Abstract: Epichlorohydrin and sodium peridate were used to conduct the epoxidation and dialdehyde oxidation of cellulose for preparing epoxidized dialdehyde oxycellulose. The prepared epoxidized dialdehyde oxycellulose was used as the carrier to immobilizeβ-galactosidase. Immobilization conditions and the enzymatic properties and microstructure of immobilizedβ-galactosidase were investigated. The results showed that the maximum activity of immobilizedβ-galactosidase was 0.528 U/g under the optimal immobilization conditions: 4 h immobilization time, pH 6.5 and 1:15 enzyme/carrier ratio (m/m). Compared with the freeβ-galactosidase, the optimal reaction temperature, thermostability and pH stability of immobilizedβ-galactosidase were increased. After the immobilization ofβ-galactosidase, it binding affinity towards substrate was also increased. In addition, the immobilizedβ-galactosidase remained 64% of its original activity after its 5th repeated use. Infrared spectrum and scanning electron microscope analysis showed that the epoxy group and aldehyde group of epoxidized dialdehyde oxycellulose could covalently react with amino groups ofβ-galactosidase to form immobilizedβ-galactosidase.

Key words: epoxidized dialdehyde oxycellulose, β-galactosidase, immobilization