Sustainable process for fractionation of lignin by the microwave-assisted chemical additive approach: Towards sugarcane leaf biorefinery and characterization

Abstract

The microwave assisted pretreatment on sugarcane leaf (SCL) biomass for delignification was studied to enhance cellulose digestibility. In this work, microwave assisted with additives were used to delignification SCL for maximize sugar yield recovery. Single factorial and Central composite design (CCD) were employed to optimize the microwave assisted pretreatment conditions for improve delignification efficiency and the sugar yield recovery. The optimized pretreatment conditions were determined to be 4 min pre-treatment time, 500 W microwave power, 1.0 M Na₂CO₃ and 10 % biomass loading condition produce maximum reducing sugar yield (601 mg g^-1) and glucose sugar yield (231 mg g^-1) were achieved during saccharification. Pretreated biomass produced reducing sugar and glucose yields that were 4.5 and 4.1 times higher than those of untreated (native) SCL-N biomass, respectively. Additionally, the recyclability study of black liquor, obtained from optimized conditioned treatment of SCL-MSC (Microwave-assisted sodium carbonate pretreated SCL) resulted in considerable saccharification yield up to three pretreatment cycles. The ¹H NMR and ¹³C NMR spectra studies illustrate that aromatic units present in SCL fractionated lignin samples. The variations of structure features and chemical compositions of the raw and pretreated SCL biomass were analyzed by SEM, XRD and XPS analysis. Overall, SCL-MSC pretreatment condition significantly delignification of SCL and led to the maximum sugar production optimized strategies pretreatment conditions was produced maximum amount of sugar, which is great potential for bio-refinery product development.

Keywords: Bio-refinery product; Delignification; Optimized strategies; Reducing sugar; Saccharification.