Abstract: Papain was immobilized on a denatured egg white protein as the support with glutaraldehyde as the cross-linker. The effects of pH, the concentration of glutaraldehyde, time and the amount of the enzyme on the activity of the immobilized papain were examined through the experiments of orthogonal test. The optimal condition for the immobilization was set up, i.e., glutaraldehyde concentration is 5%; pH 6.0; the quantity of enzyme used 12 mg/(g support) and the reaction time 20 h. At the same time, the comparative study on the properties of free and immobilized p apain was made. The optimal temperature and pH are 90 ℃ and 9.0, respectively . The K_m for the immobilized enzyme is 53.6 mg/mL. The thermostability and thermotolerance of the immobilized enzyme are obviously increased compared to those of the free one.

Key words: papain, immobilization, egg white protein, glutaraldehyde