title: Highly thermostable xylanase of the thermophilic fungus Talaromyces thermophilus: purification and characterization.
abstract: A thermostable xylanase from a newly isolated thermophilic fungus Talaromyces thermophilus was purified and characterized. The enzyme was purified to homogeneity by ammonium sulfate precipitation, diethylaminoethyl cellulose anion exchange chromatography, P-100 gel filtration, and Mono Q chromatography with a 23-fold increase in specific activity and 17.5% recovery. The molecular weight of the xylanase was estimated to be 25 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration. The enzyme was highly active over a wide range of pH from 4.0 to 10.0. The relative activities at pH5.0, 9.0, and 10.0 were about 80%, 85.0%, and 60% of that at pH7.5, respectively. The optimum temperature of the purified enzyme was 75 degrees C. The enzyme showed high thermal stability at 50 degrees C (7 days) and the half-life of the xylanase at 100 degrees C was 60 min. The enzyme was free from cellulase activity. K (m) and V (max) values at 50 degrees C of the purified enzyme for birchwood xylan were 22.51 mg/ml and 1.235 micromol min(-1) mg(-1), respectively. The enzyme was activated by Ag(+), Co(2+), and Cu(2+); on the other hand, Hg(2+), Ba(2+), and Mn(2+) inhibited the enzyme. The present study is among the first works to examine and describe a secreted, cellulase-free, and highly thermostable xylanase from the T. thermophilus fungus whose application as a pre-bleaching aid is of apparent importance for pulp and paper industries.
authors.affiliation: Laboratoire de Génétique Moléculaire des Eucaryotes, Centre de Biotechnologie de Sfax, Sfax, Tunisia.
authors.forename: Ines
authors.initials: I
authors.lastname: Maalej
authors.forename: Ines
authors.initials: I
authors.lastname: Belhaj
authors.forename: Najla Fourati
authors.initials: NF
authors.lastname: Masmoudi
authors.forename: Hafedh
authors.initials: H
authors.lastname: Belghith
mesh_terms: D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003636:DEAE-Cellulose; D043364:Endo-1,4-beta Xylanases / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D004795:Enzyme Stability; D006868:Hydrolysis; D007700:Kinetics; D012117:Resins, Synthetic; D032901:Talaromyces / Q000201:enzymology* / Q000378:metabolism; D013696:Temperature; D014990:Xylans / Q000378:metabolism
chemical_list: D012117:Resins, Synthetic; D014990:Xylans; C042855:Mono Q; D003636:DEAE-Cellulose; D043364:Endo-1,4-beta Xylanases