The aim of this study is to investigate the aerobic methane oxidation (AME), a process potentially useful for wastewaters treatment using methane as external electron donor in membrane biofilm reactor (MBfR). MBfR was operated at different O-2: CH4 ratios (0.25-1) to provide optimum reactor conditions for denitrification which will be held in subsequent studies. According to our results, none of the dissolved organic metabolites or methanol was detected by analytical techniques during methane oxidation studies. However, study findings played a key role in selecting the suitable environmental conditions for denitrification. The O-2: CH4 ratio of 0.35 was found optimum reactor conditions providing safety gas mixtures and non-methane containing gas outlet hence without methane losses to the atmosphere.