Methane oxidation capacity of methanotrophs isolated from different soil ecosystems

Abstract

Methane is one of the potential greenhouse gases contributing to global climate change, with a global warming potential of about 25 times than that of carbon dioxide. Aerobic methane oxidation (methanotrophy) is the key process that counteracts emission of methane to atmosphere. In this study, methane oxidation capacity of different methane-oxidizing bacteria (methanotrophs) isolated from six different ecosystems was investigated. Methanotrophic consortium isolated from dumpsite proved to be most effective in oxidizing methane. Initially, methane oxidation rate was found to be 0.72 ± 0.036 mM/day; in course of the study consortium M5 showed an increase in methane oxidation rate up to 1.7 ± 0.016 mM/day. A maximum of 0.78 mol of CO2 production was found during methane oxidation in methanotrophs from dumpsite (M5). While varying temperatures, methane oxidation rate was in the range of 1.3–1.7 mM/day which has been found in the temperature range of 30–40 °C. Even at higher temperature (50 °C), 0.076 ± 0.14 mM of the methane was utilized per day. Methane oxidation was assessed by Michaelis–Menten kinetics. By varying the methane concentration, methane oxidation was studied and kinetic parameters such as V max and K m were derived using Lineweaver–Burk plot and found to be 1.497 mM/day and 2.23 mM, respectively. In methane mitigation approach, Methane soil sink is very essential because a balance between methane production by methanogens and consumption by methanotrophs plays an important role in methane emission reduction. Enhancing the methane soil sink will be a cost-effective method to cut down methane emission.