Using Laccases in the Nanoflower to Synthesize Viniferin

The pH stability of the free laccase and the immobilized laccase was determined by incubating the enzyme in different buffers (pH 3.0-8.0) for 6 h at 35 °C. The buffers used were Na2HPO4–sodium citrate buffer (pH 3.0-8.0). The immobilized laccase was collected by centrifugation (3500 g for 3 min) and air-dried. The residual specific activities of free or immobilized laccase were then determined at its optimum pH according to the assay in Section 3.4 described in the text. As can be seen from Figure S1, there is no significant difference in the specific activities of immobilized laccase incubated by different pH buffers ranging from 3 to 7 (p > 0.05). In contrast, the specific activity of free laccase treated by buffer (pH 4.0) is significantly higher than that of the cases incubated by other buffers (pH 3–8) (p < 0.05). After incubation by buffers (pH 3.0 and pH 5.0), free laccase has significantly higher specific activity compared with the cases treated by different buffers in the pH range 6–8 (p < 0.05). The specific activity of free laccase incubated by buffer (pH 8.0) is significantly lower than that of the cases treated by the buffers (pH 6.0 and pH 7.0) (p < 0.05). The above-mentioned results demonstrate that laccase in the nanoflower is less sensitive to pH change compared with the free laccase.