preprints.org > biology and life sciences > biochemistry and molecular biology > doi: 10.20944/preprints202306.1993.v1

Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Version 1 : Received: 27 June 2023 / Approved: 28 June 2023 / Online: 28 June 2023 (10:12:10 CEST)

Enzyme immobilization is known to enhance polypeptide resistance towards environmental changes, particularly in terms of their stability. The Y509E mutant of β-xylosidase from Geobacil-lus stearothermophilus (XynB2Y509E) (which also bears xylanase activity) has been immobilized in chitosan spheres through either entrapment or covalent bond formation methods. In the immo-bilization by entrapment, besides observing a total loss of xylanase activity, it was found that chitosan concentration affects the process efficiency. Additionally, the maturation time of the spheres and the alkaline pH used to precipitate the spheres affect the β-xylosidase activity of the enzyme. In covalent bond immobilization, it was found that the pH during the modification with glutaraldehyde, as well as the subsequent protein binding, were key factors in preserving the dual enzymatic activity. The activity expressed after immobilization by covalent bonding was 23% higher compared to the activity expressed following entrapment immobilization, with values of 122.3 and 99.4 U. g-1, respectively. Both biocatalysts showed increased thermal and pH stability, along with an improved storage capacity, as they retained 40% and 88% of their activi-ty after being stored at 4 C for two months. Moreover, XynB2Y509E immobilized by covalent binding also exhibited outstanding reusability, retaining a 92% of activity after ten cycles of re-use.

β-xylosidase; chitosan; enzyme immobilization; G. stearothermophilus; xylanase

Biology and Life Sciences, Biochemistry and Molecular Biology

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