Production of high concentration bioethanol from reed by combined liquid hot water and sodium carbonate-oxygen pretreatment

Abstract

This study aimed to establish a method of producing high-concentration bioethanol from reed with reduced distillation-energy demand. Reed was subjected to a pretreatment combining liquid hot water (LHW) and sodium carbonate with oxygen (LHW–Na2CO3/O2) to increase substrate concentration and further achieve high bioethanol concentration through fed-batch semi-simultaneous saccharification and fermentation (fed-batch S-SSF). An oxygen pressure of 0.8 MPa, a Na2CO3 dosage of 16%, a reaction temperature of 160 °C, and a reaction time of 60 min were determined to be optimal, resulting in the highest bioethanol concentration (66.5 g L−1). Bioethanol concentration increased by 75.9% and resulted in a 76.6% decrease in distillation energy compared with those obtained by single-stage LHW pretreatment at 170 °C. After the LHW–Na2CO3/O2 pretreatment, the rate of lignin removal was 71.4%, and almost all hemicellulose was removed. Lignin and hemicellulose removal weakened the interactions among cellulose, hemicellulose, and lignin. We focused on the maximum utilization of biomass resources and decrease in energy expenditure, which highlighted the potential use of the combined LHW–Na2CO3/O2 pretreatment with fed-batch S-SSF method in the industrialization of bioethanol production from reed.