Inhibition of N-Vanillylnonanamide in anaerobic digestion of lipids in food waste: Microorganisms damage and blocked electron transfer

[Display omitted] •N-Vanillylnonanamide was added to the glycerol trioleate, a common oil in food waste.•The effects of N-Vanillylnonanamide on anaerobic digestion were deeply analyzed.•N-Vanillylnonanamide less than 1 wt% had little influence on methane yield.•N-Vanillylnonanamide more than 40 wt% resulted in a decrease of 84 % of methane yield.•Inhibition on cell structure, metabolites, electron transfer, and enzyme was analyzed. To study the inhibited degradation metabolism and anaerobic digestion of typical lipids in food waste, an artificially produced capsaicin, N-Vanillylnonanamide, a typical soluble component in waste lipids, was added to a glycerol trioleate anaerobic digestion system. The microorganisms damage and blocked electron transfer caused by N-Vanillylnonanamide during anaerobic digestion were further clarified. Scanning electron microscopy and transmission electron microscopy images demonstrated that N-Vanillylnonanamide (≥4 wt%) structurally damaged microorganisms via cell membrane breakage, which impair their function. N-Vanillylnonanamide inhibited the activities of the key enzyme CoA, AK, F420, and CoM, which are relevant for both degradation metabolism and anaerobic digestion. 16S rRNA analysis showed that dominant bacterial and archaeal communities markedly decreased after anaerobic digestion of glycerol trioleate with N-Vanillylnonanamide (≥4 wt%). For example, the proportion of Methanosarcina decreased from 30 % to 6 %. Current-voltage curves indicated that the electron transfer rate in the community of microorganisms decreased by 99 % from 4.67 × 10−2 to 5.66 × 10−4 s−1 in response to N-Vanillylnonanamide (40 wt%). The methane yield during anaerobic digestion of glycerol trioleate decreased by 84.0 % from 780.21–142.10 mL/g-total volatile solids with N-Vanillylnonanamide (40 wt%).