Sequential dilute acid and alkali deconstruction of sugarcane bagasse for improved hydrolysis: Insight from small angle neutron scattering (SANS)

Abstract

Cellulosic bioethanol is a promising renewable and substitute source of energy. To make the bioconversion of LCB to fuels cost effective and energy efficient, it is essential to reduce the recalcitrance of LCB and unravel the process of biomass deconstruction. Present study employed sequential dilute acid-alkali pretreatment of sugarcane bagasse (SCB) for enhancing its bioconversion to ethanol. Box-Behnken and D-optimal designs were used to optimise the process of dilute acid and alkali pretreatments sequentially, resulting in an optimum concentration of 3% (v/v) and 5% (w/v) for H2SO4 and NaOH with solid SCB loadings of 18 and 15% (w/w), respectively, for 30 min at 121 °C. The effectiveness of sequential pretreatment was supported by increased cellulose content (83%), drop in hemicellulose, enhanced delignification and 60% enzymatic hydrolysis of SCB by in-house Trichoderma reesei cellulases at enzyme dose of 20 FPU/g. The favourable multi-length scale ultrastructural changes in SCB induced by pretreatment were confirmed by FT-IR, SEM, EDX, TGA, XRD and small angle neutron scattering (SANS). SANS revealed increase in small pore radii from 11.1 to 18.5 Å, indicating improved biomass porosity after sequential pretreatment. Thus, sequential pretreatment of LCB effectively reduced the recalcitrance and could be more useful in lignocellulosic biorefinery applications.