title: Purification and characterisation of a β-1,4-xylanase from Remersonia thermophila CBS 540.69 and its application in bread making.
abstract: This work reports the first investigation of Remersonia thermophila hemicellulosic hydrolytic enzyme production, with subsequent purification of an extracellular endo-β-1,4-xylanase (RtXyl) and its application in bread making. The research describes RtXyl purification from sorghum-induced submerged liquid cultures of this moderately thermophilic, aerobic, ascomycete fungus. The purified enzyme is a single subunit protein with a molecular mass of 42 kDa and exhibits glycosyl hydrolase family-10-like activity over a broad pH and temperature range. Optimal activity was measured at pH 6.0 and 65 °C respectively, which is suitable for bread making applications. Substrate specificity studies revealed that RtXyl is purely xylanolytic with no side-activities against other plant polysaccharides. The RtXyl catalytic efficiency (K cat/K m) was highest with oats spelt xylan (810.90 mg mL(-1) s(-1)), wheat arabinoxylan (809.52 mg mL(-1) s(-1)) and beechwood xylan (417.40 mg mL(-1) s(-1)) with less efficiency towards insoluble oats spelt xylan (236.40 mg mL(-1) s(-1)). Hydrolysis products analysed by thin layer chromatography yielded a range of xylosaccharides, predominantly xylotriose and xylobiose. RtXyl application in a basic wheat bread recipe at low dosages (0.297 XU/g) showed its suitability to increase loaf volume by 8.0 % compared with the control bread. RtXyl increased loaf softness by 19.6 % while reducing bread staling by 20.4 % up to 4 days of storage.
authors.affiliation: Shannon Applied Biotechnology Centre, Department of Applied Science, Limerick Institute of Technology, Moylish Park, Limerick, Ireland, katrina.mcphilips@lit.ie.
authors.forename: Katrina
authors.initials: K
authors.lastname: McPhillips
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Waters
authors.forename: Cécile
authors.initials: C
authors.lastname: Parlet
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Walsh
authors.forename: Elke K
authors.initials: EK
authors.lastname: Arendt
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Murray
mesh_terms: D001203:Ascomycota / Q000201:enzymology*; D001939:Bread; D002384:Catalysis; D043364:Endo-1,4-beta Xylanases / Q000302:isolation & purification* / Q000378:metabolism*; D004795:Enzyme Stability; D006868:Hydrolysis; D011134:Polysaccharides / Q000378:metabolism; D014908:Triticum / Q000737:chemistry; D014990:Xylans / Q000378:metabolism
chemical_list: D011134:Polysaccharides; D014990:Xylans; C007916:hemicellulose; C085118:arabinoxylan; D043364:Endo-1,4-beta Xylanases