Specific lignin and cellulose depolymerization of sugarcane bagasse for maximum bioethanol production under optimal chemical fertilizer pretreatment with hemicellulose retention and liquid recycling

Abstract

By screening out total nine sugarcane cultivars that contain directly-fermentable sugars, this study examined largely varied hexoses yields from direct enzymatic hydrolysis of bagasse residues. Using two representative sugarcane bagasse substrates, this study sorted out optimal K3PO4 pretreatments by performing classic response surface methodology, which respectively extracted 58% and 63% lignin and significantly reduced cellulose CrI and DP values in two pretreated bagasse residues. These consequently led to remarkably raised cellulose accessibility by 1.4- and 3.6 folds for near-complete biomass enzymatic saccharification with hexoses yields close to 100% (% cellulose). Notably, unlike physical (hot water, steam explosion) and chemical (acid, alkali) pretreatments as previously examined, this optimal pretreatment (6.4% K3PO4, 144.0 °C, 1 h) could not significantly extract arabinose-rich hemicellulose, suggesting that almost all xylose of hemicelluloses was applicable for engineered yeast co-fermentation to achieve maximum bioethanol at 29% (% dry matter) without the necessity of solid-liquid separation, water washing, and detoxification process. Furthermore, this study collected all K3PO4 liquid waste as chemical fertilizer into rice culture for much enhanced plant growth and biomass production up to 1.5 folds. Therefore, this work has proposed a mechanism model to highlight a cost-effective and green-like strategy for high yield of bioethanol with potential value-added bioproducts by using sugarcane bagasse and other lignocellulose residues.