Original Article | 2012, Vol.34, No.5, pp. 509-516
Characterization of the decolorizing activity of azo dyes by Bacillus subtilis azoreductase AzoR1
Montira Leelakriangsak and Sukallaya Borisut
pp. 509 - 516
Abstract
The product of the Bacillus subtilis gene azoR1 is annotated as a putative azoreductase, production of which is induced in response to thiol-reactive compounds. Here we report on the decolorization of four azo dyes by azoreductase activity. The ability of overexpressed AzoR1 strain ORB7106 to catalyze decolorization of azo dyes was investigated on agar plates and in liquid cultures. The decolorization efficacy of a mutant, ORB7106, which has lost negative control of azoR1 expression, was significantly better than the parental strain (JH642), providing evidence that the azoR1 gene product is an azoreductase with the ability to decolorize azo dyes. ORB7106 showed 40-98% azo dye decolorization within 48 h. The bacterium exhibited a remarkable color removal capability over a wide range of Methyl Red concentrations (10-200 mg l-1), pH (5-9) and temperatures (25-45°C). A significant increase in the decolorization activity was observed after induction of AzoR1 production. The results suggested that AzoR1 production could be induced by Methyl Red. The decolorizing activity is primarily associated with the cytosolic fraction and requires NADH as a cofactor.
