Advances in engineered microbes for sustainable biofuel production: Current research and future outlook on lignocellulose utilization

The upsurge in global warming, combined with the depletion of fossil fuels, has led researchers interested in other fuel sources. The search for alternative fossils moved towards the biological; degradation of waste biomass for the production of biofuels such as biohydrogen, biodiesel and bioethanol. The capability of biofuel production can be enhanced by the utilization of a model strain that holds the ability to operate at high substrate, transport sugar through deregulated pathways, and increase metabolic fluxes for improved production. Biofuel production by microorganisms shares similar properties with petroleum-based fuels. Achieving a sufficiently high yield of fuel necessitates the practical use of engineered microbes. The purpose of this review is to provide a comprehensive overview of the sources, pretreatment strategies, and production technologies involving metabolic engineering for biofuel generation. The lignocellulosic biomass has been identified as the major sources of biomass with physical treatment reported to be the most followed pre-treatment strategy. Metabolic engineering of microbes is preferred over other production techniques due to its higher efficiency, optimization of metabolic pathways, increased enzyme production and reduced by-product formation. The recent advances in engineered microbes focus on the optimization of metabolic pathways, CRISPR/Cas9, Gene Editing and modular engineering. This review also focuses on the economic and environmental concerns of biofuel production on feedstock utilization, management practices, and production scale. Finally, this paper highlights the future endeavours of the implantation of effective low-cost technologies for biofuel production in advancing culture conditions and genetic modification of biofuel-generating microbial species.