Abstract
Anaerobic degradation of three dihydric phenols, viz., resorcinol, catechol and hydroquinone was studied in mono and binary substrate systems in three upflow anaerobic fixed-film fixed-bed reactors of similar dimensions. In order to predict the metabolic pathways existing in the microbial consortia for anaerobic degradation of these compounds, downstream intermediates of reductive and carboxylation pathways for phenol were fed to the three reactors acclimated to the three dihydric phenols. Catechol and hydroquinone acclimated reactors demonstrated marginal degradation of the downstream intermediates of the reductive pathway for phenol, viz., cyclohexanol and cyclohexanone. However, the same reactors could degrade benzoic acid, which is the downstream intermediate of the carboxylation pathway for phenol, to the extent of 83%. This indicates good expression of the carboxylation pathway in these two reactors. The resorcinol acclimated reactor, on the other hand, degraded cyclohexanol, cyclohexanone and benzoic acid with poor efficiency suggesting that the majority of resorcinol is catabolized by a hitherto unknown pathway. Binary mixture studies revealed that utilization of catechol and hydroquinone from the binary mixed feed in resorcinol acclimated reactor was poor. In the catechol acclimated reactor, catechol aided better utilization of resorcinol when compared to that of hydroquinone. In the hydroquinone acclimated reactor, high resorcinol utilization efficiency was seen from the resorcinol-catechol mixed feed. The study highlights the biochemical specificity acquired by microbial consortia when exposed to different substrates for acclimation.
Published Version
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