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A rapid regulation with different response intensities of the pmoA gene guarantees process robustness towards methane surges in continuous and feast-famine bioreactors
- Rodríguez, Elisa, López, Juan Carlos, Prieto, Patricia, Merchán, Laura, García-Encina, Pedro A., Lebrero, Raquel, Muñoz, Raul
- Biochemical engineering journal 2019 v.144 pp. 193-197
- bioreactors, carbon dioxide production, gene expression, genes, greenhouse gases, mass transfer, messenger RNA, methane, methanotrophs, transcription (genetics)
- A rapid recovery of methanotrophic activity from process fluctuations such as surges in CH4 inlet load is of utmost importance in bioreactors to guarantee a robust abatement of this potent greenhouse gas. However, the response of methanotrophs in CH4 abatement engineered ecosystems facing recurrent operational upsets has not been systematically investigated. The genetic and process performance response of methanotrophs to a gradual 2.8-fold increase in CH4 inlet load in continuous and feast-famine bioreactors was characterized by measuring their pmoA gene transcripts and the CH4 degradation capacities and CO2 production rates, respectively. Both bioreactors exhibited a high robustness in terms of CH4 removal towards CH4 inlet load increase. Higher CH4 elimination and CO2 production during shock load suggested the occurrence of CH4 mass transfer limitations. Consistently, a rapid regulation of the pmoA gene (less than one hour after CH4-shock load), characterized by several transient events of increased expression, was observed in both bioreactors. However, the pmoA gene expression in the feast-famine bioreactor exhibited a less intense response to the increase in CH4 load compared to the continuous system, which suggested a possible adaptation of the pmoA transcriptional response of methanotrophs to the previous history of the culture.