Degradation of tannin at high concentrations by a bacterial consortium isolated from tannery effluent soil

Author(s): K.Veenagayathri, N.Vasudevan

Tannins are defined as naturally occurring water-soluble poly-phenolic compounds having wide prevalence in plants. Hydrolysable and condensed tannins are the two major classes of tannins. These compounds have a range of effects on various organisms, fromtoxic effects of animals to growth inhibition of microorganisms. Catechin a major component of tannin is considered to be recalcitrant and some microorganisms have developed mechanisms to degrade catechin. Tannase, a key enzyme in the degradation of hydrolysable tannins, is present in a diverse group of microorganisms, including rumen bacteria. This enzyme is being increasingly used in a number of processes. Presently, there is a need for increased understanding of the biodegradation of condensed tannins. The aim of this study was to enrich and isolate bacterial consortium from a tannery soil that are capable of utilizing higher concentration of tannin and catechin as sole source of carbon. We have assessed the aerobic biodegradation of catechin and tannin by the consortium that was isolated froma polluted soil by enrichment with tannin. The results of the experiments demonstrated that the consortium could degrade 500mg/L of tannin and 750mg/L of catechin, where complete degradation was achieved in 96 h. Themixtures of tannin and catechin gave a removal efficiency of 79%and 87 % respectively. Isolation of such consortium might be useful for the treatment of industrial wastes particularly in environments contaminated with tannery wastewater.

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