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 (q_max) and affinity for the target pollutant (K_s), 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 q_max and K_s 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 q_max by a factor of ≈2.3 and Ks by a factor of ≈3.1.