Polysaccharides and Lignin Extraction of Sugarcane Leaves for Enhancing Anaerobic Digestion

Abstract

This study investigated two alkaline pretreatment methods applied to SCL to enhance cellulose accessibility and maximize fermentable sugar production. Sugarcane leaves (SCLs) were subjected to two separate pretreatments to enhance delignification for biogas production: alkaline pretreatment using a 10% (w/v) NaOH solution and oxidative pretreatment using a 10% (w/v) sodium chlorite solution. NaOH pretreatment removed 54% of the initial lignin content, while sodium chlorite pretreatment achieved 66% lignin removal, thereby improving the accessibility of cellulose and hemicellulose for enzymatic hydrolysis. Following pretreatment, sugarcane leaves (SCLs) yielded a cellulose recovery of 74.8% (w/w) relative to the initial cellulose content of the leaves. High-performance liquid chromatography (HPLC) analysis of the hydrolyzed cellulose fraction revealed a monomeric sugar composition of 82.3% d-glucose, 15.2% d-xylose, and 2.5% d-arabinose (weight/weight). Enzymatic hydrolysis using Cellic® CTec2 at a loading of 20 FPU/g cellulose converted the cellulose into fermentable sugars, achieving a reducing sugar yield of 168 mg/g cellulose and 53.57% glucose yield of cellulose, as quantified by HPLC. The methane yield from the cellulose fraction of pretreated sugarcane leaves (SCLs) reached a cumulative value of 138.51 NmL/g VS, approximately 8.2 times higher than the 16.91 NmL/g VS obtained from untreated SCL.