CN114014896B - Separation and purification method of high-purity 3' -sialyllactose - Google Patents

Abstract

The application belongs to the field of separation and purification of sialyllactose, and in particular relates to a separation and purification method of high-purity 3 '-sialyllactose, which comprises the steps of heating a conversion solution, inactivating enzyme, filtering, adjusting the pH value of filtrate to be alkaline, filtering, adjusting the pH value of the filtrate to be neutral, concentrating, ion adsorbing, drying and the like to obtain separated and purified 3' -SL; the application comprehensively improves the removal rate of macromolecular substances such as proteins in the conversion liquid by adopting two modes of heating to inactivate enzyme and adjusting pH to alkalinity, simultaneously controls the concentration of 3' -SL in the concentrated liquid, has an important effect on further improving the purity of the product 3' -SL by anion-cation adsorption purification, and ensures that the purity of the product 3' -SL obtained by the method is more than or equal to 96 percent.

Description

Separation and purification method of high-purity 3' -sialyllactose

Technical Field

The application belongs to the field of separation and purification of sialyllactose, and in particular relates to a separation and purification method of high-purity 3' -sialyllactose.

Background

Human Milk Oligosaccharides (HMOS) are the third most abundant component of human milk after lactose and fat, and have important biological functions. Sialyloligosaccharide (SL) is an acidic human milk oligosaccharide, and can be classified into 3' -sialyllactose (3 ' -SL) and 6' -sialyllactose (6 ' -SL) according to the position of sialic acid binding to lactose moiety, and the prior studies have shown that 3' -SL has an important role in infants, including neutralizing toxins produced by intestinal bacteria, preventing bacteria or viruses from adhering to the surface of intestinal epithelium, and the like. Although 3'-SL has important biological functions, the method for producing and purifying 3' -SL with low cost substrate is still lack of economical and efficient industrial production methods, so that the method for producing and purifying 3'-SL has important significance for popularization and application of 3' -SL.

The existing method for preparing sialyllactose is as the application number CN201910787973.7, the patent name is a method for preparing sialyllactose, the application adopts a single-bacterium multienzyme method to combine a one-step purification and immobilization method to fix multienzyme, CTP regeneration and multienzyme recycling in the preparation process of sialyllactose by a one-pot method are realized, the method has the advantages of high yield, low cost, short period and the like, but the purity of 3' -SL prepared by the method needs to be further improved, so the application develops a method for further separating and purifying 3' -SL in the conversion liquid based on the multienzyme catalysis to further improve the purity of the product 3' -SL.

Disclosure of Invention

Aiming at the problems existing in the prior art, the application aims to provide a separation and purification method of high-purity 3' -sialyllactose, which is used for further separating and purifying 3' -SL in a multi-enzyme catalyzed conversion solution, wherein the purity of the 3' -SL separated and purified by the method is not lower than 96%.

Based on the above purpose, the technical scheme adopted by the application is as follows:

a method for separating and purifying high-purity 3' -sialyllactose comprises the following steps:

s1: heating and inactivating enzyme of the conversion solution, filtering with a filter membrane of 30-100 nm, and collecting filtrate;

s2: regulating the pH value of the filtrate collected in the step S1 to be alkaline, filtering through a 3000 Da-5000 Da membrane, and collecting the filtrate;

s3: regulating the pH value of the filtrate collected in the step S2 to be neutral, filtering and concentrating through a membrane of 800Da to 1000Da, and collecting concentrate on the membrane;

s4: and (3) adsorbing the concentrated solution on the membrane obtained in the step (S3) by anion-cation exchange resin, concentrating and drying to obtain the 3' -SL.

According to the application, the conversion solution is subjected to heating enzyme deactivation treatment in the step S1, so that proteins such as enzymes and thalli and other large-particle impurities in the conversion solution are heated, precipitated and separated out, and filtered by a filter membrane with the diameter of 30-100 nm, so that the thalli, the large-particle impurities and the separated proteins such as enzymes in the conversion solution are effectively removed, and when the pore diameter of the filter membrane exceeds the range, the thalli is incompletely removed, and the product purity is low.

In the step S2, the pH of the filtrate is regulated to be alkaline, so that the pH of the filtrate reaches the isoelectric point of the residual protein in the conversion liquid, the protein is further promoted to be precipitated, and the protein in the conversion liquid is further removed by filtering through a 3000 Da-5000 Da membrane. The membrane of 3000 Da-5000 Da is selected for filtering and impurity removing, because the molecular weight of 3'-SL is less than 3000Da, the 3' -SL can pass through the membrane to enter filtrate during filtering, and the impurity is trapped in the membrane. When the molecular weight of the membrane exceeds the range of 3000Da to 5000Da, macromolecular impurities and the target 3' -SL permeate through the organic membrane together, and the aim of separating the target and the impurities cannot be achieved.

Then in step S3, the pH of the filtrate is adjusted to be neutral, and the filtrate is filtered and concentrated by using a 800 Da-1000 Da membrane, and the obtained concentrated solution is adsorbed by anion-cation exchange resin, concentrated and dried to prepare the 3' -SL. Also, when the molecular weight of the organic film exceeds the range of 800Da to 1000Da, small molecular impurities such as lactose, glycerol, sialic acid, etc. cannot be separated from the target 3'-SL, so that the purity of the 3' -SL is difficult to further improve.

In the process of removing impurities and purifying through the film of the application S1-S3, the film passing sequence is carried out according to the particle size of impurities in the conversion liquid, firstly, macroscopic impurities with large particle size are removed by filtration, then, some residual proteins are removed, finally, lactose, glycerol, sialic acid and parts smaller than the target substances are removed, the film passing sequence is tried to be replaced or part of film passing procedures are omitted in the actual operation process, the film passing efficiency is greatly reduced due to the fact that the film blocking is extremely easy to occur after the film passing sequence is found, and the purity of the final product can not reach the prior level after part of film passing procedures are omitted.

In addition, the experiment shows that the effective removal of protein in the conversion liquid has an important effect on further improving the purity of the product 3' -SL, and the heat denaturation precipitation mode is generally adopted to remove the protein due to the complexity of components in the conversion liquid.

Further, in the step S2, the pH of the filtrate collected in the step S1 is adjusted to 10-12.

Since the components in the conversion solution are complicated, the type of the protein therein is difficult to be known, and the isoelectric point thereof is determined, and the application carries out protein precipitation tests by respectively adjusting the pH of the filtrate collected in the step S1 to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12, and as a result, it is found that when the pH of the filtrate is below 8, no precipitation occurs, and when the pH=9, a small amount of precipitation occurs, and when the pH is 10 to 12, a large amount of precipitation occurs. Therefore, the pH of the filtrate collected in step S1 is optionally adjusted to 10 to 12.

Further, in step S2, the ph=10 of the filtrate collected in step S1 is adjusted.

Since the preliminary test has proved that a large amount of precipitate is precipitated when the pH of the filtrate collected in step S1 is adjusted to 10, since the alkali in the filtrate needs to be neutralized by acid in the later stage, if the pH is adjusted too high in the earlier stage, the salt amount formed by the subsequent neutralization of the acid and the alkali is too large, the pressure of the subsequent desalination is increased, and even the purity of the target product is reduced, so that it is preferable to control the ph=10 of the filtrate collected in step S1.

Further, the concentration of 3' -SL in the concentrated solution on the membrane in the step S3 is 10-30 g/L.

Experiments show that the concentration of 3'-SL in the concentrated solution has important influence on the adsorption and purification process of anion-cation exchange resin and the purity of 3' -SL as an end product, when the concentration of 3'-SL in the concentrated solution is higher than 30g/L, the concentration of 3' -SL in the concentrated solution not only causes the loss of resin, but also causes poor desalting effect, and a large amount of salt residues influence the yield and purity of the product, so that the yield of the product is reduced to 85 percent and the purity is not higher than 90 percent; when the concentration of 3' -SL in the concentrated solution is lower than 10g/L, the treatment system of the anion-cation exchange resin is enlarged, and the treatment efficiency is greatly reduced; when the concentration of 3'-SL in the concentrated solution is 10-30 g/L, the yield of the product 3' -SL is not lower than 91%, and the purity of the 3'-SL is not lower than 96%, so that the concentration of the 3' -SL in the concentrated solution on the membrane in the step S3 is adjusted to be 10-30 g/L, and simultaneously, higher yield and higher purity of the product can be obtained.

Further, the method for heating and inactivating enzyme of the conversion solution in the step S1 is as follows: heating the conversion solution at 80-100 ℃ for 8-15 min.

Further, the purity of the 3' -SL prepared by purification and drying of the steps S1-S4 is more than or equal to 96 percent.

Compared with the prior art, the application has the following beneficial effects:

the application carries out heating enzyme deactivation and filtration on the conversion liquid, adjusts the pH value of the filtrate to be alkaline, then filters the filtrate, adjusts the pH value of the filtrate to be neutral, carries out concentration, ion adsorption and drying treatment to obtain purified 3' -SL.

Drawings

FIG. 1 is a schematic diagram of the process flow of the present application.

Detailed Description

For a better description of the objects, technical solutions and advantages of the present application, the present application will be further described with reference to the following specific examples. It will be appreciated by persons skilled in the art that the specific embodiments described herein are for purposes of illustration only and are not intended to be limiting.

The test methods used in the examples are conventional methods unless otherwise specified; the materials, reagents and the like used, unless otherwise specified, are all commercially available. The conversion solution used in the present application is derived from a conversion solution prepared by a method described in the method for preparing sialyllactose under the patent name of CN 201910787973.7.

Example 1

The embodiment provides a method for separating and purifying high-purity 3' -sialyllactose, which is shown in fig. 1 and comprises the following steps:

s1: heating the conversion solution at 90 ℃ for 10min, inactivating the activity of enzymes in the conversion solution, promoting the denaturation and precipitation of proteins, promoting the denaturation and precipitation of thalli, large-particle impurities and non-enzyme proteins in the conversion solution, filtering and removing the precipitates by using a 30nm ceramic filter membrane, adding water with the minimum circulation volume of 2 times of the ceramic membrane to further circulate the membrane for filtering after reaching the minimum circulation volume of the ceramic membrane, and further removing the precipitated precipitates to obtain clear liquid containing 3'-SL, wherein the yield of the 3' -SL in the conversion solution is as high as 95%.

S2: adding alkali into the clear liquid collected in the step S1, regulating the pH value of the clear liquid to be=10, promoting proteins in the clear liquid such as CMP kinase, polyphosphate kinase, CMP-sialic acid synthetase and other impurity proteins released by cell disruption to reach isoelectric points thereof to gather and precipitate, filtering by using a 3000Da organic membrane to remove protein precipitates and macromolecular impurities such as sodium hexametaphosphate, and in the step, adding water with the volume of 4-6 times of the initial membrane to the filtering system to perform circulating membrane filtration, collecting filtrate, and effectively removing macromolecular substances such as sodium hexametaphosphate in the clear liquid.

In the process of adjusting the pH of the clear liquid collected in the step S1, the inventor finds that the pH of the clear liquid is below 8 and no precipitate is separated out by respectively adjusting the pH of the clear liquid collected in the step S1 to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 because the components in the clear liquid are complex and the types of the proteins in the clear liquid are difficult to be determined so as to determine the isoelectric point of the proteins; when ph=9, a small amount of precipitate is precipitated, and when pH is 10-12, a large amount of precipitate is precipitated, so that the pH of the clear liquid collected in step S1 is adjusted to 10-12, a large amount of protein impurities can be further removed, and in order to avoid excessive neutralization and salification of subsequent acid and alkali caused by excessive pH, pressure and poor desalting effect of subsequent desalting are further caused, and the purity of the target product is reduced, so that the pH of the clear liquid collected in step S1 is adjusted to 10 more conveniently.

S3: adding acid into the filtrate obtained in the step S2 to adjust the pH of the filtrate to be neutral, filtering and removing impurities through a 1000Da organic membrane, concentrating, and collecting concentrated solution on the membrane, wherein the filtering and removing impurities mainly refers to removing substances such as salt, magnesium chloride heptahydrate, sialic acid and the like. In the step, water which is 5-10 times of the initial membrane passing volume is added into a filtering system for circulating membrane filtration, concentrated solution on the membrane is collected, and the concentration of 3'-SL in the concentrated solution on the membrane is detected in real time by utilizing high performance liquid chromatography until the concentration of 3' -SL in the concentrated solution on the membrane is 10-30 g/L, and the circulating membrane filtration concentration is stopped.

S4: deeply desalting the concentrated solution obtained in the step S3 by utilizing a method of anion-cation exchange: firstly, the cation resin is utilized for adsorption and purification, then the anion is utilized for adsorption and purification to further remove salt substances in the concentrated solution, and the conductivity in the conversion solution can be reduced by about 90 percent through anion-cation exchange desalination. And concentrating and drying (freeze-drying or spray-drying) the desalted liquid to obtain 3'-SL, wherein the purity of the 3' -SL obtained by separation after the treatment of the steps S1-S4 is not lower than 96%.

Experiments show that the concentration of 3'-SL in the concentrated solution obtained in the step S3 has important influence on the adsorption and purification process of anion-cation exchange resin and the purity of 3' -SL as an end product, when the concentration of 3'-SL in the concentrated solution is higher than 30g/L, the concentration of 3' -SL in the concentrated solution not only can cause the loss of resin, but also has poor desalting effect, so that a large amount of salt residues influence the yield and purity of the product, and the yield of the product is reduced to 85 percent, and the purity is not higher than 90 percent; when the concentration of 3' -SL in the concentrated solution is lower than 10g/L, the treatment system of the anion-cation exchange resin is enlarged, and the treatment efficiency is greatly reduced; when the concentration of 3'-SL in the concentrated solution is 10-30 g/L, the yield of the product 3' -SL is not lower than 91%, and the purity of the 3'-SL is not lower than 96%, so that the concentration of the 3' -SL in the concentrated solution on the membrane in the step S3 is controlled to be 10-30 g/L, and higher yield and higher purity of the product can be obtained.

Example 2

The embodiment provides a separation and purification method of high-purity 3' -sialyllactose, which comprises the following steps:

s1: heating the 3' -SL conversion solution at 90 ℃ for 10min, inactivating the activity of enzymes in the conversion system, and enabling heat-sensitive proteins to be denatured, precipitated and separated out; filtering the heated conversion solution by a 30nm ceramic membrane to remove thalli, large-particle impurities and precipitated impurity proteins, obtaining clear liquid containing 3' -SL, and adding water for dialysis until the yield is not lower than 95%.

S2: adding alkali into the 3' -SL clear liquid to adjust the pH value to 10, causing the unheated denatured protein to settle at isoelectric point, then filtering by 3000D organic membrane, further removing settled protein and some soluble macromolecular impurities (such as sodium hexametaphosphate in a conversion system), and adding water for dialysis until the yield is not lower than 90%.

S3: and (3) adding acid into the clear solution which passes through the 3000D membrane to adjust the pH value to 7, then passing through the 1000D organic membrane to remove monovalent salt and micromolecular impurities in the clear solution, adding water to dialyze until the conductivity of the concentrated solution is not changed, and collecting the membrane supernatant, wherein the concentration of 3' -SL in the membrane supernatant is in the range of 10-30 g/L.

S4: then further desalting the membrane supernatant by using ion exchange resin; adding 0.1% active carbon into the desalted clear liquid for decoloring, and concentrating and spray drying to obtain 3' -SL with the purity of 98%.

Comparative example 1

The 3'-SL was isolated and purified by the method described in example 2, and this comparative example was different from example 2 only in that the "pH of the 3' -SL supernatant was adjusted to 10" by adding alkali and the "pH of the supernatant after having been collected by membrane 3000D was adjusted to 7" in the steps S2 and S3 were not subjected to the treatment process, and the rest of the steps were the same as in example 2.

The purity of 3' -SL obtained by separation and purification by the method described in this comparative example was 95%.

Comparative example 2

With reference to the method described in example 2, this comparative example differs from example 2 only in that step S1 is not subjected to the "heating of the 3' -SL conversion at 90℃for 10min" treatment, and the remaining steps are the same as in example 2.

The purity of 3' -SL obtained by separation and purification by the method described in this comparative example was 80%.

Comparative example 3

With reference to the method described in example 2, this comparative example differs from example 2 only in that the "heating the 3'-SL conversion solution at 90℃for 10min" treatment process was not performed in step S1, while the "adjusting the pH of the 3' -SL supernatant to 10 by adding alkali" and the "adjusting the pH of the supernatant after collection of 3000D film to 7" treatment process was not performed in step S2 and step S3, and the remaining steps were the same as in example 2.

The purity of 3' -SL obtained by separation and purification by the method described in this comparative example was 60%.

As is clear from comparison of the results of example 2, comparative example 1, comparative example 2 and comparative example 3, the present application comprehensively improves the purity of 3' -SL obtained by final separation by heat-treating the conversion solution and adjusting pH despite the complicated components in the conversion solution.

Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present application and not for limiting the scope of the present application, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present application may be modified or substituted equally without departing from the spirit and scope of the technical solution of the present application.

Claims (3)

1. The method for separating and purifying the high-purity 3' -sialyllactose is characterized by comprising the following steps of:

s1: heating and inactivating enzyme of the conversion solution, filtering with a filter membrane of 30-100 nm, and collecting filtrate; the method for heating and inactivating enzyme of the conversion solution in the step S1 comprises the following steps: heating the conversion solution at 80-100 ℃ for 8-15 min;

s2: regulating the pH value of the filtrate collected in the step S1 to be alkaline, filtering through a 3000 Da-5000 Da membrane, and collecting the filtrate; in the step S2, the pH value of the filtrate collected in the step S1 is regulated to 10-12;

s3: regulating the pH value of the filtrate collected in the step S2 to be neutral, filtering and concentrating through a membrane of 800Da to 1000Da, and collecting concentrate on the membrane; the concentration of 3' -SL in the concentrated solution on the membrane in the step S3 is 10-30 g/L;

s4: and (3) adsorbing the concentrated solution on the membrane obtained in the step (S3) by anion-cation exchange resin, concentrating and drying to obtain the 3' -SL.

2. The method according to claim 1, wherein in step S2 the ph=10 of the filtrate collected in step S1 is adjusted.

3. The process according to claim 1 or 2, wherein the purity of the 3' -SL obtained in steps S1 to S4 is not less than 96%.