Coupled biological and chemical catalysis for jet biofuel production: a review

Abstract

The use of fossil fuels in the aviation sector is accelerating global warming by emitting carbon dioxide into the atmosphere, calling for carbon neutral jet fuels. Unlike road transport, which is transitioning to electrification, aviation requires high-energy–density fuels, making liquid alternatives essential. Here we review the production of jet biofuels with emphasis on current production technologies, microbial engineering for lipid synthesis, catalytic conversion of lipids, and economic and life cycle assessment aspects. Microbial lipids, including free fatty acids, can be produced from various carbon sources such as sugars, lignocellulose, methane, methanol, and formate. Catalytic upgrading of lipids can be achieved by hydroprocessing, hydrodeoxygenation, hydrocracking, and hydroisomerization. Metabolic engineering strategies to enhance lipid biosynthesis include increasing the precursor supply, repressing β-oxidation, controlling fatty acid chain length, and applying systems-level optimization using flux balancing, biosensor-guided regulation, and evolutionary engineering. These strategies have enabled the production of 98.9 g lipids and 50 g free fatty acids per liter. Pichia pastoris employing methanol as a substrate can produce up to 23 g/L of free fatty acids. Catalytic upgrading via hydrodeoxygenation and hydrocracking achieves conversion efficiencies over 90% and jet fuel selectivity above 70%. Techno-economic and life cycle assessments indicate that microbial oil-based sustainable aviation fuels could be cost-competitive and environmentally favorable.