Evaluating the Effect of Residual Lignin Contents and Fermentation Systems on Bioethanol Production

Abstract

Peroxide-acetic acid (Peroxide-HAc) pretreatment is a simplified and cost-effective technology due to its mild conditions without the catalysis of strong acids, which was introduced to treat sugarcane bagasse (SCB) in this paper. Then pretreated SCB was used to produce bioethanol using thermophilic Saccharomyces cerevisiae in deionized water (DW) and sodium citrate buffer solution (SCS) fermentation systems, respectively. Results: showed that peroxide-HAc pretreatment can selectively remove lignin and change morphological structures, thus positively increasing saccharification and fermentation efficiency downstream. SCB pretreated at 100 °C obtained the lowest residual lignin content of 2.88% and achieved the highest ethanol yield of 92.10% (0.45 g/g-biomass) in DW system. In particular, SCS can decrease the residual sugars content of pretreated SCB during simultaneous saccharification and co-fermentation (SSCF) process. The addition of Tween 80 improved SSCF of SCB pretreated at 80 °C likely because Tween 80 can block residual lignin adsorption with enzymes. The concentration of acetic acid and glycerol byproducts from SCB pretreated at 80 °C can be decreased by SCS and DW systems, respectively, comparing to SCS and DW systems with additing Tween 80. This study provided a systematic process route for the bioethanol production by mild pretreatment method.