Thermostable xylanase

A method for producing a thermostable xylanase selected from the thermostable xylanase XP1 or XP2 having the following physicochemical properties:

• (1) Thermostable xylanase XP1 having the following physicochemical properties:
• I) Action:
• hydrolyzing the 1,4-.beta.-D-xyloside bond of xylan to thereby produce reducing sugars of xylooligosaccharides
• ii) Substrate specificity:
• acting on prepared xylans including birch xylan and oat spelt xylan, as well as xylan-containing materials including hardwood kraft pulp and oat spelt bran
• iii) Optimum pH and stable pH ranges:
• optimum pH for reaction ranging from 5 to 8 and the pH at which said xylanase is stable ranging from 3 to 9
• iv) Appropriate temperature range for action:
• 50.degree. to 80.degree. C.
• v) Thermostability:
• retaining about 90% or more enzyme activity after a 30 min treatment at 50.degree. C. and exhibiting a residual activity of about 50% or more even after a 30 min treatment at 60.degree. C.
• vi) Isoelectric point:
• around 8.1
• vii) Molecular weight:
• approximately 22,500 as determined by SDS polyacrylamide gel electrophoresis
• viii) Inhibition:
• weakly inhibited by iodoacetic acid and EDTA and strongly inhibited by Hg.sup.2+ and SDS
• (2) Thermostable xylanase XP2 having the following physicochemical properties:
• I) Action:
• hydrolyzing the 1,4-p-.beta.-D-xyloside bond of xylan to thereby produce reducing sugars of xylose and xylooligosaccharides
• ii) Substrate specificity:
• acting on prepared xylans including birch xylan and oat spelt xylan, as well as xylan-containing materials including hardwood kraft pulp and oat spelt bran
• iii) Optimum pH and stable pH ranges:
• optimum pH for reaction ranging from 5 to 8 and the pH at which said xylanase is stable ranging from 4.5 to 9
• iv) Appropriate temperature range for action:
• 60 to 90.degree. C.
• v) Thernostability:
• exhibiting a residual activity of about 90% or more after a 30 min treatment at 70.degree. C.
• vi) Isoelectric point:
• around 8.5
• vii) Molecular weight:
• approximately 32,000 as determined by SDS polyacrylamide gel electrophoresis
• viii) Inhibition:
• weakly inhibited by Mn.sup.2+, Co.sup.2+, Cu.sup.2+, EDTA and iodoacetic acid and strongly inhibited by Hg.sup.2+ and SDS, comprising culturing on a medium a microorganism belonging to the genus Bacillus which produces said thermostable xylanase and subsequently recovering the thermostable xylanase from the resultant culture.