We describe a PS4 variant polypeptide derivable from a parent polypeptide having non-maltogenic exoamylase activity, in which the PS4 variant polypeptide comprises an amino acid substitution at position 307 to lysine (K) or arginine (R), with reference to the position numbering of a Pseudomonas saccharophilia exoamylase sequence shown as SEQ ID NO: 1. Preferably, the PS4 variant polypeptide further comprises an amino acid substitution at position 70, preferably G70D. The amino acid at positions 272 and 303 of the sequence of the are preferably histidine (H) and glycine (G).
1. A non-naturally occurring variant polypeptide of SEQ ID NO: 1 having amylase activity and comprising an amino acid substitution at position 307 to lysine (K) or arginine (R), with reference to the position numbering of SEQ ID NO: 1.
2. The polypeptide according to claim 1 , wherein the polypeptide is prepared from a parent polypeptide having exoamylase activity.
3. A method of treating a food product with the polypeptide of claim 1 comprising contacting the food product with the polypeptide.
4. A process for treating a starch comprising contacting the starch with a polypeptide as set out in claim 1 and allowing the polypeptide to generate from the starch one or more linear products.
5. A process of preparing a food or feed product comprising admixing a polypeptide as set out in claim 1 with a food or feed ingredient.
6. A process according to claim 5 , in which the food product comprises a dough or a dough product, preferably a processed dough product, or in which the food product is a bakery product.
7. A process for making a bakery product comprising: (a) providing a starch medium; (b) adding to the starch medium a polypeptide as set out in claim 1 ; and (c) applying heat to the starch medium during or after step (b) to produce a bakery product.
8. A food product or feed product comprising the polypeptide as set out in claim 1 with a food or feed ingredient.
9. An improver composition for a dough, in which the improver composition comprises the polypeptide as set out in claim 1 , and at least one further dough ingredient or dough additive.
10. A composition comprising a flour and the polypeptide as set out in claim 1 .
11. A combination of the polypeptide as set out in claim 1 , together with any one or more of the following:
(a) maltogenic alpha-amylase also called glucan 1,4-a-maltohydrolase (EC 3.2.1.133) from Bacillus stearothermophilus , or a variant, homologue, or mutants thereof which have maltogenic alpha-amylase activity;
(b) a bakery xylanase (EC 3.2.1.8) from e.g. Bacillus sp., Aspergillus sp., Thermomyces sp. or Trichoderma sp.;
(c) a-amylase (EC 3.2.1.1) from Bacillus amyloliqufaciens or a variant, homologue, or mutants thereof which have alpha-amylase activity; and
(d) a lipase such as glycolipase from Fusarium heterosporum.
12. A food or feed product produced by treatment with a combination of the polypeptide according to claim 1 and the enzyme(s) according to claim 11 .
13. The polypeptide according to claim 2 , wherein the parent polypeptide has nonmaltogenic exoamylase activity.
14. The polypeptide according to claim 1 , wherein the amino acid substitution is H307K.
15. The polypeptide according to claim 1 , wherein the amino acid substitution is H307R.
16. The polypeptide according to claim 1 , wherein the polypeptide further comprises an amino acid substitution at position 70 with reference to the position numbering of SEQ ID NO: 1.
17. The polypeptide according to claim 16 , wherein the amino acid substitution is G70D.
18. The polypeptide according to claim 17 , wherein the polypeptide comprises H307K, a histidine (H) at position 272, and a glycine (G) at position 303, with reference to the position numbering of SEQ ID NO: 1.
19. The polypeptide according to claim 17 , wherein the polypeptide comprises H307R, a glycine (G) at position 303, and a histidine (H) at position 272, with reference to the position numbering of SEQ ID NO: 1.
20. The polypeptide according to claim 1 , wherein the polypeptide further comprises one or more mutation(s) selected from the group consisting of positions: 33, 34, 70, 121, 134, 141, 146, 157, 161, 178, 179, 223, 229, 309 or 334, with reference to the position numbering of SEQ ID NO: 1.
21. The polypeptide according to claim 20 , wherein the one or more mutation(s) are selected from the group consisting of: N:33Y, D34N, G121F, G134R, A141P, Y146G, I157L, S161A, L178F, A179T, G223E, S229P, A309P and S334P.
22. The polypeptide according to claim 1 comprising SEQ ID NO: 21.
23. The polypeptide according to claim 1 comprising SEQ ID NO: 23.
24. The polypeptide according to claim 2 , wherein the parent polypeptide is a non-maltogenic exoamylase.
25. The polypeptide according to claim 24 , wherein the parent polypeptide is a glucan 1,4-alpha-maltotetrahydrolase (EC 3.2.1.60).
26. The polypeptide according to claim 2 , wherein the parent polypeptide is a Pseudomonas saccharophila exoamylase.
27. The polypeptide according to claim 2 , wherein the parent polypeptide is a non-maltogenic exoamylase from Pseudomonas saccharophila having a sequence shown as SEQ ID NO: 1.
28. The polypeptide according to claim 1 , wherein the polypeptide has a higher thermostability compared to a parent polypeptide from which it is prepared when tested under the same conditions.
29. The polypeptide according to claim 1 , wherein the polypeptide has a half life (t½) at 60 degrees C. increased by 15% or more compared to a parent polypeptide from which it is prepared when tested under the same conditions.
30. A method according to claim 3 , wherein the food product is a tortilla.
31. A process according to claim 5 , wherein the food product is a tortilla.
32. A process according to claim 6 , wherein the bakery product is a tortilla.
33. A process according to claim 7 , wherein the bakery product is a tortilla.
34. A food product according to claim 8 , wherein the food product is a tortilla.