Carboxylation of o-cresol by an anaerobic consortium under methanogenic conditions.

The metabolism of o-cresol under methanogenic conditions by an anaerobic consortium known to carboxylate phenol to benzoate was investigated. After incubation with the consortium at 29 degrees C for 59 days, o-cresol was transformed to 3-methylbenzoic acid, which was not further metabolized by the consortium. Proteose peptone in the culture medium was essential for the transformation of o-cresol. In addition, a transient compound detected in the culture was identified as 4-hydroxy-3-methylbenzoic acid. o-Cresol-6d was transformed by the consortium to deuterated hydroxy-methylbenzoic acid and deuterated methylbenzoic acid. These results demonstrate that o-cresol is carboxylated in the para position relative to the phenolic hydroxyl group and dehydroxylated by the anaerobic consortium.