Immobilization of phytase using a polyvinyl alcohol carrier system

The phytase produced by Aspergillu niger CN-50 were immobilized by compound gels of sodium alginate,polyvinyl alcohol(PVA) and PVA-cryogel.The results showed that gel network is favour to mass transfer due to PVA composite porous structure.Alginate could prevent enzyme leakage.The embedding method was more effective than the other two methods.The mechanical properties and chemical stability of phytase have been improved after immobilization.In addition,it can be repeated for several times for hydrolysising sodium phytate.The enzymatic characteristics were further investigated.The results showed that the optimum pH of free and immobilized phytase were 5.5 and 7.0,respective.Their optimum reaction temperature were 45 and 60 ℃,respective.The Km of immobilized enzyme(20 mg / ml) is greater than that of free enzyme(14 mg / ml).In addition,the operation of the enzyme,temperature and storage stability were improved by immobilized phytase.