Optimization of Lignocellulosic Waste Pretreatment for Bioethanol Production Using Response Surface Methodology

Abstract

The increasing energy demands and depletion of fossil fuel reserves necessitate advancing sustainable alternatives like second-generation bioethanol derived from lignocellulosic biomass. This study explores the optimization of various pre-treatment methods and fermentation parameters to enhance bioethanol yield from agricultural, vegetable, fruit, and mixed lignocellulosic wastes. Five chemical pre-treatment methods were evaluated for their effectiveness in cellulose and hemicellulose breakdown, including sulfuric acid, kraft lignin, alkaline peroxide, organosolv, and soda lignin. Sulfuric acid and organosolv treatments showed superior performance in reducing sugar release. Enzymatic hydrolysis using Trichoderma reesei and Aspergillus niger further enhanced saccharification, with A. niger demonstrating significantly higher cellulase activities. Co-fermentation with Saccharomyces cerevisiae was optimized using Response Surface Methodology (RSM), considering inoculum size, temperature, pH, and time. The highest ethanol yield—8.18% and 64.57 g/L—was obtained from organosolv pretreated mixed biomass under optimized conditions. These findings underscore the potential of integrating statistical optimization and advanced pre-treatment for efficient and scalable bioethanol production from waste biomass.