Methanogenic biodegradation of C 9 to C 12 n -alkanes initiated by Smithella via fumarate addition mechanism

In the present study, a methanogenic alkane-degrading (a mixture of C 9 to C 12 n -alkanes) culture enriched from production water of a low-temperature oil reservoir was established and assessed. Significant methane production was detected in the alkane-amended enrichment cultures compared with alkane-free controls over an incubation period of 1 year. At the end of the incubation, fumarate addition metabolites (C 9 to C 12 alkylsuccinates) and assA genes (encoding the alpha subunit of alkylsuccinate synthase) were detected only in the alkane-amended enrichment cultures. Microbial community analysis showed that putative syntrophic n -alkane degraders ( Smithella ) capable of initiating n -alkanes by fumarate addition mechanism were enriched in the alkane-amended enrichment cultures. In addition, both hydrogenotrophic ( Methanocalculus ) and acetoclastic ( Methanothrix ) methanogens were also observed. Our results provide further evidence that alkanes can be activated by addition to fumarate under methanogenic conditions.