A modified starch-based surfactant and its preparation method and application

Abstract

The present invention relates to the field of surfactant technology, and more particularly to a modified starch-based surfactant and its preparation method and application, comprising the following steps: step one, mixing hydrophobic modified starch with phosphate buffer to form a mixed solution of 8-13wt%; step two, adding modified α-amylase to the mixed solution in step one, warming to 60-70°C and shaking for 20-30min, deactivating the enzyme after the reaction, and obtaining a modified starch-based surfactant after concentration; the modified starch-based surfactant is a cationic surfactant; the mass of the modified α-amylase is 0.01-0.1% of the mass of hydrophobic modified starch. The modified starch-based surfactant of the present invention is suitable for the field of water treatment, can not only play a good emulsification stability, but also has a certain antibacterial effect, the preparation method of the modified starch-based surfactant is efficient, can avoid the problem of low biological enzyme activity and unstable biological enzyme at high temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of surfactants, and in particular to a modified starch-based surfactant and a preparation method and application thereof. Background Art

[0002] Surfactants, due to their unique molecular structure and diverse properties, play a vital role in many industrial fields. From detergents and cosmetics in daily life to pharmaceuticals and textiles in the industrial field, surfactants are everywhere. In recent years, with the advancement of science and technology and the enhancement of environmental awareness, the research and application of surfactants are facing new challenges and opportunities, especially in emerging fields such as scale inhibitors, which has become a hot topic of research. The basic properties of surfactants are derived from their special molecular structure, with a long-chain non-polar hydrophobic group at one end and a water-soluble hydrophilic group at the other end. This structure enables surfactants to form micelles in solution, thereby exhibiting various unique properties, such as reducing surface tension, changing wettability, and improving emulsion stability. In the field of detergents, surfactants, as key ingredients, can significantly improve washing effects and water efficiency; in cosmetics, surfactants are used to emulsify and stabilize formulas, and at the same time as cleansers and makeup removers, help people keep their skin clean and healthy. In addition, in the fields of pharmaceuticals and textiles, surfactants also play an irreplaceable role.

[0003] Starch, as a natural polymer compound, is widely present in nature and is the main energy storage material in plants. Its molecular structure is composed of multiple glucose units connected by glycosidic bonds and has unique hydrophilicity. With the enhancement of environmental awareness and the popularization of the concept of sustainable development, the manufacture of surfactants using starch as raw material has become a research hotspot. Some researchers have successfully developed some new starch-based surfactants by modifying starch. For example, CN101787383B discloses a "synthesis method of starch-based surfactant N-butyl glucose lauramide". Starch is enzymolyzed with amylase and saccharifying enzyme respectively, and then n-butylamine, water, colorimetric agent and rhodium catalyst are added to react to obtain N-butyl glucosamine, and then N-butyl glucosamine is acylated with lauric acid and aminoacylase to obtain N-butyl glucose lauramide surfactant. The surfactant has a simple preparation process, low cost, high raw material utilization rate, and the product has the characteristics of low surface tension, excellent foaming performance, non-toxicity, non-irritation, and easy biodegradability.

[0004] For example, CN108409872B discloses "a method for preparing octenyl succinic anhydride modified starch ester by double enzyme enzymatic hydrolysis", which includes the preparation of octenyl succinic anhydride starch ester; amylase enzymatic hydrolysis: adjusting the pH to acidic, dissolving the amylase in a buffer solution and adding it to the octenyl succinic acid starch ester, and reacting under stirring to obtain the octenyl succinic acid modified starch ester with better emulsification stability.

[0005] The above-mentioned patents all adopt the method of modifying starch with biological enzymes. However, biological enzymes have problems such as low activity, poor stability, and poor adaptability, which limit their use. Moreover, the above-mentioned patents do not mention or solve this technical problem.

[0006] Therefore, it is urgent to develop a method for preparing starch-based surfactants by efficiently modifying starch with bio-enzymes. Summary of the invention

[0007] The main purpose of the present invention is to provide a modified starch-based surfactant and a preparation method thereof. The modified starch-based surfactant is suitable for the field of water treatment, and not only can play a good emulsification stability, but also has a certain antibacterial effect. The preparation method of the modified starch-based surfactant is efficient and can avoid the problems of low biological enzyme activity and instability of biological enzymes at high temperatures.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] In one aspect, the present invention provides a method for preparing a modified starch-based surfactant, comprising the following steps:

[0010] Step 1, mixing the hydrophobically modified starch and the phosphate buffer into a mixed solution of 8-13 wt %;

[0011] Step 2: adding the modified α-amylase to the mixed solution in step 1, heating to 60-70°C and shaking for 20-30 minutes, killing the enzyme after the reaction, and concentrating to obtain a modified starch-based surfactant;

[0012] The modified starch-based surfactant is a cationic surfactant; the mass of the modified α-amylase is 0.01-0.1% of the mass of the hydrophobic modified starch.

[0013] In some embodiments, the method for preparing the hydrophobically modified starch comprises the following steps:

[0014] A1. Under an inert gas atmosphere, 3-bromopyrrolidine aldehyde and the compound shown in formula I are

[0015] (I) was mixed and added to acetone, the temperature was raised to reflux state, and the mixture was stirred at constant temperature for 40 to 50 hours. After the reaction was completed, the mixture was concentrated and dried under reduced pressure, and then subjected to column chromatography to obtain the compound shown in Formula II

[0016] (II);

[0017] A2. Under an inert gas atmosphere, the compound of formula II in step A1, 3-butenoic acid, triphenylphosphine palladium acetate and sodium peracetate are mixed, added to tetrahydrofuran, heated to reflux and stirred at constant temperature for 24 to 28 hours, and after the reaction is completed, column chromatography is performed to obtain a compound of formula III.

[0018] (III);

[0019] A3, starch and deionized water are mixed to form a 10-30wt% emulsion, sodium silicate is added to the system, and then urea is added to adjust the pH of the system to 9-10, the temperature is raised to 80-90°C, the compound represented by formula III in step A2 is added to the system and stirred at a constant temperature for 1-3h, and then cooled to room temperature to obtain hydrophobically modified starch;

[0020] Wherein n is an integer of 7 to 16, and R is a halogen.

[0021] Starch structure contains a large number of hydroxyl groups, but due to the effect of internal hydrogen bonds, its water solubility is poor. By modifying starch, the internal hydrogen bonding effect can be reduced to improve its water solubility. At the same time, the hydroxyl groups can react with a variety of groups to give starch the characteristic of modifiability. Currently, a large number of researchers have introduced lipophilic groups into the starch structure to make starch form hydrophilic and lipophilic surfactants.

[0022] The hydrophobic modified starch of the present application not only has a certain surface activity after enzymatic hydrolysis, but also has a certain bactericidal ability. Its application in water treatment agents can prevent the generation of microbial sludge and damage metal equipment. The reason may be that the hydrophobic modified starch of the present application contains a certain quaternary ammonium salt structure, which can reduce the ability of microorganisms to enrich metal equipment and thus slow down equipment corrosion.

[0023] In some embodiments, in step A1, the molar ratio of 3-bromopyrrolidine aldehyde to the compound represented by formula I is 1:(1-2).

[0024] In some embodiments, in step A2, the molar ratio of the compound represented by formula II to 3-butenoic acid is 1:(1~1.5).

[0025] In some embodiments, in step A3, the mass ratio of the starch to the compound represented by formula III is 1:(0.2~0.6).

[0026] In some embodiments, the method for preparing the modified α-amylase comprises the following steps:

[0027] B1, dissolving chitosan in acetic acid solution to form a chitosan solution;

[0028] B2, mixing and dispersing the regenerated cellulose and water to form a mixed solution;

[0029] B3, mixing the chitosan solution in step B1 with the polyvinyl alcohol solution, and then adding the mixed solution in step B2 to the system, stirring at room temperature for 1 to 2 hours to form an emulsion, then filtering, and freeze-drying to obtain a chitosan / regenerated cellulose gel;

[0030] B4. Under an inert protective gas atmosphere, cool thionyl chloride to -5~0°C, add 1,3-acetone dicarboxylic acid at a constant temperature, heat to room temperature and stir for 4~6 hours. After the reaction is completed, quench, extract, combine the organic phases, and concentrate and dry under reduced pressure to obtain compound A;

[0031] B5, adding compound A in B4 to the chitosan / regenerated cellulose gel in step B3, adding tetrahydrofuran, heating to 50-60°C and stirring at a constant temperature for 1-3 hours, filtering after the reaction is completed, freeze-drying, washing with ethanol solution, and freeze-drying again to obtain modified chitosan / regenerated cellulose gel;

[0032] B6. Mix α-amylase with a phosphate buffer having a pH of 6 to 7, then add the modified chitosan / regenerated cellulose gel in step B5, react under ultrasonic vibration at room temperature for 20 to 30 hours, then filter and rinse with a phosphate buffer having a pH of 6 to 7 to obtain a modified α-amylase.

[0033] α-amylase, also known as x-1,4-glucan-4-glucanohydrolase, is widely distributed in animals, plants and microorganisms. It can randomly act on the α-1,4-glycosidic bonds inside starch, glycogen, oligosaccharides or polysaccharide molecules to hydrolyze starch into a series of small molecules such as dextrin, maltose, oligosaccharides and glucose. Although α-amylase has been widely used in many fields, it still has many problems during use, such as low enzyme activity, poor stability and adaptability, short activity retention time, difficulty in regeneration and poor reusability, which seriously limit the use of α-amylase and invisibly increase production costs.

[0034] The modified α-amylase of the present application has a certain heat stability and still has a certain enzyme activity at a relatively high temperature. At the same time, the modified α-amylase has high catalytic performance and high stability, and can be naturally degraded after the reaction without affecting the environment. The reason may be that, on the one hand, the modified α-amylase is loaded into a modified chitosan / regenerated cellulose gel structure by covalent bonding, which reduces the fluidity of the α-amylase and thus improves the heat stability, catalytic performance and storage stability of the α-amylase; on the other hand, the raw materials used for the modified α-amylase are chitosan and regenerated cellulose, which are environmentally friendly, and the formed gel has a certain natural degradation ability without affecting the environment.

[0035] In some embodiments, the mass ratio of chitosan to regenerated cellulose is 1:(1-3).

[0036] In some embodiments, in step B5, the mass ratio of compound A to chitosan / regenerated cellulose gel is (1.2~1.8):1.

[0037] Another aspect of the present invention provides a modified starch-based surfactant prepared by the above scheme.

[0038] In another aspect, the present invention provides an application of a modified starch-based surfactant in the field of water treatment.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The modified starch-based surfactant of the present invention is prepared by enzymatically hydrolyzing hydrophobic modified starch with modified α-amylase. The modified starch-based surfactant is suitable for the field of water treatment. It not only has good emulsification stability, but also has a certain antibacterial effect. At the same time, the preparation method is efficient and can avoid the problems of low biological enzyme activity and instability of biological enzymes at high temperatures.

[0041] (2) The hydrophobically modified starch of the present invention contains a large number of hydrophilic and hydrophobic groups in its structure, which can play a role in surface activity. At the same time, after enzymatic hydrolysis, the molecular weight of the surfactant can be reduced, thereby reducing the viscosity of the system.

[0042] (3) The modified α-amylase of the present invention is loaded into a modified chitosan / regenerated cellulose gel structure by a covalent bonding method, thereby reducing the fluidity of the α-amylase and thus improving the heat stability, catalytic performance and storage stability of the α-amylase; in addition, the raw materials used for the modified α-amylase are chitosan and regenerated cellulose, which are environmentally friendly, and the formed gel has a certain natural degradation ability and has no impact on the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1This is the hydrogen nuclear magnetic resonance spectrum of the compound represented by formula II in Preparation Example 1.

[0044] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the compound represented by formula III in Preparation Example 1. DETAILED DESCRIPTION

[0045] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0046] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0047] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. Various modifications and variations may be made to the specific embodiments of the present invention specification without departing from the scope or spirit of the present invention, which will be apparent to those skilled in the art. Other embodiments obtained from the present invention specification will be apparent to the technician. The present application specification and examples are exemplary only.

[0048] It should be noted that the operations of "drying", "filtering" and "stirring" described in the present invention are routine operations of those skilled in the art and can be selected according to actual operations.

[0049] In the following preparation examples, starch was purchased from Langfang Pengcai Fine Chemical Co., Ltd.; chitosan was purchased from Anhui Xinsheng Biotechnology Co., Ltd.; lignin fiber was purchased from Shandong Taicheng Fiber Co., Ltd.; α-amylase was purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd.

[0050] Preparation Example 1

[0051] The preparation method of hydrophobically modified starch comprises the following steps:

[0052] A1. Under N2 atmosphere, 50mmol 3-bromopyridine aldehyde and 75mmol 1-chlorodecane were added to 100mL acetone, the temperature was raised to reflux state, and the mixture was stirred at constant temperature for 45h. After the reaction was completed, the mixture was concentrated and dried under reduced pressure, and then subjected to column chromatography to obtain the compound shown in Formula II

[0053] (II);

[0054] Figure 1 The NMR image of the compound shown in Formula II is analyzed as follows: 1 H NMR (400 MHz, ) δ 9.66 (s,1H), 8.83 (dd, J = 8.0, 1.3 Hz, 2H), 8.38 (dd, J = 12.0, 1.4 Hz, 2H), 7.93(dd, J = 8.0, 6.2 Hz, 2H), 4.52 (t, J = 4.0 Hz, 3H), 2.04 (tt, J = 8.0, 6.5Hz, 3H), 1.63-1.44 (m, 1H), 1.35-1.21 (m, 10H), 0.96-0.81 (m, 3H);

[0055] A2. Under N2 atmosphere, 50 mmol of the compound of formula II in step A1, 20 mmol of 3-butenoic acid, 2.5 mmol of triphenylphosphine palladium acetate and 150 mmol of sodium peracetate were mixed, added to 200 mL of tetrahydrofuran, heated to reflux and stirred at constant temperature for 26 hours. After the reaction was completed, column chromatography was performed to obtain a compound of formula III.

[0056] (III);

[0057] Figure 2 The NMR image of the compound shown in Formula III is analyzed as follows: 1 H NMR (400 MHz, ) δ 9.48 (dd,J = 4.0, 1.3 Hz, 1H), 9.02 (ddd, J = 8.0, 2.3, 1.4 Hz, 1H), 8.89 (dd, J =4.0, 1.5 Hz, 1H), 8.20-8.04 (m, 2H), 4.65 (t, J = 8.0 Hz, 2H), 2.09 (tt, J =8.0, 6.3 Hz, 2H), 1.66-1.53 ​​(m, 5H), 1.38-1.23 (m, 5H), 0.95-0.82 (m, 2H);

[0058] A3. Mix 10g of starch with deionized water to prepare a 20wt% emulsion, add 0.05g of sodium silicate to the system, then add urea to adjust the pH of the system to 9.5, raise the temperature to 85°C, add 4g of the compound represented by formula III in step A2 to the system and stir at a constant temperature for 2h, then cool to room temperature to obtain hydrophobically modified starch.

[0059] Preparation Example 2

[0060] The preparation method of hydrophobically modified starch is the same as that of Preparation Example 1, except that an equal mole of 1-chloroheptane is used instead of 1-chlorodecane.

[0061] Preparation Example 3

[0062] The preparation method of hydrophobically modified starch is the same as that of Preparation Example 1, except that 1-chlorodecane is not added.

[0063] Preparation Example 4

[0064] The preparation method of hydrophobically modified starch is the same as that of Preparation Example 1, except that in step A3, the amount of the compound represented by formula III is 1 g.

[0065] Preparation Example 5

[0066] The preparation method of modified α-amylase comprises the following steps:

[0067] B1, dissolving 2 g of chitosan in 100 mL of 1 wt % acetic acid solution to form a chitosan solution;

[0068] B2, 4 g of lignin fiber was mixed and dispersed evenly with 200 mL of water to form a mixed solution;

[0069] B3, mixing the chitosan solution in step B1 with 50 mL of 10 wt% polyvinyl alcohol solution, and then adding the mixed solution in step B2 to the system, stirring at room temperature for 1.5 h to form an emulsion, then filtering and freeze-drying to obtain a chitosan / lignin fiber gel;

[0070] B4. Under N2 atmosphere, cool 100 mL of thionyl chloride to -3°C, add 6 g of 1,3-acetone dicarboxylic acid at constant temperature, warm to room temperature and stir for 5 h. After the reaction is completed, quench, extract, combine the organic phases, and concentrate and dry under reduced pressure to obtain compound A;

[0071] B5, adding 4.8g of compound A in B4 to 3g of chitosan / lignin fiber gel in step B3, adding 100mL of tetrahydrofuran, heating to 55°C and stirring at constant temperature for 2h, filtering after the reaction, freeze-drying, washing with 65wt% ethanol solution, and freeze-drying again to obtain modified chitosan / lignin fiber gel;

[0072] B6. Mix 10 g of α-amylase with 800 mL of phosphate buffer at pH 6.5, then add 2 g of the modified chitosan / lignin fiber gel in step B5, react under ultrasonic vibration at room temperature for 25 h, then filter and rinse with phosphate buffer at pH 6.5 to obtain modified α-amylase.

[0073] Preparation Example 6

[0074] The preparation method of modified α-amylase comprises the following steps:

[0075] B1, dissolving 2 g of chitosan in 100 mL of 1 wt % acetic acid solution to form a chitosan solution;

[0076] B2, mix 2g of lignin fiber with 200mL of water to form a mixed solution;

[0077] B3, mixing the chitosan solution in step B1 with 50 mL of 10 wt% polyvinyl alcohol solution, and then adding the mixed solution in step B2 to the system, stirring at room temperature for 1.5 h to form an emulsion, then filtering and freeze-drying to obtain a chitosan / lignin fiber gel;

[0078] B4. Under N2 atmosphere, cool 100 mL of thionyl chloride to -3°C, add 6 g of 1,3-acetone dicarboxylic acid at constant temperature, warm to room temperature and stir for 5 h. After the reaction is completed, quench, extract, combine the organic phases, and concentrate and dry under reduced pressure to obtain compound A;

[0079] B5, adding 3.6g of compound A in B4 to 3g of chitosan / lignin fiber gel in step B3, adding 100mL of tetrahydrofuran, heating to 55°C and stirring at constant temperature for 2h, filtering after the reaction, freeze-drying, washing with 65wt% ethanol solution, and freeze-drying again to obtain modified chitosan / lignin fiber gel;

[0080] B6. Mix 10 g of α-amylase with 800 mL of phosphate buffer at pH 6.5, then add 2 g of the modified chitosan / lignin fiber gel in step B5, react under ultrasonic vibration at room temperature for 25 h, then filter and rinse with phosphate buffer at pH 6.5 to obtain modified α-amylase.

[0081] Preparation Example 7

[0082] The preparation method of modified α-amylase comprises the following steps:

[0083] B1, dissolving 2 g of chitosan in 100 mL of 1 wt % acetic acid solution to form a chitosan solution;

[0084] B2, mix 6g of lignin fiber with 200mL of water to form a mixed solution;

[0085] B3, mixing the chitosan solution in step B1 with 50 mL of 10 wt% polyvinyl alcohol solution, and then adding the mixed solution in step B2 to the system, stirring at room temperature for 1.5 h to form an emulsion, then filtering and freeze-drying to obtain a chitosan / lignin fiber gel;

[0086] B4. Under N2 atmosphere, cool 100 mL of thionyl chloride to -3°C, add 6 g of 1,3-acetone dicarboxylic acid at constant temperature, warm to room temperature and stir for 5 h. After the reaction is completed, quench, extract, combine the organic phases, and concentrate and dry under reduced pressure to obtain compound A;

[0087] B5, adding 5.4g of compound A in B4 to 3g of chitosan / lignin fiber gel in step B3, adding 100mL of tetrahydrofuran, heating to 55°C and stirring at constant temperature for 2h, filtering after the reaction, freeze-drying, washing with 65wt% ethanol solution, and freeze-drying again to obtain modified chitosan / lignin fiber gel;

[0088] B6. Mix 10 g of α-amylase with 800 mL of phosphate buffer at pH 6.5, then add 2 g of the modified chitosan / lignin fiber gel in step B5, react under ultrasonic vibration at room temperature for 25 h, then filter and rinse with phosphate buffer at pH 6.5 to obtain modified α-amylase.

[0089] Preparation Example 8

[0090] The preparation method of modified α-amylase is the same as that of Preparation Example 5, except that the amount of compound A in step B5 is 6.5 g.

[0091] Preparation Example 9

[0092] The preparation method of the modified α-amylase is the same as that of Preparation Example 5, except that the amount of lignin fiber is 8 g.

[0093] Example 1

[0094] A method for preparing a modified starch-based surfactant comprises the following steps:

[0095] Step 1: Mix 2 g of hydrophobically modified starch with 20 mL of pH 6.5 phosphate buffer to prepare a 10 wt% mixed solution;

[0096] Step 2: Add 0.01 g of modified α-amylase to the mixed solution in step 1, heat to 65° C. and shake for 25 min. After the reaction is completed, inactivate the enzyme and concentrate to obtain a modified starch-based surfactant.

[0097] Among them, the hydrophobic modified starch is prepared by Preparation Example 1, and the modified α-amylase is prepared by Preparation Example 5.

[0098] Example 2

[0099] A method for preparing a modified starch-based surfactant comprises the following steps:

[0100] Step 1: Mix 2 g of hydrophobically modified starch with 25 mL of phosphate buffer at pH 6.5 to prepare a mixed solution of 8 wt %;

[0101] Step 2: Add 0.002 g of modified α-amylase to the mixed solution in step 1, heat to 70° C. and shake for 20 min. After the reaction is completed, inactivate the enzyme and concentrate to obtain a modified starch-based surfactant.

[0102] Among them, the hydrophobic modified starch is prepared by Preparation Example 1, and the modified α-amylase is prepared by Preparation Example 5.

[0103] Example 3

[0104] A method for preparing a modified starch-based surfactant comprises the following steps:

[0105] Step 1: Mix 2 g of hydrophobically modified starch with 15 mL of pH 6.5 phosphate buffer to prepare a 13 wt% mixed solution;

[0106] Step 2: Add 0.02 g of modified α-amylase to the mixed solution in step 1, heat to 60° C. and shake for 30 min. After the reaction is completed, inactivate the enzyme and concentrate to obtain a modified starch-based surfactant.

[0107] Among them, the hydrophobic modified starch is prepared by Preparation Example 1, and the modified α-amylase is prepared by Preparation Example 5.

[0108] Example 4

[0109] A method for preparing a modified starch-based surfactant, the specific implementation method is the same as Example 1, except that the modified α-amylase is prepared by Preparation Example 6.

[0110] Example 5

[0111] A method for preparing a modified starch-based surfactant, the specific implementation method is the same as Example 1, except that the modified α-amylase is prepared by Preparation Example 7.

[0112] Example 6

[0113] A method for preparing a modified starch-based surfactant, the specific implementation method is the same as Example 1, except that the hydrophobic modified starch is prepared by Preparation Example 2.

[0114] Example 7

[0115] A method for preparing a modified starch-based surfactant, the specific implementation method is the same as Example 1, except that the hydrophobic modified starch is prepared by Preparation Example 4.

[0116] Comparative Example 1

[0117] A method for preparing a modified starch-based surfactant, the specific implementation method is the same as Example 1, except that α-amylase is used instead of modified α-amylase.

[0118] Comparative Example 2

[0119] A method for preparing a modified starch-based surfactant, the specific implementation method is the same as Example 1, except that the hydrophobic modified starch is prepared by Preparation Example 3.

[0120] Comparative Example 3

[0121] A method for preparing a modified starch-based surfactant, the specific implementation method is the same as that of Example 1, except that octenyl succinic anhydride starch ester is used instead of the hydrophobically modified starch.

[0122] The preparation method of octenyl succinic anhydride starch ester is prepared by referring to "Example 1" disclosed in the patent publication number CN108409872B.

[0123] Performance Testing:

[0124] (1) Enzyme activity test: 1 g of modified α-amylase was mixed with 100 mL of deionized water, and the enzyme solution was obtained after filtration. A 1% (w / v) soluble starch solution was prepared in 100 mL of phosphate buffer solution (10 mM, pH = 5.0). The solution was placed in a boiling water bath for gelatinization and then cooled to 50°C. 900 μL of the gelatinized solution was added with 100 μL of the enzyme solution at 50°C and reacted for 10 min. 1 mL of DNS was then immediately added to terminate the reaction. The solution was boiled in a water bath for 5 min for color development and then cooled in an ice water bath. The absorbance of the reaction system was measured at 540 nm. The amount of enzyme required to catalyze the production of a product equivalent to the reducing power of 1 μmol of maltose per minute was defined as one activity unit.

[0125] The modified α-amylases prepared in Preparation Examples 5 to 9 were tested according to method (1). The test results are shown in Table 1.

[0126] Table 1

[0127]

[0128] According to the data in Table 1, the modified α-amylases prepared in Preparation Examples 5 to 7 have good enzyme activity at 50°C; Preparation Example 8 changes the mass ratio of compound A and chitosan / lignin fiber gel, which increases the cross-linking density of the modified chitosan / lignin fiber gel, which is not conducive to the loading of α-amylase and leads to a decrease in the enzyme activity of the modified α-amylase; Preparation Example 9 changes the mass ratio of chitosan to lignin fiber, which increases the cross-linking density of the modified chitosan / lignin fiber gel, which is not conducive to the loading of α-amylase and leads to a decrease in the enzyme activity of the modified α-amylase.

[0129] (2) Surface tension: 1 g of modified starch-based surfactant was mixed with deionized water to form a 5 wt % solution. The surface tension was measured using a JYW-200A fully automatic surface tension meter and a platinum sheet method. For the specific test method, refer to the test method disclosed in paragraph

[0103] of publication number CN110041382A.

[0130] (3) Antibacterial performance: Refer to SY-T 5890-93 "Bactericide Performance Evaluation Method" for testing.

[0131] The modified starch-based surfactants prepared in the examples and comparative examples were tested according to methods (2) and (3). The test results are shown in Table 2.

[0132] Table 2

[0133]

[0134] According to the data in Table 2, the modified starch-based surfactants prepared in Examples 1 to 5 have good surface activity and excellent antibacterial and antimicrobial ability; in Example 6, the surface activity of the modified starch-based surfactant is weakened due to the use of equimolar 1-chloroheptane instead of 1-chlorodecane; in Example 7, the surface activity of the modified starch-based surfactant is slightly reduced due to the change in the mass ratio of starch to the compound shown in Formula III, and the antibacterial and antimicrobial effect is slightly reduced; in Comparative Example 1, α-amylase is used instead of modified α-amylase, and the hydrolysis and modification ability of α-amylase is poor at the same temperature and time, resulting in a decrease in the surface activity of the modified starch-based surfactant; in Comparative Example 2, 1-chlorodecane is not added, resulting in the modified starch not being a cationic surfactant, and the surface activity is reduced, and the antibacterial and antibacterial effect is poor; in Comparative Example 3, octenyl succinic anhydride starch ester is used instead of hydrophobic modified starch, resulting in a decrease in the antibacterial and antimicrobial performance of the modified starch-based surfactant.

[0135] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a modified starch-based surfactant, characterized in that: The steps include: Step 1, mixing the hydrophobically modified starch and the phosphate buffer into a mixed solution of 8-13 wt %; Step 2: adding the modified α-amylase to the mixed solution in step 1, heating to 60-70°C and shaking for 20-30 minutes, killing the enzyme after the reaction, and concentrating to obtain a modified starch-based surfactant; The modified starch-based surfactant is a cationic surfactant; the mass of the modified α-amylase is 0.01-0.1% of the mass of the hydrophobic modified starch; The preparation method of the hydrophobically modified starch comprises the following steps: A1. Under an inert gas atmosphere, 3-bromopyrrolidine aldehyde and the compound shown in formula I are (I) was mixed and added to acetone, the temperature was raised to reflux state, and the mixture was stirred at constant temperature for 40 to 50 hours. After the reaction was completed, the mixture was concentrated and dried under reduced pressure, and then subjected to column chromatography to obtain the compound shown in Formula II （Ⅱ）； A2. Under an inert gas atmosphere, the compound of formula II in step A1, 3-butenoic acid, triphenylphosphine palladium acetate and sodium peracetate are mixed, added to tetrahydrofuran, heated to reflux and stirred at constant temperature for 24 to 28 hours, and after the reaction is completed, column chromatography is performed to obtain a compound of formula III. （Ⅲ）； A3, starch and deionized water are mixed to form a 10-30wt% emulsion, sodium silicate is added to the system, and then urea is added to adjust the pH of the system to 9-10, the temperature is raised to 80-90°C, the compound represented by formula III in step A2 is added to the system and stirred at a constant temperature for 1-3h, and then cooled to room temperature to obtain hydrophobically modified starch; Wherein n is an integer of 7 to 16, and R is a halogen; The preparation method of the modified α-amylase comprises the following steps: B1, dissolving chitosan in acetic acid solution to form a chitosan solution; B2, mixing and dispersing the regenerated cellulose and water to form a mixed solution; B3, mixing the chitosan solution in step B1 with the polyvinyl alcohol solution, and then adding the mixed solution in step B2 to the system, stirring at room temperature for 1 to 2 hours to form an emulsion, then filtering, and freeze-drying to obtain a chitosan / regenerated cellulose gel; B4. Under an inert protective gas atmosphere, cool thionyl chloride to -5~0°C, add 1,3-acetone dicarboxylic acid at a constant temperature, heat to room temperature and stir for 4~6 hours. After the reaction is completed, quench, extract, combine the organic phases, and concentrate and dry under reduced pressure to obtain compound A; B5, adding compound A in B4 to the chitosan / regenerated cellulose gel in step B3, adding tetrahydrofuran, heating to 50-60°C and stirring at a constant temperature for 1-3 hours, filtering after the reaction is completed, freeze-drying, washing with ethanol solution, and freeze-drying again to obtain modified chitosan / regenerated cellulose gel; B6. Mix α-amylase with a phosphate buffer having a pH of 6 to 7, then add the modified chitosan / regenerated cellulose gel in step B5, react under ultrasonic vibration at room temperature for 20 to 30 hours, then filter and rinse with a phosphate buffer having a pH of 6 to 7 to obtain a modified α-amylase.

2. The method for preparing a modified starch-based surfactant according to claim 1, characterized in that: In step A1, the molar ratio of the 3-bromopyrrolidine aldehyde to the compound represented by formula I is 1:(1-2).

3. The method for preparing a modified starch-based surfactant according to claim 1, characterized in that: In step A2, the molar ratio of the compound represented by formula II to 3-butenoic acid is 1:(1-1.5).

4. The method for preparing a modified starch-based surfactant according to claim 1, characterized in that: In step A3, the mass ratio of the starch to the compound represented by formula III is 1:(0.2-0.6).

5. The method for preparing a modified starch-based surfactant according to claim 1, characterized in that: The mass ratio of chitosan to regenerated cellulose is 1:(1-3).

6. The method for preparing a modified starch-based surfactant according to claim 1, characterized in that: In step B5, the mass ratio of compound A to chitosan / regenerated cellulose gel is (1.2~1.8):

1.

7. A modified starch-based surfactant obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the modified starch-based surfactant according to claim 7 in the field of water treatment.

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