Ultrasound-Assisted Pretreatment of Lignocellulosic Biomass for Bioethanol Production

The structural complexity of lignocellulosic biomass (LCB) hindered exploiting the vast applications of its valorized products. The production of bioethanol fuels from this biomass is highly influenced by the cost of pretreatments, hydrolysis, and separation processes. The coupling of two or more pretreatment technologies, either simultaneously or stepwise, has a great advantage in overcoming the biomass's recalcitrant nature and in improving the product yields. Ultrasound-assisted pretreatment, hydrolysis, and fermentation technology show promising results for process intensifications of bioethanol production. Ultrasonication improves the productivity of bioethanol production by increasing the mass transfer kinetics and changing the cell morphology. Therefore, it has great potentials to reduce the cost and enhance the rate and yield of bioethanol production via the cavitation effect. Therefore, investigating the depolymerization and fractionations of LCB via ultrasound-assisted enzymatic hydrolysis, ultrasound-assisted pretreatment, and ultrasound-assisted fermentation process, as well as optimizing process conditions, opens the path for exploiting the full potentials of the technology as well as utilization of renewable resources. Thus, this book chapter reviews the research on ultrasound-assisted enzymatic hydrolysis, ultrasound-assisted pretreatment, and ultrasound-assisted fermentation processes.