Stabilization of dimeric β-glucosidase from Aspergillus niger via glutaraldehyde immobilization under different conditions

• Published in: Enzyme and microbial technology 2018-03, Vol.110, p.38-45
• Main Authors: Vazquez-Ortega, Perla Guadalupe, Alcaraz-Fructuoso, Maria Teresa, Rojas-Contreras, Juan A., López-Miranda, Javier, Fernandez-Lafuente, Roberto
• Format: Article
• Language: English
• Subjects: Amino-agarose beads; Enzyme immobilization; Glucosidase; Glutaraldehyde versatility; Improved enzyme activity upon immobilization; Stabilization of multimeric enzymes
• ISSN: 0141-0229; 1879-0909
• DOI: 10.1016/j.enzmictec.2017.12.007

[Display omitted] •Immobilization via ion exchange improved dimeric enzyme Β-glucosidase stability, but there were risks of enzyme leakage.•The enzyme was also immobilized exploiting the versatility of glutaraldehyde chemistry.•Treatment of the ion exchanged enzyme with glutaraldehyde greatly improved enzyme stability.•Glutaraldehyde modified enzyme is more active than free enzyme at pH 4–7, but less active at pH 8. The dimeric enzyme β-glucosidase from Aspergillus niger has been immobilized on different amino-agarose beads at pH 5 and 7, exploiting the versatility of glutaraldehyde. The stability of the free enzyme depended on enzyme concentration. Immobilization via ion exchange improved enzyme stability/activity, depending on the immobilization pH. However, the enzyme was desorbed in 75 mM NaCl at pH 7 and some stability/enzyme concentration dependence still existed. Treatment: of these biocatalysts with glutaraldehyde increased enzyme stability (e.g. at pH 5, after incubation under conditions where the enzyme just ionically exchanged was fully inactivated, the activity of the glutaraldehyde treated enzyme remained unaltered). Immobilization on glutaraldehyde pre-activated supports yielded a higher increase in enzyme activity, but the stabilization was lower. While when measuring the enzyme activity at pH 4 there were no changes after immobilization, all immobilized enzymes were more active than the free enzyme at pH 6 and 7 (2–3 times). The Ki/Km ratio did not significantly decrease in any immobilized biocatalysts, and in some cases it worsened in a significant way (by a 9 fold factor using preactivated supports). The new biocatalysts are significantly more stable and avoid enzyme subunit desorption, being the immobilization pH a key point in their design.