Response of mixed methanotrophic consortia to different methane to oxygen ratios.

Methane (CH) and oxygen (air) concentrations affect the CH oxidation capacity (MOC) and mixed methanotrophic community structures in compost (fresh) and landfill (age old) top cover soils. A change in the mixed methanotrophic community structure in response has implications for landfill CH bio-filter remediation and possible bio-product outcomes (i.e., fatty acid methyl esters (FAME) content and profiles and polyhydroxybutyrate (PHB) contents). Therefore the study aimed to evaluate the effect of variable CH to oxygen ratios (10-50% CH in air) on mixed methanotrophic community structures enriched from landfill top cover (LB) and compost soils (CB) and to quantify flow on impacts on MOC, total FAME contents and profiles, and PHB accumulation. A stable consortium developed achieving average MOCs of 3.0±0.12, 4.1±0.26, 6.9±0.7, 7.6±1.3 and 9.2±1.2mgCHgDWh in LB and 2.9±0.04, 5.05±0.32, 6.7±0.31, 7.9±0.61 and 8.6±0.48mgCHgDWh in CB for a 20day cultivation period at 10, 20, 30, 40 and 50% CH, respectively. CB at 10% CH had a maximal FAME content of 40.5±0.8mgFAMEgDW, while maximal PHB contents (25mggDW) was observed at 40% CH in LB. Despite variable CH/O ratios, the mixed methanotrophic community structures in both LB and CB were relatively stable, dominated by Methylosarcina sp., and Chryseobacterium, suggesting that a resilient consortium had formed which can now be tested in bio-filter operations for CH mitigations in landfills.