A-xylosidase enhanced conversion of plant biomass into fermentable sugars
The invention relates to increasing the availability of fermentable sugars from plant biomass, such as glucose and xylose. As described herein, α-xylosidases can be employed with cellulases to enhance biomass conversion into free, fermentable sugar residues.
1. A method, comprising:
a) providing;
i) a plant biomass comprising a hemicellulose material; and
ii) an enzyme mixture comprising at least about 5% by weight of isolated Aspni5|43342 α-xylosidase, or an α-xylosidase with at least 95% sequence identity to SEQ ID NO:1, and at least 50% by weight of a cellulase mixture comprising cellobiohydrolase, endoglucanase, β-1,4-glucanase, β-glucosidase, endoxylanase, and β-xylosidase; and
b) incubating said biomass with said enzyme mixture using at least about 2 mg of an isolated α-xylosidase per gram biomass for a time and under conditions sufficient to create a depolymerized hemicellulose material;
wherein said depolymerized hemicellulose material comprises a plurality of free fermentable xylose and glucose residues.
2. The method of claim 1 , wherein the α-xylosidase with at least 95% sequence identity to SEQ ID NO:1 has one or more conservative amino acid substitutions.
3. The method of claim 1 , wherein said method further comprises pretreating said plant biomass with alkaline hydrogen peroxide, acid, ammonia, ionic liquids, steam or a combination thereof.
4. The method of claim 1 , wherein said depolymerized hemicellulose material is at least 50% depolymerized into the plurality of free fermentable xylose and glucose residues.
5. The method of claim 1 , wherein said cellulase mixture further comprises at least one enzyme selected from the group of α-fucosidase, β-galactosidase, α-arabinosidase, α-glucuronidase polysaccharide mono-oxygenase, esterase and combinations thereof.
6. The method of claim 1 , wherein said isolated α-xylosidase lacks a quaternary structure.
7. The method of claim 1 , wherein said isolated α-xylosidase is a secreted α-xylosidase.
8. The method of claim 1 , wherein said isolated α-xylosidase has a pH optimum of approximately 4.0.
9. The method of claim 1 , wherein said isolated α-xylosidase comprises or is derived from a fungal extracellular extract.
10. The method of claim 9 , wherein said fungal extracellular extract is an Aspergillus niger extracellular extract.
11. The method of claim 1 , wherein said plant biomass comprises a dicot xyloglucan.
12. The method of claim 1 , wherein said plant biomass comprises a monocot xyloglucan.
13. The method of claim 1 , wherein said plant biomass comprises grass xyloglucan or corn stover.
14. The method of claim 1 , wherein said incubating is performed at a temperature ranging from approximately 40° C. to 50° C.
15. The method of claim 1 , wherein said incubating is performed at a pH of approximately 4-5.