Abstract:Laccase is widely used in the textile industry for dye decolorization, fabric surface modification, and textile bleaching. Screening for a laccase that is alkaline stable and suitable for textile dye decolorization is challenging. A novel alkaline laccase (LacNC) was obtained from Neobacillus cucumis and expressed in Escherichia coli. LacNC is a monomeric protein with a molecular weight of 58 ku. The optimum pH values for LacNC were 6.0, 7.0, and 8.0 when 2,6-dimethoxyphenol, syringaldazine (SGZ), and guaiacol, respectively, were used as substrates. The optimal temperature for LacNC was 55 ℃ for the guaiacol substrate. The activity of LacNC remained more than 85% in the pH range of 5.0~11.0. After incubation at 40 ℃ for 1 h, the activity of LacNC was still higher than 80%. In addition, the decolorization rates of indigo carmine and malachite green by LacNC were more than 90% and 80% in 3 h, respectively, and the decolorization rate of reactive black B by LacNC reached 85% in 24 h. In this study, a new alkaline laccase demonstrating high decolorization efficiency for synthetic dyes under alkaline conditions was obtained. Hence, this laccase is an environmentally friendly candidate for treating wastewater in the textile industry.
