Immobilization of β-1,4-xylanase isolated from Bacillus licheniformis S3

Industrial applications require enzymes to be highly stable and economically viable in terms of reusability. Enzyme immobilization is an exciting alternative to improve the stability of enzymatic processes. Immobilization of β-1,4-xylanase produced by Bacillus licheniformis S3 is performed by using two polymer supports (agar-agar and calcium alginate). The maximum enzyme immobilization yield was achieved at a concentration of 3% agar, whereas a combination of sodium alginate, 4%, and calcium chloride, 0.3 M, was used for the formation of immobilized beads. The immobilization process increased the optimum reaction time from 10 min to 35 and 40 min for agar and calcium alginate, respectively, and the incubation temperature increased from 55°C to 60°C for agar, but it remained unchanged for calcium alginate. The pH profile of free and immobilized xylanase was quite similar in both cases. Both the techniques altered the kinetic parameters of immobilized β-1,4-xylanase as compared with the free enzyme. The diffusion limit of high molecular weight xylan caused a decline in V_max of the immobilized enzyme, whereas there was an increase in the K_m value. However, calcium alginate-immobilized enzyme displayed broad thermal stability as compared with agar-agar-immobilized enzyme and retained 57.1% of its initial activity at 80°C up to 150 min. Biotechnological characterization showed that the reusability of enzymes was the most striking finding, particularly of immobilized xylanase using agar-agar as immobilization carrier, which after six cycles retained 23% activity.