Expression of a deep-sea bacterial laccase from Halomonas alkaliantarctica and its application in dyes decolorization

Abstract

Introduction Laccase is a copper-containing polyphenolic oxidase widely found in bacteria, archaea, fungi, animals, and plants. As a green biocatalyst with considerable potential for numerous environmental and industrial applications, the enzyme production efficiency of laccase in nature is low, and the cost is high. Purpose To examine the characterization and potential applications of laccase in this study, a novel laccase from Halomonas alkaliantarctica (LacHa) was cloned and heterologously expressed in Escherichia coli. Results To achieve heterologous and efficient laccase expression, a bacterial laccase gene designed as LacHa from Halomonas alkaliantarctica of deep sea was cloned and expressed in E. coli. The results showed that the optimum temperature and pH of the enzyme reaction were 45°C and 7.5. The 100 μM Cu2+ and Fe2+ ions had the strongest stimulatory effect on laccase activity, the surface-active agent SDS and organic solvent 5% ethanol had opposite effect. EDTA, and 5% DMSO have no effect on LacHa activity. The activity of LacHa was enhanced 1.5 fold by chloride at concentrations lower than 500 mM, and 57.6% of its initial activity remained in the reaction system containing 1000 mM NaCl. Furthermore, LacHa showed decolorization rates ranging from 90.28% to 100% for indigo carmine and two azo dyes without mediators, with wide pH (5.0-9.0) and temperature (25-65°C) ranges. Conclusions In the present study, LacHa was expressed and showed unusual properties, suggesting its great application potential in the treatment of textile industries or environmental applications.