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

Methane-oxidizing activity in natural samples is typically measured by amen ding (CH4)-C-14 to the sample and then following the accumulation of (CO2)- C-14. Current biological techniques to synthesize (CH4)-C-14 yield signific ant quantities of (CO)-C-14 that when oxidized to (CO2)-C-14 would artifici ally inflate the measured methane-oxidizing activity of a sample. We presen t here a new method to biologically produce highly-pure (CH4)-C-14 using Me thanothrix sp. Strain CALS-1 which produces very little CO. Using this meth od,(CH4)-C-14 was produced at nearly 100% efficiency and at a high specific activity (2.2 GBq.mmol(-1)) equal to the parent compound, [2-C-14] sodium acetate. Furthermore, only trace quantities of H-2 and CO were produced wit h only one molecule of CO produced for every 17000 molecules of CH4. When c ompared to the standard CH, generation method, this technique produced 97% purer CH4. (C) 1999 Elsevier Science B.V. All rights reserved.