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Methanogenesis conducted by archaea acts as a competing metabolic pathway that diverts available carbon and electrons away from exo-electrogenic metabolism in mixed culture inoculated microbial fuel cells (MFCs). Statin-class compounds are known to selectively inhibit eukaryotic and archaeal versions of HMG Co-A reductase (class-I) enzyme and the bacterial version of the same enzyme (class-II) is known to be unresponsive to statins. The results of this study demonstrated that the two model statin compounds Simvastatin and Atorvastatin were effective in suppressing methanogenesis in MFCs when applied in moderate concentrations (5 mg/L and 40 mg/L respectively) in MFC anodes. Power densities increased 2 fold compared to control (to 63 ± 1.8 mW/m2) and 2.5 fold (to 69.5 ± 1.8 mW/m2) with Simvastatin and Atorvastatin addition respectively. There was an almost complete suppression of CH4 production with the addition of both statins into MFC anodes as shown by gas composition analysis. Quantitative FISH (qFISH) analysis showed that methanogens Methanosarcina, Metanobacteria and Methanomicrobiales together with all archaea were almost completely suppressed when statins were supplemented into MFC anodes. This study demonstrated that the statins addition can be used to boost power densities in MFCs.

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A microbiological isolation and growth medium that can effectively discriminate electrochemically active exoelectrogenic bacteria from other non-exoelectrogenic bacteria, is currently unavailable. In this study, we developed a novel chromogenic growth and isolation solid medium based on MnO2 that can selectively allow the growth of exoelectrogenic bacteria and change the medium colour in the process. Known exoelectrogenic bacteria such as Shewanella oneidensis MR1 and other such bacteria from functional microbial fuel cell (MFC) anodes were capable of growing and changing colour in the novel growth medium. On the contrary, non-exoelectrogenic bacteria such as Escherichia coli ATCC 25922 were incapable of growing and inducing a colour change in the novel medium. Further biochemical characterisation of these isolated exoelectrogenic bacteria by Raman micro-spectroscopy demonstrated that these bacteria over express cytochrome proteins that are vital in extracellular electron transfer events. This medium is a convenient method to isolate exoelectrogenic bacteria from complex environmental samples.