Variants of glucoamylase
View Patent ↗The present invention relates to combinatorial variants of a parent glucoamylase that have altered properties for reducing the synthesis of condensation products during hydrolysis of starch. Accordingly the variants of a parent glucoamylase are suitable such as for use within brewing and glucose syrup production. Also disclosed are DNA constructs encoding the variants and methods of producing the glucoamylase variants in host cells.
1. A method for reducing the ratio between isomaltose synthesis and starch hydrolysis activity (IS/SH ratio) during the hydrolysis of starch comprising contacting a starch solution with a glucoamylase variant, said glucoamylase variant comprising the following amino acid substitutions:
D44R and A539R; or
D44R, N61I and A539R,
the positions corresponding to the respective position in SEQ ID NO:2,
wherein said glucoamylase variant has at least 90% amino acid sequence identity to the entire length of the amino acid sequence set forth in SEQ ID NO: 2,
wherein said glucoamylase variant exhibits a reduced IS/SH ratio compared to said parent glucoamylase during the hydrolysis of starch.
2. The method of claim 1 , wherein the parent glucoamylase has at least 90% sequence identity to SEQ ID NO: 2.
3. A glucoamylase variant comprising the following amino acid substitutions:
D44R and A539R; or
D44R, N61I and A539R,
the positions corresponding to the respective position in SEQ ID NO:2,
wherein said glucoamylase variant has at least 90% sequence identity to the entire length of the amino acid sequence set forth in SEQ ID NO: 2.
4. The glucoamylase variant according to claim 3 , wherein the glucoamylase variant has at least 95% sequence identity to SEQ ID NO: 2.
5. The glucoamylase variant according to claim 3 , wherein the glucoamylase variant has at least 98% sequence identity to SEQ ID NO:2.
6. The glucoamylase variant according to claim 3 comprising SEQ ID NO: 2 having the following amino acid substitutions:
D44R and A539R; or
D44R, N61I and A539.
7. The glucoamylase variant according to claim 3 consisting of SEQ ID NO:2 and having the following amino acid substitutions:
D44R and A539R; or
D44R, N61I and A539.
8. The glucoamylase variant according to claim 3 , wherein the glucoamylase variant has a starch binding domain that has at least 96% sequence identity with the starch binding domain of SEQ ID NO: 2.
9. The glucoamylase variant according to claim 3 , wherein the glucoamylase variant has a catalytic domain that has at least 90% sequence identity with the catalytic domain of SEQ ID NO: 2.
10. The glucoamylase variant according to claim 3 , wherein the parent glucoamylase is selected from a glucoamylase obtained from a Trichoderma spp., an Aspergillus spp., a Humicola spp., a Penicillium spp., a Talaromycese spp., or a Schizosaccharmyces spp.
11. The glucoamylase variant according to claim 3 , wherein the parent glucoamylase is obtained from a Trichoderma spp. or an Aspergillus spp.
12. The glucoamylase variant according to claim 3 , which glucoamylase exhibit an enhanced production of fermentable sugar(s) as compared to the parent glucoamylase.
13. The glucoamylase variant according to claim 3 , which glucoamylase exhibit an enhanced production of fermentable sugars in the mashing step of the brewing process as compared to the parent glucoamylase.
14. The glucoamylase variant according to claim 3 , which glucoamylase exhibit a reduced ratio between isomaltose synthesis and starch hydrolysis activity (IS/SH ratio) as compared to the parent glucoamylase.
15. The glucoamylase variant according to claim 3 , which glucoamylase exhibit an enhanced real degree of fermentation as compared to the parent glucoamylase.
16. The glucoamylase variant according to claim 3 , which glucoamylase has been purified.
17. A polynucleotide encoding the glucoamylase variant according to claim 3 .
18. A vector comprising the polynucleotide according to claim 17 .
19. A host cell comprising a vector according to claim 18 .
20. A host cell which has stably integrated into the chromosome a nucleic acid encoding the variant glucoamylase according to claim 3 .
21. A cell comprising the polynucleotide of claim 17 .
22. The cell according to claim 21 which is a bacterial, fungal or yeast cell.
23. The cell according to claim 22 , which is Trichoderma spp.
24. The cell according to claim 22 , which is a protease deficient and/or xylanase deficient and/or native glucanase deficient host cell.
25. A method of expressing a glucoamylase variant, the method comprising obtaining a host cell or a cell according to claim 21 and expressing the glucoamylase variant from the cell or host cell, and optionally purifying the glucoamylase variant.
26. The method according to claim 25 comprising purifying the glucoamylase variant.
27. An enzymatic composition comprising at least one glucoamylase variant according to claim 3 .
28. The enzymatic composition according to claim 27 , wherein the composition is selected from among a starch hydrolyzing composition, a saccharifying composition, a detergent, an alcohol fermentation enzymatic composition, and an animal feed.
29. The enzymatic composition according to claim 27 comprising at least one additional enzyme selected among amylase, protease, pullulanase, cellulase, glucanase, xylanase, arabinofuranosidase, ferulic acid esterase, xylan acetyl esterase, and a further glucoamylase.
30. A method for producing a wort for brewing comprising forming a mash from a grist, and contacting the mash with a glucoamylase variant comprising the following amino acid substitutions:
D44R and A539R; or
D44R, N61I and A539R
the positions corresponding to the respective position in SEQ ID NO:2 wherein said glucoamylase variant has at least 90% sequence identity to the entire length of the amino acid sequence set forth in SEQ ID NO: 2.