Physicochemical properties of free and calcium alginate immobilized alkaline pectin lyase from Bacillus cereus

Abstract

Purified pectin lyase from <em>Bacillus cereus </em>was successfully immobilized in alginate beads with a high binding efficiency of 84.55%. The optimal immobilization was achieved using 2.5% (w/v) alginate concentration. Both free and immobilized enzyme showed optimum pH of 10.0 and temperatures of 40 and 45°C respectively. Pectin lyase gave maximum activity at a substrate concentration of 0.5% w/v for free and 0.75% w/v for the immobilized enzyme and relatively similar <em>V</em>_max values were obtained for both free (3.3 µmol/min) and immobilized pectin lyase (3.6 µmol/min). The <em>K</em>_mfor the immobilized pectin lyase (0.19 mg/ml) was slightly higher than that of the free (0.16 mg/ml) enzyme. The maximum inhibition of 50.2% was observed in the presence of Hg²⁺ion for free pectin lyase and immobilized enzyme showed maximum inhibition of 67.32% in the presence of Na<strong>⁺</strong> ion with statistically significant p-value (p < 0.05). Thermal stability was not significantly altered by immobilization. Thermal stability of free and immobilized pectin lyase was relatively similar at different temperatures. The immobilized pectin lyase retained almost 53% of its original activity up to 7^th cycle. Furthermore, during storage at 4°C, immobilized pectin lyase retained relative activity of 79.77% and free enzyme retained 63.63% relative activity upto 35 days of storage, this indicated that the immobilization improved stability of the enzyme.