Characterization of a Novel One-Domain Halotolerant Laccase from Parageobacillus thermoglucosidasius and Its Application in Dye Decolorization.

Laccases are widespread multi-copper oxidases and generally classified into three-domain laccases and two-domain laccases. In this study, a novel laccase PthLac from Parageobacillus thermoglucosidasius harbored only one domain of Cu-oxidase_4 and showed no sequence relatedness or structure similarity to three-domain and two-domain laccases. PthLac was heterologously expressed in Escherichia coli, purified, and characterized. The optimum temperature and pH of PthLac on guaiacol were at 60 ℃ and pH 6, respectively. The effects of various metal ions on PthLac were analyzed. All the tested metal ions did not suppress the activity of PthLac, except for 10 mM Cu, which increased the activity of PthLac to 316%, indicating that PthLac was activated by Cu. Meanwhile, PthLac kept 121% and 69% activity when incubated at concentrations of 2.5 and 3 M NaCl for 9 h, suggesting the long-term halotolerancy of this enzyme. In addition, PthLac showed resistance to the organic solvents and surfactants, and displayed dye decolorization capacity. This study enriched our knowledge about one-domain laccase and its potential industrial applications.