Abstract
A thermo-activation and thermostable laccase isoenzyme (Lac 37 II) produced by Trametes trogii S0301 at 37°C was purified to apparent homogeneity by anionic exchange chromatography and sephadex G-75 chromatography, with 12.3% of yeiled and a specific activity of 343.1 U mg–1. The molecular weight of the purified Lac 37 II was estimated to be approximately 56 kDa in 12% sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The optimal pH and temperature for the protein was 2.7 and 60°C, respectively. The purified Lac 37 II showed higher resistance to all tested metal ions and organic solvents except for Fe2+ and Cd2+ at 37°C and the activity of the purified Lac 37 was significantly enhanced by Cu2+ at 50 mM. The Kcat, Km, and Kcat/Km of Lac 37 II were 2.977 s–1, 16.1 μM, and 184.9 s–1 μM–1, respecively, in the condition of pH 2.7 and 60°C using ABTS as a substrate. Peptide-mass fingerprinting analysis showed that the Lac 37 II matched to the gene-deduced sequences of lcc3 in T. trogii BAFC 463, other than Lcc1, Lcc 2, and Lcc 4. Compared with laccase prepared at 28°C, the onset of thermo-activation of Lac 37 II activity occurred at 30°C with an increase of 10%, and reached its maximum at the temperatures range of 40–60°C with an increase of about 40% of their original activity. Furthermore, Lac 37 II showed the efficient decolorization ability toward triphenylmethane dyes at 60°C, with decolorization rates of 100 and 99.1% for 25 mg L–1 malachite and crystal violet in 5 h, respectively, when hydroxybenzotriazole (HBT) was used as a mediator. In conclusion, it is the first time to report a thermo-activation laccase from a thermophilic T. trogii strain, which has a better enzyme property and higher decolorization ability among fungal laccases, and it also has a further application prospective in the field of biotechnology.
Highlights
Laccases (EC1.10.3.2) are a group of copper-containing polyphenol oxidases that are known as “blue enzymes” for green chemistry due to their ability of oxidize diverse substrates which are similar to lignin or the degradation products of major lignin with molecular oxygen as the final electron acceptor
The main objectives of current study were (i) to purify and identify the laccase of T. trogii S0301 produced at 37◦C; (ii) to characterize this laccase isoenzyme; and (iii) to assess the potential application of this laccase isoenzyme by dye decolorization experiments
The thermo-active laccase isoenzymes have been observed in the thermophilic or thermotolerant strains, such as Melanocarpus albomyces, M. thermophila, and S. thermophilum (Kiiskinen et al, 2002; Younes and Sayadi, 2011)
Summary
Laccases (EC1.10.3.2) are a group of copper-containing polyphenol oxidases that are known as “blue enzymes” for green chemistry due to their ability of oxidize diverse substrates which are similar to lignin or the degradation products of major lignin with molecular oxygen as the final electron acceptor Due to their high catalytic efficiency and broad substrate specificity, laccases are used in various fields, including biopulping, delignification, biobleaching, environmental pollutants bioremediation, dye decolorization, etc. The expression of different laccase isoenzymes in the same strain depends on many factors such as the presence of inducers (especially Cu2+ and phenolic compounds), the ratio of carbon and nitrogen, age of the culture and heat shock treatment (Baldrian, 2006; Piscitelli et al, 2011; Janusz et al, 2013; Zhuo et al, 2016; Bertrand et al, 2017). The main objectives of current study were (i) to purify and identify the laccase of T. trogii S0301 produced at 37◦C; (ii) to characterize this laccase isoenzyme; and (iii) to assess the potential application of this laccase isoenzyme by dye decolorization experiments
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