Integrated choline chloride/citric acid-microwave pretreatment for efficient nanolignin extraction and bioethanol production from cocoa pod husk waste
Aditya Yadav, Cheng‐Di Dong, Diksha Sharma, Mei‐Ling Tsai, Peipei Sun, Parushi Nargotra, Chiu‐Wen Chen, Kamlesh Choure, Vishal Sharma
Abstract
The necessity to address environmental issues has driven efforts toward exploring sustainable bio-based materials as a viable alternative to conventional energy sources. The current study explores the utilization of cocoa pod husk (CPH) biomass for lignin extraction and cellulose production, aiming to contribute to the eco-friendly production of lignin nanoparticles and bioethanol. A synergistic green deep eutectic solvent (DES) (choline chloride/citric acid)-microwave method was employed to effectively fractionate CPH biomass, resulting in an impressive 77.58% lignin removal at 600 W microwave power. The extracted lignin (211.56 mg/g biomass) was utilized to synthesize lignin nanoparticles that were subsequently characterized. Enzyme-driven hydrolysis of the residual cellulose yielded a reducing sugar content of 198.34 mg/g biomass, demonstrating a saccharification efficiency of 70.78%. Fermentation of monomeric sugars by Saccharomyces cerevisiae and Scheffersomyces stipitis , respectively, gave a maximum ethanol yield of 130 mg/g biomass with a high fermentation efficiency (67.17%). The alterations in the CPH's surface structure and morphology following sequential pretreatment were assessed through FT-IR, BET, and SEM analyses, facilitating effective enzymatic hydrolysis. The current investigation adds to the increasing recognition of sustainable approaches in leveraging waste biomass resources toward a more environmentally conscious future.