Extracellular-proton-transfer driving high energy-conserving methanogenesis in anaerobic digestion

Anaerobic digestion (AD) is a promising technology to realize the conversion from organic matters to methane, which is highly mediated by syntrophic microbial community via mutualistic interactions. However, small energy available in methanogenic conversion usually limits the metabolic activity. To adapt such energy-limited environment, efficient energy conservation is critical to support active physiological functions of anaerobic consortia for methanogenic metabolism. In this study, the contribution of extracellular proton transfer (EPT) enhancement to achieving energy-conserving methanogenesis in AD was explored. Proton-conductive medium (PCM) was applied to construct efficient proton transport pathway, and a large number of protons from extracellular water were found available to upregulate methanogenesis in AD, as indicated by the increase in the content of