阅读说明：本技术 一种精制棉籽蛋白的方法 (Method for refining cottonseed protein ) 是由 丁姣 陈文杰 尹国强 赖锐豪 周向阳 冯聘娴 欧阳湘怡 柯杰明 赖诗敏 于 2019-10-25 设计创作，主要内容包括：本发明公开一种精制棉籽蛋白的方法,该方法是将脱酚棉籽粕经过尿素预处理后,通过碱液浸提得到棉籽蛋白粗浸提液,然后经透析、酸沉、洗涤、干燥,精制得到棉籽蛋白固体粉末。采用本发明的方法,可以精制得的棉籽蛋白分子量在8~14kD、纯度大于98%,其与合成高聚物的相容性较好,可用于制备力学性能较好的棉籽蛋白基复合材料。(The invention discloses a method for refining cottonseed protein, which comprises the steps of pretreating dephenolized cottonseed meal by urea, leaching by alkali liquor to obtain a crude cottonseed protein leaching solution, dialyzing, precipitating by acid, washing, drying and refining to obtain solid cottonseed protein powder.)

1. A method for refining cottonseed protein, comprising the steps of:

(1) urea pretreatment, namely placing the dephenolized cottonseed meal into a reactor, adding a urea solution with the mass of 10 ~ 30 times and the concentration of 3 ~ 7mol/L of the dephenolized cottonseed meal, stirring for 12 hours at the temperature of 40 ~ 60 ℃, filtering, and then washing with deionized water to obtain the pretreated dephenolized cottonseed meal;

(2) alkali liquor leaching, namely placing dephenolized cottonseed meal subjected to urea pretreatment into a reactor, adding 10 ~ 20 times of the dephenolized cottonseed meal in mass and newly prepared alkali liquor with the concentration of 0.03 ~ 0.10.10 mol/L, stirring for 1 ~ 4h at 40 ~ 60 ℃, centrifuging for 5 ~ 10min at 3000r/min, and filtering to obtain a cottonseed protein crude leaching solution;

(3) dialyzing and purifying, namely filling the crude cottonseed protein leaching solution into a dialysis bag, dialyzing in deionized water at the temperature of 4 ℃ and ~ 25 ℃ for 5 ~ 7 days, replacing the deionized water every 8 ~ 12 hours, and collecting dialysate, wherein the dialysate is pure cottonseed protein liquid;

(4) precipitating cottonseed protein by adjusting pH of cottonseed protein solution to 4.5 ~ 5.5.5 with dilute hydrochloric acid to obtain a large amount of protein precipitate, centrifuging, filtering, washing with distilled water, and drying to obtain pure light brown cottonseed protein powder.

2. The method of claim 1, wherein said fresh alkaline solution of step (2) is one or a combination of sodium hydroxide, potassium hydroxide and ammonia water, and the total concentration is 0.03 ~ 0.10.10 mol/L.

3. The method of claim 1, wherein the molecular weight cut-off of the dialysis bag of step (3) is 8 ~ 14 kD.

4. The method for refining cottonseed protein as claimed in claim 1, wherein the drying method in step (4) is freeze drying.

Technical Field

The invention belongs to the technical field of macromolecules, relates to a method for refining cottonseed protein, and particularly relates to refined cottonseed protein with good compatibility with synthetic polymers.

Background

The cottonseed meal is a byproduct of cottonseed shelling and deoiling, contains abundant protein and is an important plant protein resource. The amino acids contained in Cottonseed Protein (CP) have a certain nutritional value and are therefore often processed into animal feed. However, cottonseed protein has not been widely used in the field of materials, because the conventional extraction process of cottonseed protein is generally carried out in the environment of high temperature, strong acid and strong base, which easily causes protein denaturation and lower purity of cottonseed protein, and influences the physicochemical properties and processability of the cottonseed protein as a material.

China is a big country for cotton planting, and the annual yield of the cotton seeds reaches over 800 million tons in recent years. In addition to cottonseed oil, there are over 500 million tons of waste cottonseed meal, which contains about 20% protein. At present, the extraction of cottonseed protein from cottonseed meal mainly comprises an alkali dissolution and acid precipitation method, a salt extraction method, an enzymolysis method and the like.

The traditional alkali-dissolving and acid-precipitating method is to leach cottonseed meal for a period of time by using alkali liquor with a certain concentration, then to adjust the pH value of the mixture by using acid solution after centrifugal separation, and is a method for precipitating and separating out cottonseed protein. The invention patent with application number 201310382819.4 discloses a method for extracting cottonseed protein by using sodium hydroxide and sodium sulfite composite alkali liquor, wherein Zhangning, snow and the like adopt sodium hydroxide alkali liquor to extract cottonseed protein, and plum red and the like adopt ammonia water solution to extract cottonseed protein. The method is simple to operate and low in cost, but the extracted cottonseed protein is low in purity and high in protein denaturation rate, so that the cottonseed protein is difficult to further process into materials for utilization. In addition, this process produces large amounts of spent acid and spent caustic.

The invention patent with application number 201510364396.2 discloses a process for extracting cottonseed protein, which adopts NaCl as salt solution, and extracts cottonseed meal for 75 ~ 85 min according to the material-to-liquid ratio (14 ~ 16): 1 at 38 ~ 42 ℃, and the cottonseed protein extracted by the method has low protein denaturation rate, but has low yield and purity, and is difficult to be further processed and utilized in the field of materials.

The enzyme extraction method is to utilize specific enzyme to decompose cottonseed meal, thereby extracting cottonseed protein. The invention patent with application number 201711472292.9 discloses a method for producing cottonseed protein, which adopts one or two of cellulase and ligninooxidase to extract cottonseed protein from dephenolized cottonseed meal. The method has mild reaction, does not damage the stability of the cottonseed protein and generate side reaction, but has lower extraction rate and low protein purity.

In order to further apply the cottonseed protein to the field of material processing, the extracted and refined cottonseed protein needs to have higher purity, lower protein denaturation rate, good protein structure stability and better compatibility with synthetic high polymer.

Disclosure of Invention

The invention provides a method for refining cottonseed protein, and aims to solve the problems that the cottonseed protein extracted by the existing method has more impurities and poor compatibility with a synthesized high polymer.

In order to achieve the above object, the present invention provides a method for refining cottonseed protein, which is characterized in that the molecular weight of the refined cottonseed protein is mainly concentrated between 8 ~ 14kD, the purity is more than 98%, and the cottonseed protein can be mixed with some synthetic high polymers in different proportions and mixed with deionized water or fluorine-containing reagents.

(1) Urea pretreatment, namely placing the dephenolized cottonseed meal into a reactor, adding a urea solution with the mass of 10 ~ 30 times and the concentration of 3 ~ 7mol/L of the dephenolized cottonseed meal, stirring for 12 hours at the temperature of 40 ~ 60 ℃, filtering, and then washing with deionized water to obtain the pretreated dephenolized cottonseed meal;

(2) alkali liquor leaching, namely placing dephenolized cottonseed meal subjected to urea pretreatment into a reactor, adding 10 ~ 20 times of the dephenolized cottonseed meal in mass and newly prepared alkali liquor with the concentration of 0.03 ~ 0.10.10 mol/L, stirring for 1 ~ 4h at 40 ~ 60 ℃, centrifuging for 5 ~ 10min at 3000r/min, and filtering to obtain a cottonseed protein crude leaching solution;

(3) dialyzing and purifying, namely filling the crude cottonseed protein leaching solution into a dialysis bag, dialyzing in deionized water at 4 ~ 25 and 25 ℃ for 5 ~ 7 days, replacing the deionized water every 8 ~ 12h, and collecting dialysate, wherein the dialysate is refined cottonseed protein liquid;

(4) precipitating cottonseed protein by adjusting pH of cottonseed protein solution to 4.5 ~ 5.5.5 with dilute hydrochloric acid to obtain a large amount of protein precipitate, centrifuging, filtering, washing with distilled water, and drying to obtain pure light brown cottonseed protein powder.

Preferably, the concentration of the urea solution in the step (1) is 4 ~ 5mol/L, and the addition amount of the urea solution is 12 times of that of the dephenolized cottonseed meal.

Preferably, the fresh lye solution in the step (2) is one or the combination of sodium hydroxide, potassium hydroxide and ammonia water, and the total concentration is 0.03 ~ 0.10.10 mol/L, and further preferably 0.05mol/L of the fresh sodium hydroxide solution.

Preferably, the molecular weight cut-off of the dialysis bag in the step (3) is 8 ~ 14kD, and the dialysis temperature is 4 ~ 10 ℃.

Preferably, the pH value of the cottonseed protein liquid is adjusted to 4.7 ~ 5.0.0 in the step (4), and the drying is freeze drying.

Compared with the prior art, the technical scheme of the invention has the beneficial effects that the purified cottonseed protein with specific molecular weight is prepared by adopting the methods of low-temperature dialysis and freeze drying, so that the purified cottonseed protein can be mixed with some synthetic high polymers in any proportion and dissolved in deionized water or fluorine-containing reagent. The refined cottonseed protein is changed into valuable, can be prepared into various cottonseed protein-based composite materials, and further widens the application of the waste cottonseed meal in the field of new materials.

Drawings

FIG. 1 is a process flow diagram of the present invention for refining cottonseed protein.

FIG. 2 is an infrared spectrum of the purified cottonseed protein of the invention.

FIG. 3 is a surface and cross-sectional microscopic morphology of a film formed by blending refined cottonseed protein and PVA.

FIG. 4 is a microscopic topography of the surface and cross section of the film formed by blending the refined cottonseed protein and PEO.

FIG. 5 is a microscopic appearance diagram of the refined cottonseed protein and TPU composite nanofiber of the invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.

The invention provides a method for refining cottonseed protein, which comprises the following steps:

(1) urea pretreatment, namely placing the dephenolized cottonseed meal into a reactor, adding a urea solution with the mass of 10 ~ 30 times and the concentration of 3 ~ 7mol/L of the dephenolized cottonseed meal, stirring for 12 hours at the temperature of 40 ~ 60 ℃, filtering, and then washing with deionized water to obtain the pretreated dephenolized cottonseed meal;

(2) alkali liquor leaching, namely placing dephenolized cottonseed meal subjected to urea pretreatment into a reactor, adding 10 ~ 20 times of the dephenolized cottonseed meal in mass and newly prepared alkali liquor with the concentration of 0.03 ~ 0.10.10 mol/L, stirring for 1 ~ 4h at 40 ~ 60 ℃, centrifuging for 5 ~ 10min at 3000r/min, and filtering to obtain a cottonseed protein crude leaching solution;

(3) dialyzing and purifying, namely filling the crude cottonseed protein leaching solution into a dialysis bag, dialyzing in deionized water at the temperature of 4 ℃ and ~ 25 ℃ for 5 ~ 7 days, replacing the deionized water every 8 ~ 12 hours, and collecting dialysate, wherein the dialysate is refined cottonseed protein liquid;

(4) precipitating cottonseed protein by adjusting pH of cottonseed protein solution to 4.5 ~ 5.5.5 with dilute hydrochloric acid to obtain a large amount of protein precipitate, centrifuging, filtering, washing with distilled water, and drying to obtain pure light brown cottonseed protein powder.

Wherein the concentration of the urea solution in the step (1) is 4 ~ 5mol/L, and the addition amount is 12 times of that of the dephenolized cottonseed meal.

The newly prepared alkali liquor in the step (2) is one or a combination of sodium hydroxide, potassium hydroxide and ammonia water, and the total concentration is 0.03 ~ 0.10.10 mol/L, and more preferably 0.05 mol/L.

The cut-off molecular weight of the dialysis bag in the step (3) is 8 ~ 14kD, and the dialysis temperature is 4 ℃ ~ 10 ℃.

And (4) adjusting the pH value of the cottonseed protein liquid to 4.7 ~ 5.0.0, wherein the drying is freeze drying.

The structure, molecular weight, purity and compatibility with synthetic macromolecules of the refined cottonseed protein are characterized and tested by Fourier transform infrared spectroscopy, SDS-polyacrylamide gel electrophoresis, a Kjeldahl method and a blending casting method.

1. Fourier transform infrared spectroscopy_。

The structure of the cottonseed protein powder was characterized by Fourier transform infrared spectroscopy (Spectrum 100 infrared spectrometer, Perkin-Elmer, Fremont, CA, USA). The data were analyzed and found to be 3272cm^-1The peak of hydrogen bond association of N-H and O-H appears, 1637,1544 and 1399 cm^-1Characteristic peaks of amide I type (C = O stretching vibration peak), amide II type (in-plane N-H bending vibration and C-N stretching vibration) and amide III type (C = O bending vibration and C-N stretching vibration) respectively appear; 1044 cm^-1And a C-O stretching vibration peak of the cottonseed protein appears.

2. SDS-polyacrylamide gel electrophoresis_。

The molecular weight of the cottonseed protein is tested by an electrophoresis apparatus and an SDS-polyacrylamide gel electrophoresis technology, and the molecular weight of the cottonseed protein refined according to the invention is mainly concentrated at 8kD ~ 14 kD.

3. Kjeldahl method_。

And (3) measuring the purity of the refined cottonseed protein by adopting a Kjeldahl method. The purity of the cottonseed protein obtained by the refining of the invention is more than 99% +/-1%.

4. Compatibility analysis of cottonseed protein and synthetic high polymer_。

Dissolving the refined cottonseed protein powder in alkaline deionized water or hexafluoroisopropanol, uniformly blending with the synthetic high polymer solution, pouring into a polypropylene container, and solidifying to form a film after the solvent is evaporated. And observing the microscopic morphology of the blending film through a scanning electron microscope to judge the compatibility of the cottonseed protein and the synthetic high polymer. The blending film prepared by blending the refined cottonseed protein and various high polymers such as PVA, PEO, TPU, PLA, gelatin and the like has smooth surface appearance and uniform section appearance under the observation of an electron microscope. Therefore, the cottonseed protein refined by the invention has better compatibility with the synthetic high polymer.