Advances in the microbial biosynthesis of methyl ketones

Methyl ketone, a fatty acid derivative, has attracted extensive attention due to its remarkable properties such as a high cetane number, low freezing point, immiscibility with water, and high compatibility with diesel and other quality biofuel properties. Methyl ketones are downstream products of fatty acid metabolism in microorganisms, making them readily accessible through metabolic engineering. In addition, methyl ketones are easily isolated during biological fermentation, as they can be extracted by organic solvents in medium. Consequently, the utilization of microorganisms for the production of methyl ketones as a viable biofuel alternative has garnered growing interest and achieved substantial advancements. This review aims to comprehensively and critically examine the latest advances in biosynthetic pathways for the synthesis of methyl ketones and corresponding metabolic engineering strategies. These pathways include fatty acid synthesis pathway, fatty acid β-oxidation derived pathway, CoA-dependent pathway, 2-butanone synthesis pathway and polyketide synthases synthesis pathway. Furthermore, key challenges and perspectives have been discussed for advancing research in the field of methyl ketone biosynthesis.