Effects of conductive carbon nanomaterials on methanogens

Nano-sized conductive carbon materials have been reported to stimulate methanogenesis by anaerobic microbiomes, while other studies have shown their antibiotic effects on methanogenic and other microbes. The present study examined effects of conductive carbon nanoparticles (carbon black Valcan, CB) on methanogenesis by anaerobic-digester sludge. We found that a high concentration (2% w/v) of CB substantially inhibited methanogenesis from glucose, where acetate was accumulated. Pyrosequencing of 16S rRNA gene fragments amplified from methanogenic sludge samples revealed that methanogens specifically decreased in the presence of CB, suggesting that methanogens are severely damaged by CB.