Quantitative analysis of methane monooxygenase (MMO) explains process robustness in continuous and feast-famine...

The ability of methanotrophs to rapidly respond to intentional or accidental stress conditions caused by operational failures or process fluctuations is of utmost importance to guarantee the robustness of CH₄ abatement biotechnologies. In this study, the performance of a continuous and two feast-famine (5:5 days feast-famine cycles) stirred tank reactors treating diluted CH₄ emissions (4-5% v/v) was comparatively assessed for 149 days. The robustness of the three bioreactors towards a 5 days CH₄ deprivation episode was thoroughly evaluated at a molecular level (pmoA gene expression level) and correlated to macroscopic process performance. The bioreactors recovered their steady-state abatement performance (in terms of CH₄ elimination capacity and CO₂ production rate) within 1.5-2 h following CH₄ supply resumption concomitantly with a maximum in pmoA gene expression, regardless of the previous operational mode. However, while methanotrophs from the continuous unit maintained higher basal levels of pmoA expression as a strategy for a rapid CH₄ metabolism initiation, the strategy of the feast-famine adapted-methanotrophs consisted on a more accurate regulation of their pmoA transcripts levels along with a higher and/or more rapid induction of the pmoA gene by CH₄ availability.