OBTAINING HIGHLY CONCENTRATED HMO SOLUTIONS BY REVERSE OSMOSIS
The present invention relates to a method for concentrating aqueous solutions of human milk oligosaccharides, in which an aqueous solution comprising at least one human milk oligosaccharide is subjected to a reverse osmosis process by means of a reverse osmosis membrane and is thereby concentrated to a final osmotic pressure of at least 70 bar measured with a freezing point osmometer. Moreover, the present invention refers to an according use of a reverse osmosis membrane, a corresponding reverse osmosis system containing such a membrane and a spray-dried HMO product obtainable by the method.
1 .- 15 . (canceled)
16 . A method for concentrating aqueous solutions of human milk oligosaccharides comprising subjecting an aqueous solution comprising at least one human milk oligosaccharide to a reverse osmosis process by means of a reverse osmosis membrane and concentrating the at least one human milk oligosaccharide to a final osmotic pressure of at least 70 bar measured with a freezing point osmometer.
17 . The method according to claim 16 wherein the at least one human milk oligosaccharide comprises, preferably is 2′-fucosyllactose.
18 . The method according to claim 16 wherein the method does not comprise a step in which water is evaporated.
19 . The method according to claim 16 wherein the reverse osmosis membrane has a retention for NaCl between 93 and 99.6%.
20 . The method according to claim 16 wherein the reverse osmosis membrane is a dairy reverse osmosis membrane.
21 . The method according to claim 16 wherein the method comprises the following subsequent steps:
i) an aqueous solution comprising at least one HMO, especially 2′-FL, is subjected to a reverse osmosis process by means of a RO membrane, especially a dairy RO membrane, and is thereby concentrated to a final osmotic pressure of at least 70 bar measured with a freezing point osmometer,
ii) the at least one HMO, especially 2′-FL, is crystallized from the concentrated solution, and
iii) the crystals of the at least one HMO, especially of 2′-FL are separated from the mother liquor by physical means, for example by filtration, and optionally washed and/or dried.
22 . The method according to claim 21 wherein between steps i) and ii) the solution is further concentrated by evaporation of water in an evaporating device.
23 . The method according to claim 21 wherein prior to step ii) acetic acid is added to the concentrated solution.
24 . The method according to claim 16 wherein the method comprises the following subsequent steps:
i) an aqueous solution comprising at least one HMO, especially 2′-FL, is subjected to a reverse osmosis process by means of a RO membrane, especially a dairy RO membrane, and is thereby concentrated to a final osmotic pressure of at least 70 bar measured with a freezing point osmometer,
ii) acetic acid is added to the concentrated solution obtained in step i),
iii) the at least one HMO, especially 2′-FL, is crystallized from the concentrated and acetic acid containing solution obtained in step ii),
iv) the crystals of the at least one HMO, especially of 2′-FL, containing acetic acid are separated from the mother liquor by physical means, for example by filtration, and optionally washed and/or dried,
v) the crystals obtain in step iv) are re-dissolved to form an aqueous solution comprising the at least one HMO, especially 2′-FL, and acetic acid,
vi) the solution obtained in step v) is subjected to a diafiltration process by means of a NF or open RO membrane or by means of ion-exchange chromatography (IEX), wherein the acetic acid is at least partially removed from the solution, and
vii) the solution obtained in step vi) is subjected to spray drying in a spray drying unit to obtain a spray-dried product containing at least one HMO, especially 2′-FL.
25 . The method according to claim 24 wherein between steps i) and ii) the solution is further concentrated by evaporation of water in an evaporating device.
26 . The method according to claim 24 wherein in step vii), prior to spray drying, the acetic acid content of the aqueous HMO, especially 2′-FL solution is reduced by applying NF or open RO membranes in a diafiltration process.
27 . A method comprising utilizing a reverse osmosis membrane in a reverse osmosis process for concentrating aqueous solutions of human milk oligosaccharides to final osmotic pressures of at least 70 bar measured with a freezing point osmometer.
28 . A reverse osmosis system containing
a RO membrane, especially a dairy RO membrane, and
an aqueous solution comprising at least one HMO, especially 2′-FL, and having an osmotic pressure of at least 70 bar measured with a freezing point osmometer.
29 . A spray-dried product containing at least one HMO, especially 2′-FL, being obtainable by the method according to claim 16 .
30 . The product according to claim 29 wherein it has an acetic acid content of not more than 0.3 wt. %.