Carbon isotope fractionation during acetoclastic methanogenesis by Methanosaeta concilii in culture and a lake sediment.

The isotope enrichment factors (epsilon) in Methanosaeta concilii and in a lake sediment, where acetate was consumed only by Methanosaeta spp., were clearly less negative than the epsilon usually observed for Methanosarcina spp. The fraction of methane produced from acetate in the sediment, as determined by using stable isotope signatures, was 10 to 15% lower when the appropriate epsilon of Methanosaeta spp. was used.