Ultrasound-Assisted Non-Enzymatic Pretreatment of Banana Pseudostem for Bioethanol Production: A Critical Review

The global rise in fossil fuel consumption and greenhouse gas emissions has accelerated the search for sustainable energy alternatives, with bioethanol from lignocellulosic biomass emerging as a promising solution. Among these, bioethanol derived from lignocellulosic biomass has gained considerable attention. Banana pseudostem (BPS), a readily available agricultural byproduct-particularly in India, which contributes over 26% to global banana production-presents a valuable feedstock due to its rich cellulose content and year-round availability. For every tonne of banana fruit harvested, approximately three tonnes of pseudostem are generated, much of which is currently underutilized or discarded. This review focuses on ultrasound-assisted, non-enzymatic pretreatment techniques aimed at improving cellulose accessibility in BPS for efficient bioethanol production. Ultrasonic treatment effectively disrupts lignin structures, enhancing the surface area and porosity of the biomass without incurring the high costs typically associated with enzymatic hydrolysis. Additionally, the review explores various microbial fermentation approaches, emphasizing optimized strains that enhance ethanol yield from pretreated BPS.