Study on Immobilized Lysozyme and Enzymatic Properties of Surface-deacetylated Chitin Granules

In this study, lysozyme was immobilized by using surface-deacetylated chitin granules as a carrier and glutaraldehyde as a crosslinking agent. Orthogonal array design was used to optimize the key parameters of the immobilization, according to the comprehensive evaluation of protein utilization ratio, activity recovery and storage stability, on the basis of MBTH activity assay using half-deacetylated chitosan as a substrate. The effect of immobilization on the enzymatic properties of lysozyme was investigated. The results showed that the optimum immobilization conditions were as follows:deacetylation time 25 min, concentration of glutaraldehyde 5% and pH5.0 for the carrier activation. Compared with dissociative lysozyme, immobilized lysozyme in this condition reduced its apparent optimum pH from 4.0 to 3.5.The optimum temperature increased from 75 to 80℃ and maintained 95% or more of activity within 70~90℃.The kinetic parameters, K_m was estimated to be 1.75 mg/mL for free and 2.69 mg/mL for immobilized lysozyme. The activity after storage for 15 d could still be maintained 66%. Therefore, immobilization increased the thermal stability and storage stability of lysozyme, which might confer it a wider range of applications.