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Ammonium conversion and its feedback effect on methane oxidation of Methylosinus sporium

He, Ruo, Chen, Min, Ma, Ruo-Chan, Su, Yao, Zhang, Xuan
Journal of bioscience and bioengineering 2017 v.123 no.4 pp. 466-473
Methylosinus sporium, active sites, ammonia, ammonium compounds, ammonium nitrogen, biomass, carbon, methane, methanotrophs, nitrate nitrogen, nitrites, nitrogen, nitrogen dioxide, oxidation, pH, toxic substances
Ammonium (NH4⁺) is not only nitrogen source that can support methanotrophic growth, but also it can inhibit methane (CH4) oxidation by competing with CH4 for the active site of methane monooxygenase. NH4⁺ conversion and its feedback effect on the growth and activity of methanotrophs were evaluated with Methylosinus sporium used as a model methanotroph. Nitrogen sources could affect the CH4-derived carbon distribution, which varied with incubation time and nitrogen concentrations. More CH4-derived carbon was incorporated into biomass in the media with NH4⁺–N, compared to nitrate–nitrogen (NO3⁻–N), as sole nitrogen source at the nitrogen concentrations of 10–18 mmol L⁻¹. Although ammonia (NH3) oxidation activity of methanotrophs was considerably lower, only accounting for 0.01–0.06% of CH4 oxidation activity in the experimental cultures, NH4⁺ conversion could lead to the pH decrease and toxic intermediates accumulation in the their habits. Compared with NH4⁺, nitrite (NO2⁻) accumulation in the NH4⁺ conversion of methanotroph had stronger inhibition on its activity, especially the joint inhibition of NO2⁻ accumulation and the pH decrease during the NH4⁺–N conversion. These results suggested that more attention should be paid to the feedback effects of NH4⁺ conversion by methanotrophs to understand effects of NH4⁺ on CH4 oxidation in the environments.