Abstract: Glucoamylase from Aspergillus niger(EC3.2.1.3) was immobilized on porous starch graft copolymer beads (PSGC) which were synthesized in our laboratory. Some of the factors which influence the activity of the immobilized enzyme and the stability of the immobilized enzyme were investigated. The activity and special activity is 1340 IUper gram dry gel and 58.1 IUper millgram protein respectively when GA was immobilized under best condition found by ourselves. The optimium pHof the immobilized glucoamylase shifted 1.2 unit towards basic direction as compared to that of soluble enzyme. The thermostability of immobilized glucoamylase is longer than that of soluble enzyme, the operational half life of immobilized glucoamylase was 28 d and 8d with 20% dextrin as substrate at 55 ℃ and 60 ℃, respectively.

Key words: Porous starch graft copolymer beads, Immobilized glucoamylase, Enzyme stability