Effects of microbial electrolysis cell on anaerobic digestion of food waste: Acidification and recovery

The effects of a microbial electrolysis cell (MEC) applying 1.2 V on the acidification and recovery in the anaerobic digestion (AD) of food waste were studied by semi-continuous experiments. The experimental results showed that the MEC reduced the accumulation of volatile fatty acids (VFAs), enhanced acidification, accelerated the conversion of VFAs during recovery, and accelerated recovery by decreasing the relative abundance of Aminobacterium and norank_f__W27 and increasing that of Methanobacterium. The MEC reduced the production of propionic and butyric acids by decreasing the abundance of functional enzymes (such as fumarate reductase, propionate CoA-transferase, phosphate butyryltransferase, and butyrate kinase) and bacteria (such as Aminobacterium and norank_f__W27). The MEC increased the rates of four AD steps with a maximal rate of 11.47–32.32 %. The MEC promoted electron transfer by enriching the electroactive bacterium Trichococcus (10.91–28.80 %) and Methanosaeta (8.17–24.43 %). The MEC increased the abundance of the most critical functional enzymes in the bacterial community during the entire test and those in the archaeal community during recovery.