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Use of Tyrosinase Enzyme from Bacillus thuringiensis for the Decontamination of Water Polluted with Phenols

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Author(s): Hamed M. El-Shora | M. Metwally

Journal: Biotechnology
ISSN 1682-296X

Volume: 7;
Issue: 2;
Start page: 305;
Date: 2008;
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Keywords: Bacillus thuringiensis | tyrosinase | pollution | phenol | water

ABSTRACT
The present study aimed to evaluate the enzymatic treatment using tyrosinase (E.C. 1.14.18.1) from Bacillus thuringiensis in phenol removal from wastewater. In this study, the tyrosinase was isolated and purified from Bacillus thuringiensis. The purification process included ammonium sulfate precipitation, DEAE-Sepharose and phenyl Sepharose. The final specific activity was 130 U mg-1 protein and purification fold of 31. The enzyme had maximal activity at 35 °C. Sixty nine percent of its activity was recovered at 40 °C. Polyethyleneglycol (PEG), Tween 20, SDS and Triton X-100 were tested for their ability to prevent the inactivation of tyrosinase during removal of 2,4-dichlorophenol (2,4-DCP) from water. 2,4-DCP was disappeared greatly in tyrosinase-treated water samples amended with the various tested compounds particularly PEG over that observed in nonamended samples. The enhancement of phenol removal by PEG was dependent on its molecular weight. In case of 4-chlorophenol, increasing the PEG concentration to 0.6 g L-1 caused a substantial increase in the pollutant removal. The transformation of 4-chlorophenol by tyrosinase was inferior as compared with that of 2,4-DCP, which may indicate that the reaction products from 4-chlorophenol were stronger inhibitors of tyrosinase activity than those originating from 2,4-DCP. The commercially available carbon completely removed the colored products from the treated water without reducing the removal efficiency of tyrosinase. Chitosan eliminated the colored products of the reaction but the decolorization was accompanied by a reduction in 2,4-DCP removals. On the basis of the present results it is evident that using the different additives to polluted water may improve considerably the quality of wastewater treated with the bacterial tyrosinase.

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Tangokurs Rapperswil-Jona

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