ANAEROBIC DEGRADATION OF 2-METHYLBENZOIC ACID BY A METHANOGENIC CONSORTIUM

2-Methylbenzoic has been detected as a metabolite in anaerobic consortia that degrade m-cresol and it was found to accumulate in cultures incubated under methanogenic conditions. This study was initiated to determine whether 2-methylbenzoic acid could be degraded under methanogenic conditions. Near stoichiometric amounts of methane were obtained from 2-methylbenzoic acid in enrichment cultures inoculated with 25% (v/v) domestic anaerobic sewage sludge. However, lag times of 12-36 weeks typically were required before 2-methylbenzoic acid degradation began, and it was difficult to maintain the activity of the cultures. A transient metabolite was detected but not identified. It appeared to be the product of 2-methylbenzoic acid hydroxylation because its trimethylsilyl derivative had a molecular weight of 296, but it was not 4-hydroxy-2-methylbenzoic acid, the intermediate of m-cresol metabolism from which 2-methylbenzoic acid likely originates.