Characterization and Dye Decolorization Potential of Two Laccases from the Marine-Derived Fungus sp.

Two laccase-encoding genes from the marine-derived fungus sp. have been cloned in for heterologous production, and the recombinant enzymes have been characterized to study their physicochemical properties, their ability to decolorize textile dyes for potential biotechnological applications, and their activity in the presence of sea salt. The optimal pH and temperature of Lac1 and Lac2 differed in relation to the substrates tested, and both enzymes were shown to be extremely stable at temperatures up to 50 °C, retaining 100% activity after 3 h at 50 °C. Both enzymes were stable between pH 4-6. Different substrate specificities were exhibited, and the lowest and highest catalytic efficiency values were obtained against syringaldazine and 2,6-dimethoxyphenol (DMP) for Lac1 and Lac2, respectively. The industrially important dyes-Acid Yellow, Bromo Cresol Purple, Nitrosulfonazo III, and Reactive Black 5-were more efficiently decolorized by Lac1 in the presence of the redox mediator 1-hydroxybenzotriazole (HBT). Activities were compared in saline conditions, and Lac2 seemed more adapted to the presence of sea salt than Lac1. The overall surface charges of the predicted Lac three-dimensional models showed large negatively charged surfaces for Lac2, as found in proteins for marine organisms, and more balanced solvent exposed charges for Lac1, as seen in proteins from terrestrial organisms.