RESORCINOL, CATECHOL AND HYDROQUINONE BIODEGRADATION IN MONO AND BINARY SUBSTRATE MATRICES IN UPFLOW ANAEROBIC FIXED-FILM FIXED-BED REACTORS

Anaerobic degradation of three dihydric phenols, viz., resorcinol, cat echol and hydroquinone was studied in mono and binary substrate system s in three upflow anaerobic fixed-film fixed-bed reactors of similar d imensions. In order to predict the metabolic pathways existing in the microbial consortia for anaerobic degradation of these compounds, down stream intermediates of reductive and carboxylation pathways for pheno l were fed to the three reactors acclimated to the three dihydric phen ols. Catechol and hydroquinone acclimated reactors demonstrated margin al degradation of the downstream intermediates of the reductive pathwa y for phenol, viz., cyclohexanol and cyclohexanone. However, the same reactors could degrade benzoic acid, which is the downstream intermedi ate of the carboxylation pathway for phenol, to the extent of 83%. Thi s indicates good expression of the carboxylation pathway in these two reactors. The resorcinol acclimated reactor, on the other hand, degrad ed cyclohexanol, cyclohexanone and benzoic acid with poor efficiency s uggesting 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 acc limated reactor was poor. In the catechol acclimated reactor, catechol aided better utilization of resorcinol when compared to that of hydro quinone. In the hydroquinone acclimated reactor, high resorcinol utili zation efficiency was seen from the resorcinol-catechol mixed feed. Th e study highlights the biochemical specificity acquired by microbial c onsortia when exposed to different substrates for acclimation.