Overexpression of a Laccase with Dye Decolorization Activity from Bacillus sp. Induced in Escherichia coli.

Laccases from bacteria have been widely studied in the past 2 decades due to the higher growth rate of bacteria and their excellent thermal and alkaline pH stability. In this study, a novel laccase gene was cloned from Bacillus sp., analyzed, and functionally expressed in Escherichia coli. The laccase was highly induced in the E. coli expression system with a maximum intracellular activity of 16 U mg-1 protein. The optimal temperature and pH of the purified laccase were 40°C and 4.6, respectively, when ABTS (2,2'-azino-bis[3-ethylbenzothiazoline-6-sulfonate]) was used as the substrate. The purified laccase showed high stability in the pH range of 3.0-9.0, and retained more than 70% of its activity after 24 h of incubation at 40°C with a pH value of 9.0. Furthermore, the enzyme exhibited extremely high temperature and ion metal tolerance. The half-life of the purified laccase at 70°C was 15.9 h. The purified laccase could efficiently decolorize 3 chemical dyes, especially in the presence of ABTS as a mediator. The high production of this laccase in E. coli and exceptional characteristics of the recombinant enzyme protein make it a promising candidate for industrial applications.