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 as a 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 20-140 mg L−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.