Emerging approaches in lignocellulosic biomass pretreatment and anaerobic bioprocesses for sustainable biofuels production

The development of advanced biofuels from waste organic matter, such as lignocellulosic biomass, is critical for global sustainable waste management and to delay climate change by reducing greenhouse gas emissions via partial replacement of fossil fuels. However, the inherent recalcitrance of lignocellulosic biomass due to the presence of inhibitory components, mainly lignin, limits the hydrolysis of its carbohydrate content, representing a key hurdle augmenting biofuel production. Therefore, pretreatment of lignocellulosic biomass is crucial to promote its fragmentation, increase its surface area and solubility, and lower the cellulose crystallinity and lignin content for sustainable biorefinery. Conventional pretreatment processes have several drawbacks, including high operational costs, corrosion of equipment, and generation of toxic effluents and by-products. To offset the negative impacts of these limitations on biofuel production, here, we have discussed and critically compared various eco-friendly approaches for the efficient conversion of biomass to ensure high yields of biofuels as a commercial solution. Moreover, a range of microbes and enzymes have been highlighted that effectively utilize lignocellulosic biomass to obtain energy and convert its complex polymeric structure into a biodegradable one, facilitating its subsequent valorization. Furthermore, the importance of multi-omics approaches was discussed to gain functional insights into the lignocellulolytic microbial communities and their interspecies symbiosis during the hydrolysis of organic biomass. Finally, the limitations of previous studies, challenges, industrial perspectives, and future outlooks for the development of economical, energy-saving, and eco-friendly strategies toward the sustainable valorization of lignocellulosic biomass were summarized.