Production,purification and characterization of a thermostable laccase from a tropical white-rot fungus |
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Authors: | Guo Li-Qiong Lin Shuo-Xin Zheng Xiao-Bing Huang Zi-Rou Lin Jun-Fang |
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Institution: | (1) Department of Bioengineering, College of Food Science, South China Agricultural University, 482 Wushan Street, 510640 Tianhe, Guangzhou, China;(2) Institute of Biomass Research, South China Agricultural University, 510640 Guangzhou, China;(3) Chu Kochen Honors College, Zhejiang University, 310058 Hangzhou, China; |
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Abstract: | A thermostable laccase was isolated from a tropical white-rot fungus Polyporus sp. which produced as high as 69,738 units of laccase l−1 in an optimized medium containing 20 g of malt extract l−1, 2 g of yeast extract l−1, 1.5 mM CuSO4. The laccase was purified to electrophoretic purity with a final purification of 44.70-fold and a recovery yield of 21.04%.
The purified laccase was shown to be a monomeric enzyme with a molecular mass of 60 kDa. The optimum temperature and pH value
of the laccase were 75°C and pH 4.0, respectively, for 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonate) (ABTS). The Michaelis–Menten
constant (K
m
) of the laccase was 18 μM for ABTS substrate. The laccase was stable at pH values between 5.5 and 7.5. About 80% of the initial
enzyme activity was retained after incubation of the laccase at 70°C for 2 h, indicating that the laccase was intrinsically
highly thermostable and with valuable potential applications. The laccase activity was promoted by 4.0 mM of Mg2+, Mn2+, Zn2+ and Ca2+, while inhibited by 4.0 mM of Co2+, Al3+, Cu2+, and Fe2+, showing different profiles of metal ion effects. |
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