Potential use of thermophilic bacteria for second-generation bioethanol production using lignocellulosic feedstocks: a review

Abstract One of the promising feedstock over the present first-generation feedstock for renewable and cost-effective bioethanol production is lignocellulosic biomass (LCB). In recent years, various efforts have been invested in producing bioethanol from LCB using thermophilic bacteria, which have various advantages over their mesophilic counterparts. Their broad substrate range and production of different thermostable enzymes for degrading different polymeric precursors make them a promising candidate for bioethanol production from LCB. However, thermophilic bacteria have certain disadvantages, like low bioethanol tolerance and yield, making their use difficult for industrial applications. Modification of culture parameters and evolutionary adaptations are alone not enough to pave the path for higher bioethanol production from thermophiles. This review provides an overview of thermophilic bacteria, focusing on the recent developments in genetic engineering techniques for increasing ethanol tolerance and creating higher ethanologenic strains. Additionally, this review explores the milestones of reported thermophilic bacteria to produce bioethanol using LCB as a substrate.