Self-assembled surfactant as well as preparation and application thereof

Abstract

The invention provides a self-assembled surfactant as well as preparation and application thereof. The preparation method comprises the following steps: adding an anionic surfactant and a nonionic surfactant into a buffer solution, uniformly mixing, and heating until the anionic surfactant and the nonionic surfactant are completely molten, so as to obtain the self-assembled surfactant. Wherein the anionic surfactant is one or more of lignosulfonate, secondary alkyl sulfonate and alpha-olefin sulfonate; the nonionic surfactant is one or more of polyethylene glycol, fatty alcohol-polyoxyethylene ether, polyoxyethylene alkyl ether and polyoxyethylene nonyl phenyl ether. The specific anionic surfactant and the nonionic surfactant are compounded, self-assembly is completed through heating, and the obtained self-assembly surfactant can remarkably improve the enzymolysis efficiency of lignocellulose.

Description

Technical Field

[0001] This invention belongs to the field of engineering and technological research and experimental development technology, including biomass liquid fuel production, cellulosic ethanol production, and raw material cellulose separation technology. More specifically, it relates to a self-assembling surfactant and its preparation and application. Background Technology

[0002] Lignocellulose, as the most abundant renewable organic resource on Earth, is widely found in agricultural waste (such as straw and corn cobs), forestry residues (such as sawdust and bark), and industrial byproducts (such as black liquor). If not effectively developed, it not only wastes resources but may also lead to anaerobic fermentation producing methane (25 times more potent than carbon dioxide in terms of greenhouse effect) due to long-term accumulation, or release particulate matter and toxic gases through incineration, causing air pollution. Therefore, converting it into glucose through enzymatic hydrolysis can achieve high-value utilization of biomass resources. Furthermore, glucose, as a basic chemical raw material, can be further converted into biomass liquid fuels (such as ethanol), bio-based materials (such as polylactic acid), and biochemicals (such as citric acid), forming a complete industrial chain from waste to high-value-added products, significantly improving resource utilization efficiency and economic value.

[0003] Existing research indicates that adding lignin sulfonate during the enzymatic hydrolysis of lignocellulose can improve hydrolysis efficiency by stripping away the non-productive adsorption of lignin to the enzyme. However, preliminary experiments have shown that the improvement effect of lignin sulfonate alone is still limited. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a method for preparing self-assembled surfactants. By compounding specific anionic and nonionic surfactants and completing self-assembly through heating, the enzymatic hydrolysis efficiency of lignocellulose can be significantly improved, with an improvement far exceeding the effect of either anionic or nonionic surfactants alone.

[0005] The first objective of this invention is to provide a method for preparing a self-assembling surfactant.

[0006] A second objective of the present invention is to provide a self-assembling surfactant prepared by the above method.

[0007] A third objective of this invention is to provide the application of the aforementioned self-assembling surfactant in the enzymatic hydrolysis of lignocellulose.

[0008] A fourth objective of this invention is to provide an enzymatic hydrolysis method for lignocellulose.

[0009] The above-mentioned objective of this invention is achieved through the following technical solution: This invention provides a method for preparing a self-assembled surfactant, specifically: adding anionic surfactant and nonionic surfactant to a buffer solution, mixing well, and heating until completely melted to obtain the self-assembled surfactant; The anionic surfactant is one or more of lignin sulfonate, secondary alkyl sulfonate (SAS), and α-olefin sulfonate (AOS); the nonionic surfactant is one or more of polyethylene glycol, fatty alcohol polyoxyethylene ether (AEO), polyoxyethylene alkyl ether, and polyoxyethylene nonylphenyl ether.

[0010] Preferably, the mass ratio of the anionic surfactant to the nonionic surfactant is (0.5-3):4.

[0011] Preferably, the lignin sulfonate is one or more of calcium lignin sulfonate, sodium lignin sulfonate, and magnesium lignin sulfonate; the secondary alkyl sulfonate is one or more of sodium secondary alkyl sulfonate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate; and the α-olefin sulfonate is one or more of sodium alkenyl sulfonate and sodium hydroxyalkyl sulfonate.

[0012] Preferably, the polyethylene glycol is one or more of PEG-4000, PEG-6000, and PEG-8000; the fatty alcohol polyoxyethylene ether is one or more of lauryl alcohol polyoxyethylene ether and isotretinoin polyoxyethylene ether; the polyoxyethylene alkyl ether is one or more of polyethylene glycol monohexadecyl ether and polyethylene glycol monolauryl ether; and the polyoxyethylene nonylphenyl ether is one or more of nonylphenol polyether-2, nonylphenol polyether-5, and nonylphenol polyether-10.

[0013] Preferably, the pH of the buffer solution is 3 to 7.

[0014] Preferably, the buffer solution is one or more of acetic acid-sodium acetate buffer solution and citric acid-sodium citrate buffer solution.

[0015] Preferably, the concentration of the anionic surfactant in the buffer solution is 0.0005–0.003 g / mL.

[0016] Preferably, the mixing is carried out at 250–350 rpm, and most preferably at 300 rpm.

[0017] Preferably, the heating temperature is 50–120 °C, and most preferably 80 °C.

[0018] Preferably, before adding the buffer solution, the anionic surfactant and the nonionic surfactant are mixed thoroughly.

[0019] More preferably, the mixing process is accompanied by heating.

[0020] More preferably, the heating temperature is 50–150 °C, and most preferably 120 °C.

[0021] More preferably, the mixing is carried out at 250–350 rpm, and most preferably at 300 rpm.

[0022] The self-assembling surfactants prepared by the above method utilize the hydrophobic and electrostatic interactions between anionic and nonionic surfactants to self-assemble into smaller colloids. When used for the degradation of lignocellulose, they can significantly improve the enzymatic hydrolysis efficiency of lignocellulose. Therefore, the self-assembling surfactants prepared by the above method, and their application in the enzymatic hydrolysis of lignocellulose, should be within the scope of protection of this invention.

[0023] Based on this, the present invention also provides an enzymatic hydrolysis method for lignocellulose, specifically: adding lignocellulose, the above-mentioned self-assembling surfactant, and cellulase to a buffer solution for enzymatic hydrolysis.

[0024] Preferably, the lignocellulose is one or more of the following: corn stalks, corn cobs, rice stalks, corn cob residue, sugarcane bagasse, peanut shells, edible fungi substrate, pine wood, poplar wood, fir wood, wheat straw, rice straw, rice husks, and bacterial cellulose.

[0025] Preferably, the lignocellulose is further pretreated, such as by one or more of the following: acid pretreatment, alkali pretreatment, organic solvent pretreatment, acid-organic solvent mixed pretreatment, alkali-organic solvent pretreatment, DES pretreatment, and ionic liquid pretreatment. For example, the lignocellulose may be corn cob residue that has undergone acid pretreatment.

[0026] Preferably, the mass ratio of lignocellulose to self-assembling surfactant is (16-38):(0.4-5), and most preferably 38:0.45.

[0027] Preferably, the ratio of lignocellulose to cellulase is 1 g: (5-20) FPU.

[0028] Preferably, the pH of the buffer solution is 3 to 7.

[0029] More preferably, the buffer solution is an acetic acid-sodium acetate buffer solution or a citrate-sodium citrate buffer solution.

[0030] Preferably, the final concentration of the lignocellulose in the buffer solution is 350–400 g / L, and most preferably 380 g / L.

[0031] It should be noted that the mass of the lignocellulose involved in this invention is based on oven-dry mass.

[0032] Preferably, the enzymatic hydrolysis temperature is 40–60 °C.

[0033] Preferably, the enzymatic hydrolysis time is 48–120 h.

[0034] Preferably, the enzymatic hydrolysis is performed simultaneously with stirring, such as stirring at 100–300 rpm.

[0035] Preferably, after enzymatic hydrolysis, solid-liquid separation is also performed.

[0036] More preferably, the solid-liquid separation is performed by centrifugation, such as centrifugation at 3000-6000 rpm for 5-10 minutes.

[0037] The present invention has the following beneficial effects: This invention combines specific anionic and nonionic surfactants and completes self-assembly through heating. The resulting self-assembled surfactant can significantly improve the enzymatic hydrolysis efficiency of lignocellulose. Detailed Implementation

[0038] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0039] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0040] Lignocellulose: Corn cob residue after acid pretreatment, purchased from Hebei Yigao Bioenergy Co., Ltd., China.

[0041] Cellulase (Cellic CTec2) was purchased from Novozymes (China) Co., Ltd.

[0042] PEG-8000 (99% purity), calcium lignosulfonate (96% purity, molecular weight 528.61 g / mol), sodium hydroxyalkyl sulfonate, lauryl alcohol polyoxyethylene ether, sodium dodecyl sulfonate, nonylphenol polyether-5, sodium laurate, sodium dodecyl sulfate, n-octanol, and sorbitan monooleate were purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0043] Example 1: Preparation of self-assembled surfactants Calcium lignosulfonate and PEG-8000 were added to a pressure-resistant bottle at a mass ratio of 0.5:4 and stirred at 120 °C and 300 rpm until homogeneous. Then, an acetate-sodium acetate buffer solution with a pH of 4.8 was added (to make the concentration of calcium lignosulfonate in the acetate-sodium acetate buffer solution 0.0015 g / mL). The mixture was stirred and heated at 80 °C and 300 rpm until completely melted to obtain the self-assembled surfactant.

[0044] Example 2 Preparation of self-assembled surfactants Calcium lignosulfonate and PEG-8000 were added to a pressure-resistant bottle at a mass ratio of 2:4 and stirred at 50 °C and 350 rpm until homogeneous. Then, an acetate-sodium acetate buffer solution with a pH of 3 was added (to make the concentration of calcium lignosulfonate in the acetate-sodium acetate buffer solution 0.003 g / mL). The mixture was stirred and heated at 50 °C and 350 rpm until completely melted to obtain the self-assembled surfactant.

[0045] Example 3 Preparation of self-assembled surfactants Calcium lignosulfonate and PEG-8000 were added to a pressure-resistant bottle at a mass ratio of 3:4 and stirred at 150 °C and 250 rpm until homogeneous. Then, an acetate-sodium acetate buffer solution with a pH of 7 was added (to make the concentration of calcium lignosulfonate in the acetate-sodium acetate buffer solution 0.0005 g / mL). The mixture was stirred and heated at 120 °C and 250 rpm until completely melted to obtain the self-assembled surfactant.

[0046] Example 4 Preparation of self-assembled surfactants Calcium lignosulfonate and PEG-8000 were added to a pressure-resistant bottle at a mass ratio of 0.5:4, and then an acetate-sodium acetate buffer solution with a pH of 4.8 was added (to make the concentration of calcium lignosulfonate in the acetate-sodium acetate buffer solution 0.0015 g / mL). The mixture was stirred and heated at 80°C and 300 rpm until completely melted to obtain the self-assembled surfactant.

[0047] Example 5 Preparation of self-assembled surfactants Same as Example 1, except that calcium lignosulfonate is replaced with an equal mass of sodium hydroxyalkyl sulfonate, and PEG-8000 is replaced with an equal mass of lauryl alcohol polyoxyethylene ether.

[0048] Example 6 Preparation of self-assembled surfactants Same as Example 1, except that calcium lignosulfonate is replaced with an equal mass of sodium dodecyl sulfonate, and PEG-8000 is replaced with an equal mass of nonylphenol polyether-5.

[0049] Comparative Example 1 Add PEG-8000 to a pressure-resistant bottle and stir at 120 °C and 300 rpm until well mixed. Then add an acetate-sodium acetate buffer solution with a pH of 4.8 (to make the concentration of PEG-8000 in the acetate-sodium acetate buffer solution 0.012 g / mL) and stir and heat at 80 °C and 300 rpm until completely melted.

[0050] Comparative Example 2 Add calcium lignosulfonate to a pressure-resistant bottle and stir at 120 °C and 300 rpm until well mixed. Then add an acetate-sodium acetate buffer solution with a pH of 4.8 (to make the concentration of calcium lignosulfonate in the acetate-sodium acetate buffer solution 0.0015 g / mL) and stir and heat at 80 °C and 300 rpm until completely melted.

[0051] Comparative Example 3 Add calcium lignosulfonate and PEG-8000 in a mass ratio of 0.5:4 to a pressure-resistant bottle, then add acetate-sodium acetate buffer solution with pH 4.8 (to make the concentration of calcium lignosulfonate in the acetate-sodium acetate buffer solution 0.0015 g / mL) and mix well.

[0052] Comparative Example 4 Same as Example 1, except that calcium lignosulfonate is replaced with an equal mass of sodium laurate.

[0053] Comparative Example 5 Same as Example 1, except that calcium lignosulfonate is replaced with an equal mass of sodium dodecyl sulfate.

[0054] Comparative Example 6 Same as Example 1, except that PEG 8000 is replaced with an equal mass of n-octanol.

[0055] Comparative Example 7 Same as Example 1, except that PEG 8000 is replaced with an equal mass of sorbitan monooleate.

[0056] Test Example 1 Add 50 mL of acetate-sodium acetate buffer (pH=4.8), 0.225 g of the products obtained in Examples 1-6 and Comparative Examples 1-7 (as experimental group, with an equal mass of acetate-sodium acetate buffer at pH 4.8 as blank control group), and 95 FPU of Cellic CTec2 to 19 g of lignocellulose at room temperature. After enzymatic hydrolysis for 120 h in a constant temperature shaker at 50 ℃ and 150 rpm, centrifuge at 4500 rpm for 8 min, take the supernatant and dilute it 200 times with deionized water. Finally, determine the glucose concentration by high performance liquid chromatography (HPLC, LC20A type, Shimadzu, Japan), and calculate the glucose enhancement rate according to "glucose enhancement rate (%) = (experimental group - blank group) / blank group × 100%". The results are shown in Table 1. The conditions for the high performance liquid chromatograph were as follows: Shodex-KS801 column, column temperature 60 ℃, mobile phase pure water, and flow rate 0.4 mL / min.

[0057] Table 1

[0058] It is evident that when the products obtained in Examples 1-6 are used for the enzymatic hydrolysis of lignocellulose, their glucose hydrolysis efficiency is significantly better than that of Comparative Examples 1-7 and the blank control group. This indicates that it is precisely because the present invention combines specific anionic surfactants and nonionic surfactants and completes self-assembly through heating that the self-assembled surfactant can achieve such excellent lignocellulose enzymatic hydrolysis efficiency.

[0059] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a self-assembled surfactant, characterized in that, Anionic surfactant and nonionic surfactant are added to buffer solution, mixed well, and heated until completely melted to obtain the self-assembled surfactant. The anionic surfactant is one or more of lignin sulfonate, secondary alkyl sulfonate, and α-olefin sulfonate; the nonionic surfactant is one or more of polyethylene glycol, fatty alcohol polyoxyethylene ether, polyoxyethylene alkyl ether, and polyoxyethylene nonylphenyl ether.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the anionic surfactant to the nonionic surfactant is (0.5–3):

4.

3. The preparation method according to claim 1, characterized in that, The lignin sulfonate is one or more of calcium lignin sulfonate, sodium lignin sulfonate, and magnesium lignin sulfonate; the secondary alkyl sulfonate is one or more of sodium secondary alkyl sulfonate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate; and the α-olefin sulfonate is one or more of sodium alkenyl sulfonate and sodium hydroxyalkyl sulfonate.

4. The preparation method according to claim 1, characterized in that, The polyethylene glycol is one or more of PEG-4000, PEG-6000, and PEG-8000; the fatty alcohol polyoxyethylene ether is one or more of lauryl alcohol polyoxyethylene ether and isotretinoin polyoxyethylene ether; the polyoxyethylene alkyl ether is one or more of polyethylene glycol monohexadecyl ether and polyethylene glycol monolauryl ether; and the polyoxyethylene nonylphenyl ether is one or more of nonylphenol polyether-2, nonylphenol polyether-5, and nonylphenol polyether-10.

5. The preparation method according to claim 1, characterized in that, The pH of the buffer solution is 3 to 7.

6. The preparation method according to claim 1, characterized in that, The concentration of the anionic surfactant in the buffer solution is 0.0005–0.003 g / mL.

7. The preparation method according to claim 1, characterized in that, The heating temperature is 50–120 °C.

8. A self-assembling surfactant prepared by any one of claims 1 to 7.

9. The application of the self-assembling surfactant of claim 8 in the enzymatic hydrolysis of lignocellulose.

10. A method for enzymatic hydrolysis of lignocellulose, characterized in that, Lignocellulose, the self-assembling surfactant of claim 8, and cellulase are added to a buffer solution for enzymatic hydrolysis.

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