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 (V _max ) resulted 2.1x10^-13 to 3.4x10^-11 hr^-1cell^-1, and half saturation constant (K _M ) was 5.1x10^-5 to 6.5x10^-4 mol L^-1. The molar ratio of consumed O₂ to oxidised CH₄ was 1.5-1.8