Distinct polymer extraction and cellulose DP reduction for complete cellulose hydrolysis under mild chemical pretreatments in sugarcane

Abstract

In this study, liquid hot water (LHW) and chemical (H2SO4, NaOH, CaO) pretreatments were performed in Saccharum species including sugarcane bagasse. In comparison, the LHW and CaO pretreatments significantly enhanced biomass enzymatic hydrolysis, leading to much high bioethanol yield obtained at 19% (% dry matter) with an almost complete hexoses-ethanol conversion in the desirable So5 bagasse sample. Despite the LHW and CaO are distinctive for extracting hemicellulose and lignin, both pretreatments largely reduced cellulose degree of polymerization for enhanced lignocellulose enzymatic saccharification. Further chemical analysis indicated that the pretreated So5 sample had much lower cellulose crystalline index, hemicellulosic Xyl/Ara and lignin S/H ratio than those of other biomass samples, which explained that the So5 had the highest bioethanol yield among Saccharum species. Therefore, a mechanism model was proposed to elucidate how mild pretreatments could enhance biomass enzymatic saccharification for a high bioethanol production in the desirable sugarcane bagasse.