Advancements in medium chain fatty acids biosynthesis from organic waste: current state, challenges and future...

Microbial conversion of organic waste into medium chain fatty acids (MCFAs) as the promising strategy to simultaneously achieve waste treatment and resource recovery has attracted increasing attentions in recent years. This review extensively summarized the organics conversion process, key influencing factors and emerging innovative strategies to enhance the MCFAs production. Moreover, the economic feasibility, challenges and research perspectives were also discussed. During the MCFAs production from organic waste, microorganisms involved in hydrolysis, acidogenesis and chain elongation processes coexist and collaborate to realize substrate conversion. Although competitive pathways such as methanogenesis, excessive ethanol oxidation and acrylate pathway disperse the carbon flow, adding chemical inhibitors, adjusting operation parameters and selecting suitable substrates can effectively suppress these competitive processes and promote the MCFA yield. Substrate properties, operational conditions and microbial community are critical factors influencing MCFAs biosynthesis. In addition, strategies such as exogenous additives, co-fermentation, electro-fermentation and microbial strengthening are feasible methods to boost MCFAs production. Furthermore, techno-economic assessment confirmed that MCFAs biosynthesis from organic waste is an economically feasible approach, but low MCFA yield, system instability and restriction of system scale-up are the main challenges for industrial application. This review provided useful information to carbon recovery from organic wastes and technique development.