阅读说明：本技术 一种利用丙酮水溶液分离提高玉米秸秆酶水解木质素抗氧化活性的方法 (Method for improving antioxidant activity of corn straw enzymatic hydrolysis lignin by separating acetone aqueous solution ) 是由 李明飞 徐迎红 于 2020-07-16 设计创作，主要内容包括：本发明提出一种利用丙酮水溶液分离提高玉米秸秆酶水解木质素抗氧化活性的方法,包括以下步骤：(1)将丙酮和水在室温下按照一定比例混合得到丙酮水溶液；(2)将木质素和步骤(1)所得丙酮水溶液按照一定液比混合；(3)将步骤(2)所得混合溶液在一定转速下室温搅拌一定的时间,离心去除不溶性木质素；(4)将步骤(3)所得的溶液25℃条件下挥发除去溶剂,得到木质素。本发明利用丙酮水溶液对玉米秸秆酶水解木质素进行分离,获得高抗氧化活性的木质素。丙酮分离操作简单、不产生有害物质,为天然抗氧化剂的生产提供有力的技术支持。(The invention provides a method for improving the antioxidant activity of corn straw enzymatic hydrolysis lignin by separating acetone aqueous solution, which comprises the following steps: (1) mixing acetone and water at room temperature according to a certain proportion to obtain an acetone aqueous solution; (2) mixing lignin and the acetone aqueous solution obtained in the step (1) according to a certain liquid ratio; (3) stirring the mixed solution obtained in the step (2) at a certain rotating speed for a certain time at room temperature, and centrifuging to remove insoluble lignin; (4) and (4) volatilizing the solution obtained in the step (3) at 25 ℃ to remove the solvent to obtain the lignin. The invention separates the corn straw enzymatic hydrolysis lignin by using acetone aqueous solution to obtain the lignin with high antioxidant activity. The acetone separation operation is simple, no harmful substance is generated, and powerful technical support is provided for the production of natural antioxidant.)

1. A method for improving the antioxidant activity of corn straw enzymatic hydrolysis lignin by separating acetone aqueous solution comprises the following operation steps:

(1) mixing acetone and water at room temperature according to a certain proportion to obtain an acetone aqueous solution;

(2) mixing lignin and the acetone aqueous solution obtained in the step (1) according to a certain liquid ratio;

(3) stirring the mixed solution obtained in the step (2) at a certain rotating speed for a certain time at room temperature, and centrifuging to remove insoluble lignin;

(4) and (4) volatilizing the solution obtained in the step (3) at 25 ℃ to remove the solvent to obtain the lignin.

2. The method of claim 1, wherein: the acetone in step (1) was 99.5% analytical grade acetone.

3. The method of claim 1, wherein: the concentration of the acetone aqueous solution prepared in the step (1) is 30-50%.

4. The method of claim 1, wherein: and (3) refluxing the enzymolysis residues of the corn straws serving as the lignin in the step (2) for 1 hour under the conditions of 1% NaOH and a liquid ratio of 1:10(m/m), filtering the product, and precipitating the filtrate with HCl with the pH value of 1 to prepare the lignin.

5. The method of claim 1, wherein: the liquid ratio in the step (2) is 1:10(m/m) to 1:100 (m/m).

6. The method of claim 1, wherein: the rotating speed in the step (3) is 100 rpm-400 rpm.

7. The method of claim 1, wherein: the time in the step (3) is 0.5 to 2 hours.

8. The method of claim 1, wherein: the centrifugation described in step (3) is carried out for 5min at a centrifuge of 4000 rpm.

Technical Field

The invention relates to a method for improving the antioxidant activity of lignin, in particular to a method for improving the antioxidant activity of corn straw enzymatic hydrolysis lignin by separating acetone aqueous solution.

Background

Lignin is an abundant renewable resource and is widely present in plant fiber raw materials. It is estimated that worldwide plants undergo photosynthesis to produce about five billion tons of lignin per year, and that industrial production yields between forty and fifty thousand tons of lignin. Despite the enormous reserves of lignin, most of it is used only as a low-value fuel production energy source. With the increasing demand for sustainable resources, lignin has been increasingly regarded as a natural renewable aromatic compound. Therefore, the performance of the lignin is improved, the application range of the lignin is widened, and the method has wide prospect and market value.

The lignin molecule of the gramineous plant is an amorphous high polymer with a three-dimensional structure formed by connecting 3 structural units of guaiacyl, syringyl and p-hydroxyphenyl through ether bonds and carbon-carbon bonds. The lignin molecule has a three-dimensional structure, contains a proper carbon-hydrogen ratio, and has functional groups such as hydroxyl, carboxyl, carbonyl, methoxyl and the like. However, lignin has problems of complex structure, non-uniform physicochemical properties, and the like, and the application of lignin is limited to a great extent. Research shows that the chemical properties of lignin are related to the molecular weight and the polydispersity index of the lignin, and the polydispersity of the lignin can significantly influence the application of the lignin, so that the separation and purification of the lignin are particularly important for high-value utilization.

The lignin contains a large amount of active hydroxyl groups, can form hydrogen bonds with organic polymers, and captures free radicals in the oxidation process, so that the lignin has certain oxidation resistance. Research on the antioxidant performance of lignin is carried out, and the lignin is expected to be used as a natural antioxidant. However, the heterogeneity of the structure and molecular weight of lignin causes different components with high antioxidant activity and low antioxidant activity to exist in the lignin, and the overall antioxidant activity of the lignin sample is reduced. Therefore, there is a need for an efficient separation method to obtain lignin with higher oxidation resistance. Common lignin separation and purification methods include acid precipitation, ultrafiltration membrane separation, and organic solvent separation. Compared with other separation methods, the organic solvent separation method is a better choice, the operation is simple, and the solvent can be reused. The acetone is used as an organic solvent with low boiling point, no sulfur and easy recovery, and can dissolve most of lignin to form a uniform and stable dissolving environment. The method for separating lignin by using acetone has more advantages in operation and economy. Research shows that the antioxidant activity of lignin can be effectively improved by acetone separation.

The antioxidant is a compound capable of combining and stabilizing free radicals, and is widely applied to the industries of food, medicine, chemical industry and the like. The antioxidant can prevent the object from being adversely affected by oxidation and the like by trapping and neutralizing free radicals, and is mainly used for preventing or delaying the oxidation of grease, and avoiding the destruction, browning and fading of nutrients. Several of the major synthetic antioxidants currently on the market include Butylated Hydroxytoluene (BHT), Butylated Hydroxyanisole (BHA), Propyl Gallate (PG), and the like. Although synthetic antioxidants occupy an important position in the market, the problems of complex synthetic route, high cost, high toxicity and the like still exist. The toxicity of the natural antioxidant is far lower than that of the synthetic antioxidant, and the cost can be greatly reduced by partially replacing the prior phenolic antioxidant with natural polyphenols such as lignin and the like. The phenolic hydroxyl of the lignin plays a role of a stabilizer in the reaction induced by active substances such as oxygen and the like, and can delay the aging of composite materials and biological systems. The good oxidation resistance of the lignin opens up a wide prospect for the application of the lignin in the fields of industry, medicine, food and the like.

Disclosure of Invention

The invention aims to solve the problem of weak oxidation resistance of the original lignin, and provides a method for improving the oxidation resistance of enzymatic hydrolysis lignin of corn straws by using acetone aqueous solution separation, aiming at obtaining the lignin with high oxidation resistance.

A method for improving the antioxidant activity of corn straw enzymatic hydrolysis lignin by separating acetone aqueous solution comprises the following operation steps:

(1) mixing acetone and water at room temperature according to a certain proportion to obtain an acetone aqueous solution;

(2) mixing lignin and the acetone aqueous solution obtained in the step (1) according to a certain liquid ratio;

(3) stirring the mixed solution obtained in the step (2) at a certain rotating speed for a certain time at room temperature, and centrifuging to remove insoluble lignin;

(4) and (4) volatilizing the solution obtained in the step (3) at 25 ℃ to remove the solvent to obtain the lignin.

Wherein the acetone in step (1) is 99.5% analytical grade acetone.

Wherein, the concentration of the acetone aqueous solution prepared in the step (1) is 30-50%.

Wherein the lignin used in the step (2) is prepared by refluxing enzymolysis residues of corn straws for 1h under the conditions of 1% NaOH and a liquid ratio of 1:10(m/m), filtering a product, and precipitating the obtained filtrate with HCl with pH of 1 to prepare the lignin.

Wherein the liquid ratio in the step (2) is 1:10(m/m) to 1:100 (m/m).

Wherein the rotating speed in the step (3) is 100 rpm-400 rpm.

Wherein the time in the step (3) is 0.5-2 h.

Wherein the centrifugation in the step (3) is performed for 5min at a centrifuge of 4000 rpm.

Compared with the prior art, the invention has the following beneficial effects:

the method utilizes the acetone aqueous solution to separate the enzymatic hydrolysis lignin of the corn straws, thereby effectively improving the antioxidant activity of the lignin. The method is simple to operate, does not generate harmful substances, and provides powerful technical support for the production of the natural antioxidant.

Detailed Description

In order to describe the technical scheme of the invention in detail, the following is further illustrated by combining with the examples, but the following examples are only exemplified as the embodiment of the invention, and do not limit the invention in any way, and those skilled in the art can understand that the modifications within the scope not departing from the spirit and concept of the invention fall into the protection scope of the invention. Unless otherwise specified, reagents and equipment used in the following examples are commercially available products.