Selective bioelectrochemical purification of propionate from food waste hydrolysate

Dark fermentation enables hydrogen production while generating propionate-rich streams from food waste. However, efficient separation of propionate from short-chain fatty acid (SCFA) mixtures remains challenging and costly in the downstream processes. Therefore, strategies enabling selective purification of propionate prior to separation from the fermentation broth are highly desirable. In this study, a bioelectrochemically assisted bench-scale process was developed as a proof-of-concept pretreatment to enhance selective purification of propionate prior to downstream processing. A single-chamber rotating disc bioelectrochemical reactor (RDBER) was used to selectively purify the hydrolysate via enhancing the consumption of butyrate by an electroactive biofilm of a recently published butyrate-oxidizing microbial consortium. In the RDBER, different hydraulic retention times (HRTs) without and with pH control were evaluated to investigate their effects on propionate fraction among SCFAs and process stability. The results show that with a pH of 7.0–7.3 and an HRT of 8 days, a propionate fraction of up to 95.5% can be achieved, with its concentration doubling compared to the feed. ... mehrThese results demonstrate the potential of this process as a pretreatment step prior to downstream separation, with the aim of reducing separation complexity and enhancing propionate recovery.