Microbial advanced oxidation aroused by bacteria-algae symbiosis induced abiotic methane production in anaerobic...

The slow decomposition of recalcitrant substrate limits the conversion efficiency of anaerobic digestion. Microbial advanced oxidation, capable of in-situ generating reactive oxygen species (ROS) with the microbial aerobic/anaerobic respiration, provided a potential way to strengthen the substrate-methane conversion in anaerobic digestion. In this study, microalgae were inoculated in anaerobic system and formed redox oscillation under the intermittent illumination, which ultimately increased the methane production by 27.4 %. With the redox oscillation, •OH, the typical ROS, showed a 6.27-fold increase in production (72.95 ± 9.06 μM vs. 10.03 ± 1.49 μM), facilitating the decomposition of lignocelluloses. Notably, abiotic methanation was observed in anaerobic digestion with the occurrence of microbial advanced oxidation. ROS quenching experiments revealed that abiotic methanation roughly accounted for 17.5 % of the total methane production. Microbial advanced oxidation formed by redox oscillation showed the potential to strengthen anaerobic digestion. Notably, for the first time, it was confirmed that abiotic methanation could be established in anaerobic digestion with the ROS generated by microbial advanced oxidation, which offered a new perspective to understand and improve the performances of natural and engineered ecosystems.