Pretreatment, enzymatic hydrolysis and fermentation of pearl millet (bajra) for bioethanol production

Introduction: The growing need for renewable and sustainable energy sources is intensifying interest in lignocellulosic biomass as a potentially viable feedstock used in bioethanol production. Pearl millet straw, a readily available agricultural residue, represents a valuable substrate due to its high cellulose and hemicellulose content. Methods: The present study investigated the feasibility of producing bioethanol from pearl millet straw biomass. The reaction of temperature, acid concentration, hydrolysis time, and substrate concentration were examined using Response Surface Methodology (RSM) with an L27 orthogonal array design. Comparative analyses of alkali and acid pretreatments were performed to enhance lignin removal and cellulose accessibility. Results: The results indicated that alkali pretreatment was more effective than acid pretreatment, achieving approximately 2% higher delignification and improved cellulose exposure (590 mg/g). The optimized parameters for enzymatic hydrolysis, determined through RSM, were pH 5.5, incubation time of 16 h, enzyme concentration of 200 μl, and temperature of 60°C, yielding 605 mg/g of glucose and 465 mg/g of xylose.Discussion: Characterization studies using SEM and FTIR analyses confirmed significant structural and chemical modifications in pretreated samples, including enhanced surface porosity and lignin removal, validating the efficacy of the pretreatment approach. Limitations: Further research is required to optimize the fermentation stage and evaluate the overall bioethanol yield under scaled-up operational conditions. Objectives: This study focus to identify and upgrade the main parameters influencing hydrolysis efficiency and sugar release to establish an effective process for bioethanol production from pearl millet straw.