Improved enzyme properties upon glutaraldehyde cross-linking of alginate entrapped xylanase from Bacillus licheniformis

Enzyme immobilization is an exciting alternative to improve the stability of enzymatic processes and economic viability in terms of reusability. In the current study, purified xylanase from B. licheniformis Alk-1 was immobilized within glutaraldehyde activated calcium alginate beads and characterized in respect of free enzyme. Immobilization increases the optimum pH and temperature of entrapped and cross-linked enzyme from pH = 8.0 to 9.0 and 50-60 °C. The kinetics parameter of immobilized (cross-linked) enzyme showed an increase in Km (from 4.36 mg/mL to 5.38 mg/mL) and decrease in Vmax (from 383 IU/mg/min to 370 IU/mg/min). Immobilization increases the optimum reaction time for xylan degradation of immobilized xylanase from 15 to 30 min when compare to free form. The storage stability study suggested that the immobilized enzyme retains 80% of its original activity at 4 °C after 30 days compared to free enzyme (5%). Further, immobilization improved enzyme stability in presence of different additives. The immobilized (cross-linked) enzyme also exhibited adequate recycling efficiency up to five reaction cycles with 37% retention activity. The finding of this study suggests improvement of overall performance of immobilized xylanase in respect to free form and can be used to make a bioreactor for various applications such as poultry feed preparations.