Abstract:

Lipase (Candida sp. 99-125) was immobilized on nylon net by glutaraldehyde as cross-linking agent. Effects of
various parameters on the activity of immobilized lipase and characteristics of immobilized lipase were investigated. The
maximum enzyme activity achieved at the following conditions: glutaraldehyde concentration of 3%, cross-linking time of
60 min, enzyme concentration of 10 mg/mL, and immobilized time of 6 h. The optimal temperature of immobilized lipase
shifted from 45 ℃ to 50 ℃, compared with free lipase. The immobilized lipase maintained high activity in a broad pH range
of 5.0 to 7.0, with optimum pH at 7.0, which was identical to that of the free lipase. Thermal, pH, and operational stabilities
of lipase were greatly improved after immobilization onto nylon net. Immobilized lipase retained about 80% of the initial
activity after fifth repeated use. The Km (0.57 mol/L) and Vmax (0.29 × 10-3 mol/(L•s)) of immobilized lipase using olive oil as
substrate was significantly higher as compared to free lipase. The immobilization of lipase decreased its affinity to substrate
as compared to free lipase.

Key words: immobilized lipase, Nylon net, glutaraldehyde, stability, kinetics