Polypeptide

1. A non-naturally occurring PS4 variant polypeptide derivable from a parent polypeptide, the parent polypeptide having non-maltogenic exoamylase activity, which PS4 variant polypeptide comprises an alanine substitution at a position corresponding to position 223 of the Pseudomonas saccharophila exoamylase sequence of SEQ ID NO: 1, wherein the PS4 variant polypeptide has at least 95% sequence identity with the polypeptide of SEQ ID NO: 1 and non-maltogenic exoamylase activity and a higher thermostability compared to the parent polypeptide when tested under the same conditions, and which has a higher pH stability compared to the parent polypeptide when tested under the same conditions.

2. The PS4 variant polypeptide according to claim 1 , wherein the parent polypeptide comprises a glucan 1,4-alpha-maltotetrahydrolase EC 3.2.1.60.

3. The PS4 variant polypeptide according to claim 2 , wherein the parent polypeptide is a non-maltogenic exoamylase of Pseudomonas saccharophila or Pseudomonas stutzeri.

4. The PS4 variant polypeptide according to claim 3 , wherein the parent polypeptide is a non-maltogenic exoamylase from Pseudomonas saccharophila having the sequence of SEQ ID NO: 1 or SEQ ID NO: 9.

5. The PS4 variant polypeptide according to claim 1 , wherein the thermostability is determined by establishing a half life (t 1/2 ), at 60 degrees C. for the variant polypeptide and comparing it with that of the parent polypeptide.

6. The PS4 variant polypeptide according to claim 1 , which has a higher pH stability compared to the parent polypeptide when tested under the same conditions, wherein the pH is between pH 5 to pH 10.5.

7. The PS4 variant polypeptide according to claim 6 , which has 10% or more pH stability compared to the parent polypeptide, wherein the pH is between pH 5 to pH 10.5.

8. The PS4 variant polypeptide according to claim 1 , which comprises the sequence of SEQ ID NO: 4 (PSac-G223A).

9. The PS4 variant polypeptide according to claim 5 , wherein the half life (t 1/2 ) at 60 degrees C. is increased by 15% or more relative to the parent polypeptide.

10. The PS4 variant polypeptide according to claim 5 , wherein the half life (t 1/2 ) at 60 degrees C. is increased by 50% or more relative to the parent polypeptide.

11. The PS4 variant polypeptide according to claim 5 , wherein the half life (t 1/2 ) at 60 degrees C. is increased by 100% or more relative to the parent polypeptide.

12. The PS4 variant polypeptide according to claim 1 , which has a higher enzymatic activity compared to the parent polypeptide.

13. The PS4 variant polypeptide according to claim 12 , wherein the activity is tested using a waxy maize starch incubation test.

14. The PS4 variant polypeptide according to claim 6 , which has 20% or more pH stability compared to the parent polypeptide.

15. The PS4 variant polypeptide according to claim 6 , which has 50% or more pH stability compared to the parent polypeptide.

16. The PS4 variant polypeptide according to claim 1 , wherein the variant polypeptide is obtainable by altering the sequence of a parent polypeptide having non-maltogenic exoamylase activity, by introducing an alanine substitution at a position corresponding to position 223 of the Pseudomonas saccharophila exoamylase sequence of SEQ ID NO: 1 such that the variant polypeptide has higher thermostability compared to the parent polypeptide when tested under the same conditions.

17. The polypeptide according to claim 16 , which is obtainable by altering the sequence of a nucleic acid which encodes the parent polypeptide.

18. A composition comprising the PS4 variant polypeptide according to claim 1 and a maltogenic alpha-amylase.

19. A non-naturally occurring PS4 variant polypeptide derivable from a parent polypeptide, the parent polypeptide having non-maltogenic exoamylase activity, wherein said PS4 variant polypeptide has non-maltogenic exoamylase activity and a higher thermostability compared to the parent polypeptide when tested under the same conditions, and which has a higher pH stability compared to the parent polypeptide when tested under the same conditions, and wherein said PS4 variant polypeptide is a polypeptide (a) which comprises all of SEQ ID NO: 1 except that it has alanine at a position corresponding to position 223 of SEQ ID NO: 1, or (b) which has alanine at a position corresponding to position 223 of SEQ ID NO: 1 and has at least 95% sequence identity with the polypeptide of SEQ ID NO: 1.

20. A composition comprising the PS4 variant polypeptide according to claim 19 and a maltogenic alpha-amylase.

21. A non-naturally occurring PS4 variant polypeptide derivable from a parent polypeptide, the parent polypeptide having non-maltogenic exoamylase activity, wherein the PS4 variant polypeptide has (a) alanine at a position corresponding to position 223 of SEQ ID NO: 1, or (b) proline at a position corresponding to position 141 of SEQ ID NO: 1, wherein the PS4 variant polypeptide has at least 95% sequence identity with the polypeptide of SEQ ID NO: 1 and non-maltogenic exoamylase activity and a higher thermostability compared to the parent polypeptide when tested under the same conditions, and which has a higher pH stability compared to the parent polypeptide when tested under the same conditions.

22. The polypeptide according to claim 19 which is obtainable by altering the sequence of a nucleic acid which encodes the non-maltogenic exoamylase from Pseudomonas saccharophila.

23. A composition comprising the PS4 variant polypeptide according to claim 21 and a maltogenic alpha-amylase.

24. A non-naturally occurring PS4 variant polypeptide derivable from a parent polypeptide, the parent polypeptide having non-maltogenic exoamylase activity, which PS4 variant polypeptide has (a) alanine at a position corresponding to position 223 of SEQ ID NO: 1, (b) proline at a position corresponding to position 141 of SEQ ID NO: 1, or (c) alanine and proline at positions corresponding to position 223 and 141 of SEQ ID NO: 1, respectively, wherein the PS4 variant polypeptide has at least 95% sequence identity with the polypeptide of SEQ ID NO: 1 and non-maltogenic exoamylase activity and a higher thermostability compared to the parent polypeptide when tested under the same conditions, and which has a higher pH stability compared to the parent polypeptide when tested under the same conditions.

25. A non-naturally occurring polypeptide having at least 95% sequence identity with the polypeptide of SEQ ID NO: 1 in which the starch binding domain has been removed and wherein said polypeptide has (a) alanine at a position corresponding to position 223 of SEQ ID NO: 1, (b) proline at a position corresponding to position 141 of SEQ ID NO: 1, or (c) alanine and proline at positions corresponding to position 223 and 141 of SEQ ID NO: 1, respectively, wherein the polypeptide has non-maltogenic exoamylase activity.

26. A non-naturally occurring polypeptide having at least 95% sequence identity with the polypeptide of SEQ ID NO: 4 in which the starch binding domain has been removed and wherein the said polypeptide has alanine at a position corresponding to position 223 of SEQ ID NO: 1, wherein the polypeptide has non-maltogenic exoamylase activity.

27. A non-naturally occurring polypeptide having at least 95% sequence identity with the polypeptide of SEQ ID NO: 3 in which the starch binding domain has been removed and wherein the said polypeptide has proline at a position corresponding to position 141 of SEQ ID NO: 1, wherein the polypeptide has non-maltogenic exoamylase activity.

28. A composition comprising a polypeptide as claimed in any one of claim 25 , 26 or 27 and a maltogenic alpha-amylase.