High purity 14CH4 generation using the thermophilic acetotrophic methanogen Methanothrix sp. strain CALS-1

Methane-oxidizing activity in natural samples is typically measured by amending 14CH4 to the sample and then following the accumulation of 14CO2. Current biological techniques to synthesize 14CH4 yield significant quantities of 14CO that when oxidized to 14CO2 would artificially inflate the measured methane-oxidizing activity of a sample. We present here a new method to biologically produce highly-pure 14CH4 using Methanothrix sp. Strain CALS-1 which produces very little CO. Using this method, 14CH4 was produced at nearly 100% efficiency and at a high specific activity (2.2 GBq.mmol-1) equal to the parent compound, [2-14C] sodium acetate. Furthermore, only trace quantities of H2 and CO were produced with only one molecule of CO produced for every 17,000 molecules of CH4. When compared to the standard CH4 generation method, this technique produced 97% purer CH4.