Application of solid-phase biocatalysts has become important during the last decades. Enzymes could be immobilized on various supports and by different methods. The properties of immobilized biocatalysts are influenced by the characteristics of enzyme, support material and the immobilization method. A suitable support should have high affinity to proteins, reactive functional groups, hydrophilicity, mechanical stability and rigidity. Chitosan is a natural polyaminosaccharide which offers the above characteristics, therefore it is often used for enzyme immobilization (Martino et al., 1996; Sheu et al., 1998). Chitosan microspheres suitable for enzyme immobilization were prepared by emulsion cross-linking method (Agnihotri et al., 2004). Aqueous chitosan solution was added dropwise into an oil phase consisted of sunflower oil and n-hexadecane. Cross-linking was performed with glutaraldehyde which make possible the covalent attachment of enzymes. �-Galactosidase, which is applied in dairy industry for lactose hydrolysis, was immobilized onto the microspheres. The solid-phase biocatalyst was characterized and the storage and operational stabilities were investigated.