bioethanol from lignocellulose can be reduced by adopting in situ-produced crude enzymes produced by Aspergillus fumigatus combined with FB-S-SSF of sodium carbonate-pretreated rice straw at a high biomass load, which provides a new idea for effectively reducing the production cost of bioethanol from lignocellulose.