Bioupcycling methane into triacylglycerol for the production of sustainable aviation fuel by methanotrophic bacteria

The growing demand for aviation fuel has driven the pursuit of sustainable and eco-friendly alternatives to traditional petroleum-based fuels. The development of sustainable aviation fuel (SAF) through the conversion of greenhouse gases into triacylglycerol (TAG) by microorganisms has emerged as a promising field of research. In this study, Methylomicrobium buryatense 5GB1S was metabolically engineered for the first time to accumulate TAG by introducing heterologous genes encoding enzymes involved in TAG biosynthesis and manipulating carbon flux for endogenous intermediates. The carbon, nitrogen, and energy metabolisms in TAG-producing M. buryatense 5GB1S were elucidated by transcriptomic analyses to further facilitate TAG production. Ultimately, a self-activated two-stage cultivation was developed in 3 L fermenters to maximize TAG production by harnessing the inherent nitrogen-fixing capability of M. buryatense 5GB1S. The final engineered strain TAG6 achieved the highest TAG titer of 224.42 mg/L, representing a 9-fold enhancement over the initial engineered strain TAG1. The methane-derived TAG exhibited a favorable cetane number (CN) suitable for SAF production and a significantly reduced carbon footprint. These findings highlight a promising route for upcycling methane into SAF, making a significant step towards mitigating carbon emissions and promoting sustainable biofuel production.