Potential for direct interspecies electron transfer in an electric-anaerobic system to increase methane production from sludge digestion

• Published in: Scientific reports Vol. 5; no. 1; p. 11094
• Main Authors: Zhao, Zhiqiang, Zhang, Yaobin, Wang, Liying, Quan, Xie
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 09.06.2015; Nature Publishing Group
• Subjects: 631/45; 631/61/168; Anaerobiosis; Diet; Digestion; Electrodes; Electron transfer; Electron Transport; Experiments; Fermentation; Fluorescence in situ hybridization; Humanities and Social Sciences; Hydrogen; Laboratories; Metabolism; Methane; Methane - metabolism; Methanogenesis; Microbial activity; multidisciplinary; Science; Sewage; Sludge; Sludge digestion; Species
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep11094

Direct interspecies electron transfer (DIET) between Geobacter species and Methanosaeta species is an alternative to interspecies hydrogen transfer (IHT) in anaerobic digester, which however has not been established in anaerobic sludge digestion as well as in bioelectrochemical systems yet. In this study, it was found that over 50% of methane production of an electric-anaerobic sludge digester was resulted from unknown pathway. Pyrosequencing analysis revealed that Geobacter species were significantly enriched with electrodes. Fluorescence in situ hybridization (FISH) further confirmed that the dominant Geobacter species enriched belonged to Geobacter metallireducens . Together with Methanosaeta species prevailing in the microbial communities, the direct electron exchange between Geobacter species and Methanosaeta species might be an important reason for the “unknown” increase of methane production. Conductivity of the sludge in this electric-anaerobic digester was about 30% higher than that of the sludge in a control digester without electrodes. This study not only revealed for the first time that DIET might be the important mechanism on the methanogenesis of bioelectrochemical system, but also provided a new method to enhance DIET by means of bioelectric enrichment of Geobacter species.