A method for extracting bovine colostrum immunoglobulin

Abstract

The present application relates to the technical field of protein separation and purification, and specifically discloses a method for extracting bovine colostrum immunoglobulin. The method comprises the following steps: centrifugal degreasing: degreasing the bovine colostrum by centrifugation, followed by filtering the intermediate layer to obtain colostrum whey; ammonium sulfate salting out: diluting the colostrum whey, then adding a saturated ammonium sulfate solution, stirring, standing, centrifuging, removing the supernatant A, adding phosphate buffer to the precipitate A, stirring evenly, adding a saturated ammonium sulfate solution, standing, centrifuging, removing the precipitate B, adding a saturated ammonium sulfate solution to the supernatant B, centrifuging, removing the supernatant C, and obtaining the precipitate C; and purification: desalting the precipitate C using a gel column, concentrating it by ultrafiltration, and separating it by column chromatography to obtain the bovine colostrum immunoglobulin.

Description

Technical Field

[0001] The present application relates to the technical field of protein separation and purification, and in particular to a method for extracting bovine colostrum immunoglobulin. Background Art

[0002] Bovine colostrum generally refers to the milk secreted by dairy cows within seven days, and particularly within three days, after giving birth. In contrast to colostrum, the milk secreted over the next 300 days is called normal milk or cow's milk. Bovine colostrum not only contains the nutrients found in normal milk, such as protein, fat, lactose, fatty acids, amino acids, and minerals, but is also rich in a variety of physiologically active factors, including immunoglobulins, lactoferrin, growth factors, cytokines, lactoperoxidase, and lysozyme. Immunoglobulins are the most important type of immune factor, primarily IgG, IgM, and secretory IgA, with secretory IgA also known as SIgA.

[0003] SIgA is a major immune antibody discovered in exocrine fluids in the early 1960s. It is mainly found in breast milk, gastrointestinal tract and respiratory tract exocrine fluids. It is the first immune barrier to prevent pathogens such as bacteria and viruses from invading the body in the respiratory tract, digestive tract, urogenital tract, etc. It is the most important antibody for human mucosal immunity. The surface area of ​​human mucosa is about 400m 2 The mucosa is the primary barrier separating the body's internal environment from the outside world. It is exposed to a wide variety of pathogens and serves as a gateway for pathogenic microorganisms to invade the body. SIgA is the most important humoral immune molecule secreted by the mucosa, accounting for 80% of the total mucosal immunoglobulin. It is the most important mucosal protective antibody and plays a vital role in resisting infection in the respiratory and gastrointestinal tracts.

[0004] There are two types of IgA: serum type and secretory type. The serum type is mainly composed of IgA monomers, and the secretory type SIgA is composed of two IgA monomers, which are connected by J chains and secretory segments. Its molecular weight is about

[0005] The secretory fragment is 390 kDa and is named SIgA to distinguish it from serum IgA monomer. The secretory fragment not only increases SIgA's stability but also protects it from hydrolytic enzymes in the secretions, preventing it from being degraded by proteases, gastric acid, and digestive enzymes in the respiratory and digestive tracts. This allows SIgA to exert a powerful anti-infective effect in the gastrointestinal tract. Studies have shown that SIgA can block the attachment of avian influenza viruses, whereas single-chain IgA and IgG do not.

[0006] SIgA, distributed on mucosal surfaces, is a crucial bioactive component of these mucosal surfaces that protects against viruses, pathogens, and toxins. It serves as the body's first line of immune defense against infection. SlgA possesses both immune barrier and immune clearance functions. It blocks specific sites on bacterial surfaces where they bind to intestinal epithelial cells, preventing pathogens and toxins from reaching the mucosal epithelium and from colonizing and invading the mucosal epithelium in the digestive and respiratory tracts, thereby protecting the respiratory and digestive tracts. Furthermore, SlgA specifically binds to viruses, toxins, and pathogens on mucosal surfaces, depriving them of their ability to adhere and thus preventing their invasion. It also forms immune complexes with antigens from viruses, bacteria, and microbial pathogens. These complexes are blocked by mucosal barriers or excreted through secretions such as sputum and feces, protecting the body's health. However, IgG and monomeric IgA cannot form immune complexes and therefore cannot eliminate pathogens. SIgA can prevent enteroaggregative Escherichia coli from adhering to cells, thus preventing persistent diarrhea in neonates. The significant decrease in the incidence of gastroenteritis, diarrhea, otitis media, neonatal sepsis, and allergies in breastfed infants and young children is attributed to the significant role played by the abundant SIgA in colostrum. The protective effects of SIgA against infection have been confirmed in numerous clinical and research studies, and its use in preventing respiratory and digestive tract diseases has been widely reported both domestically and internationally.

[0007] Compared to conventional non-secretory antibodies, SIgA is used directly and locally for respiratory and digestive tract immunization. It is convenient to use, requires a small dosage, and does not require bloodstream entry, making it ideal for emergency production and preparation under specific conditions. Unlike other immunoglobulins, SIgA does not activate complement and, therefore, does not cause inflammation or allergic reactions. Instead, it directly prevents the adherence of pathogens to the epithelium, achieving a localized anti-infective effect. Furthermore, SIgA is highly stable, with a half-life on mucosal surfaces three times that of IgG, and its protective effect in the human exocrine tract can last for over four months. Therefore, developing a highly effective, non-toxic SLgA formulation that effectively neutralizes viruses and prevents viral and bacterial adhesion could open up a new, non-antibiotic approach for the prevention and treatment of respiratory and digestive tract diseases caused by viral and bacterial pathogens.

[0008] The most significant difference in immunoglobulin composition between bovine colostrum and human colostrum lies in the SLgA content. In human colostrum, SLgA predominates, accounting for over 90% of the total Ig content. The average SIgA content is approximately 6-40 mg / ml. In contrast, IgG accounts for 80-90% of the total Ig content in bovine colostrum, while SLgA accounts for approximately 5%. The SIgA content in bovine colostrum is typically around 3.2-6.2 mg / ml, 50-100 times that of normal milk. Therefore, some researchers believe that adding SLgA to bovine colostrum can increase the SLgA content and thus enhance breast milk-like properties. Currently, there is no commercially available information on highly purified SIgA derived from bovine colostrum, either domestically or internationally. This is likely due to the much lower SIgA content in bovine colostrum compared to human colostrum. Furthermore, bovine colostrum contains a large amount of IgG dimers with similar physical and chemical properties to SIgA, making the preparation of highly purified SIgA extremely difficult. Furthermore, the chemical composition of bovine colostrum is much more complex than that of bovine serum, making SIgA purification even more challenging. Therefore, currently there are only high-purity LgG derived from bovine serum and high-purity SLgA derived from human colostrum products available at home and abroad, but there is no sales information for high-purity SIgA derived from bovine colostrum.

[0009] The challenge in preparing high-purity SIgA from bovine colostrum lies in removing the large amount of IgG dimers, which have similar properties to SIgA, to improve its purity. To date, SIgA purification methods primarily include ion exchange and molecular sieve methods, followed by affinity chromatography, thiophilic chromatography, ultrafiltration, and enzymatic hydrolysis. However, due to the complex structure of SIgA, it is difficult to purify it with a single method. Consequently, SIgA preparation typically relies on a combination of purification methods. While SIgA can be extracted, the resulting product purity is generally around 90%. Summary of the Invention

[0010] In order to improve the purity of the prepared immunoglobulin product, the present application provides a method for extracting bovine colostrum immunoglobulin.

[0011] The present application provides a method for extracting bovine colostrum immunoglobulin, which adopts the following technical solution:

[0012] A method for extracting bovine colostrum immunoglobulin comprises the following steps:

[0013] Centrifugal degreasing: The bovine colostrum is degreased by centrifugation, and then the middle layer is filtered to obtain colostrum whey;

[0014] Ammonium sulfate salting out: dilute the colostrum whey, then add saturated ammonium sulfate solution, stir, let stand, centrifuge, remove the supernatant A, add phosphate buffer to the precipitate A, stir evenly, add saturated ammonium sulfate solution, let stand, centrifuge, remove the precipitate B, add saturated ammonium sulfate solution to the supernatant B, centrifuge, remove the supernatant C, and obtain precipitate C; purification: desalt the precipitate C on a gel column, concentrate it by ultrafiltration, and separate it by column chromatography to obtain bovine colostrum immunoglobulin.

[0015] By adopting the above technical solution, bovine colostrum is first centrifuged and defatted, and then the middle layer is filtered to remove the bottom cell sediment and the upper fat layer to obtain colostrum whey; then the colostrum whey is salted out three times to obtain precipitate C, and finally the precipitate C is purified to obtain immunoglobulins with higher purity.

[0016] In a specific embodiment, in the centrifugal defatting step, the bovine colostrum is centrifuged and defatted, and then the middle layer is filtered to obtain a filtrate; rennet is added to the filtrate, stirred evenly, and coagulated at a constant temperature of 30-40°C, followed by centrifugation, and the upper clear layer is filtered to obtain colostrum whey.

[0017] By adopting the above technical solution, chymosin is added to the filtrate, which facilitates the formation of colostrum whey, thereby improving the purity of the prepared immunoglobulin.

[0018] In a specific embodiment, the weight ratio of the chymosin to the filtrate is 1:(300-350).

[0019] By adopting the above technical solution, the present application further defines the ratio of chymosin to filtrate, thereby further improving the purity of the prepared immunoglobulin.

[0020] In a specific embodiment, in the ammonium sulfate salting out step, the colostrum whey is diluted, and then a saturated ammonium sulfate solution is added and stirred to obtain a mixed solution, and the saturation of the mixed solution is made to be 45%-55%. The mixture is allowed to stand and centrifuged, and the supernatant A is removed. A phosphate buffer is added to the precipitate A, and the mixture is stirred evenly. Then, a saturated ammonium sulfate solution is added, and the mixture is allowed to stand and centrifuged to remove the precipitate B. A saturated ammonium sulfate solution is added to the supernatant B, and the mixture is centrifuged. The supernatant C is removed to obtain a precipitate C.

[0021] By adopting the above technical solution, the saturation of the mixed solution is limited when the saturated ammonium sulfate solution is added for the first time, thereby further improving the purity of the prepared immunoglobulin.

[0022] In a specific embodiment, in the ammonium sulfate salting out step, the colostrum whey is diluted, and then a saturated ammonium sulfate solution is added and stirred to obtain a mixed solution, and the saturation of the mixed solution is made to be 45%-55%. The mixed solution is allowed to stand at 0-6°C for 3-18 hours, centrifuged, and the supernatant A is removed. A phosphate buffer is added to the precipitate A, stirred evenly, and then a saturated ammonium sulfate solution is added. The mixture is allowed to stand and centrifuged to remove the precipitate B. A saturated ammonium sulfate solution is added to the supernatant B, centrifuged, and the supernatant C is removed to obtain a precipitate C.

[0023] In a specific embodiment, the volume ratio of the colostrum whey to the phosphate buffer is 1:(0.8-1.2).

[0024] By adopting the above technical solution, the present application further defines the ratio of colostrum whey to phosphate buffer, thereby improving the extraction effect of immunoglobulins.

[0025] In a specific embodiment, in the ammonium sulfate salting-out step, phosphate buffer is added to precipitate A, stirred evenly, and then a saturated ammonium sulfate solution is added to make the saturation of the mixed solution 35%-45%, and the mixture is allowed to stand and centrifuged to remove precipitate B. Saturated ammonium sulfate solution is added to the supernatant B, centrifuged, and the supernatant C is removed to obtain precipitate C.

[0026] In a specific embodiment, in the ammonium sulfate salting-out step, a saturated ammonium sulfate solution is added to the supernatant B so that the saturation of the supernatant B is 30%-40%, and the supernatant C is removed by centrifugation to obtain a precipitate C.

[0027] By adopting the above technical solution, the present application further limits the saturation of the mixed solution when adding the saturated ammonium sulfate solution twice, thereby further improving the purity of the prepared immunoglobulin.

[0028] In summary, this application includes at least one of the following beneficial technical effects:

[0029] 1. In this application, bovine colostrum is first centrifuged and defatted, and then the middle layer is filtered to remove the bottom cell sediment and the upper fat layer to obtain colostrum whey; then the colostrum whey is salted out three times to obtain precipitate C, and finally the precipitate C is purified to obtain immunoglobulins with higher purity;

[0030] 2. In the present application, rennet is added to the filtrate to facilitate the formation of colostrum whey, thereby improving the purity of the immunoglobulin obtained; 3. In the present application, the saturation of the mixed solution is limited when the saturated ammonium sulfate solution is added for the first time, thereby further improving the purity of the immunoglobulin obtained. DETAILED DESCRIPTION

[0031] The present application is further described in detail below with reference to the embodiments.

[0032] All raw materials in the examples can be obtained commercially, among which chymosin was provided by Tai'an Jiangzhou Biotechnology Co., Ltd.

[0033] Example

[0034] Example 1

[0035] Example 1 provides a method for extracting bovine colostrum immunoglobulin, comprising the following steps:

[0036] Centrifugal degreasing: Add bovine colostrum into a centrifuge and centrifuge at 4°C, 4000 r / min for 30 minutes to remove the bottom sediment and the upper fat layer to obtain the middle layer. Filter the middle layer through 8 layers of gauze to obtain colostrum whey.

[0037] Ammonium sulfate salting out: dilute the colostrum whey with physiological saline to make the concentration of colostrum whey become 1 / 2 of the original, then add saturated ammonium sulfate solution, stirring while adding to obtain a mixed solution, and make the saturation of the mixed solution 45%, let it stand at 4°C for 6 hours, then centrifuge at 4°C, 4000r / min for 15 minutes, remove the supernatant A, add phosphate buffer to the precipitate A, stir evenly to dissolve the precipitate A, and then add saturated ammonium sulfate solution to make the saturation of the mixed solution 35%, let it stand at 4°C for 6 hours, centrifuge at 4°C, 4000r / min for 15 minutes, remove the precipitate B, add saturated ammonium sulfate solution to the supernatant B, make the saturation of the supernatant B 30%, let it stand at 4°C, The mixture was centrifuged at 4000 r / min for 15 min, and the supernatant C was removed to obtain precipitate C; wherein the pH of the saturated ammonium sulfate solution was 7, the pH of the phosphate buffer was 7.4, and the volume ratio of the colostrum whey to the phosphate buffer was 1:0.6.

[0038] Purification: Precipitate C was fully dissolved with phosphate buffer, centrifuged at 10,000 r / min for 10 minutes, the supernatant was added to a dextran gel column for desalting, eluted with PBS buffer, and the protein peak containing SIgA was collected; the protein peak containing SIgA was ultrafiltered and concentrated using an ultrafiltration membrane with a molecular weight cutoff of 100,000 kDa, and supplemented with PBS buffer, with the added PBS buffer being 8 times the volume of the mixed solution in the dextran gel column, and ultrafiltration and concentration was completed to a volume of 25 ml to obtain an ultrafiltration concentrate; saturated ammonium sulfate solution was added to the ultrafiltration concentrate to make the saturation of the mixed solution 35%. The mixture was allowed to stand at 4°C for 8 hours, then centrifuged at 10,000 rpm for 10 minutes. The precipitate was fully dissolved with PBS buffer, followed by centrifugation at 10,000 rpm for 10 minutes. The supernatant was added to a polyacrylamide sepharose column for desalting and eluted with PBS buffer, collecting 4 ml per tube at a flow rate of 0.8 ml / min. Two protein peaks were collected, combined, and equilibrated with buffer dialyzate to obtain a dialysate. The dialysate was added to a sepharose column at a rate of 1 ml / min, and two breakthrough peaks were collected. After combining the two breakthrough peaks, a saturated ammonium sulfate solution was added to bring the saturation of the mixture to 35%. The mixture was allowed to stand at 4°C for 12 hours, followed by centrifugation at 10,000 rpm for 10 minutes. PBS buffer was added to the precipitate to dissolve the precipitate, which was then added to an ultrasensitive sepharose column and eluted at a rate of 1 ml / min to collect the second elution peak, which was bovine colostrum immunoglobulin.

[0039] Example 2

[0040] The difference between Example 2 and Example 1 is that in the centrifugal defatting step, bovine colostrum is added to a centrifuge and centrifuged at 4°C and 4000 r / min for 30 minutes to remove the bottom sediment and the upper fat layer to obtain an intermediate layer. The intermediate layer is filtered through 8 layers of gauze to obtain a filtrate, rennet is added to the filtrate, stirred evenly, and coagulated at a constant temperature of 35°C. Subsequently, the mixture is centrifuged at 4°C and 4000 r / min for 30 minutes, and the upper clear layer is filtered through gauze to obtain colostrum whey; wherein the weight ratio of rennet to filtrate is 1:275; and the remaining steps are consistent with Example 1.

[0041] Example 3

[0042] The difference between Example 3 and Example 2 is that in the centrifugal defatting step, the weight ratio of rennet to filtrate is 1:300; the remaining steps are consistent with Example 2.

[0043] Example 4

[0044] The difference between Example 4 and Example 2 is that in the centrifugal defatting step, the weight ratio of rennet to filtrate is 1:325; the remaining steps are consistent with Example 2.

[0045] Example 5

[0046] The difference between Example 5 and Example 2 is that in the centrifugal defatting step, the weight ratio of rennet to filtrate is 1:350; the other steps are consistent with Example 2.

[0047] Example 6

[0048] The difference between Example 6 and Example 2 is that in the centrifugal defatting step, the weight ratio of rennet to filtrate is 1:375; the remaining steps are consistent with Example 2.

[0049] Example 7

[0050] The difference between Example 7 and Example 4 is that in the ammonium sulfate salting-out step, the colostrum whey is diluted with physiological saline to reduce the concentration of the colostrum whey to 1 / 2 of the original concentration, and then a saturated ammonium sulfate solution is added while stirring to obtain a mixed solution, and the saturation of the mixed solution is 50%; the remaining steps are consistent with Example 4.

[0051] Example 8

[0052] The difference between Example 8 and Example 4 is that in the ammonium sulfate salting-out step, the colostrum whey is diluted with physiological saline so that the concentration of the colostrum whey becomes 1 / 2 of the original concentration, and then a saturated ammonium sulfate solution is added while stirring to obtain a mixed solution, and the saturation of the mixed solution is 55%; the remaining steps are consistent with Example 4.

[0053] Example 9

[0054] The difference between Example 9 and Example 7 is that in the ammonium sulfate salting-out step, the volume ratio of colostrum whey to phosphate buffer is 1:0.8, and the remaining steps are consistent with Example 7.

[0055] Example 10

[0056] The difference between Example 10 and Example 7 is that in the ammonium sulfate salting-out step, the volume ratio of colostrum whey to phosphate buffer is 1:1, and the remaining steps are consistent with Example 7.

[0057] Example 11

[0058] The difference between Example 11 and Example 7 is that in the ammonium sulfate salting-out step, the volume ratio of colostrum whey to phosphate buffer is 1:1.2, and the remaining steps are consistent with Example 7.

[0059] Example 12

[0060] The difference between Example 12 and Example 7 is that in the ammonium sulfate salting-out step, the volume ratio of colostrum whey to phosphate buffer is 1:1.4, and the remaining steps are consistent with Example 7.

[0061] Example 13

[0062] The difference between Example 13 and Example 10 is that in the ammonium sulfate salting out step, phosphate buffer is added to the precipitate A and stirred evenly to dissolve the precipitate A, and then a saturated ammonium sulfate solution is added to make the saturation of the mixed solution 40%. The remaining steps are consistent with Example 10.

[0063] Example 14

[0064] The difference between Example 14 and Example 10 is that in the ammonium sulfate salting out step, phosphate buffer is added to the precipitate A and stirred evenly to dissolve the precipitate A, and then a saturated ammonium sulfate solution is added to make the saturation of the mixed solution 45%. The remaining steps are consistent with Example 10.

[0065] Example 15

[0066] The difference between Example 15 and Example 13 is that in the ammonium sulfate salting-out step, a saturated ammonium sulfate solution is added to the upper clear liquid B so that the saturation of the upper clear liquid B is 35%, and the remaining steps are consistent with Example 13.

[0067] Example 16

[0068] The difference between Example 16 and Example 13 is that in the ammonium sulfate salting-out step, a saturated ammonium sulfate solution is added to the upper clear liquid B so that the saturation of the upper clear liquid B is 40%, and the remaining steps are consistent with Example 13.

[0069] Comparative Example

[0070] Comparative Example 1

[0071] The difference between Comparative Example 1 and Example 1 is that in the ammonium sulfate salting out step, the colostrum whey is diluted with physiological saline to make the concentration of the colostrum whey become 1 / 2 of the original, and then a saturated ammonium sulfate solution is added while stirring to obtain a mixed solution, and the saturation of the mixed solution is 45%, and the mixture is allowed to stand at 4°C for 6 hours, and then centrifuged at 4°C and 4000 r / min for 15 minutes, the supernatant A is removed, and phosphate buffer is added to the precipitate A, stirred evenly to dissolve the precipitate A, and then a saturated ammonium sulfate solution is added to make the saturation of the mixed solution 35%, and the mixture is allowed to stand at 4°C for 6 hours, and centrifuged at 4°C and 4000 r / min for 15 minutes, the supernatant B is removed to obtain precipitate B, and the precipitate B is directly purified. The remaining steps are consistent with Example 1.

[0072] Performance test purity: The bovine colostrum immunoglobulin in each example was tested by high performance liquid chromatography to measure the SIgA content.

[0073] Table 1 Performance test results of bovine colostrum immunoglobulin

[0074]

[0075]

[0076] Combining Example 1 and Comparative Example 1, the purity of the bovine colostrum immunoglobulin in Example 1 is much higher than that in Comparative Example 1. It can be seen that when extracting SIgA, salting out the colostrum whey three times improves the purity of the obtained bovine colostrum immunoglobulin.

[0077] Combining Example 1 and Example 2, the purity of bovine colostrum immunoglobulin in Example 2 is higher than that in Example 1. It can be seen that in the centrifugal defatting step, adding rennet to the filtrate facilitates the formation of colostrum whey, thereby improving the purity of the obtained immunoglobulin.

[0078] Combined with Examples 2-6, the purity of bovine colostrum immunoglobulin in Example 3-5 is relatively high. It can be seen that in the centrifugal defatting step, rennet is added to the filtrate, and the optimal ratio of rennet to filtrate is 1:(300-350), and the purity of the obtained immunoglobulin is relatively high.

[0079] Combining Examples 4, 7, and 8, the purity of the bovine colostrum immunoglobulin in Example 7 is the highest. It can be seen that in the ammonium sulfate salting-out step, the saturated ammonium sulfate solution is added for the first time to increase the saturation of the mixed solution, and the purity of the obtained immunoglobulin shows a trend of first increasing and then decreasing.

[0080] Combining Example 7 and Examples 9-12, the purity of bovine colostrum immunoglobulin in Examples 9-11 is higher. It can be seen that in the ammonium sulfate salting out step, phosphate buffer is added to dissolve precipitate A, and the optimal ratio of colostrum whey to phosphate buffer is 1: (0.8-1.2).

[0081] Combining Example 10, Example 13 and Example 14, the purity of the bovine colostrum immunoglobulin in Example 13 is the highest. It can be seen that in the ammonium sulfate salting out step, the saturated ammonium sulfate solution is added for the second time to increase the saturation of the mixed solution, and the purity of the obtained immunoglobulin shows a trend of first increasing and then decreasing.

[0082] Combining Example 13, Example 15 and Example 16, the purity of the bovine colostrum immunoglobulin in Example 15 is the highest. It can be seen that in the ammonium sulfate salting out step, the saturated ammonium sulfate solution is added for the third time to increase the saturation of the mixed solution, and the purity of the obtained immunoglobulin shows a trend of first increasing and then decreasing.

[0083] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for extracting bovine colostrum immunoglobulin, characterized in that: The following steps are involved: Centrifugal defatting: The bovine colostrum is centrifuged to defatted, and then the middle layer is filtered to obtain the filtrate; Add rennet to the filtrate, stir evenly, and curdle the milk at a constant temperature of 30-40°C, followed by centrifugation, and filter the supernatant to obtain colostrum whey; the weight ratio of the rennet to the filtrate is 1:(300-350); Ammonium sulfate salting out: dilute the colostrum whey, then add saturated ammonium sulfate solution and stir to obtain a mixed solution, and make the saturation of the mixed solution 45%-55%. Let it stand, centrifuge, remove supernatant A, add phosphate buffer to precipitate A, stir evenly, and then add saturated ammonium sulfate solution to make the saturation of the mixed solution 35%-45%. Let it stand, centrifuge, remove precipitate B, add saturated ammonium sulfate solution to supernatant B to make the saturation of supernatant B 30%-40%, centrifuge, remove supernatant C, and obtain precipitate C; Purification: Desalt the precipitate C gel column, concentrate it by ultrafiltration, and separate it by column chromatography to obtain bovine colostrum immunoglobulin.

2. The method for extracting bovine colostrum immunoglobulin according to claim 1, wherein: In the ammonium sulfate salting out step, the colostrum whey is diluted, and then a saturated ammonium sulfate solution is added and stirred to obtain a mixed solution, and the saturation of the mixed solution is 45%-55%. The mixed solution is allowed to stand at 0-6°C for 3-18 hours, centrifuged, and the supernatant A is removed. A phosphate buffer is added to the precipitate A, and the mixture is stirred evenly. A saturated ammonium sulfate solution is then added, and the mixture is allowed to stand and centrifuged to remove the precipitate B. A saturated ammonium sulfate solution is added to the supernatant B, and the mixture is centrifuged and the supernatant C is removed to obtain a precipitate C.

3. The method for extracting bovine colostrum immunoglobulin according to claim 2, wherein: The volume ratio of the colostrum whey to the phosphate buffer is 1:(0.8-1.2).

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