Characteristics of Spore-Bound Laccase from <i>Bacillus subtilis</i> WD23 and its Use in Dye Decolorization

Abstract

Treatment of xenobiotic compounds such as textile dyes with bacterial laccases is limited to the acid pH range and moderate temperatures. A bacterial strain, designated as WD23, was isolated from forest soil using Luria-Bertani medium supplemented with 0.4 mmol/L Cu2+. The isolated strain was identified as Bacillus subtilis by physiological and biochemical tests and 16S rDNA sequence analysis. Here we charactered the spore-bound laccase of B. subtilis WD23 and used the laccase to decolorize dyes. The spores of the strain showed laccase-like activity, oxidizing syringaldazine, 2,6-dimethoxyphenol and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonate acid)(ABTS). The optimum pH and temperature for the spore-bound laccase were 6.8 and 60°C, respectively. It also showed higher stabilities over a broad pH range, the pH half-life was more than 6 months at pH 6.8. The spore laccase could efficiently decolorize 50~90% of anthraquinone and azo dyes in 24 h. The spore laccase can play an important role in bioremediation.