Degradation of phenol by a bacterial consortium under methanogenic conditions

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Abstract
An anaerobic bacterial consortium was shown to carboxylate phenol to benzoate under methanogenic conditions. Benzoate accumulated in the culture medium and was completely degraded when the incubation period was prolonged. Two potential intermediates of phenol metabolism, namely cyclohexanol and cyclohexanone, were not accumulated or transformed by the consortium. Proteose peptone must be added to the culture medium for the carboxylation of phenol to occur and glucose could not replace proteose peptone. Inhibition of methanogenesis did not affect the carboxylation of phenol and the presence or absence of hydrogen in the gaseous atmosphere did not prevent the accumulation of benzoate. The consortium was composed of various microbiological forms dominated by Gram-negative rods. Phenol-carboxylating microorganisms were evaluated to about ≥ 1 × 108 cells/mL by using diluted inocula. These results suggest that the carboxylation of phenol is accomplished by co-metabolism and that proteose peptone or some degradation products serve as carbon and energy sources for the growth of the carboxylating bacteria, which appear to be present in large numbers in the consortium. Key words: phenol, degradation, anaerobic, consortium, methanogenesis.