title: Agar-agar entrapment increases the stability of endo-β-1,4-xylanase for repeated biodegradation of xylan.
abstract: Microbial xylanases, specially endo-β-1,4-xylanase catalyzes the hydrolysis of xylan, is considered one of the most significant hydrolases. It has numerous applications but most extensively is utilized in paper and pulp industry as a bio-bleaching agent. Immobilization technique is comprehensively studied with the expectation of modifying and improving enzyme stability and characteristics for commercial purposes. Currently, matrix entrapment technique is applied to immobilize endo-β-1,4-xylanase within agar-agar gel beads produced by Geobacillus stearothermophilus KIBGE-IB29. Maximal enzyme immobilization yield was achieved at 2.5% of agar-agar concentration. Optimized conditions demonstrated an increase in the optimal reaction time from 05 min to 30 min and incubation temperature from 50 °C to 60 °C with reference to free enzyme whereas; no effect was observed for optimum pH. Entrapment technique uniquely changed the kinetic parameters of immobilized endo-β-1,4-xylanase (Km: 0.5074 mg min(-1) to 0.5230 mg min(-1) and Vmax: 4773 U min(-1) to 968 U min(-1)) as compared to free enzyme. However, immobilized enzyme displayed broad thermal stability and retained 79.0% of its initial activity at 80 °C up to 30 min whereas; free enzyme completely lost its activity at this temperature. With respect to economic feasibility, the immobilized enzyme showed impressive recycling efficiency up to six reaction cycles.
authors.affiliation: The Karachi Institute of Biotechnology and Genetic Engineering (KIBGE), University of Karachi, University Road, Karachi 75270, Pakistan.
authors.forename: Zainab
authors.initials: Z
authors.lastname: Bibi
authors.affiliation: The Karachi Institute of Biotechnology and Genetic Engineering (KIBGE), University of Karachi, University Road, 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, University Road, Karachi 75270, Pakistan. Electronic address: ali_kibge@yahoo.com.
authors.forename: Shah Ali
authors.initials: SA
authors.lastname: Ul Qader
authors.affiliation: The Karachi Institute of Biotechnology and Genetic Engineering (KIBGE), University of Karachi, University Road, Karachi 75270, Pakistan.
authors.forename: Afsheen
authors.initials: A
authors.lastname: Aman
mesh_terms: D000362:Agar / Q000737:chemistry*; D001673:Biodegradation, Environmental; D043364:Endo-1,4-beta Xylanases / Q000378:metabolism*; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000378:metabolism*; D056506:Geobacillus / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D013379:Substrate Specificity; D013696:Temperature; D013997:Time Factors; D014990:Xylans / Q000378:metabolism*
chemical_list: D004800:Enzymes, Immobilized; D014990:Xylans; D000362:Agar; D043364:Endo-1,4-beta Xylanases
keywords: Agar–agar; Catalytic properties; Immobilization; Matrix entrapment; Xylanase