초록/요약

Kinetic and enzymatic inhibition experiments were performed to investigate the effects of methanethiol (MT) and hydrogen sulfide (H<inf>2</inf>S) on methane oxidation by a methane-oxidizing consortium. In the coexistence of MT and H<inf>2</inf>S, the oxidation of methane was delayed until MT and H<inf>2</inf>S were completely degraded. MT and H<inf>2</inf>S could be degraded, both with and without methane. The kinetic analysis revealed that the methane-oxidizing consortium showed a maximum methane oxidation rate (V <inf>max</inf>) of 3.7mmolg-dry cell weight (DCW)-1h-1 and a saturation constant (K <inf> m </inf>) of 184.1μM. MT and H<inf>2</inf>S show competitive inhibition on methane oxidation, with inhibition values (K <inf> i </inf>) of 1504.8 and 359.8μM, respectively. MT was primary removed by particulate methane monooxygenases (pMMO) of the consortium, while H<inf>2</inf>S was degraded by the other microorganisms or enzymes in the consortium. DNA and mRNA transcript levels of the pmoA gene expressions were decreased to ~106 and 103 pmoA gene copy numberg-DCW-1 after MT and H<inf>2</inf>S degradation, respectively; however, both the amount of the DNA and mRNA transcript recovered their initial levels of ~107 and 105 pmoA gene copy numberg-DCW-1 after methane oxidation, respectively. The gene expression results indicate that the pmoA gene could be rapidly reproducible after methane oxidation. This study provides comprehensive information of kinetic interactions between methane and sulfur compounds. © 2015 The Society for Biotechnology, Japan.