Purification and Properties of a Thermostable Xylanase GH 11 from Penicillium occitanis Pol6
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Purification and Properties of a Thermostable Xylanase GH 11 from Penicillium occitanis Pol6 Dorra Driss & Fatma Bhiri & Mariem Siela & Raoudha Ghorbel & Semia Ellouz Chaabouni
Received: 13 March 2012 / Accepted: 1 August 2012 # Springer Science+Business Media, LLC 2012
Abstract An extracellular, endo-β-1,4-xylanase was purified to homogeneity from the culture filtrate of the filamentous fungus Penicillium occitanis Pol6, grown on oat spelt xylan. The purified enzyme (PoXyn2) showed a single band on SDS–PAGE with an apparent molecular weight of 30 kDa. The xylanase activity was optimal at pH 3.0 and 65 °C. The specific activity measured for oat spelt xylan was 2,368 Umg−1. The apparent Km and Vmax values were 8.33 mgml−1 and 58.82 μmolmin−1 ml−1, respectively, as measured on oat spelt xylan. Thin-layer chromatography experiments revealed that purified PoXyn2 degrades xylan in an endo-fashion releasing xylobiose as main end product. The genomic DNA and cDNA encoding this protein were cloned and sequenced. This PoXyn2 presents an open reading frame of 962 bp, not interrupted by any introns and encoding for a mature protein of 320 amino acids and 29.88 kDa. Keywords Penicillium occitanis pol6 . Endo-1,4-β-xylanase . Purification . Characterization . DNA sequence
Introduction Xylan is a major structural polysaccharide in plant cell walls, and xylan is the second most abundant polysaccharide in nature after cellulose. Depending on the source, the xylan backbone may be substituted to varying degrees with glucuronosyl, 4-O-methyl-D-glucuronopyranosyl, α-L-arabinofuranosyl, acetyl, feruloyl, and/or p-coumaroyl residues. Xylanases (EC 3.2.1.8, endo-1,4-β-D-xylan xylanohydrolase) are O-glycoside hydrolases that D. Driss (*) : F. Bhiri : M. Siela : R. Ghorbel : S. E. Chaabouni Unité Enzymes et Bioconversions, Ecole Nationale d’Ingénieurs de Sfax, University of Sfax, BP 1173, 3038 Sfax, Tunisia e-mail: [email protected] F. Bhiri : R. Ghorbel : S. E. Chaabouni Unité de service Bioreacteur couplé à un Ultrafiltre, Ecole Nationale d’Ingénieurs de Sfax, University of Sfax, BP 1173, 3038 Sfax, Tunisia
Appl Biochem Biotechnol
cleave internal β-1,4-D-xylosidic linkages in the xylan backbone and initiate the depolymerization of heteroxylan polymers. Xylan-degrading enzymes have attracted much attention because of their many important practical applications in various industrial processes, including the modification of cerealbased foodstuffs [1], improving the digestibility of animal feedstocks [2], and the delignification of paper pulp [3]. In recent years, additional eco-friendly applications in paper/paper product manufacture and recycling, in textile manufacture, in baking, in the release of aroma and antioxidant molecules, and in the production of biopharmaceuticals, which are targeted at both selective and extensive modification of xylans, have provided an increased impetus to identify and obtain new xylanases with different specificities and properties [4, 5]. All endo-β-1,4-xylanases (EC 3.2.1.8) catalyse the random cl
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