Promoting methane production during anaerobic digestion with biochar: Is it influenced by quorum sensing?

Biochar has been proved to improve methane production in anaerobic digestion (AD) of food waste, but the role of biochar related to quorum sensing (QS)-mediated inter-microbial communication during AD has not been sufficiently revealed. Results indicated that about 20 % increase in cumulative methane production in the digester with BC700 addition (298.8 mL/gVS) over that without biochar. The concentration of QS signal molecule (especially N-acyl-homoserine lactones) increased with the addition of biochar, and particularly the concentration of 3OC6-HSL (9.0615 μg/L) in the digester containing BC700 increased significantly. Accordingly, the electroactive microorganisms were enriched predominantly such as DMER64 and Methanospirillum. The abundance of key enzyme activities (including acetate kinase and coenzyme F420) increased with BC700 addition, especially coenzyme F420 which was higher by 33.0 % compared to without biochar. The microbial metabolism functions based on metagenomics suggested that carbon metabolism, extracellular electron transfer, and QS related genes were enhanced with the addition of biochar. This study provided new evidence about the underlying role of QS-mediated inter-microbial communication and extracellular electron transfer in elucidating the mechanism of biochar-enhanced methanogenesis.