Converting Biowastes into Medium-chain Fatty Acid via Microbial Chain Elongation: A Mini Review

Abstract

The valorisation of organic biowastes into medium-chain fatty acids (MCFAs) via microbial chain elongation has emerged as a promising strategy to recover carbon and energy while supporting a circular bioeconomy. MCFA production is primarily driven by the reversed β-oxidation (RBO) pathway, in which short-chain carboxylates are elongated using electron donors such as ethanol or lactate. Compared with conventional disposal routes or petrochemical synthesis, microbial chain elongation enables the sustainable conversion of diverse waste streams into high-value platform chemicals applicable to fuels, solvents, and specialty chemicals. This mini-review summarises recent advances in MCFA production from biowastes, with a particular focus on the biochemical fundamentals of the RBO pathway, key chain-elongating microorganisms, and the roles of different electron donors and carbon sources. We further discuss process engineering and ecological strategies for enhancing MCFA yields and steering product specificity, including feedstock pretreatment, electron donor supplementation, and regulation of operating parameters such as temperature, pH, and extraction. Finally, current challenges and future perspectives are highlighted, with emphasis on the apparent biological limitation to high-speed MCFA products.