A green and sustainable approach on statistical optimization of laccase mediated delignification of sugarcane tops for enhanced saccharification

Abstract

Bioethanol production from lignocellulosic biomass is a promising approach towards finding an alternative for transportation fuels that is driven by the prerequisite to lessen our dependency on fossil fuels, increase energy security and mitigate greenhouse gas emission. Recalcitrance of lignocellulosic biomass is a major hindrance in bioethanol production. Hence, an efficient pretreatment method is necessary for degradation of lignin and providing accessibility of holocellulose for hydrolysis. In an attempt to overcome this bottleneck, laccase mediated delignification of sugarcane tops was studied using central composite design (CCD) based on response surface methodology (RSM). The effect of different process parameters such as temperature, pH, solid loading, enzyme titre and incubation time were evaluated. It was observed that under optimum conditions of pH 7, solid loading of 21% (w/v), enzyme titre of 430.3 IU/mL, temperature of 40 °C and incubation of 6 h, maximum delignification of 79.1% was achieved. Compositional analysis, energy density measurement and water retention capacity of the biomass was also conducted along with GC-MS analysis for identification of low molecular compounds formed during delignification. Structural characterization of the biomass before and after pretreatment process were analysed by Scanning Electron Microscopy (SEM), Fourier-Transform Infra-Red Spectroscopy (FTIR) and X-Ray Diffraction Spectroscopy (XRD) that further substantiated the delignification of sugarcane tops.