A pearl whitening method based on a complex enzyme

Abstract

This invention discloses a pearl whitening method based on a complex enzyme, comprising the following steps: (1) Pretreatment: washing and drying the pearl; (2) Enzymatic hydrolysis: immersing the pretreated pearl in a buffer solution containing the complex enzyme and shaking it at 30℃-60℃ and pH 4.0-7.0 for 2-24 hours, wherein the complex enzyme is a free enzyme or an immobilized enzyme; (3) Posttreatment: washing and drying the enzymatically hydrolyzed pearl to obtain whitened pearl; In step (2), the complex enzyme includes carotenoid degrading enzyme, melanin degrading enzyme, porphyrin degrading enzyme and coenzyme, and the total enzyme activity concentration of the complex enzyme ranges from 50U / mL to 200U / mL. This scheme, by combining the coenzyme with three pigment degrading enzymes, overcomes the limitations of the dense structure of pearl, improves the accessibility of the three pigment degrading enzymes to the internal pigment molecules, achieves efficient degradation of the internal pigments of pearl under mild conditions, while maintaining the structural integrity and natural luster of the pearl, with low overall energy consumption, no toxic chemical reagent emissions, and environmental friendliness.

Description

Technical Field

[0001] This invention relates to the field of pearl processing technology, and in particular to a pearl whitening method based on a compound enzyme. Background Technology

[0002] Pearls are organic gemstones secreted by mollusks. Their main component is aragonite-type calcium carbonate, with small amounts of organic matter (such as conchiolin) and pigments. The color of a pearl is determined by the type and amount of pigment. Pearls with darker or mixed colors usually require whitening treatment to increase their commercial value.

[0003] Traditional pearl whitening methods mainly include chemical oxidation bleaching (such as using hydrogen peroxide) and light treatment. While chemical oxidation is highly effective, it easily damages the surface structure of pearls, causing the nacre to peel off, reducing luster, and leaving behind chemical residues that are environmentally unfriendly. Light treatment, on the other hand, is time-consuming and its effects are inconsistent.

[0004] Therefore, it is of great significance to develop a gentle, efficient, and environmentally friendly method for pearl whitening. Summary of the Invention

[0005] Therefore, it is necessary to provide a pearl whitening method based on compound enzymes to address the above problems. This method uses compound enzymes to achieve efficient degradation of pigments inside the pearl while maintaining the structural integrity and luster of the pearl.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A pearl whitening method based on a complex enzyme includes the following steps: (1) Pretreatment: washing and drying the pearl; (2) Enzymatic hydrolysis: immersing the pretreated pearl in a buffer solution containing a complex enzyme and shaking it for 2-24 hours at a temperature of 30℃-60℃ and a pH of 4.0-7.0, wherein the complex enzyme is a free enzyme or an immobilized enzyme; (3) Posttreatment: washing and drying the enzymatically hydrolyzed pearl to obtain whitened pearl.

[0008] In step (2), the complex enzyme includes carotenoid degrading enzyme, melanin degrading enzyme, porphyrin degrading enzyme and coenzyme, and the total enzyme activity concentration of the complex enzyme ranges from 50 U / mL to 200 U / mL.

[0009] Preferably, the complex enzyme comprises, by weight, the following components:

[0010] 1-5 parts of carotenoid-degrading enzyme;

[0011] 1-3 parts of melanin-degrading enzyme;

[0012] 0.5-2 parts of porphyrin-degrading enzyme;

[0013] 0.1 to 1 part of coenzyme.

[0014] Preferably, the carotenoid degrading enzyme in the complex enzyme is a carotenoid lysing dioxygenase.

[0015] Preferably, in the complex enzyme, the melanin-degrading enzyme is selected from at least one of laccase, lignin peroxidase, and manganese peroxidase.

[0016] Preferably, the porphyrin-degrading enzyme in the complex enzyme is a peroxidase.

[0017] Preferably, in the complex enzyme, the coenzyme is selected from at least one of protease, lipase, and pectinase.

[0018] Preferably, the buffer solution is selected from one of citrate-disodium hydrogen phosphate buffer, acetate-sodium acetate buffer, or Tris-HCl buffer, and the concentration of the buffer solution is 0.05 mol / L to 0.2 mol / L.

[0019] Preferably, the solution containing the complex enzyme also contains a surfactant, which is one or more of Tween-80, Triton X-100 or sodium dodecyl sulfate, and the amount of the surfactant added is 0.01%-0.1% (w / v).

[0020] Preferably, in step (2), the pretreated pearls are first immersed in a weak acid with a pH of 4-6 for 0.5-2 hours, and then immersed in a buffer solution containing a complex enzyme for enzymatic hydrolysis. The weak acid includes, but is not limited to, organic weak acids such as citric acid, acetic acid, and malic acid.

[0021] Preferably, when the composite enzyme is an immobilized enzyme, the carrier of the composite enzyme is at least one selected from aminated magnetic nanoparticles, chitosan, sodium alginate, mesoporous silica, cellulose, and agarose. Aminated magnetic nanoparticles are preferred, as they allow for magnetic separation and recovery of the immobilized enzyme, making recovery convenient and rapid.

[0022] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0023] 1. In this invention, three pigment-degrading enzymes, namely carotenoid degrading enzyme, melanin degrading enzyme and porphyrin degrading enzyme, are used to specifically and directionally remove the main pigment types in pearls, avoiding the non-selective oxidative damage of traditional chemical bleaching, and effectively maintaining the nacreous structure and natural luster of pearls.

[0024] 2. In this invention, by adding an auxiliary enzyme to the compound enzyme, it works synergistically with the three pigment-degrading enzymes, overcoming the limitations of the dense structure of pearl, improving the accessibility of the three pigment-degrading enzymes to the internal pigment molecules, achieving efficient degradation of the internal pigments of pearl under mild conditions, while maintaining the structural integrity and natural luster of pearl, with low overall energy consumption, no toxic chemical reagent emissions, and environmental friendliness. Detailed Implementation

[0025] The embodiments of this application are described in detail below. The described embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0026] In this invention, except for the components specifically described for synthesis, all other components and reagents involved are conventional commercially available products or can be obtained through conventional technical means in the art. Unless otherwise stated, the materials, methods, and embodiments of this invention are exemplary only and not limiting.

[0027] This application provides a pearl whitening method based on a complex enzyme, comprising the following steps: (1) pretreatment: washing and drying the pearl; (2) enzymatic hydrolysis: immersing the pretreated pearl in a buffer solution containing a complex enzyme and shaking it at a temperature of 30℃-60℃ and a pH of 4.0-7.0 for 2h-24h, wherein the complex enzyme is a free enzyme or an immobilized enzyme; (3) posttreatment: washing and drying the enzymatically hydrolyzed pearl to obtain whitened pearl.

[0028] In step (2), the complex enzyme includes carotenoid degrading enzyme, melanin degrading enzyme, porphyrin degrading enzyme and coenzyme, and the total enzyme activity concentration of the complex enzyme ranges from 50 U / mL to 200 U / mL.

[0029] By employing three pigment-degrading enzymes—carotenoid degrading enzyme, melanin degrading enzyme, and porphyrin degrading enzyme—this method specifically targets and removes the main pigment types in pearls. Furthermore, the combination of auxiliary enzymes with these three pigment-degrading enzymes creates a synergistic effect, overcoming the limitations of the dense structure of pearls and improving the accessibility of the three pigment-degrading enzymes to internal pigment molecules. This achieves highly efficient degradation of internal pigments in pearls under mild conditions, while maintaining the structural integrity and natural luster of the pearl. The overall process is energy-efficient, produces no toxic chemical reagents, and is environmentally friendly.

[0030] In step (2), the pearl can also be treated in a buffer solution containing only coenzymes for 0.5 to 2 hours, and then the three pigment-degrading enzymes—carotenoid degrading enzyme, melanin degrading enzyme, and porphyrin degrading enzyme—can be added to continue the enzymatic hydrolysis reaction. This is more conducive to the penetration of the three pigment-degrading enzymes into the pigment molecules inside the pearl, thereby achieving efficient degradation of the pigments inside the pearl under mild conditions.

[0031] The complex enzyme comprises, by weight, 1-5 parts of carotenoid degrading enzyme, 1-3 parts of melanin degrading enzyme, 0.5-2 parts of porphyrin degrading enzyme, and 0.1-1 parts of coenzyme. In step (2), the complex enzyme can be added to the buffer solution simultaneously in proportion; alternatively, the coenzyme can be added first for enzymatic hydrolysis, followed by the addition of the three pigment degrading enzymes (carotenoid degrading enzyme, melanin degrading enzyme, and porphyrin degrading enzyme) in proportion to continue the enzymatic hydrolysis reaction.

[0032] In the complex enzyme, the carotenoid degrading enzyme is a carotenoid lysing dioxygenase (CCD), preferably a CCD enzyme derived from Staphylococcus pasteurellum, or a recombinant expression enzyme derived from plants, such as the recombinant expression enzyme VvCCD1 derived from grapes. The carotenoid lysing dioxygenase (CCD) can be purchased or prepared.

[0033] For example, the preparation method of CCD enzyme derived from Staphylococcus pasteurellium can be as follows: Staphylococcus pasteurellium TS-82 is inoculated into a fermentation medium and cultured at 30℃-37℃ with shaking for 24-48 hours. The cells are collected by centrifugation, and the mixture is sonicated to obtain a crude enzyme solution. This solution is then purified by freeze-drying, ion exchange chromatography, and molecular sieve chromatography to obtain electrophoretically pure CCD enzyme. Specifically, the preparation method can be as follows: Staphylococcus pasteurellium TS-82 (CGMCC) is inoculated into LB medium and cultured at 37℃ with shaking for 24 hours. The cells are collected by centrifugation. The cells are resuspended in 50mM phosphate buffer (pH 7.0), sonicated (400W, 5s working / 5s intermittent, 30min total), and the supernatant is collected by centrifugation to obtain the crude enzyme solution. The crude enzyme solution was concentrated by freeze-drying and then sequentially passed through a MonoQ anion exchange column (equilibration buffer: 20 mM Tris-HCl pH 8.0, eluent: 0-0.5 M NaCl gradient) and a Superdex 200 molecular sieve chromatography. The activity peak was collected to obtain the purified CCD enzyme. SDS-PAGE showed a single band with a molecular weight of approximately 45 kDa. Of course, it can also be prepared using other methods.

[0034] In this invention, the melanin-degrading enzyme in the composite enzyme is selected from at least one of laccase, lignin peroxidase, and manganese peroxidase. All of these enzymes are commercially available.

[0035] In this invention, the porphyrin-degrading enzyme in the complex enzyme is a peroxidase. The peroxidase can be obtained through procurement.

[0036] In this invention, the coenzyme in the composite enzyme is selected from at least one of protease, lipase, and pectinase. The coenzyme is used to hydrolyze the organic coating layer on the surface of the pearl and promote the penetration of pigment-degrading enzymes into the interior of the pearl. The protease includes, but is not limited to, proteinase K and neutral protease.

[0037] In this invention, the buffer solution is selected from one of citrate-disodium hydrogen phosphate buffer, acetate-sodium acetate buffer, or Tris-HCl buffer, and the concentration of the buffer solution is 0.05 mol / L-0.2 mol / L.

[0038] In this invention, the solution containing the complex enzyme also contains a surfactant, which is one or more of Tween-80, Triton X-100 or sodium dodecyl sulfate, and the amount of surfactant added is 0.01%-0.1% (w / v).

[0039] In this invention, in step (2), the pretreated pearl is first immersed in a weak acid solution with a pH of 4-6 for 0.5-2 hours, and then immersed in a buffer solution containing a complex enzyme for enzymatic hydrolysis. The weak acid includes, but is not limited to, organic weak acids such as citric acid, acetic acid, and malic acid. After the pretreated pearl undergoes weak acid treatment, the coenzyme in the complex enzyme solution may or may not be removed. The weak acid treatment can remove organic matter and other substances coating the pearl surface.

[0040] In this invention, when the composite enzyme is an immobilized enzyme, the carrier of the composite enzyme is at least one selected from aminated magnetic nanoparticles, chitosan, sodium alginate, mesoporous silica, cellulose, and agarose. The aminated magnetic nanoparticles include, but are not limited to, Fe3O4@SiO2-NH2. Taking Fe3O4@SiO2-NH2 as an example, the specific preparation method of the immobilized enzyme is as follows: a buffer solution containing the composite enzyme is mixed with the carrier, and the mixture is shaken at 4°C for 2 hours to adsorb the enzyme. Glutaraldehyde is added to a final concentration of 0.5%, and cross-linking continues for 4 hours. After magnetic separation and washing, the immobilized enzyme is obtained. Of course, when using other carriers, the preparation method only requires adjustment of the carrier and reaction conditions, which will not be elaborated here.

[0041] The effects of the technical solution of this application will be further illustrated below through several specific application examples.

[0042] Example 1:

[0043] A pearl whitening method based on a complex enzyme includes the following steps: (1) Pretreatment: Select a dark-colored variegated pearl (containing yellow, gray and pink variegation), ultrasonically clean it with deionized water for 10 min, and dry it at room temperature; (2) Immerse the pretreated pearl in a buffer solution containing complex enzyme A, and shake it at 40℃ and pH 5.0 for 12 h.

[0044] Among them, the complex enzyme A is a free enzyme, and the complex enzyme A includes, by weight, 2 parts of carotenoid lysin dioxygenase, 1 part of laccase, 0.5 parts of peroxidase and 0.2 parts of proteinase K, the buffer is 0.1 mol / L acetate-sodium acetate buffer (pH 5.0), the total enzyme activity concentration is 100 U / mL, and 0.05% (w / v) Tween-80 is added; (3) Post-treatment: the enzymatically hydrolyzed pearl is washed and dried to obtain the whitened pearl sample.

[0045] Example 2:

[0046] A pearl whitening method based on a complex enzyme includes the following steps: (1) Pretreatment: Select a dark-colored variegated pearl (containing yellow, gray, and pink variegation), ultrasonically clean it with deionized water for 10 min, and dry it at room temperature; (2) Immerse the pretreated pearl in a buffer containing 0.2 parts of proteinase K, pretreat it at 40℃ and pH 5.0 for 1 h, then add 2 parts of carotenoid lysin, 1 part of laccase and 0.5 parts of peroxidase, and react at 50℃ and pH 5.0 for 12 h; wherein, the buffer is 0.1 mol / L acetate-sodium acetate buffer (pH 5.0), and the total enzyme activity concentration is 100 U / mL; (3) Posttreatment: Wash and dry the enzymatically hydrolyzed pearl to obtain a whitened pearl sample.

[0047] Example 3:

[0048] A pearl whitening method based on a complex enzyme includes the following steps: (1) Pretreatment: Select dark-colored variegated pearls (containing yellow, gray, and pink spots), ultrasonically clean them with deionized water for 10 min, and dry them at room temperature; (2) Immerse the pretreated pearls in a buffer solution containing immobilized enzymes, and shake them at 40℃ and pH 5.0 for 12 h; (3) Posttreatment: Wash and dry the enzymatically hydrolyzed pearls to obtain whitened pearl samples. After each batch of treatment, the immobilized enzymes are magnetically recovered and reused for the next batch. Steps (2) and (3) are repeated, and the immobilized enzymes are used 5 times to obtain 5 batches of whitened pearl samples.

[0049] In the immobilized enzyme, the carrier is Fe3O4@SiO2-NH2, the enzyme is complex enzyme A, the buffer is 0.1 mol / L acetate-sodium acetate buffer (pH 5.0), and the total enzyme activity concentration is 100 U / mL.

[0050] Comparative Example 1:

[0051] A method for whitening pearls includes the following steps:

[0052] (1) Pretreatment: Select dark-colored variegated pearls (containing yellow, gray and pink variegation), ultrasonically clean them with deionized water for 10 min, and dry them at room temperature;

[0053] (2) Immerse the pretreated pearls in 2% H2O2 at 50℃ for 8 hours;

[0054] (3) Post-processing: Wash and dry the treated pearls to obtain whitened pearl samples.

[0055] Comparative Example 2:

[0056] A method for whitening pearls includes the following steps:

[0057] (1) Pretreatment: Select dark-colored variegated pearls (containing yellow, gray and pink variegation), ultrasonically clean them with deionized water for 10 min, and dry them at room temperature;

[0058] (2) The pretreated pearls were immersed in a buffer solution containing compound enzyme B and shaken for 12 hours at 40°C and pH 5.0. The compound enzyme B was a free enzyme, and the compound enzyme B included 2 parts by weight of carotenoid lysing dioxygenase, 1 part of laccase and 0.5 parts of peroxidase. The buffer solution was 0.1 mol / L acetate-sodium acetate buffer (pH 5.0), the total enzyme activity concentration was 100 U / mL, and 0.05% (w / v) Tween-80 was added.

[0059] (3) Post-processing: Wash and dry the treated pearls to obtain whitened pearl samples.

[0060] Comparative Example 3:

[0061] A method for whitening pearls includes the following steps:

[0062] (1) Pretreatment: Select dark-colored variegated pearls (containing yellow, gray and pink variegation), ultrasonically clean them with deionized water for 10 min, and dry them at room temperature;

[0063] (2) The pretreated pearls were immersed in 0.1 mol / L acetate-sodium acetate buffer (pH 5.0) and shaken for 12 h at 40 °C and pH 5.0.

[0064] (3) Post-processing: Wash and dry the treated pearls to obtain whitened pearl samples.

[0065] Comparative Example 4:

[0066] A method for whitening pearls includes the following steps:

[0067] (1) Pretreatment: Select dark-colored variegated pearls (containing yellow, gray and pink variegation), ultrasonically clean them with deionized water for 10 min, and dry them at room temperature;

[0068] (2) The pretreated pearls were immersed in a buffer solution containing carotenoid lysing dioxygenase and shaken for 12 h at 40 °C and pH 5.0. The buffer solution was 0.1 mol / L acetate-sodium acetate buffer (pH 5.0) with a total enzyme activity concentration of 100 U / mL and 0.05% (w / v) Tween-80 was added.

[0069] (3) Post-processing: Wash and dry the treated pearls to obtain whitened pearl samples.

[0070] Comparative Example 5:

[0071] A method for whitening pearls includes the following steps:

[0072] (1) Pretreatment: Select dark-colored variegated pearls (containing yellow, gray and pink variegation), ultrasonically clean them with deionized water for 10 min, and dry them at room temperature;

[0073] (2) The pretreated pearls were immersed in a buffer solution containing complex enzyme C and reacted with shaking at 40°C and pH 5.0 for 12 hours. The complex enzyme C was a free enzyme, which included 2 parts by weight of carotenoid lysin and 1 part of laccase. The buffer solution was 0.1 mol / L acetate-sodium acetate buffer (pH 5.0), the total enzyme activity concentration was 100 U / mL, and 0.05% (w / v) Tween-80 was added.

[0074] (3) Post-processing: Wash and dry the treated pearls to obtain whitened pearl samples.

[0075] Comparative Example 6:

[0076] A method for whitening pearls includes the following steps:

[0077] (1) Pretreatment: Select dark-colored variegated pearls (containing yellow, gray and pink variegation), ultrasonically clean them with deionized water for 10 min, and dry them at room temperature;

[0078] (2) The pretreated pearls were immersed in a buffer solution containing compound enzyme D and shaken for 12 hours at 40°C and pH 5.0. The compound enzyme D was a free enzyme, and the compound enzyme D included 2 parts by weight of carotenoid lysing dioxygenase and 0.5 parts by weight of peroxidase. The buffer solution was 0.1 mol / L acetate-sodium acetate buffer (pH 5.0), the total enzyme activity concentration was 100 U / mL, and 0.05% (w / v) Tween-80 was added.

[0079] (3) Post-processing: Wash and dry the treated pearls to obtain whitened pearl samples.

[0080] The whitening pearl samples obtained in Examples 1-3 and Comparative Examples 1-6 were tested for their effects. The testing methods are as follows:

[0081] Whiteness increase value (ΔL*): The L* value (whiteness) of pearls before and after treatment was measured using a Konica Minolta CM-3600A spectrophotometer. The difference between the two values ​​is the whiteness increase value (ΔL*).

[0082] The test results are shown in Table 1 below:

[0083] Table 1: Test results of the whitening effect of the whitening pearl samples obtained in Examples 1-3 and Comparative Examples 1-6:

[0084] Example 1 15.2 The pearls are evenly whitened, blemishes have largely disappeared, and there are no cracks on the surface. Example 2 15.6 The pearls are evenly whitened, blemishes have largely disappeared, and there are no cracks on the surface. Example 3 (used once) 14.8 The pearls are evenly whitened, blemishes have largely disappeared, and there are no cracks on the surface. Comparative Example 1 13.2 The whitening process was even, blemishes largely disappeared, and micro-cracks appeared on the surface. Comparative Example 2 12.3 The whitening effect was mediocre, some blemishes remained, and there were no cracks on the surface. Comparative Example 3 0.2 No whitening effect, no obvious color change, no surface cracks Comparative Example 4 8.5 The whitening effect was minimal, removing only some of the yellow pigment; gray and pink blemishes remained, and there were no cracks on the surface. Comparative Example 5 11.3 The whitening effect is average; noticeable pinkish blemishes remain, but there are no cracks on the surface. Comparative Example 6 10.8 The whitening effect is average; noticeable gray spots remain, and there are no cracks on the surface.

[0085] As shown in Table 1 above, the compound enzyme system exhibits a significant whitening effect, with a whitening improvement that is significantly superior to traditional hydrogen peroxide bleaching, while also preserving the pearl's luster and structure. The synergistic effect of the coenzyme and the three pigment-degrading enzymes is key to the highly efficient whitening; the absence of any one of these core components will lead to a substantial decrease in effectiveness.

[0086] The whitening effect of five batches of whitened pearl samples obtained by using the immobilized enzyme five times consecutively in Example 3 was tested, and the results are shown in Table 2 below:

[0087] Table 2: Whitening effect test results of 5 batches of whitening pearl samples obtained by continuous use of immobilized enzyme in Example 3 (5 times).

[0088] 1 14.8 100 2 14.2 95.9 3 13.1 88.5 4 11.9 80.4 5 10.5 70.9

[0089] As shown in Table 2 above, the activity of the immobilized complex enzyme decreased slightly with increasing usage, but the overall decrease was gradual, and it maintained a relative activity of 70.9% even after 5 repeated uses. The pearl whiteness remained at a high level after multiple uses, indicating that the immobilized enzyme has good operational stability, can be recycled and reused, and has potential for industrial application.

[0090] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, alterations, deletions of some features, additions of features, or recombinations of features to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the innovative principles of the present invention shall still fall within the scope of the technical solutions of the present invention.

Claims

1. A pearl whitening method based on a complex enzyme, characterized in that, Includes the following steps: (1) Pretreatment: Clean and dry the pearls; (2) Enzymatic hydrolysis: The pretreated pearls are immersed in a buffer solution containing a complex enzyme and shaken for 2-24 hours at a temperature of 30℃-60℃ and a pH of 4.0-7.

0. The complex enzyme is a free enzyme or an immobilized enzyme. (3) Post-treatment: The enzymatically hydrolyzed pearls are washed and dried to obtain whitened pearls. In step (2), the complex enzyme includes carotenoid degrading enzyme, melanin degrading enzyme, porphyrin degrading enzyme and coenzyme, and the total enzyme activity concentration of the complex enzyme ranges from 50 U / mL to 200 U / mL.

2. The pearl whitening method based on a complex enzyme according to claim 1, characterized in that, The complex enzyme comprises, by weight, the following: 1-5 parts of carotenoid-degrading enzyme; 1-3 parts of melanin-degrading enzyme; 0.5-2 parts of porphyrin-degrading enzyme; 0.1 to 1 part of coenzyme.

3. The pearl whitening method based on a compound enzyme according to claim 1, characterized in that, In the complex enzyme, the carotenoid degrading enzyme is a carotenoid lysing dioxygenase.

4. The pearl whitening method based on a complex enzyme according to claim 1, characterized in that, In the complex enzyme, the melanin-degrading enzyme is selected from at least one of laccase, lignin peroxidase, and manganese peroxidase.

5. The pearl whitening method based on a compound enzyme according to claim 1, characterized in that, In the complex enzyme, the porphyrin-degrading enzyme is a peroxidase.

6. The pearl whitening method based on a complex enzyme according to claim 1, characterized in that, In the complex enzyme, the coenzyme is selected from at least one of protease, lipase, and pectinase.

7. The pearl whitening method based on a complex enzyme according to claim 1, characterized in that, The buffer solution is selected from one of citrate-disodium hydrogen phosphate buffer, acetate-sodium acetate buffer, or Tris-HCl buffer, and the concentration of the buffer solution is 0.05 mol / L-0.2 mol / L.

8. The pearl whitening method based on a complex enzyme according to claim 1, characterized in that, The buffer solution containing the complex enzyme also contains a surfactant selected from one or more of Tween-80, Triton X-100, or sodium dodecyl sulfate, and the amount of the surfactant added is 0.01%-0.1% (w / v).

9. The pearl whitening method based on a compound enzyme according to claim 1, characterized in that, In step (2), the pretreated pearls are first immersed in a weak acid with a pH of 4-6 for 0.5-2 hours, and then the pearls are immersed in a buffer solution containing a complex enzyme for enzymatic hydrolysis.

10. The pearl whitening method based on a complex enzyme according to claim 1, characterized in that, When the composite enzyme is an immobilized enzyme, the carrier of the composite enzyme is at least one of aminated magnetic nanoparticles, chitosan, sodium alginate, mesoporous silica, cellulose, and agarose.