Evaluation of the influence of methane and copper concentration and methane mass transport on the community structure and biodegradation kinetics of methanotrophic cultures

The environmental conditions during culture enrichment, which ultimately determine its maximum specific biodegradation rate (qmax) and affinity for the target pollutant (Ks), play a key role in the performance of bioreactors devoted to the treatment of methane emissions. This study assessed the influence of Cu2+ and CH4 concentration and the effective CH4 supply rate during culture enrichment on the structure and biodegradation kinetics of methanotrophic communities. The results obtained demonstrated that an increase in Cu2+ concentration from 0.05 to 25 μM increased the qmax and Ks of the communities enriched by a factor of ≈3, even if the Cu2+ concentration did not seem to have an effect on the enzymatic "copper switch" and only pMMO was detected. In addition, high Cu2+ concentrations supported lower diversity coefficients (Hs ≈ 1.5× lower) and apparently promoted the growth of more adapted methanotrophs such as Methylomonas. Despite no clear effect of CH4 concentration on the population structure or on the biodegradation kinetics of the communities enriched was recorded at the two low CH4 concentrations studied (1 and 8%), a higher agitation rate increased the qmax by a factor of ≈2.3 and Ks by a factor of ≈3.1