Manipulating and Effect of Electron Acceptors on Caproate Production Based on Food Waste Two-Phase Chain Elongation Fermentation System

A two-phase fermentation was proposed in the current study to enhance MCFAs production from food waste. In particular, effect of acetate to butyrate ratio (ABR) on MCFAs production was investigated which can be regulated by different pH and organic loading during the acidification phase. Medium ABR (1.00) was obtained when pH is 5.5 and organic loading is 20g VS/L in FW acidification fermentation. Subsequent chain elongation fermentation demonstrated that the highest yield of caproate 9.67 g/L with selectivity of 79%, and highest ethanol conversion efficiency of 1.11 was achieved in medium ABR system. Microbial community study showed that medium ABR significantly enrich the functional bacteria especially Clostridium kluyveri . The study provides a new method for chain elongation enhancement without addition of other additives in food waste fermentation system, and gives a guide for the regulation of the short-chain fatty acids distribution in its acidification phase