GALACTO-OLIGOSACCHARIDE HAVING A TERMINAL MANNOSE RESIDUE, ITS PREPARATION AND APPLICATION

Abstract

The present invention provides a new type of galacto-oligosaccharide, having a mannose residue instead of a glucose residue at the reducing end. The invention also relates to compositions comprising this galacto-oligosaccharide, its preparation and use in nutritional compositions.

Claims

1. Galacto-oligosaccharide of the formula (Gal).sub.m-Man not being epilactose, wherein m has a value in the range 2-8.

2. Composition comprising (i) at least one galacto-oligosaccharide of the formula (Gal)m-Man, wherein m has a value in the range 2-8, and (ii) at least one galacto-disaccharide of the formula Gal-Man.

3. Composition according to claim 2 comprising 0.1-99 wt % galacto-oligosaccharides of the formula (Gal)m-Man, wherein m has a value in the range 2-8, and 1-99.9 wt % galacto-disaccharides of the formula Gal-Man based on the total weight of oligosaccharides and disaccharides in the composition.

4. Composition comprising (i) at least one galacto-oligosaccharide according to claim 1 in admixture with (ii) at least one galacto-oligosaccharide of the formula (Gal)n-Glu, wherein n has a value in the range 1-8.

5. Composition according to claim 4 comprising at least one galacto-oligosaccharide with the formula (Gal)n-Glu wherein n has a value in the range 2-8 and optionally at least one galacto-disaccharide with the formula Gal-Glu.

6. Composition according to claim 4 wherein the total content of compounds with the formula (Gal)m-Man with m being in the range 2-8 in said composition is at least 3 wt % based on the total weight of oligosaccharides and disaccharides.

7. Process for the preparation of the galacto-oligosaccharide according to claim 1, the process comprising the steps of: (i) reacting a lactose with epimerase, thereby obtaining epilactose, and (ii) reacting said epilactose with a β-galactosidase, thereby obtaining the galacto-oligosaccharide according to claim 1.

8. Process according to claim 7 wherein the epilactose formed in step (i) is purified before being contacted with the β-galactosidase in step (ii).

9. Process according to claim 8 wherein the steps (i) and (ii) are conducted in a one-pot reaction, thereby contacting lactose with both said epimerase and said β-galactosidase.

10. Process for the preparation of the galacto-oligosaccharide according to claim 1, the process comprising the step of contacting a galacto-oligosaccharide with the formula (Gal)n-Glu wherein n=2-8, optionally in admixture with a galacto-disaccharide with the formula Gal-Glu, with epimerase, thereby forming a galacto-oligosaccharide of formula (Gal)m-Man, wherein m=2-8 and optionally a galacto-disaccharide of the formula Gal-Man.

11. Nutritional composition comprising the galacto-oligosaccharide of claim 1, additionally comprising one or more proteins, probiotics, lipids, and/or further carbohydrates.

12. Galacto-oligosaccharide according to claim 1, wherein m has a value in the range 2-5.

13. Composition according to claim 2, wherein m has a value in the range 2-5.

14. Composition according to claim 3 comprising 5-95 wt % galacto-oligosaccharides of the formula (Gal).sub.m-Man, wherein m has a value in the range 2-5, and 5-95 wt % galacto-disaccharides of the formula Gal-Man based on the total weight of oligosaccharides and disaccharides in the composition.

15. Composition according to claim 4, wherein n has a value in the range 1-5.

16. Composition according to claim 6, wherein the total content of compounds with the formula (Gal).sub.m-Man with m being in the range 2-8 in said composition is at least 5 wt % based on the total weight of oligosaccharides and disaccharides.

Description

EXAMPLES

Example 1

[0068] Aqueous lactose slurries of pH=6.5 were prepared by slurrying 81 g lactose crystals in a 65 g 1 M natrium citrate buffer solution. A beta-galactosidase (Bacillus circulans) and/or a cellobiose-2-epimerase were added in the amounts listed in Table 1. The slurries were stirred with a magnetic bar and thermostated at 59° C. in a water bath. After 20 hours, the reactions were stopped by adding 1.5% (v/v) 1 M HCl, in order to denature the enzyme.

[0069] The carbohydrate composition of the resulting mixtures was analyzed by Dionex HPLC and displayed in Table 2.

TABLE-US-00001 TABLE 1 Epimerase Biolacta N5 experiment (U/gram lactose) (LU/gram lactose) A 3.90 B 1 3.90 C 1 D 1 1.95

[0070] Experiment A resulted in the formation of a conventional galacto-oligosaccharide composition. Experiment C showed the formation epilactose. Experiments B and D resulted in additional peaks, not observed in experiments A and C, indicating the formation of M-GOS. Interestingly, it was found that with a reduced dosage of beta-galactosidase (experiment D), the formation of conventional GOS was suppressed, while increasing the percentage of M-GOS.

TABLE-US-00002 TABLE 2 Carbohydrate composition of the reaction mixture (in wt %) Exp. A Exp. B Exp. C Exp. D gal 1.8 1.42 0.88 gluc 13.66 12.09 12.76 mannose 2.03 1.54 allolactose 4.07 3.43 2.19 lactose 20.7 14.57 49.23 19.97 lactulose 1.88 2.46 6.13 2.47 epilactose 12.01 36.08 14.11 GOS (m = 2-5) 57.89 44.05 40.37 M-GOS (m = 2-5) 19.95 22.29

Example 2

[0071] Commercial Vivinal® GOS (ex-FrieslandCampina) was used to prepare 100 gram of an aqueous GOS solution, having a solids content of 54 wt % and a pH of 6.5. This pH was set by the addition of 1 ml 1M natrium citrate.

[0072] 8 units of a cellobiose-2-epimerase (i.e. 1 Unit epimerase/gram lactose present in the said GOS solution) were added, to initialize the epimerization.

[0073] The slurries were stirred with a magnetic bar and thermostated at 59° C. in a water bath. After 20 hours, the reactions were stopped by adding 1.5% (v/v) 1 M HCl, in order to denature the enzyme.

[0074] The obtained product was analyzed by Dionex HPLC for its GOS profile and sugar composition by estimation of the peak percentage and the results are displayed in Table 3.

[0075] This experiment resulted in the formation of two extra components: epilactose and M-GOS. This shows that addition of epimerase to a commercial GOS product is able to convert the remaining lactose into epilactose and the lactose-based GOS into M-GOS. This means that addition of epimerase is not only able to introduce a novel functional component, but also to increase the total non-digestible oligosaccharide content.

TABLE-US-00003 TABLE 3 Carbohydrate composition of the reaction mixture (in wt %) Component Vivinal ® GOS Product of Example 2 galactose 2.01 2.27 glucose 13.49 12.66 allo-lactose 4.81 4.96 lactose 15.46 11.59 lactulose 1.44 2 epilactose 6.06 M-GOS (m = 2) 3.79 GOS 62.79 56.67