Cometabolic Vinyl Chloride Degradation at Acidic pH Catalyzed by Acidophilic Methanotrophs Isolated from Alpine Peat Bogs

Abstract

Remediation of toxic chlorinated ethenes via microbial reductive dechlorination can lead to ethene formation; however, the process stalls in acidic groundwater, leading to the accumulation of carcinogenic vinyl chloride (VC). This study explored the feasibility of cometabolic VC degradation by moderately acidophilic methanotrophs. Two novel isolates, Methylomonas sp. strain JS1 and Methylocystis sp. strain MJC1, were obtained from distinct alpine peat bogs located in South Korea. Both isolates cometabolized VC with CH 4 as the primary substrate under oxic conditions at pH at or below 5.5. VC cometabolism in axenic cultures occurred in the presence (10 μM) or absence (<0.01 μM) of copper, suggesting that VC removal had little dependence on copper availability, which regulates expression and activity of soluble and particulate methane monooxygenases in methanotrophs. The model neutrophilic methanotroph Methylosinus trichosporium strain OB3b also grew and cometabolized VC at pH 5.0 regardless of copper availability. Bioaugmentation of acidic peat soil slurries with methanotroph isolates demonstrated enhanced VC degradation and VC consumption below the maximum concentration level of 2 μg L −1 . Community profiling of the microcosms suggested species-specific differences, indicating that robust bioaugmentation with methanotroph cultures requires further research.

Comparative genomic analysis of Methylocystis sp. MJC1 as a platform strain for polyhydroxybutyrate biosynthesis

“…The maximum growth rate of the Methylocystis sp. MJC1 in the exponential growth phase was 0.12 h -1 , which is higher than the previously reported cell growth rate of MJC1 (0.063 h -1 ) cultured in DNMS (dilute nitrate mineral salts) medium with the addition of copper [ 18 ]. During 4 days of fermentation, the Methylocystis sp.…”

“…The growth rate of Methylocystis sp. MJC1 has been reported to be up to 0.063 h -1 when copper was added to the medium [ 18 ]. Interestingly, the maximum growth rate (0.12 h -1 ) was higher in the copper-less medium, indicating potentially higher growth rates in the presence of active sMMO.…”

“…In an attempt to develop a methanotrophic platform, a novel type II methanotrophic strain, Methylocystis sp. MJC1, isolated from distinct alpine peat bogs in Ulsan, Korea, was characterized in this study [ 18 ]. The genome of Methylocystis sp.…”

Acidophilic methanotrophs: Occurrence, diversity, and possible bioremediation applications

“…The potential for acidophilic methanotrophs to biodegrade pollutants is largely unknown, and evaluation of potential applications of these organisms has just begun in recent years (Choi et al, 2021 ; Semrau, 2011 ; Shao et al, 2019 ; Szwast, 2021 ). This pursuit is important, particularly for chlorinated solvents because, as previously noted, traditional bioremediation approaches are not as effective at low pH for completely dechlorinating CVOCs, particularly chlorinated ethenes.…”

“…is largely ineffective at reducing chlorinated ethenes to ethene in naturally acidic aquifers, because it is typically inhibited at pH < ~5.5 (Eaddy, 2008 ; Lacroix et al, 2014 ; Rowlands, 2004 ; Steffan & Vainberg, 2013 ; Vainberg et al, 2009 ; Yang, 2012 ; Yang et al, 2017 ). Although much more research is required, acidophilic methanotrophs have recently been observed to degrade a range of CVOCs at pH <5.5, suggesting that cometabolic treatment may be an option for CVOCs and other contaminants in acidic aquifers (Choi et al, 2021 ; Semrau, 2011 ; Shao et al, 2019 ; Szwast, 2021 ).…”