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Thermostable Xylanases from Rhodothermus marinus

Dahlberg, Leif LU (1996)
Abstract (Swedish)
Popular Abstract in Swedish

Populärvetenskaplig sammanfattning



Det magnifika skådespelet av erupterande geysrar, varma, rykande källor av skilda slag samt kokande lerpölar är en uppseendeväckande syn. Dessa extrema miljöer av hög temperatur och mycket låga pH-värden verkar långt ifrån livsbejakande. Trots detta finns liv representerat i form av mikroorganismer som här har funnit sina ideala livsmiljöer. Bakterier som älskar höga temperaturer kallas för termofiler. Om en termofil trivs bäst vid 65 °C betyder det att också att alla dess biologiska molekyler, som enzymer, måste fungera bra vid denna temperatur. Det sägs att enzymerna är aktiva och stabila vid denna temperatur. Söker man efter ett visst enzym... (More)
Popular Abstract in Swedish

Populärvetenskaplig sammanfattning



Det magnifika skådespelet av erupterande geysrar, varma, rykande källor av skilda slag samt kokande lerpölar är en uppseendeväckande syn. Dessa extrema miljöer av hög temperatur och mycket låga pH-värden verkar långt ifrån livsbejakande. Trots detta finns liv representerat i form av mikroorganismer som här har funnit sina ideala livsmiljöer. Bakterier som älskar höga temperaturer kallas för termofiler. Om en termofil trivs bäst vid 65 °C betyder det att också att alla dess biologiska molekyler, som enzymer, måste fungera bra vid denna temperatur. Det sägs att enzymerna är aktiva och stabila vid denna temperatur. Söker man efter ett visst enzym och vill att enzymet skall vara stabilt vid 65 °C - och kanske ännu högre temperaturer - så kan man finna det hos mikroorganismer som lever vid höga temperaturen. Enzymer finns i alla levande organismer där de katalyserar nedbrytning och uppbyggnad av olika molekyler. För varje biologiskt ämne finns det ett enzym som kan bryta ned det, så även för vedens beståndsdelar. Ved består i huvudsak av cellulosa, hemicellulosa och lignin. För att bryta ned hemicellulosan xylan, krävs en rad olika enzymers samtidiga närvaro. Viktigast är dock enzymet xylanas. Värmestabila xylanaser har funnit tillämpningar inom pappers- och massa industrin, dels i modifiering av vedfibrerna men framförallt som ett miljövänligt alternativ i blekning av vedmassa. Blekning med enzymer har flera förespråkare bland de stora massafabrikanterna i Sverige. I Finland, Kanada och USA, har konceptet använts i flera år. Efter den alkaliska kokningen av vedmassan finns ett skal av hemicellulosa, huvudsakligen xylan, utanpå cellulosa fibrerna. Detta skal förhindrar vidare utlösning av lignin. Ligninet brunfärgar massan. Trots att 90 % av ligninet försvinner i ett alkaliskt kok så är massan fortfarande brun. Papper gjort av sådan massa duger till kartonger men inte till skriv- och tryckpapper. Resterande lignin måste tas bort med olika blekmetoder. Klorgas är bäst r (Less)
Abstract
Abstract



Hot springs in Iceland can serve as sources of thermophilic, xylanolytic bacteria secreting very thermostable xylanolytic enzymes. The aerobic, thermophilic bacteria Rhodothermus marinus secretes multiple xylanases and xylosidases. One of the xylanases was purified to electrophoretic homogeneity and was characterized. The N-terminal sequence showed no homology with other xylanases. The purified enzyme had a half-life of nearly three hours at 80 °C and the end products of hydrolysis were xylobiose and xylotriose. This strongly suggests that the thermostable enzyme is a true endo-1,4-ß-xylanase. The catalytic domain of one of the xylanase genes in R. marinus was sequenced and was overexpressed in E. coli. The... (More)
Abstract



Hot springs in Iceland can serve as sources of thermophilic, xylanolytic bacteria secreting very thermostable xylanolytic enzymes. The aerobic, thermophilic bacteria Rhodothermus marinus secretes multiple xylanases and xylosidases. One of the xylanases was purified to electrophoretic homogeneity and was characterized. The N-terminal sequence showed no homology with other xylanases. The purified enzyme had a half-life of nearly three hours at 80 °C and the end products of hydrolysis were xylobiose and xylotriose. This strongly suggests that the thermostable enzyme is a true endo-1,4-ß-xylanase. The catalytic domain of one of the xylanase genes in R. marinus was sequenced and was overexpressed in E. coli. The xylanase belongs to family 10 of the glycosyl hydrolases. The closest homology was found to be with the Pseudomonas flourescens xylanase B catalytic domain. No homology was found with the N-terminal sequence of the purified xylanase. The gene product, the xylanase, was purified to electrophoretic homogeneity and was characterized. The half-life was 100 min at 80 °C, the thermostability of the xylanase being enhanced by the presence of calcium. The end products of hydrolysis were xylobiose and xylotriose, suggesting that this enzyme is also a true endo-1,4-ß-xylanase. The cloned xylanase showed positive preliminary results when tested for its ability to bleach and de-colour birch pulp. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Prof Antranikian, Garo, TU Hamburg-Harburg, Biotechnology/Technical Microbiology, Denickestrasse 15, D-21071 Hamburg, Germany
organization
publishing date
type
Thesis
publication status
published
subject
keywords
characterization, application, xylanolytic bacteria, thermophile, thermostability, purification, thermostable xylanase, xylosidase, Rhodothermus marinus, xylanase, gene sequence, Biotechnology, Bioteknik
pages
60 pages
publisher
Biotechnology, Lund University
defense location
Lecture hall A, Center for Chemistry and Chemical Engineering, Sölvegatan 39, Lund
defense date
1996-05-14 10:15
external identifiers
  • other:ISRN: LUTKDH/TKBT-96/1025-SE
language
English
LU publication?
yes
id
8a5b6131-7ed3-40f0-9e3b-4c8e52c12486 (old id 28406)
date added to LUP
2007-06-12 08:41:52
date last changed
2016-09-19 08:45:03
@phdthesis{8a5b6131-7ed3-40f0-9e3b-4c8e52c12486,
  abstract     = {Abstract<br/><br>
<br/><br>
Hot springs in Iceland can serve as sources of thermophilic, xylanolytic bacteria secreting very thermostable xylanolytic enzymes. The aerobic, thermophilic bacteria Rhodothermus marinus secretes multiple xylanases and xylosidases. One of the xylanases was purified to electrophoretic homogeneity and was characterized. The N-terminal sequence showed no homology with other xylanases. The purified enzyme had a half-life of nearly three hours at 80 °C and the end products of hydrolysis were xylobiose and xylotriose. This strongly suggests that the thermostable enzyme is a true endo-1,4-ß-xylanase. The catalytic domain of one of the xylanase genes in R. marinus was sequenced and was overexpressed in E. coli. The xylanase belongs to family 10 of the glycosyl hydrolases. The closest homology was found to be with the Pseudomonas flourescens xylanase B catalytic domain. No homology was found with the N-terminal sequence of the purified xylanase. The gene product, the xylanase, was purified to electrophoretic homogeneity and was characterized. The half-life was 100 min at 80 °C, the thermostability of the xylanase being enhanced by the presence of calcium. The end products of hydrolysis were xylobiose and xylotriose, suggesting that this enzyme is also a true endo-1,4-ß-xylanase. The cloned xylanase showed positive preliminary results when tested for its ability to bleach and de-colour birch pulp.},
  author       = {Dahlberg, Leif},
  keyword      = {characterization,application,xylanolytic bacteria,thermophile,thermostability,purification,thermostable xylanase,xylosidase,Rhodothermus marinus,xylanase,gene sequence,Biotechnology,Bioteknik},
  language     = {eng},
  pages        = {60},
  publisher    = {Biotechnology, Lund University},
  school       = {Lund University},
  title        = {Thermostable Xylanases from Rhodothermus marinus},
  year         = {1996},
}