22416-58-6Relevant articles and documents
β-xylosidase from Selenomonas ruminantium: Immobilization, stabilization, and application for xylooligosaccharide hydrolysis
Terrasan, César Rafael Fanchini,Aragon, Caio Casale,Masui, Douglas Chodi,Pessela, Benevides Costa,Fernandez-Lorente, Gloria,Carmona, Eleonora Cano,Guisan, Jose Manuel
, p. 161 - 171 (2016/12/16)
The tetrameric β-xylosidase from Selenomonas ruminantium is very stable in alkaline pH allowing it to easily immobilize by multipoint covalent attachments on highly activated glyoxyl agarose gels. Initial immobilization resulted only in slight stabilization in relation to the free enzyme, since involvement of all subunits was not achieved. Coating the catalyst with aldehyde-dextran or polyethylenimine, fully stabilized the quaternary structure of the enzyme rendering much more stabilization to the biocatalyst. The catalyst coated with polyethylenimine of molecular weight 1300 is the most stable one exhibiting an interesting half-life of more than 10 days at pH 5.0 and 50 °C, being, therefore, 240-fold more stable than free enzyme. Optimum activity was observed in the pH range 4.0–6.0 and at 55 °C. The catalyst retained its side activity against p-nitrophenyl α-l-arabinofuranoside and it was inhibited by xylose and glucose. Kinetic parameters with p-nitrophenyl β-d-xylopyranoside as substrate were Vmax 0.20 μmol.min?1 mg prot.?1, Km 0.45 mM, Kcat 0.82 s?1, and Kcat/Km 1.82 s?1 mM?1. Xylose release was observed from the hydrolysis of xylooligosaccharides with a decrease in the rate of xylose release by increasing substrate chain-length. Due to the high thermostability and the complete stability after five reuse cycles, the applicability of this biocatalyst in biotechnological processes, such as for the degradation of lignocellulosic biomass, is highly increased.
Molecular cloning and characterization of a novel thermostable xylanase from Paenibacillus campinasensis BL11
Ko, Chun-Han,Tsai, Chung-Hung,Tu, Jenn,Lee, Hang-Yi,Ku, Lan-Ting,Kuo, Pei-An,Lai, Yiu-Kay
supporting information; experimental part, p. 1638 - 1644 (2011/12/03)
An open reading frame (XylX) with 1131 nucleotides from Paenibacillus campinasensis BL11 was cloned and expressed in E. coli. It encodes a family 11 endoxylanase, designated as XylX, of 41kDa. The homology of the amino acid sequence deduced from XylX is only 73% identical to the next closest sequence. XylX contains a family 11 catalytic domain of the glycoside hydrolase and a family 6 cellulose-binding module. The recombinant xylanase was fused to a His-tag for affinity purification. The XylX activity was 2392IU/mg, with a Km of 6.78mg/ml and a Vmax of 4953mol/min/mg under optimal conditions (pH 7, 60°C). At pH 11, 60°C, the activity was still as high as 517IU/mg. Xylanase activities at 60°C under pH 5 to pH 9 remained at more than 69.4% of the initial activity level for 8h. The addition of Hg2+ at 5mM almost completely inhibited xylanase activity, whereas the addition of tris-(2-carboxyethyl)-phosphine (TCEP) and 2-mercaptoethanol stimulated xylanase activity. No relative activities for Avicel, CMC and d-(+)-cellobiose were found. Xylotriose constitutes the majority of the hydrolyzed products from oat spelt and birchwood xylan. Broad pH and temperature stability shows its application potentials for biomass conversion, food and pulp/paper industries.
