Synthetic Microbial Cocultivation for Targeted Production of Odd-Chain Carboxylates and Alcohols from Carbon Monoxide

Microbial fermentation of syngas (CO, H₂, CO₂) using acetogens is a promising route for the revalorisation of one-carbon feedstocks. However, product diversification from syngas using pure cultures of these microorganisms remains a challenge. Here, we present a synthetic microbial community comprising the acetogen Acetobacterium wieringae JM, the propionigenic bacterium Anaerotignum neopropionicum and the chain elongator Clostridium kluyveri, which collectively produce odd- and even-chain carboxylic acids and higher alcohols from CO/CO₂. In batch bioreactors, metabolite cross-feeding within the community enabled the production of valerate (0.61 g L^-1) and pentanol (0.33 g L^-1), which are rare products in CO-fermenting systems. Chemostat experiments showed a metabolic shift induced in the acetogen by the ethanol-consuming species. Furthermore, construction of the genome-scale metabolic model (GEM) of A. wieringae JM and a community model of the triculture allowed us to predict the performance of the culture in continuous (steady-state) process. Simulations using flux balance analysis predicted a feasible triculture with A. wieringae JM dominating the community, and provided insights into the effect of H₂ supplementation on the product spectrum. The results of our study underscore the potential of synthetic microbial communities for syngas fermentation, with genome-scale metabolic modeling serving as a powerful tool to identify metabolic shifts and guide experimental design.