Kinetics of CH4 oxidation in mixed culture.

Microbial cultures used for methane oxidation experiments were prepared by enriching under a 20 % CH4 atmosphere either leachate extracts from two different landfill sites or a digested sewage sludge. No microbes were axenically isolated, therefore the cultures were mixtures of CH4 oxidising and other aerobic microorganisms. CH4 oxidation experiments were carried out with a batch reactor, whose change in gas volume could be measured. A mixture of air and methane with CH4 concentrations ranging from 5 to 20 % was introduced into the reactor. Methane oxidation rate was expressed as a Monod equation for CH4 and a first order reaction for O2. Maximum oxidation rate (Vmax) resulted 2.1 x 10(-13) to 3.4 x 10(-11) hr(-1) cell(-1), and half saturation constant (KM) was 5.1 x 10(-5) to 6.5 x 10(-4) mol L(-1). The molar ratio of consumed O2 to oxidised CH4 was 1.5-1.8