title: Chitosan hydrogel microspheres: an effective covalent matrix for crosslinking of soluble dextranase to increase stability and recycling efficiency.
abstract: Dextranase is a unique biocatalyst that has high specificity and stereo-selectivity towards a complex biopolymer known as dextran. Dextranase has wide industrial application, but most of the time harsh environmental conditions adversely affect the functionality and stability of the enzyme. To overcome this issue, a covalent cross-linking immobilization method was adapted in the current study utilizing a nontoxic and biocompatible matrix known as chitosan. Chitosan hydrogel microspheres were synthesized using chitosan which exhibited noteworthy physical and mechanical strength. After treatment with glutaraldehyde, chitosan hydrogel microspheres were used for immobilization of dextranase. The kinetic characteristics of immobilized dextranase were compared with that of the soluble enzyme. A shift in optimum pH and temperature from 7.0 to 7.5 and 50 to 60 °C was observed after immobilization, respectively. Recycling efficiency, thermal stability, and activation energy distinctly improved after immobilization, whereas anchoring of substrate at the active site of the soluble dextranase exhibited an increase in Kmwith no change in Vmaxafter crosslinking. This technique involves the reduction in the size of carrier molecules (microspheres) that provide a larger surface area for improved immobilization efficiency. Therefore, it is concluded that increased stability and reusability of this immobilized biocatalyst makes it a promising aspirant for the utilization at commercial level.
authors.affiliation: The Karachi Institute of Biotechnology and Genetic Engineering (KIBGE), University of Karachi, Karachi, 75270, Pakistan.
authors.forename: Faiza
authors.initials: F
authors.lastname: Shahid
authors.affiliation: The Karachi Institute of Biotechnology and Genetic Engineering (KIBGE), University of Karachi, Karachi, 75270, Pakistan.
authors.forename: Afsheen
authors.initials: A
authors.lastname: Aman
authors.affiliation: The Karachi Institute of Biotechnology and Genetic Engineering (KIBGE), University of Karachi, Karachi, 75270, Pakistan.
authors.forename: Muhammad Asif
authors.initials: MA
authors.lastname: Nawaz
authors.affiliation: The Karachi Institute of Biotechnology and Genetic Engineering (KIBGE), University of Karachi, Karachi, 75270, Pakistan.
authors.forename: Asad
authors.initials: A
authors.lastname: Karim
authors.affiliation: Department of Biochemistry, University of Karachi, Karachi, 75270, Pakistan. saqader@uok.edu.pk.
authors.forename: Shah Ali
authors.initials: SA
authors.lastname: Ul Qader
mesh_terms: D001410:Bacillus megaterium / Q000378:metabolism*; D048271:Chitosan / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry; D003910:Dextranase / Q000737:chemistry; D004795:Enzyme Stability; D004798:Enzymes / Q000737:chemistry; D004800:Enzymes, Immobilized / Q000737:chemistry*; D005976:Glutaral / Q000737:chemistry; D006358:Hot Temperature; D020100:Hydrogels / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology; D007700:Kinetics; D008863:Microspheres; D015203:Reproducibility of Results; D013379:Substrate Specificity; D013499:Surface Properties; D013696:Temperature
chemical_list: D003432:Cross-Linking Reagents; D004798:Enzymes; D004800:Enzymes, Immobilized; D020100:Hydrogels; D048271:Chitosan; D003910:Dextranase; D005976:Glutaral
keywords: Bacillus megaterium; Chitosan; Covalent immobilization; Dextranase; Operational stability