Method for obtaining crystalline 2′-fucosyllactose

1. Method for selectively obtaining crystalline form A or form B of 2′-fucosyllactose from a 2′-fucosyllactose raw material, which contains 2′-FL as a main constituent and at least 0.5% by weight, based on the total amount of mono-and oligosaccharides in the raw material, of one or more mono-or oligosaccharides different from 2′-fucosyllactose, where the method comprises

a) providing a solution of the 2′-fucosyllactose raw material in water, which does not contain more than 10% by weight of organic solvents, based on the total amount of water;

b) effecting the crystallization of 2′-fucosyllactose at a temperature in the range from 0 to 52° C. by inducing conditions of a controlled supersaturation in the solution, where form A or form B of 2′-fucosyllactose is obtained and a water miscible organic solvent is added to the suspension when the crystallization is almost complete; and

c) separating crystalline form A or form B of 2′-fucosyllactose from the mother liquor;

and where during controlled supersaturation in step b) not more than 10% by weight of organic solvents are present, based on the total amount of water present during step b).

2. The method of claim 1 , where the conditions of a controlled supersaturation are induced in a manner such that the ratio c:c* of the concentration c of dissolved 2′-fucosyllactose to the equilibrium solubility c* of 2′-fucosyllactose under the conditions of controlled supersaturation is from more than 1:1 to 1.5:1, thereby effecting the crystallization of 2′-fucosyllactose.

3. The method of claim 1 , where the controlled supersaturation is induced by removing water and/or by cooling.

4. The method of claim 1 , where the crystallization is effected in the presence of solid 2′-fucosyllactose and is carried out as an evaporation crystallization.

5. The method of claim 1 , where the concentration of dissolved 2′-fucosyllactose under the conditions of controlled supersaturation is in the range from 400 to 750 g/L.

6. The method of claim 1 , where the 2′-fucosyllactose raw material contains at least one oligosaccharide selected from lactose, difucosyllactose, lactulose and fucosylated lactulose.

7. The method of claim 1 , where the solution of 2′-fucosyllactose provided in step a) does not contain more than 5000 ppm of solid insoluble material, based on the total weight of the solution.

8. The method of claim 1 , where the aqueous solution of 2′-fucosyllactose provided in step a) is obtained by a fermentation process.

9. The method of claim 1 , where the aqueous solution of 2′-fucosyllactose provided in step a) is fed to a continuously operated crystallization apparatus, which contains an aqueous suspension of 2′-fucosyllactose crystals.

10. The method of claim 9 , where step b) comprises

b1) continuously feeding the aqueous solution of 2′-fucosyllactose to a crystallization apparatus containing an aqueous suspension of 2′-fucosyllactose;

b2) continuously removing water from the aqueous suspension of 2′-fucosyllactose contained in the crystallization apparatus to maintain conditions of controlled supersaturation;

b3) continuously removing the aqueous suspension of 2′-fucosyllactose from the crystallization apparatus.

11. The method of claim 9 , where a portion of the aqueous suspension of 2′-fucosyllactose removed in step b3) is mixed with the aqueous solution of 2′-fucosyllactose of step b1) and the mixture is fed back it into the crystallization apparatus.

12. The method of claim 1 , where the solution of the 2′-fucosyllactose raw material is subjected to a crystallization in batch- or fed-batch operated crystallization apparatus.

13. The method of claim 1 , where the crystallization is carried out at a temperature in the range from 20 to 52° C. in the presence of solid 2′-fucosyllactose and where the crystallization is effected from an aqueous supersaturated solution under the conditions of controlled supersaturation, where the aqueous supersaturated solution has a concentration of dissolved 2′-fucosyllactose in the range from 410 to 630 g/L.

14. The method of claim 1 , where at least a portion of the mother liquor obtained in step c) is subjected to a crystallization of 2′-fucosyllactose by inducing conditions of a controlled supersaturation in the mother liquor.

15. The method of claim 14 , where at least a portion of the mother liquor is mixed with the solution of the 2′-fucosyllactose raw material prior to carrying out step b).

16. The method of claim 1 , which comprises a first crystallization step and a second crystallization step,

where the aqueous solution of the 2′-fucosyllactose raw material provided in step a) is subjected to a crystallization of the second crystallization step,

where in the second crystallization step the crystallization of 2′-fucosyllactose is effected by inducing conditions of a controlled supersaturation in the solution according to step b), where the aqueous suspension of the crystalline 2′-fucosyllactose obtained in the second crystallization step is subjected to a solid-liquid separation to obtain a crystalline 2′-fucosyllactose and a mother liquor,

where the mother liquor obtained in the solid-liquid separation is introduced into the first crystallization step.

17. The method of claim 16 , where the crystalline 2′-fucosyllactose obtained in the first crystallization step is dissolved in the aqueous solution of the 2′-fucosyllactose raw material prior to carrying out the second crystallization step.