Pretreatment of sugarcane postharvest leaves by γ-valerolactone/water/FeCl3 system for enhanced glucan and bioethanol production

The potential of sugarcane postharvest leaves for fermentable sugar yield and bioethanol production was analyzed using FeCl3 catalyzed gamma-valerolactone/water pretreatment in the present study. Widely cultivated Indian cane variety Co 86032 (Nayana) was selected for the analysis. Cellulose (52.7 +/- 5%), hemicellulose (33.9 +/- 3.5%) and lignin (18 +/- 0.3%) were estimated in postharvest leaves. Optimized GVL/water/FeCl3 pretreatment (70% GVL/300 mM FeCl3 in 30% water at 120 degrees C for 3 h) resulted in high delignification (74%) and hemicellulose dissolution (85.6%). Extensive removal of ester-linked ferulic acid (94.2%) and p-coumaric acid (84.4%) was also observed after pretreatment. The pretreatment-induced changes were visualized through FESEM, FTIR, XRD and confocal imaging. Only trace amounts of furfural and HMF were detected in the pretreated slurry. At 96 h of saccharification, 82.5% glucose was yielded. Fermentation of enzymatic hydrolyzate using S. cerevisiae MTCC-36 resulted in ethanol yield of 0.434 g/g glucose at 21 h. Current study revealed that, FeCl3 catalyzed GVL/water pretreatment causes effective deconstruction of cane leaves for bioethanol production.