1. A method for preparing oligosaccharide by mechanical self-assembly is characterized by comprising the following steps:

(1) mixing and stirring monosaccharide, an organic solvent and an acid catalyst;

(2) removing the organic solvent from the material obtained in the step (1), and then performing grinding decomposition self-assembly in mechanical equipment;

(3) dissolving the material obtained in the step (2) in water, and removing impurities to obtain the product;

in the step (1), the monosaccharide is xylose.

2. The method according to claim 1, wherein in the step (1), the organic solvent is any one or a combination of methyl isobutyl ketone, acetone, ethanol, tert-butyl alcohol, acetonitrile, 1, 4-dioxane, ethyl acetate, dimethyl carbonate, diethyl ether and methyl tert-butyl ether.

3. The method according to claim 1, wherein in the step (1), the solid-to-liquid ratio of the monosaccharide to the organic solvent is 1: 5-30 g/mL.

4. The method according to claim 1, wherein in the step (1), the acidic catalyst is any one or a combination of oxalic acid, hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, trifluoroacetic acid and p-toluenesulfonic acid.

5. The method according to claim 1, wherein the acidic catalyst is used in an amount of 0.1 to 3mmol/g monosaccharide in step (1).

6. The method as claimed in claim 1, wherein the stirring speed in step (1) is 800r/min and 300-.

7. The method according to claim 1, wherein in the step (2), the mechanical equipment is any one of a grinder, a ball mill, a roller mill, a sand mill, a roller mill, a rod mill and a homogenizer.

8. The method of claim 1, wherein in step (2), the self-assembly is performed by milling in a mechanical device for 0.5 to 6 hours.

9. The method according to claim 1, wherein in the step (3), the device for removing impurities is an ion exchange resin or a nanofiltration membrane.

Background

The oligosaccharide is also called oligosaccharide or oligosaccharide, and refers to a low molecular polymer formed by connecting 2-10 monosaccharide molecules through a glycosidic bond through dehydration condensation, and is a novel functional carbohydrate source. There are many oligosaccharides found so far, and currently commercially used oligosaccharides mainly include malto-oligosaccharide, isomalto-oligosaccharide, xylo-oligosaccharide, fructo-oligosaccharide, soybean oligosaccharide, tagatose, mannan, and trehalose. Research in the eighties of the last century shows that many oligosaccharides cannot be absorbed and utilized by the digestive tract of a human body, but can be utilized by intestinal microorganisms such as probiotics such as bifidobacteria and the like. In particular to xylo-oligosaccharide with polymerization degree concentrated in 2-4, the efficacy of the xylo-oligosaccharide is about 20 times of that of other polymeric saccharides, and the xylo-oligosaccharide has stronger inhibition on harmful bacteria, and is functional polymeric sugar with least effective addition amount in the current practical application. Therefore, the oligosaccharide sweetening agent is used for replacing white sugar or other sweetening agents, so that the oligosaccharide sweetening agent not only can selectively promote the proliferation of beneficial bacteria in the intestinal tract, inhibit the growth of harmful bacteria and improve the intestinal micro-ecological environment, but also has various health-care functions of reducing blood cholesterol, enhancing immunity, controlling blood sugar, resisting oxidation and the like. In summary, with the strong development of oligosaccharides in the current international market, it is a matter of great interest and significance to develop new applications in the industries of food, health products, beverages, medicines, feed additives, etc.

The preparation of conventional polysaccharides is mainly based on two techniques, namely acid-catalyzed hydrolysis or enzymatic methods. However, these methods have many drawbacks such as poor product selectivity of the acidolysis method, corrosion of equipment, large amount of inorganic wastewater; the enzymolysis method has long reaction time, expensive hydrolase, strict requirements on operation and storage conditions and the like. The most important problem is that the subsequent complicated separation and purification steps of the target product are involved.

In recent years, a newer production process is a biological enzyme method for preparing xylo-oligosaccharide by using xylan obtained in a specific pretreatment mode as a substrate, such as ZL 200410023875.X and ZL 200410044977.X, and the like, which are used for preparing xylo-oligosaccharide by carrying out enzymolysis on xylan after pretreatment of xylan-rich biomass, but the problems of complex pretreatment process at the early stage, high price of xylanase, complex culture condition requirements of enzyme-producing strains and the like still exist, and a spatial barrier generated by a natural branched chain structure of xylan not only influences the enzymolysis efficiency, but also further influences the quality purity of xylo-oligosaccharide and the like. In view of the defects of the above xylan biological enzyme method, CN 101880298A discloses a preparation method of food-grade xylo-oligosaccharide, the invention uses xylose, edible acid and polyalcohol as raw materials, the prepared xylo-oligosaccharide by-product is less, the complicated separation and purification steps in the later period can be avoided, but the preparation needs to be carried out at high temperature, the reaction conditions are harsh, and the average polymerization degree of the product is relatively high. In addition, CN 107922511 a discloses a new method for sugar polymerization, which prepares oligosaccharide by non-thermal plasma processing polymerization, without catalyst or solid support, and can further control the polymerization degree of product, but the polymerization degree of oligosaccharide produced by the method is generally higher, and the technology is not suitable for large-scale industrial production of product at present.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to solve the technical problem of the prior art and provides a method for preparing oligosaccharide by mechanical self-assembly.

In order to solve the technical problems, the invention discloses a method for preparing oligosaccharide by mechanical self-assembly, which comprises the following steps:

(1) mixing and stirring monosaccharide, an organic solvent and an acid catalyst to uniformly load the acid catalyst on the surface of the monosaccharide;

(2) removing the organic solvent from the material obtained in the step (1) to obtain a solid loaded with the catalyst; grinding the obtained solid in mechanical equipment for self-assembly;

(3) and (3) dissolving the material obtained in the step (2) in water, removing impurities, and drying to obtain oligosaccharide powder.

In the step (1), the monosaccharide is any one or a combination of several of fructose, glucose, mannose, galactose, arabinose, lyxose, rhamnose, xylose, erythrose and threose, preferably any one or a combination of several of xylose, galactose and arabinose, further preferably a combination of xylose, galactose, arabinose, galactose and arabinose, and further preferably a combination of galactose and arabinose in a mass ratio of 1: 1 in the composition of claim 1.

In the step (1), the organic solvent is any one or a combination of several of methyl isobutyl ketone, acetone, ethanol, tert-butyl alcohol, acetonitrile, 1, 4-dioxane, ethyl acetate, dimethyl carbonate, diethyl ether and methyl tert-butyl ether, preferably any one or a combination of several of dimethyl carbonate, ethyl acetate and 1, 4-dioxane, and further preferably any one or a combination of two of dimethyl carbonate and ethyl acetate.

In the step (1), the solid-to-liquid ratio of the monosaccharide to the organic solvent is 1: 5-30g/mL, preferably 1: 10-20 g/mL.

In the step (1), the acidic catalyst is any one or a combination of more of oxalic acid, hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, trifluoroacetic acid and p-toluenesulfonic acid, preferably any one or a combination of two of sulfuric acid and p-toluenesulfonic acid.

In the step (1), the amount of the acidic catalyst is 0.1 to 3mmol/g monosaccharide, preferably 0.7 to 1.4mmol/g monosaccharide, more preferably 0.8 to 1.2mmol/g monosaccharide, and still more preferably 0.9 to 1.2mmol/g monosaccharide.

In the step (1), the stirring is normal temperature stirring.

Wherein the stirring speed is 300-800 r/min.

Wherein the stirring time is 0.5-3h, preferably 0.5-2h, and more preferably 1 h.

In the step (2), the organic solvent removal is carried out by distilling under reduced pressure to remove the organic solvent.

Wherein the temperature of the reduced pressure distillation is 35-45 ℃.

In the step (2), the mechanical equipment is any one of a grinder, a ball mill, a roller mill, a sand mill, a roller mill, a rod mill and a homogenizer, preferably any one of a ball mill, a roller mill and a sand mill.

In the step (2), the types of the mechanical equipment specifically include vibration type, drum type, pin type, planetary type, high speed type, roller disc type, turbine type, flat disc type and the like.

In the step (2), the milling decomposition is intermittent milling decomposition or continuous milling decomposition, and is preferably intermittent milling decomposition.

In the step (2), the self-assembly is completed after the grinding and the decomposition are carried out for 0.5 to 6 hours in a mechanical device, preferably the self-assembly is carried out for 2 to 3 hours in a batch type, and further preferably a batch procedure of 30min of grinding and decomposition and 10min of stop time is carried out.

In the step (3), the device for removing impurities is an ion exchange resin or a nanofiltration membrane, preferably a nanofiltration membrane, and further preferably a nanofiltration membrane with a molecular weight cutoff of 200-1000 Da.

In the step (3), the drying equipment comprises an industrial dryer, a spray dryer, a microwave dryer, a freeze dryer and the like, and is preferably a spray dryer.

Has the advantages that: compared with the prior art, the invention has the following advantages:

1. the method is generally suitable for producing oligosaccharide by polymerization among and in molecules of various monosaccharides, the used raw materials are economical and easy to obtain, no by-product is generated in the process, and the commercial application value of the monosaccharide is further improved.

2. The invention adopts the mechanical self-assembly mode of acid catalytic xylose to prepare oligosaccharide, has short reaction time, no equipment corrosion, low input cost, mild reaction condition and simple post-treatment operation, and is more suitable for industrial production.

3. The oligosaccharide powder obtained by the invention is milk white, the polymerization degree is mainly concentrated at 2-4, and the oligosaccharide powder has excellent health-care activities such as promotion of intestinal bifidobacteria and the like.

Drawings

The foregoing and/or other advantages of the invention will become further apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.

FIG. 1 is a high performance anion exchange chromatogram of xylooligosaccharide obtained by mechanical self-assembly of xylose in example 1.

FIG. 2 is the electrospray ionization mass spectrum of xylo-oligosaccharide obtained by mechanical self-assembly of xylose in example 1; wherein A is an integral electrospray ionization mass spectrogram, and B is a local amplification electrospray ionization mass spectrogram.

FIG. 3 is the electrospray ionization mass spectrum of xylo-oligosaccharide obtained by mechanical self-assembly of glucose in example 21.

FIG. 4 is the electrospray ionization mass spectrum of xylo-oligosaccharide obtained by mechanical self-assembly of galactose in example 22.

FIG. 5 is the electrospray ionization mass spectrum of xylo-oligosaccharide obtained by mechanical self-assembly of arabinose in example 23.

FIG. 6 is the electrospray ionization mass spectrum of xylo-oligosaccharide obtained by mechanical self-assembly of glucose and xylose in example 24.

FIG. 7 is the electrospray ionization mass spectrum of xylooligosaccharide obtained by mechanical self-assembly of galactose and arabinose in example 25.

FIG. 8 is a two-dimensional nuclear magnetic diagram of xylo-oligosaccharide obtained by mechanical self-assembly of xylose in example 1; wherein, R alpha is alpha reducing end of xylo-oligosaccharide, NR is non-reducing end of xylo-oligosaccharide, and R beta is beta reducing end of xylo-oligosaccharide.

Detailed Description

The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.

In the following examples, the degree of polymerization was calculated as follows:

the method comprises the following steps: comparing the standard substance by a high-efficiency anion exchange chromatogram;

the second method comprises the following steps: the electrospray ionization mass spectrum is obtained by calculating according to the mass-to-charge ratio by the following formula;

DP＝(M_m/z-M_Na-M_H2O)/(M_{monosaccharides}-M_H2O)。

Example 1

Uniformly dispersing 100g of xylose in 1500mL of dimethyl carbonate, simultaneously adding 5mL of 98% sulfuric acid, continuously soaking and stirring at normal temperature and 500rpm for 1h, then removing the organic solvent by reduced pressure distillation at 40 ℃ to obtain a solid loaded with a sulfuric acid catalyst, then placing the solid in a planetary ball mill (4 x 250mL of stainless steel ball milling tank), intermittently milling the solid for 2h (30 min per milling and 10min per milling) by adopting 150 stainless steel balls/milling tank (phi 10mm 100 and phi 6mm 50) and 550rpm, dissolving the product by adding 500mL of water after the completion, removing impurities and purifying the aqueous solution by using a nanofiltration membrane, and finally spray-drying the solution to obtain high-purity xylo-oligosaccharide powder with the mass yield of 67%. The two-dimensional nuclear magnetic map of the obtained xylo-oligosaccharide is shown in FIG. 8, and it can be seen that the xylo-oligosaccharide is a polymeric sugar formed by connecting beta-1, 4 glycosidic bonds; the high-efficiency anion exchange chromatogram of the obtained xylooligosaccharide is shown in figure 1, and can be obtained that the main polymerization degree of oligosaccharide is 2-4, the oligosaccharide accounts for 95% of the total oligosaccharide content, and trace pentasaccharide and hexasaccharide (X5 and X6) exist; in addition, according to the electrospray ionization mass spectrogram of FIG. 2, the polymerization degree of the obtained xylooligosaccharide is not only distributed in 2-4, but also pentaglycan (DP)₅) Is present.

DP₂＝(305.0838-22.9898-18.0152)/(150.13-18.0152)＝2.00

DP₃＝(437.1262-22.9898-18.0152)/(150.13-18.0152)＝3.00

DP₄＝(569.1677-22.9898-18.0152)/(150.13-18.0152)＝4.00

DP₅＝(701.2230-22.9898-18.0152)/(150.13-18.0152)＝5.00。

Examples 2 to 6

Only the solvent to be immersed and stirred was changed, and the remaining parameters were the same as in example 1, as shown in Table 1.

TABLE 1

Examples	Impregnating with stirred solvent	Yield/%)	Degree of predominant polymerization
				1	Carbonic acid dimethyl ester	67	2-4
2	Ether (A)	47	2-4
				3	1, 4-dioxane	62	2-4
4	Ethanol	39	2-4
				5	Acetone (II)	30	2-4
6	Ethyl acetate	65	2-4

Examples 7 to 13

The acid catalyst was replaced only and the remaining parameters were the same as in example 1, see table 2.

TABLE 2

Note: the amount of acidic catalyst depends on the H content of the acid⁺(non-free) molar amounts are obtained in equal amounts.

Examples 14 to 16

The same parameters as in example 1 were used except that the acid catalyst was changed to 98% sulfuric acid, which is shown in Table 3.

TABLE 3

Examples	Amount of acidic catalyst	Yield/%)	Degree of predominant polymerization
				1	5mL，0.09mol	67	2-4
14	3.8mL，0.07mol	51	2-4
				15	6.3mL，0.12mol	68	2-4
16	7.5mL，0.14mol	56	2-4

Examples 17 to 19

Only the duration of the milling was changed, and the remaining parameters were the same as in example 1, as shown in Table 4.

TABLE 4

Examples	Milling time/h	Yield/%)	Degree of predominant polymerization
				1	2	67	2-4
17	1	49	2-4
				18	3	70	2-4
19	4	49	2-4

Examples 20 to 26

The monosaccharides alone were different and the remaining parameters were the same as in example 1, see table 5.

TABLE 5

In which electrospray ionization mass spectra of oligosaccharides prepared in examples 21 to 25 are shown in FIGS. 3 to 7, respectively.

Examples 27 to 30

The mechanical equipment only differs, and the remaining parameters are the same as in example 1, see table 6.

TABLE 6

Examples	Mechanical equipment	Yield/%)	Degree of predominant polymerization
				1	Planetary ball mill	67	2-4
27	Rod pin type sand mill	63	2-4
				28	High-speed homogenizer	45	2-4
29	Disc type mill	60	2-4
				30	Turbine type grinder	57	2-4

Note: the processes for preparing xylo-oligosaccharides using the apparatus described in examples 27 to 30 all employ conventional production parameters.

The present invention provides a method and a concept for preparing oligosaccharides by mechanical self-assembly, and a method and a way for implementing the technical scheme are numerous, and the above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention. All the components not specified in the present embodiment can be realized by the prior art.