Method of producing xylo-oligosaccharide
A method produces xylo-oligosaccharides from a biomass containing xylan and cellulose, which method is convenient and has a high yield of xylo-oligosaccharides because of inhibition of degradation of xylo-oligosaccharides into xylose. In the method of producing xylo-oligosaccharides, a biomass containing xylan and cellulose is hydrolyzed with a cellulase composition having at least activities of xylanase, cellobiohydrolase and β-glucosidase and substantially free of β-xylosidase activity during hydrolysis.
1. A method of producing a cellulase composition, comprising incubating a cellulase mixture not containing a biomass containing xylan and cellulose, having activities of xylanase, cellobiohydrolase, β-glucosidase and β-xylosidase originated from the genus Trichoderma and β-glucosidase activity originated from the genus Aspergillus at a temperature of 35° C. to 60° C. and pH of 5.5 to 8.0 to selectively reduce the activity of β-xylosidase while maintaining the activity of β-glucosidase, xylanase and cellobiohydrolase, to attain
a β-glucosidase activity in said cellulase composition in terms of an enzyme activity for degrading 4-nitrophenyl-β-D-glucopyranoside of at least 14,000 U/g of proteins in said cellulase composition;
a β-xylosidase activity m said cellulase composition in terms of an enzyme activity for degrading 4-nitrophenyl-β-D-xylopyranoside of 50 to 300 U/g of proteins in said cellulase composition;
a xylanase activity in said cellulase composition in terms of an enzyme activity for degrading xylan of at least 18,000 U/g of proteins in said cellulase composition; and
a cellobiohydrolase activity in said cellulase composition in terms of an enzyme
activity for degrading 4-nitrophenyl-β-D-lactopyranoside of at least 80 U/g of proteins in said cellulase composition.
2. A method of producing xylo-oligosaccharides comprising hydrolyzing a biomass containing xylan and cellulose with the cellulase composition produced by the method according to claim 1 .
3. The method according to claim 2 , wherein the pH condition during the hydrolysis is 6.0 to 8.0.
4. The method according to claim 2 , comprising hydrolyzing a product obtained by a pretreatment of said biomass containing xylan and cellulose with an alkali.
5. The method according to claim 2 , further comprising the steps of: separating the hydrolysate produced by the hydrolysis reaction into solid and liquid products; filtering the obtained liquid product through an ultrafilter; recovering the cellulase composition from the non-permeated side and obtaining xylo-oligosaccharides from the permeated side.
6. A method of producing cellulase composition comprising:
a) incubating a cellulase mixture not containing a biomass containing xylan and cellulose, having the activities of xylanase, cellobiohydrolase, β-glucosidase and β-xylosidase activities originated from genus Trichoderma at a temperature of 35° C. to 60° C. and pH of 5.5 to 8.0 to selectively reduce the activity of both β-glucosidase and β-xylosidase while maintaining the activity of xylanase and cellobiohydrolase; and
b) adding β-glucosidase into the cellulase mixture of a), to attain a β-glucosidase activity in said cellulase composition in terms of an enzyme activity for degrading 4-nitrophenyl-β-D-glucopyranoside of at least 14,000 U/g of proteins in said cellulase composition;
a β-xylosidase activity in said cellulase composition in terms of an enzyme activity for degrading 4-nitrophenyl-β-D-xylopyranoside of 50 to 300 U/g of proteins in said cellulase composition;
a xylanase activity in said cellulase composition in terms of an enzyme activity for degrading xylan of at least 18,000 U/g of proteins in said cellulase composition; and
a cellobiohydrolase activity in said cellulase composition in terms of an enzyme activity for degrading 4-nitrophenyl-β-D-lactopyranoside of at least 80 U/g of proteins in said cellulase composition.
7. A method of producing xylo-oligosaccharides comprising hydrolyzing a biomass containing xylan and cellulose with the cellulase composition produced by the method according to claim 6 .
8. The method according to claim 7 , wherein the pH condition during the hydrolysis is 6.0 to 8.0.
9. The method according to claim 7 , wherein the biomass is obtained by a pretreatment with an alkali.
10. The method according to claim 7 , further comprising the steps of: separating the hydrolysate produced by the hydrolysis reaction into solid and liquid products; filtering the obtained liquid product through an ultrafilter; recovering the cellulase composition from the non-permeated side and obtaining xylo-oligosaccharides from the permeated side.