Response of methanotrophic activity to extracellular polymeric substance production and its influencing factors

The accumulation of extracellular polymeric substance (EPS) is speculated to be related with the decrease of CH₄ oxidation rate after a peak in long-term laboratory landfill covers and biofilters. However, few data have been reported about EPS production of methanotrophs and its feedback effects on methanotrophic activity. In this study, Methylosinus sporium was used asa model methanotroph to investigate EPS production and its influencing factors during CH₄ oxidation. The results showed that methanotrophs could secret EPS into the habits during CH₄ oxidation and had a negative feedback effect on CH₄ oxidation. The EPS amount fitted well with the CH₄ oxidation activity with the exponential model. The environmental factors such as pH, temperature, CH₄, O₂, NO₃^--N and NH₄⁺-N could affect the EPS production of methanotrophs. When pH, temperature, CH₄, O₂ and N concentrations (including NO₃^--N and NH₄⁺-N) were 6.5-7.5, 30-40°C, 10-15%, 10% and 20-140mgL^-1, respectively, the high cell growth rate and CH₄ oxidation activity of Methylosinus sporium occurred in the media with the low EPS production, which was beneficial to sustainable and efficient CH₄ oxidation. In practice, O₂-limited condition such as the O₂ concentration of 10% might be a good way to control EPS production and enhance CH₄ oxidation to mitigate CH₄ emission from landfills.