Co-operative actions and degradation analysis of purified xylan-degrading enzymes from Thermomonospora fusca BD25 on oat-spelt xylan.
OBJECTIVE
To determine and quantify the products from the degradation of xylan by a range of purified xylan-degrading enzymes, endoxylanase, beta-xylosidase and alpha-l-arabinofuranosidase produced extracellularly by Thermomonospora fusca BD25.


RESULTS
The amounts of reducing sugars released from oat-spelt xylan by the actions of endoxylanase, beta-xylosidase and alpha-l-arabinofuranosidase were equal to 28.1, 4.6 and 7% hydrolysis (as xylose equivalents) of the substrate used, respectively. However, addition of beta-xylosidase and alpha-l-arabinofuranosidase preparation to endoxylanase significantly enhanced (70 and 20% respectively) the action of endoxylanase on the substrate. The combination of purified endoxylanase, beta-xylosidase and alpha-l-arabinofuranosidase preparations produced a greater sugar yield (58.6% hydrolysis) and enhanced the total reducing sugar yield by around 50%. The main xylooligosaccharide products released using the action of endoxylanase alone on oat-spelt xylan were identified as xylobiose and xylopentose. alpha-l-Arabinofuranosidase was able to release arabinose and xylobiose from oat-spelt xylan. In the presence of all three purified enzymes the hydrolysis products of oat-spelt xylan were mainly xylose, arabinose and substituted xylotetrose with lesser amount of substituted xylotriose.


CONCLUSIONS
The addition of the beta-xylosidase and alpha-l-arabinofuranosidase enzymes to purified xylanases more than doubled the degradation of xylan from 28 to 58% of the total substrate with xylose and arabinose being the major sugars produced.


CONCLUSIONS
The results highlight the role of xylan de-branching enzymes in the degradation of xylan and suggest that the use of enzyme cocktails may significantly improve the hydrolysis of xylan in industrial processes.
Tuncer
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University of Essex, Department of Biological Sciences, John Tabor Laboratories, Wivenhoe Park, Colchester, UK.
Ball
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D000190:Actinomyces / Q000201:enzymology*; D001426:Bacterial Proteins / Q000378:metabolism*; D004187:Disaccharides / Q000378:metabolism; D043364:Endo-1,4-beta Xylanases; D006026:Glycoside Hydrolases / Q000378:metabolism; D007218:Industrial Microbiology; D010209:Paper; D043325:Xylan Endo-1,3-beta-Xylosidase; D014990:Xylans / Q000378:metabolism*; D014995:Xylosidases / Q000378:metabolism
D001426:Bacterial Proteins; D004187:Disaccharides; D014990:Xylans; D006026:Glycoside Hydrolases; D014995:Xylosidases; D043325:Xylan Endo-1,3-beta-Xylosidase; C026579:exo-1,4-beta-D-xylosidase; C019713:alpha-N-arabinofuranosidase; D043364:Endo-1,4-beta Xylanases; C004173:xylobiose