Abstract
An extracellular pectinase from a mixed consortium of Bacillus sp. (BSP) was immobilized onto graphene oxide/chitosan composite (GO/CS) through covalent binding to enhance its recycling and operational stability features. Different parameters were optimized, including cross-linker concentration (%), time, pH, and GO/CS-pectinase ratios. GO/CS-pectinase was further characterized by FT-IR and XRD. The activity of GO/CS-pectinase was reached up to 804 μmolmin−1 with an immobilization efficiency of 80.64 ± 1.15 % under optimum conditions. GO/CS-pectinase exhibited a 3.0-folds higher half-life (t1/2) than free pectinase at 50, 55, and 60 °C, respectively. The Vmax and KM values of GO/CS-pectinase were found to be nearly equal to the free pectinase indicating that conformational flexibility was retained. Kd, t1/2, ∆G*, ∆H*, and ∆S* of both free pectinase and GO/CS-pectinase was 0.0339 & 0.0721 min−1, 9.62 and 40.44 min, 81.35, 90.72 kJmol−1, 47.098 & 63.635 kJmol−1, −102.86 & −81.340 Jmole−1 K−1. SEM morphological analysis further confirmed the successful binding of pectinase with GO/CS, which retained about 92 % of its original catalytic activity after ten consecutive reaction cycles. Finally, GO/CS-pectinase was employed for guava juice clarification which exhibited the turbidity reduction up to 81 % after 75 min of treatment.
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