Anaerobic degradation of methoxylated aromatic compounds by Clostridium methoxybenzovorans and a nitrate-reducing bacterium Thauera sp. strain Cin3,4 |
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Authors: | Tahar Mechichi Bharat K.C. Patel Sami Sayadi |
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Affiliation: | aLaboratoire des Bioprocédés, Centre de Biotechnologie de Sfax BP “K”, 3038 Sfax, Tunisia;bMicrobial Discovery Research Unit, Faculty of Science, Griffith University, School of Biomolecular and Biomedical Sciences, Brisbane, QLD 4111, Australia |
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Abstract: | The coupling of growth of the o-demethylating bacterium, Clostridium methoxybenzovorans SR3, with a nitrate-reducing bacterium able to degrade aromatic compounds, Thauera sp. Cin3,4, allowed complete mineralization of poorly oxidizable methoxylated aromatic compounds such as vanillate, isovanillate, vanilline, anisate, ferulate and veratrate. C. methoxybenzovorans o-demethylated these aromatic compounds to their corresponding hydroxylated derivatives and fermented the side chains to acetate and butyrate. The hydroxylated compounds and the fermentation end-products in the C. methoxybenzovorans spent growth medium were then completely metabolized to CO2 on inoculation with the Thauera strain. Kinetic studies with veratrate indicated that C. methoxybenzovorans initially o-demethylated the substrate to vanillate and then further to protocatechuate together with the production of acetate and butyrate from the demethylated side chains. Protocatechuate, acetate and butyrate were then utilized as a carbon source by the Thauera strain aerobically or anaerobically in the presence of nitrate. The results therefore suggest that mono- or dimethoxylated aromatic compounds can be completely mineralized by coupling the growth of a fermentative bacterium with a nitrate-reducing bacterium, and a metabolic pathway for this is proposed. |
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Keywords: | o-Demethylation Methoxy group Veratrate Nitrate reduction Aromatic compounds Anaerobic degradation |
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