In order to improve the stability of laccase, the
effects of three additives(glycerol, inositol and sorbitol)on the acid-base
stability of laccase were studied, and the protection mechanism of the
additives on laccase was analyzed by UV spectroscopy, fluorescence spectroscopy
and circular dichroism. The results indicated that the protective effect of the
additives on laccase was related to the type and concentration of the additives.
When the concentration of inositol was 0.2 mol/L in buffer at pH = 3, the
relative activity of laccase reached the maximum(125%). With increasing the
concentration of glycerol or sorbitol, the relative activity of laccase
increased gradually. When the concentration was 0.6 mol / L, glycerol increased
the
relative activity of laccase by 29%, and sorbitol increased the relative
activity of laccase by 15%. The optimum pH range for laccase should be at pH =
2 to 5, and the use of additives could improve the acidity of laccase. Spectral
analysis showed that these additives could form hydrogen bonds with laccase
molecules in the solution, resulting in the improvement on the acid-base
stability of laccase.