Characterization of a yeast recombinant laccase rLAC-EN3-1 and its application in decolorizing synthetic dye with the coexistence of metal ions and organic solvents

• The recombinant laccase rLAC-EN3-1 was purified from Pichia pastoris.
• rLAC-EN3-1 showed strong stability under the alkaline conditions.
• rLAC-EN3-1 had a strong ability to tolerate many metal ions and organic solvents.
• rLAC-EN3-1 can decolorize malachite green with the coexistence of metal ions and organic solvents.
• Decolorized dye showed much lower toxicity to Pleurotus ostreatus than the original dye.

The recombinant laccase rLAC-EN3-1 was purified from Pichia pastoris in which the laccase gene lac-En3-1 from Ganoderma sp.En3 was successfully expressed. The properties of the purified rLAC-EN3-1 were studied. rLAC-EN3-1 showed strong stability under the alkaline conditions. rLAC-EN3-1 also exhibited strong resistance to some enzyme inhibitors such as SDS and EDTA. The effect of various metal ions on the laccase activity of rLAC-EN3-1 was investigated. rLAC-EN3-1 could tolerate very high concentrations of CuSO4, MnSO4 and MgSO4 (100 mM). The effect of different organic solvents on the activity and stability of rLAC-EN3-1 was also determined. rLAC-EN3-1 had a very strong ability to tolerate some organic solvents widely used in the industry such as glycerin, ethylene glycol, butanediol. The results of decolorization test indicated that rLAC-EN3-1 had a strong capacity for decolorizing malachite green with the coexistence of high concentrations of different metal ions and organic solvents. Organic solvents tested in this study had little impact on the decolorization capability of rLAC-EN3-1. In addition, decolorized dye showed much lower toxicity to Pleurotus ostreatus than the original dye. Above advantages of rLAC-EN3-1 suggested that this laccase had a great potential and promising application value in the field of environmental biotechnology.