Abstract
A Bacillus sp. isolated from sediments of distillery unit was found to overproduce laccase when cultured in a synthetic media containing 1mM CuSO4 and 10% distillery spent wash as inducers along with 1% dextrose (w/v) and 0.1% tryptone (w/v) as additional carbon and nitrogen sources. The extracellular purified enzyme was highly thermostable with a calculated half-life of 23 min at 75°C. The optimal pH and temperature of the Bacillus sp. laccase were recorded to be 3.0 and 35°C, respectively. Sodium azide and solvents like methanol and acetonitrile completely inhibited enzyme activity. The average molecular weight of the purified enzyme as determined by SDS-PAGE and zymogam studies was around 70 kDa. Kinetic parameters were detected by using 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS) as substrate. At high ABTS concentrations (> 6 mM) a substrate inhibition phenomenon appeared and KM (0.60 mM), Vmax (983.00 U/min) values were determined. The polypeptide sequences showed significant similarity with Cudependent oxidoreductases through MALDI-TOF MS analysis. In addition, the crude Bacillus sp. laccase showed enormous potential for decolorization of various recalcitrant dyes. The apparent high stability of this enzyme makes it a good candidate for its possible application in biotechnology.
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