Recovery of bio-based medium-chain fatty acids with membrane filtration

Medium-chain fatty acids (MCFAs) are promising platform chemicals for biorefineries in the circular economy. An efficient and sustainable process for their recovery from biomass, however, remains elusive. This work aimed to develop a separation cascade for MCFA recovery from fermentation broth (FB) using membrane filtration. This technical-scale process consisted of a filter-press, thermal-pretreatment, ultrafiltration (UF), and nanofiltration (NF). While solid-liquid separation and UF were efficient, NF fluxes declined rapidly due to membrane fouling, limiting MCFA separation and concentration. Thermal pretreatment and UF membrane pore size had a negligible effect on filtration performance and diafiltration trials in NF proved ineffective. While process feasibility is presently constrained by membrane fouling in NF, characterization, and reduction of foulants could make the process readily viable. Overall, the membrane filtration cascade yielded a product, the NF retentate, with an MCFA concentration approximately 230% greater than that of the feedstock with an average overall recovery of 84%. Furthermore, although the concentration of MCFAs (C4-C8, 12.9 g L-1) may be inadequate for direct use, this product, being clarified and enriched, could serve as an improved feedstock for MCFA purification by alternative methods.