Fat-like nano-enzyme, synthesis method thereof and application of fat-like nano-enzyme in preparation of structural lipid

Abstract

The invention provides a fat-like nano-enzyme, a synthesis method thereof and application of the fat-like nano-enzyme in preparation of structural lipid. The synthesis method of the UiO-66-SO3H fat nano enzyme comprises the step of enabling ZrCl4, H2BDC and sodium sulfite to react in the presence of a solvent and acetic acid. According to the invention, a coordinated unsaturated metal site in UiO-66 is used as a Lewis site, and a group with # imgabs0 # acidic site is added to construct the fat-like nano-enzyme, so that efficient preparation of structural lipid is realized.

Description

Technical Field

[0001] The invention relates to a catalyst, and in particular to a fat-like nanozyme and a synthesis method thereof and application thereof in the preparation of structured lipids. Background Art

[0002] The daily average fat intake of oils and fats in people's daily diet accounts for 30%-50% of the total energy, which is of great significance to meet the essential nutritional needs of the human body. Structured lipids (SLs) refer to triacylglycerols (TAGs) obtained by chemically or enzymatically modifying natural oils and fats by introducing new fatty acids or changing the positional distribution of fatty acids in the glycerol backbone. Medium and long chain triacylglycerols (MLCTs) are a type of artificially synthesized SLs, in which medium chain fatty acids (MCFAs) and long chain fatty acids (LCFAs) coexist on the triglyceride backbone. The MCFAs contained in MLCTs give them the characteristics of fast digestion and absorption, fast decomposition and energy supply, and no accumulation in the body. Compared with medium chain triacylglycerols (MCTs) with a single fatty acid composition, MLCTs can simultaneously provide the human body with long chain polyunsaturated fatty acids (PUFAs) necessary for the human body, ensuring the supply of essential fatty acids. Long-term single intake of MCT can cause serious health problems to the human body.

[0003] Due to the limited natural sources of MLCT, the actual production is usually prepared by modifying natural oils and fats as raw materials. In recent years, the synthesis of MLCT mainly uses immobilized lipase, which is difficult to meet the needs of industrial application and large-scale production due to its high price. Compared with immobilized lipase, nanozymes have the advantages of low cost and high stability. In addition, the rapid development of synthetic methods for preparing nanozymes can better control their structural and morphological characteristics, making them a promising alternative to natural enzymes. Recent studies have shown that MOF (metal organic framework) nanozyme catalysts are based on (i) metal centers with unsaturated coordination environments, (ii) modified active sites on the framework; (iii) catalytic species encapsulated in the pores as active sites, and have unique catalytic properties. They have been widely used in organic transformation reactions. Nanozymes and their preparation still need to be further improved. Summary of the invention

[0004] To solve at least one of the problems in the prior art, the present invention provides a lipid-like nanozyme and a synthesis method thereof and an application thereof in the preparation of structured lipids. The present invention utilizes the coordinated unsaturated metal sites in UiO-66 as Lewis sites and adds The acidic site group (-SO3H) was used to construct fat-like nanozymes, achieving efficient preparation of structured lipids.

[0005] A method for synthesizing a UiO-66-SO3H type fat nanozyme comprises: reacting ZrCl4 (zirconium chloride), H2BDC (1,4-terephthalic acid) and sodium sulfite in the presence of a solvent and acetic acid.

[0006] The UiO-66-SO3H type fat nanozyme synthesized by the method of the present invention has a metal center with an unsaturated coordination environment, an active site modified on the framework, and a catalytic species wrapped in the pores as an active site, and has unique catalytic properties. The present invention utilizes the unsaturated metal site in UiO-66 as a Lewis site, adds a Acidic site groups (-SO3H) were used to construct lipid nanozymes, and Lewis and The synergistic effect of acidic sites enables the efficient preparation of structured lipids.

[0007] Specifically, the present invention adopts a hydrothermal synthesis method.

[0008] Preferably, in the synthesis method, the molar ratio of ZrCl4 to H2BDC is (0.5-2): (0.5-2), more preferably 1: 1. Studies have found that when the reaction is carried out under this ratio range, the catalytic activity of the prepared UiO-66-SO3H-based fat nanozyme is higher.

[0009] Preferably, in the synthesis method, the molar ratio of ZrCl4 to sodium sulfite is (2.5-10): 1, more preferably 5: 1. Studies have found that when the reaction is carried out under the conditions of this ratio range, the catalytic activity of the prepared UiO-66-SO3H type fat nanozyme is higher.

[0010] Preferably, in the synthesis method, the ratio of ZrCl4 to acetic acid is 1 mmol:(3-15) mL, more preferably 1 mmol:9 mL.

[0011] Acetic acid can exchange protons with sodium sulfite in the acidified reaction solution. + .

[0012] Preferably, in the synthesis method, the reaction temperature is 110-150°C, more preferably 140°C. When the reaction is carried out under the temperature range, Lewis and The acid content is higher, and the catalytic activity of the prepared UiO-66-SO3H-type fat nanozyme is higher.

[0013] Specifically, the synthesis method is carried out in a high-pressure reactor at a pressure in the range of 5-30 MPa.

[0014] Preferably, in the synthesis method, the reaction time is 20-60 hours, more preferably 40 hours.

[0015] Preferably, the solvent is DMF (N,N-dimethylformamide).

[0016] Preferably, the synthesis method further comprises the steps of washing the reaction product with DMF and methanol, and drying. The residual organic ligand can be removed by washing and drying.

[0017] In some specific embodiments, the synthesis method of the UiO-66-SO3H type fat nanozyme includes: dissolving ZrCl4 and H2BDC (for example, the molar ratio of the two is 1:1) in DMF; then adding sodium sulfite and acetic acid and stirring; fully reacting at a temperature of 110-150°C; separating (for example, centrifuging) to obtain a precipitate, washing it with DMF and methanol, and then vacuum drying to obtain the UiO-66-SO3H type fat nanozyme.

[0018] The present invention also includes the UiO-66-SO3H fat nanozyme prepared by the above method.

[0019] The present invention also includes the use of the above-mentioned UiO-66-SO3H fat nanozyme in the preparation of structured lipids, for example, for catalyzing the reaction of capric acid (C10:0) and tristearic acid triglyceride to prepare structured lipids.

[0020] The present invention also provides a method for preparing structured lipids, comprising: using capric acid (C10:0) and tristearic acid triglyceride as raw materials, and using the above-mentioned UiO-66-SO3H fat nanozyme as a catalyst to carry out an acid hydrolysis reaction.

[0021] Preferably, in the method for preparing the structured lipid, the molar ratio of capric acid (C10:0) to tristearic acid triglyceride is (1-6):1, more preferably 5:1. Studies have found that within this ratio range, the capric acid concentration provides a large amount of acyl groups during the acid hydrolysis process, which is beneficial to the formation of the product, and thus the amount of capric acid incorporated into the structured lipid can be significantly increased, thereby improving the performance of the structured lipid.

[0022] Preferably, the ratio of UiO-66-SO3H-based fat nanozyme to tristearic acid triglyceride is 1wt%-5wt%, more preferably 3wt%.

[0023] Preferably, in the method for preparing the structured lipid, the temperature of the acid hydrolysis reaction is 130-180° C., more preferably 170° C. Carrying out the reaction under the condition of this temperature range can increase the incorporation amount of capric acid in the structured lipid.

[0024] Preferably, the method for preparing the structured lipid further comprises: after the acid hydrolysis reaction, removing the UiO-66-SO3H-type fat nanozyme, dissolving the reaction product in n-hexane, and washing with a potassium hydroxide solution (30% ethanol); and rotary evaporating the n-hexane.

[0025] In some embodiments, the method for preparing the structured lipid comprises: mixing capric acid (C10:0) and tristearic acid triglyceride, and drying under reduced pressure to remove moisture in the raw materials; then adding UiO-66-SO3H, and performing acid hydrolysis under stirring conditions; after the acid hydrolysis reaction is completed, cooling the reaction mixture to room temperature, and removing UiO-66-SO3H by reduced pressure filtration; then dissolving the reaction mixture in n-hexane, and washing with potassium hydroxide solution (30% ethanol); and then rotary evaporating the hexane to obtain the structured lipid.

[0026] In some embodiments, the tristearin is derived from tea oil.

[0027] In some embodiments, the present invention prepares lipids containing medium-chain fatty acid structures.

[0028] The present invention also includes the structured lipids prepared by the above method.

[0029] Preferably, the content of MLCT in the structural lipid is 40-50%, more preferably 45.12%.

[0030] Preferably, the types of the structural lipids are MLL and MML type structural lipids and no MMM type is detected.

[0031] The structural lipid of the present invention has the advantages of high capric acid incorporation, being more conducive to digestion and absorption, being rapidly decomposed and supplied with energy, and not being accumulated in the body.

[0032] The present invention synthesizes UiO-66-SO3H-like fat nanozyme by hydrothermal method, uses tristearic acid triglyceride and capric acid as substrates, and uses gas chromatography and high performance liquid chromatography as detection means to verify the ability of the fat nanozyme to acidolyze tristearic acid triglyceride and generate structured lipids. In the acidolysis reaction, by comparing the reaction effect of adding an acid site blocking reagent, it is confirmed that the acidolysis reaction is carried out under the synergistic effect of Lewis and Bronsted acid sites and that Bronsted acid sites play a dominant role.

[0033] The hydrothermal process adopted by the present invention is simple and efficient, with mature technology, low cost and low energy consumption, which is conducive to industrial production. Compared with other technical solutions, the present invention can prepare a lipid-like nanozyme with excellent performance, good stability and effective improvement of structural lipid production through simple steps and low energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a graph showing the detection results of the amount of capric acid incorporated into the structural lipids of the embodiments of the present invention.

[0035] Figure 2 This is a graph showing the incorporation amount of capric acid in the structured lipids prepared in Comparative Examples 1-4 and Example 8.

[0036] Figure 3 Figure 2 shows the reaction mechanism of tristearate hydrolysis catalyzed by UiO-66-SO3H in Experiment 2. (a) FTIR spectrum of UiO-66-SO3H after pyridine adsorption; (b) The effect of pyridine and 2,6-dimethylpyridine on the catalytic activity of UiO-66-SO3H; (c) Lewis (Zr) 4+ ) The hydrolysis mechanism of tristearic acid glycerol catalyzed by acidic sites; (d) UiO-66-SO3H Mechanism of hydrolysis of tristearic acid glycerol catalyzed by (-SO3H) acidic sites. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0038] Example 1

[0039] This embodiment provides a UiO-66-SO3H, and the preparation method thereof is as follows:

[0040] 2mmol ZrCl4 and 2mmol H2BDC were dissolved in 800mL DMF solution. Then 0.4mmol sodium sulfite and 180mL acetic acid were added and stirred at room temperature for 30min with a magnetic stirrer. The mixture was transferred to a 1L autoclave and heat treated at 140℃ for 40h. The obtained precipitate was centrifuged and washed with DMF and methanol 3 times. It was then vacuum dried at room temperature and then heated to 140℃ for 4h to remove the residual organic ligands to obtain UiO-66-SO3H.

[0041] Example 2

[0042] This embodiment provides a method for preparing UiO-66-SO3H, which is different from Example 1 only in that the amount of ZrCl4 is adjusted so that the molar ratio of ZrCl4 to sodium sulfite is 2.5:1.

[0043] Example 3

[0044] This embodiment provides a method for preparing UiO-66-SO3H, which is different from Example 1 only in that the amount of ZrCl4 is adjusted so that the molar ratio of ZrCl4 to sodium sulfite is 10:1.

[0045] Example 4

[0046] This embodiment provides a method for preparing structured lipids (SLs), the method is as follows:

[0047] Capric acid (C10:0) and tristearic acid triglyceride (2.25 g) were mixed in a 50 mL three-necked flask equipped with a magnetic stirrer at a molar ratio of 5:1, and the prepared mixed sample was dried under reduced pressure for 1 hour to remove moisture from the raw materials. Then, 3 wt% of UiO-66-SO3H prepared in Example 1 was added to the reaction mixture. The acid hydrolysis reaction was carried out under vigorous stirring at 170°C. After the acid hydrolysis was completed, the reaction mixture was cooled to room temperature and UiO-66-SO3H was removed by reduced pressure filtration. The reaction mixture was then dissolved in n-hexane and washed with 0.8 mol / L potassium hydroxide solution (30% ethanol). Finally, the hexane phase was evaporated under reduced pressure at 45°C using a rotary evaporator to obtain structured lipids (SLs) containing medium-chain fatty acids.

[0048] Example 5

[0049] This embodiment provides a method for preparing structured lipids (SLs), which is different from Example 4 only in that the amount of capric acid (C10:0) is adjusted so that the molar ratio of capric acid (C10:0) to tristearic acid triglyceride is 1:1.

[0050] Example 6

[0051] This embodiment provides a method for preparing structured lipids (SLs), which is different from Example 4 only in that the amount of capric acid (C10:0) is adjusted so that the molar ratio of capric acid (C10:0) to tristearic acid triglyceride is 2:1.

[0052] Example 7

[0053] This embodiment provides a method for preparing structured lipids (SLs), which is different from Example 4 only in that the amount of capric acid (C10:0) is adjusted so that the molar ratio of capric acid (C10:0) to tristearic acid triglyceride is 3:1.

[0054] Example 8

[0055] This embodiment provides a method for preparing structured lipids (SLs), which is different from Example 4 only in that the amount of capric acid (C10:0) is adjusted so that the molar ratio of capric acid (C10:0) to tristearic acid triglyceride is 4:1.

[0056] Example 9

[0057] This embodiment provides a method for preparing structured lipids (SLs), which is different from Example 4 only in that the amount of capric acid (C10:0) is adjusted so that the molar ratio of capric acid (C10:0) to tristearic acid triglyceride is 6:1.

[0058] Comparative Example 1

[0059] This comparative example provides a method for preparing structured lipids (SLs), which is different from Example 4 only in that the UiO-66-SO3H prepared in Example 1 is not added.

[0060] Comparative Example 2

[0061] This comparative example provides a method for preparing structured lipids (SLs), which is different from Example 4 only in that the UiO-66-SO3H prepared in Example 1 is replaced by an equal amount of MIL-101(Cr).

[0062] The preparation method of MIL-101(Cr) is as follows: 1mmol Cr(NO3)3·9H2O and 1mmol H2BDC are dissolved in 4.77mL ultrapure water and stirred at room temperature for 30min using a magnetic stirrer. The mixture is then transferred to an autoclave and subjected to hydrothermal treatment at 200°C for 24 hours. After cooling to room temperature, the sample is collected by centrifugation to obtain MIL-101(Cr).

[0063] Comparative Example 3

[0064] This comparative example provides a method for preparing structured lipids (SLs), which is different from Example 4 only in that the UiO-66-SO3H prepared in Example 1 is replaced by an equal amount of MIL-88.

[0065] The preparation method of MIL-88 is as follows: FeCl3·6H2O (1.352 g) and C4H4O4 (0.580 g) were dissolved in 25 mL of ultrapure water under magnetic stirring. Then, the mixture was transferred to an autoclave and subjected to hydrothermal treatment at 65°C for 12 hours. After cooling to room temperature, the sample was collected by centrifugation to obtain MIL-88.

[0066] Comparative Example 4

[0067] This comparative example provides a method for preparing structured lipids (SLs), which is different from Example 4 only in that the UiO-66-SO3H prepared in Example 1 is replaced by an equal amount of UiO-66.

[0068] Synthesis of UiO-66: H2BDC (0.169 g, 1.029 mmol) and ZrCl4 (0.240 g, 1.029 mmol) were dissolved in anhydrous DMF (60 mL) at room temperature. After stirring for 30 minutes, 2 mL of glacial acetic acid was added to the mixture. The above mixture was stirred at room temperature for 10 minutes, transferred to a 100 mL Teflon liner, and heated at 120 ° C for 24 hours. After heat treatment, the resulting suspension was centrifuged, washed with DMF and methanol, and vacuum dried to obtain UiO-66.

[0069] The following experimental methods:

[0070] 1) Analysis of fatty acid composition of TAG by gas chromatography: FAs were converted into corresponding fatty acid methyl esters (FAMEs) by KOH-CH3OH solution, and the products were sampled after being filtered through a 0.22μm organic membrane to determine the full fatty acid composition. FAMEs were analyzed on an Agilent chromatograph (model 6890N), which was equipped with a split injection port, a flame ionization detector, and data acquisition. Nitrogen was used as the carrier gas with a flow rate of 1.2mL / min and a split ratio of 1:20. The temperatures of the injector and detector were set to 260℃ and 300℃, respectively. The initial temperature of the program was increased to 160℃ and then maintained for 5min. The temperature was finally increased to 200℃ at a rate of 5℃ / min and was isothermally maintained at the final temperature for another 42min. The retention time of the peaks was compared with the respective standards to determine the FAME, and the FAME content was obtained by area normalization and expressed as mass percentage.

[0071] 2) Sample determination of sn-2 fatty acids: Take 50 mg of sample in a centrifuge tube, add 2 mL Tris-HCl buffer (pH = 7.6), 0.5 mL bile salt solution (0.5 g / L), and 0.2 mL CaCl2 solution (22 g / L) in sequence. Then add 20 mg porcine pancreatic lipase, vortex shake for 1 min, and then place in a 37°C water bath for reaction for 6 min, take out and shake for 30 s every 3 min. After the reaction is completed, add 1 mL of hydrochloric acid (6 mol / L) and 2 mL of ether to the sample, centrifuge and take the supernatant, and finally concentrate to about 200 μL with nitrogen. Spot the sample on a silica gel plate for thin layer chromatography, the developing solvent is n-hexane / ether / acetic acid (50 / 50 / 1, v / v / v), iodine vapor is used for color development, and the sn-2 monoglyceride band is carefully scraped, then extracted with ether three times, dried with nitrogen, and methylated, and then analyzed by gas chromatograph, and the gas chromatography detection conditions are the same as above.

[0072] 3) Analysis of TAG components by HPLC: Reverse phase high performance liquid chromatography (RPHPLC) combined with evaporative light scattering detector (ELSD, Alltech 3300, Grace Davison Discovery Sciences, USA) was used to analyze TAG composition. ELSD was maintained at 55 °C with air gas (350 kPa) and the gain was set to 1. The sample was dissolved in n-hexane (5 mg / mL) and analyzed using an Agilent 1260 HPLC system. A light C18 column (5 μm, 250 × 4.6 mm; Jiangsu Hanbang Technology Co., Ltd., China) was used. The sample was eluted with a binary gradient of acetonitrile (A) and isopropanol (B), with a gradient of: 0 min, 90% A, 20 min, 70% A, 30 min, 55% A, 40 min, 70% A, 60 min, 90% A, 70 min, 90% A. During the elution process, the flow rate was 1 mL / min and the injection volume was 10 μL.

[0073] Triglycerides were quantified using the external standard method. Tristearic acid triglyceride, 1,2-stearic acid-3-decanoic acid triglyceride, and 1,2-decanoic acid-3-stearic acid triglyceride were used as standard substances, and the peak area of ​​triglycerides was substituted into the standard curve in the liquid phase diagram to calculate the content.

[0074] Experiment 1

[0075] The structured lipids (SLs) prepared in Example 4-9 were tested, and the results are shown in Figure 1 .

[0076] Figure 1 In the figure, the abscissa represents the structured lipids (SLs) prepared in Examples 4-9, for example, "1:1" represents the structured lipids (SLs) in Example 4; the ordinate represents the amount of fatty acid (decanoic acid) incorporated.

[0077] The acid hydrolysis reaction of tristearic acid triglyceride was carried out at 160°C for 8 hours. The obtained acid hydrolysis product was washed with KOH-ethanol solution to remove free fatty acids, and then methylated and entered the gas phase for capric acid content analysis.

[0078] Depend on Figure 1 It can be seen that by increasing the substrate molar ratio (capric acid: tristearic acid triglyceride) from 1:1 to 5:1, the insertion rate of capric acid increased from 5.9% to 17.3%, and then the capric acid insertion rate decreased slightly when the substrate molar ratio was 6:1. This is because the capric acid concentration of the mixture during the acidolysis reaction provides a large amount of acyl groups during the acidolysis process, which is conducive to the formation of the product. According to the results, the optimal substrate molar ratio of the acidolysis reaction is selected as 5:1.

[0079] The structured lipids (SLs) prepared in Comparative Examples 1-4 were tested, and the results are shown in Figure 2 .

[0080] Figure 2 In the figure, the abscissa represents the structured lipids (SLs) prepared in Comparative Examples 1-4 and Example 8. Blank, MIL-101(Cr), MIL-88, and UiO-66 represent the structured lipids in Comparative Examples 1-4, respectively, and UiO-66-SO3 represents the structured lipids in Example 8. The ordinate represents the amount of fatty acid (decanoic acid) incorporated.

[0081] like Figure 2 As shown, in the absence of a catalyst (Blank), a decanoic acid insertion rate of 2.7% was detected, indicating that tristearic acid triglyceride hardly reacts with decanoic acid under high temperature conditions. MIL-88 and MIL-101 (Cr) have exposed Fe and Cr active sites as Lewis acid catalysts for this reaction. They can catalyze the acidolysis reaction under the same conditions and obtain decanoic acid insertion rates of 5.1% and 4.6%, respectively. The decanoic acid insertion rate of UiO-66 under the same reaction conditions was increased to 7.8%. The sulfonic acid group-modified UiO-66-SO3H has a decanoic acid insertion rate of up to 14.7% for the acidolysis reaction. It is speculated that this is due to the introduction of the sulfonic acid group. The effect brought by the acidic active sites.

[0082] Experiment 2

[0083] In this experiment, UiO-66-SO3H was prepared by Example 4, and UiO-66 was prepared by Comparative Example 4.

[0084] This experiment investigates Lewis and The role of acid sites in the acidolysis reaction was first studied. The distribution of acid sites was investigated by pyridine adsorption FTIR at 150 °C. Figure 3 a, 1445 and 1606cm -1 The vibration band at 1540 cm is assigned to Lewis, -1 The band is assigned to Acid, 1490cm -1 The bands are assigned to Lewis acids and Acid. Lewis acid comes from the metal Zr center, The acid comes from the -SO3H functional group in Zr-MOFs and terephthalic acid. Quantitative analysis shows that the The acid content is 9.61umol / g and the Lewis acid content is 35.43umol / g, which is much higher than that of UiO-66. UiO-66-SO3H has a strong sulfonation strength and a high acidity density, which is conducive to promoting the catalytic acidolysis reaction.

[0085] In order to confirm the results of FTIR on pyridine adsorption, 2,6-lutidine and pyridine were used to measure the adsorption of pyridine. and Lewis sites were selectively blocked.

[0086] Then, the catalyst obtained by selectively blocking UiO-66-SO3H was prepared by 2,6-dimethylpyridine and pyridine, respectively, and the structured lipids (SLs) were prepared by the same method as in Example 4. Figure 3 b, where pristine represents untreated UiO-66-SO3H.

[0087] The untreated UiO-66-SO3H was reacted at 170℃ for 12h, and the insertion rate of medium-chain fatty acids was 22.6%. The insertion rate of medium-chain fatty acids in UiO-66-SO3H after Lewis acid sites were blocked by pyridine was 13.7% under the same catalytic conditions, and the reaction rate was lower than that of untreated UiO-66-SO3H. The insertion rate of medium-chain fatty acids in UiO-66-SO3H after the acid sites was 10.5% under the same catalytic conditions, and the reaction rate and insertion rate were much lower than those of the untreated catalyst. The results confirmed that in both cases, the activity of UiO-66-SO3H decreased after being blocked, indicating that the Lewis acid sites and The interaction between acidic sites can achieve maximum catalytic activity. Compared with pyridine, 2,6-dimethylpyridine has a more intense effect, which proves Acidic sites play a dominant role in acid hydrolysis reaction.

[0088] Lipase catalysts are commonly used to catalyze acidolysis reactions, in which triglycerides are first hydrolyzed into diglycerols and finally monoglycerols, and then new fatty acids are esterified into TAGs. In these two steps, acyl migration occurs, and accordingly, by-products such as diglycerols and monoglycerols are produced during the lipase-catalyzed acidolysis process. However, under the action of UiO-66-SO3H, the acid-catalyzed acidolysis reaction involves a different mechanism. Referring to the mechanism of action of lipase, and on the basis of the above research data, it is speculated that the possible mechanisms of the UiO-66-SO3H acidolysis reaction are divided into two situations ( Figure 3 C and Figure 3 d): The carbonyl group of triacylglycerol is easily protonated by the solid acid catalyst, in which the carbonyl oxygen in FFA interacts with the acidic center to form a carbon cation. The nucleophilic attack of methanol on the carbon cation produces a tetrahedral intermediate. Finally, the water molecule is removed and the acid is also recovered. The Lewis base site mainly catalyzes the transesterification reaction of triglycerides. It is then connected by the carboxyl group of FA to form a tetrahedral intermediate, which usually occurs in the nucleophilic reaction of carboxylic acid. Thereafter, acyloxy cleavage occurs to produce SLS. From a mechanistic point of view, diglycerides and monoglycerides cannot be generated during the acid-catalyzed process. In addition, in order to avoid hydrolysis reactions, the free water in the raw materials is completely removed under reduced pressure before the reaction. After the acidolysis reaction, no undesirable byproducts (monoglycerol and diglycerol) were detected in the liquid chromatography. The results are shown in Table 1.

[0089] Table 1 Structural composition of tristearic acid triglyceride and acid hydrolysis product triglyceride

[0090] <![CDATA[ECN a ]]> Triglycerides Glyceryl Tristearate Acid hydrolysis products (%) 30 CCC ND ND 38 CCS ND 29.71±3.99 46 CSS ND 15.14±3.77 54 SSS 96.52±2.71 54.55±4.52

[0091] a : The total number of carbon atoms in the fatty acids in triglycerides - the degree of unsaturation of triglycerides × 2.

[0092] During the acid hydrolysis reaction, fatty acids are redistributed and recombined on the glycerol backbone, and new triglycerides are generated. Table 1 shows that CSS and CCS are newly generated, with ECN of 46 and 38, respectively, and peak times of 8min and 3min. Calculations show that the contents of CCS, CSS and SSS after the acid hydrolysis reaction are 29.71%, 15.41% and 54.55%, respectively, of which CCS and CSS belong to MLCT, with a content of 45.12%, and LCT content of 54.55%. This indicates that after capric acid is inserted into tristearic acid triglyceride, it will not completely replace and form MCT.

[0093] The above experimental products were subjected to structural analysis by high performance liquid chromatography. By comparing the standard products of possible target products, it was verified that capric acid formed a medium-chain triglyceride structure after entering tristearic acid triglyceride. The product types were MLL and MML type structural lipids and no MMM type was detected. The content of MLCT was 45.12%, indicating that the technical solution provided by the present invention can prepare highly active lipid-like nanozymes. In addition, the Lewis and Acidic site content, pyridine and 2,6-lutidine selectively block Lewis and The acid site experiment proved that Lewis and Acidic sites can synergistically enhance the synthesis of structured lipids, and The acid sites play a dominant role in the acidolysis reaction, indicating that the present invention can introduce Acidic sites effectively enhance the synthesis efficiency of structured lipids.

[0094] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for synthesizing UiO-66-SO3H-based fat nanozyme, characterized in that: include: In the presence of a solvent and acetic acid, ZrCl4, H2BDC and sodium sulfite are reacted.

2. The synthesis method according to claim 1, characterized in that The molar ratio of ZrCl4 to H2BDC is (0.5-2):(0.5-2), preferably 1:

1.

3. The synthesis method according to claim 1 or 2, characterized in that The molar ratio of ZrCl4 to sodium sulfite is (2.5-10):1, preferably 5:1; and / or, The ratio of ZrCl4 to acetic acid is 1 mmol:(3-15) mL, preferably 1 mmol:9 mL.

4. The synthesis method according to claim 1 or 2, characterized in that The reaction temperature is 110-150°C, preferably 140°C.

5. The UiO-66-SO3H-type fat nanozyme prepared by the method according to any one of claims 1 to 4.

6. Use of the UiO-66-SO3H fat nanozyme according to claim 5 in the preparation of structured lipids.

7. A method for preparing a structured lipid, characterized in that: include: Capric acid and tristearic acid triglyceride are used as raw materials, and the UiO-66-SO3H fat nanozyme described in claim 5 is used as a catalyst to carry out an acid hydrolysis reaction.

8. The preparation method according to claim 7, characterized in that: The molar ratio of capric acid to tristearin is (1-6):1, preferably 5:

1.

9. The preparation method according to claim 7 or 8, characterized in that: The temperature of the acid hydrolysis reaction is 130-180°C, preferably 170°C.

10. The structured lipid prepared by the method according to any one of claims 7 to 9; Preferably, the content of MLCT in the structural lipid is 40-50%, more preferably 45.12%.

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