Isolation and characterization of a facultative methanotroph degrading malodor-causing volatile sulfur compounds

Abstract

Simultaneous removal of methane and malodor-causing volatile sulfur compounds (MVSCs), both emitted from landfills, is a desirable characteristic for methane-mitigation approaches. A methanotrophic bacterium was isolated from a microbial consortium, enriched with methane and dimethyl sulfide (DMS). It grew in the complex nutrient medium R2A without methane, and stably exhibited methanotrophic activity after facultative growth. It was identified as Sphingopyxis sp. MD2 by comparison of the 16S rRNA gene. It belongs to Sphingomonadales, whose members have not shown methanotrophic activity, phylogenetically distinct from orders of known methanotrophs. The MD2 biomass increased at a growth rate of 1.18d−1 when methane was used as the sole growth substrate. An inhibition test with allylthiourea and PCR/sequencing confirmed the presence of particulate methane monooxygenase in MD2. DMS decreased the methane oxidation rate (2634±146μmolegDCW−1h−1) by 12%, while H2S had no effect on the methane oxidation rate. Interestingly, methanethiol (MT) enhanced the methane oxidation rate by more than 50%. MD2 degraded H2S and MT, regardless of the presence of methane. MD2 also degraded DMS in the presence of methane, indicating co-metabolism. These combined results indicate that MD2 may be a promising biological resource for simultaneous removal of methane and MVSCs.