Enhanced degradation of methanethiol in enrichment cultures in the presence of methane

Abstract

Volatile organic sulfur compounds (VOSCs) are the primary components responsible for odor pollution during waste disposal and the degradation of organic matter and are harmful to human health. Understanding the metabolic mechanisms of VOSCs is valuable for the development of VOSC treatment techniques. In this study, microbial community and function of the cultures enriched with methane (CH4) and methanethiol (CH3SH) was investigated at three O2 concentrations (v/v), i.e., 21%, 10% and 5%. During the enrichment cultivation, almost no cell growth was observed in the group enriched only with CH3SH at the concentration of 400 mg m−3 within three months, while microbes exhibited growth in the group enriched with CH3SH and CH4 after incubation for ∼15 d. CH3SH-S was primarily oxidized to SO42--S in the enrichment cultures, accounting for 35.0%–85.2% of the CH3SH-S, which was accompanied by H+ production. A high O2 concentration of 21 % could enhance CH3SH oxidation and weaken the inhibitory effect of CH3SH on methanotrophic activity in the cultures. Type I and type II methanotrophs were both detected in the enrichment cultures with the relative abundance of 13.6%–50.1%. Sulfur-oxidizing bacteria including Thiobacillus, Hyphomicrobium and Pseudomonas dominated in the enrichment cultures. These results indicated that the presence of methane could stimulate the growth of CH3SH-metabolizing bacteria and thereby enhance CH3SH conversion in the enrichment cultures.