Bioelectrochemical analysis of a hyperthermophilic microbial fuel cell generating electricity at temperatures above 80 °C

Abstract

We examined whether a hyperthermophilic microbial fuel cell (MFC) would be technically feasible. Two-chamber MFC reactors were inoculated with subsurface microorganisms indigenous to formation water from a petroleum reservoir and were started up at operating temperature 80 °C. The MFC generated a maximum current of 1.3 mA 45 h after the inoculation. Performance of the MFC improved with an increase in the operating temperature; the best performance was achieved at 95 °C with the maximum power density of 165 mWm⁻², which was approximately fourfold higher than that at 75 °C. Thus, to our knowledge, our study is the first to demonstrate generation of electricity in a hyperthermophilic MFC (operating temperature as high as 95 °C). Scanning electron microscopy showed that filamentous microbial cells were attached on the anode surface. The anodic microbial consortium showed limited phylogenetic diversity and primarily consisted of hyperthermophilic bacteria closely related to Caldanaerobacter subterraneus and Thermodesulfobacterium commune.

Hyperthermophilic microorganisms were for the first time proved to be capable of transferring electrons to anode and acting biocatalysts in anodes of microbial fuel cells.

Key words:

• microbial fuel cell
• hyperthermophilic microorganism
• oil field formation water

Acknowledgments

The Engineering for Sustainable Carbon Cycle (INPEX Co.) Social Cooperation Program is a joint project of the University of Tokyo and INPEX Co. This work was supported by the Japan Society for the Promotion of Science (JSPS) under Grant-in-Aid for Scientific Research (A) (#20246128, to K.·S.) and a Grant-in-Aid for Young Scientists (B) (#23780074, to H.·K.). The authors thank Dr. Hiroshi Sagara (The Institute of Medical Science, the University of Tokyo) for SEM analysis and Prof. Ken Takai (JAMSTEC) for insightful suggestions.