The use of Statin-class compounds to suppress methanogenesis in lake sediment inoculated microbial fuel cells

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.