Abstract
Polygalacturonase (PG) from Aspergillus niger was immobilized using glyoxyl, vinylsulfone or glutaraldehyde-activated supports. The use of supports pre-activated with glutaraldehyde presented the best results. The immobilization of PG on glutaraldehyde-supports was studied under different conditions: at pH 5 for 24 h; at pH 5, 6.5 or 8 for 3 h and then incubated at pH 8 for 24 h; at pH 8 in the presence of 300 mM NaCl for 24 h, to prevent ion exchange. The immobilization under all conditions showed a significant increase in the enzyme thermal stability under inactivation conditions at pH 4-10. As a result, at temperatures over 70 degrees C or pH values over 7, the immobilized PG maintained significant levels of activity while the free PG was fully inactivated. The immobilization conditions presented a clear effect on enzyme activity, thermostability and operational stability, suggesting that the different conditions permitted to get immobilized PG having different orientations. Varying the immobilization protocol it is possible to achieve high activity or stability, and the optimal biocatalyst depends on the conditions where it will be utilized. The immobilized PG biocatalysts could be reused 10 times without a significant decrease in enzyme activity and offered very linear reaction courses. (C) 2019 Elsevier B.V. All rights reserved.