title: Production of beta-xylanase and beta-xylosidase by the extremely halophilic archaeon Halorhabdus utahensis.
abstract: The extremely halophilic archaeon, Halorhabdus utahensis, isolated from the Great Salt Lake, Utah, produced beta-xylanase and beta-xylosidase activities. Both enzymes were active over a broad NaCl range from near zero to 30% NaCl when tested with culture broth. A broad NaCl optimum was observed for beta-xylanase activity between 5% and 15% NaCl, while beta-xylosidase activity was highest at 5% NaCl. Almost half of the maximum activities remained at 27%-30% NaCl for both enzyme activities. When dialyzed culture supernatant and culture broth were employed for determination of beta-xylanase and beta-xylosidase stabilities, approximately 55% and 83% of the initial beta-xylanase and beta-xylosidase activities, respectively, remained after 24 h incubation at 20% NaCl. The enzymes were also shown to be slightly thermophilic; beta-xylanase activity exhibiting two optima at 55 degrees and 70 degrees C, while beta-xylosidase activity was optimal at 65 degrees C. SDS-PAGE and zymogram techniques revealed the presence of two xylan-degrading proteins of approximately 45 and 67 kDa in culture supernatants. To our knowledge, this paper is the first report on hemicellulose-degrading enzymes produced by an extremely halophilic archaeon.
authors.affiliation: Danish Veterinary Institute, Hangøvej 2, 8200 Arhus N, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Wainø
authors.forename: Kjeld
authors.initials: K
authors.lastname: Ingvorsen
mesh_terms: D043364:Endo-1,4-beta Xylanases / Q000096:biosynthesis*; D004795:Enzyme Stability; D019015:Geologic Sediments / Q000382:microbiology; D006216:Halobacteriaceae / Q000201:enzymology* / Q000254:growth & development / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D009994:Osmolar Concentration; D012623:Seawater / Q000382:microbiology; D012965:Sodium Chloride; D013696:Temperature; D014589:Utah; D014995:Xylosidases / Q000096:biosynthesis*
chemical_list: D012965:Sodium Chloride; D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase; D043364:Endo-1,4-beta Xylanases