Preparation and Stability of Bromelain Immobilization with Pineapple Peel Residue Carboxymethyl Cellulose/Sodium Alginate Composite Hydrogel Beads

Pineapple peel residue carboxymethyl cellulose/sodium alginate composite hydrogel beads was prepared from pineapple peel residue carboxymethyl cellulose and sodium alginate for immobilization of bromelain. The effects of the mass ratio of pineapple peel residue carboxymethyl cellulose to sodium alginate,the concentration of calcium chloride,the concentration of bromelain,the volume fraction of glutaraldehyde and the cross-linking time on the activity of immobilized enzyme were analyzed by single factor method. The results showed that the optimum preparation process of immobilized enzyme were as follows:The mass ratio of pineapple peel residue carboxymethyl cellulose to sodium alginate was 2:3,the concentration of CaCl₂ was 1.0%,the concentration of bromelain was 2.0 mg/mL,the volume fraction of glutaraldehyde was 1.0%,and the cross-linking time was 60 min. The thermal stability of the immobilized enzyme was better than that of the free enzyme. After being placed at 80℃ for 2.0 h,the relative enzyme activity of the fixed enzyme was 35.1%,while the free bromelain was almost inactivated under this condition. After being placed at pH11 for 24 h,the relative enzyme activity of the free enzyme was 43.2%,while the relative enzyme activity of the fixed enzyme was 85.1%,which indicated that the fixed enzyme was more tolerant to alkaline environment than the free enzyme. In addition,after repeated use of the immobilized enzyme for 7 times,the relative enzyme activity was 60.5%,which indicated that the immobilized enzyme had good reuse performance.