Fuelling the future: microbial engineering for the production of sustainable biofuels

Key Points Various renewable resources, including plant biomass, atmospheric CO 2 and methane from landfill gas, can be used through several pathways for sustainable biofuel production. These metabolic pathways for biofuel production include ethanol pathways, keto acid pathways, isoprenoid pathways, CoA-dependent reverse β-oxidation and fatty acid biosynthesis. Recent research in this area has included metabolic engineering of microorganisms to improve their production of biofuels. There are several possible strategies for the optimization of biofuel production, including the redesign of central metabolism for carbon conservation, the balancing of redox cofactors and prolonging the production phase. In this article, James Liao et al . review how microorganisms can be explored for the production of next-generation biofuels. They discuss the different substrates that are available for biofuel production and how these substrates can be directed to various biosynthetic pathways, and they highlight examples of microbial engineering aimed at optimizing biofuel production. Global climate change linked to the accumulation of greenhouse gases has caused concerns regarding the use of fossil fuels as the major energy source. To mitigate climate change while keeping energy supply sustainable, one solution is to rely on the ability of microorganisms to use renewable resources for biofuel synthesis. In this Review, we discuss how microorganisms can be explored for the production of next-generation biofuels, based on the ability of bacteria and fungi to use lignocellulose; through direct CO 2 conversion by microalgae; using lithoautotrophs driven by solar electricity; or through the capacity of microorganisms to use methane generated from landfill. Furthermore, we discuss how to direct these substrates to the biosynthetic pathways of various fuel compounds and how to optimize biofuel production by engineering fuel pathways and central metabolism.