title: Expression of Aeromonas punctata ME-1 exo-xylanase X in E. coli for efficient hydrolysis of xylan to xylose.
abstract: exo-Xylanase X from Aeromonas punctata ME-1 was functionally expressed in Escherichia coli with a carboxy terminal His tag (6×) and a molecular mass of 39.42 kDa, which is in agreement with the prediction from its amino acid composition. The recombinant exo-xylanase reached 186 mg l(-1) after induction by isopropyl β-D-1-thiogalactopyranoside. Its optimal temperature and pH were 50 °C and 6, respectively. The enzyme showed not only an exo-xylanase activity with K m of 3.90 mg ml(-1) and V max of 12.9 U μg(-1) for hydrolysis of Remazol Brilliant Blue-xylan but also a considerable exo-glucanase activity (27.9 U mg(-1)) on P-nitrophenyl β-D-cellobioside. It hydrolyzed xylan predominantly to xylobiose, xylotriose, xylotetraose, and xylose. An enzyme mixture of exo-xylanase and endo-xylanase (50 μg ml(-1) each) yielded a larger amount (330 mg l(-1)) of xylose from beechwood xylan than the controls (270 and 150 mg l(-1)) using them alone at 100 μg ml(-1), indicating a synergistic action between the two xylanases favoring the hydrolysis of beechwood xylan to release more xylose.
authors.affiliation: Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research (A*STAR), 1 Pesek Road, Jurong Island, 627833, Singapore.
authors.forename: Veeresh
authors.initials: V
authors.lastname: Juturu
authors.forename: Tong Mei
authors.initials: TM
authors.lastname: Teh
authors.forename: Jin Chuan
authors.initials: JC
authors.lastname: Wu
mesh_terms: D000333:Aeromonas / Q000201:enzymology / Q000235:genetics; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D043364:Endo-1,4-beta Xylanases / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006868:Hydrolysis; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D014990:Xylans / Q000737:chemistry*; D014994:Xylose / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D011993:Recombinant Fusion Proteins; D014990:Xylans; D014994:Xylose; D043364:Endo-1,4-beta Xylanases