Application of ethanol-type fermentation in establishment of direct interspecies electron transfer: A practical engineering case study

Abstract

A promising strategy for establishing direct interspecies electron transfer (DIET)-based syntrophic metabolism during anaerobic digestion (AD) is to stimulate the methanogenic communities with ethanol to rapidly produce biological electrical connections. In this study the strategy was further explored in an engineering-scale up-flow anaerobic sludge blanket (UASB) reactor treating bagasse wastes. The results demonstrated that, under the conditions employed, the ethanol-abundant acidogenic products from ethanol-type fermentation could stimulate the UASB reactor to form the aggregates with a higher conductivity (22.6 ± 0.6 uS/cm) than that in the laboratory-scale UASB reactor treating brewery wastes (8.1 ± 1.7 uS/cm), in which DIET was the primary working mode of interspecies electron exchange. Furthermore, these aggregates also presented a positive response with granular active carbon (GAC) to methanogenesis, suggesting that the DIET-based methanogenic communities were established. As a result, the engineering-scale UASB reactor was capable of maintaining stability in response to the environmental disturbance. Microbial community analysis revealed that specific and substantial enrichments of Petrimonas (21.8% of abundance) and Methanothrix species (64.8%) were detected in the aggregates. These results, and the known ability of Petrimonas species to transfer electrons to elemental sulfur, suggested that Petrimonas species might participate in DIET with Methanothrix species.