Hen egg-white lysozyme (HEWL) can be covalently immobilized on a polymeric support (hydroxypropyl methylcellulose acetate succinate, AS-L), which is soluble above pH 5.5 but insoluble below pH 4.5. Commercial preparation of HEWL was used for the immobilization study. The immobilized enzyme (HEWL-AS) has much higher specific activity than those of free HEWL. The effects of pH and temperature on the activity and thermal stability of HEWL-AS were studied and compared with those of free HEWL. HEWL-AS retained nearly half of its initial chitinase activity even after heating at 70 °C for 50 min. The half-life at 4 °C was 4 days for free HEWL and 25 days for HEWL-AS. Following repeated pH cycles between 7 and 4.5, HEWL-AS retained nearly 50% of its original activity after 10 batches of chitinolytic reactions.