阅读说明：本技术 一种用大麻皮制备纳米纤维素的方法 (Method for preparing nano cellulose by using hemp skin ) 是由 田英华 李闯 丛珊滋 刘晓兰 吴红艳 于 2021-02-09 设计创作，主要内容包括：本发明属于纤维工业技术领域,具体涉及一种用大麻皮制备纳米纤维素的方法,包括如下步骤：(1)对大麻皮进行预处理,得到预处理的大麻纤维；(2)用果胶酶和半纤维素酶对步骤(1)中预处理的大麻纤维进行脱胶处理,得到脱胶的大麻纤维；(3)对步骤(2)中脱胶的大麻纤维进行粉碎,过筛,得到大麻纤维粉；(4)对步骤(3)中的大麻纤维粉进行生物酶处理,得到大麻皮纳米纤维溶液；(5)对步骤(4)中所得大麻皮纳米纤维溶液进行超声波处理,离心,上清液冷冻干燥,得到大麻皮纳米纤维素。本发明中制备纳米纤维素采用的是生物酶法,是一种环境友好的做法,所制备的大麻纳米纤维素结构不受破坏,性能更优。(The invention belongs to the technical field of fiber industry, and particularly relates to a method for preparing nano cellulose by using hemp skin, which comprises the following steps: (1) pretreating hemp skin to obtain pretreated hemp fibers; (2) carrying out degumming treatment on the hemp fibers pretreated in the step (1) by using pectinase and hemicellulase to obtain degummed hemp fibers; (3) crushing the hemp fibers degummed in the step (2), and sieving to obtain hemp fiber powder; (4) carrying out bio-enzyme treatment on the hemp fiber powder in the step (3) to obtain hemp skin nanofiber solution; (5) and (4) carrying out ultrasonic treatment on the hemp skin nanofiber solution obtained in the step (4), centrifuging, and carrying out freeze drying on the supernatant to obtain the hemp skin nanofiber. The method for preparing the nano cellulose adopts a biological enzyme method, is an environment-friendly method, and the structure of the prepared hemp nano cellulose is not damaged and has better performance.)

1. A method for preparing nano cellulose by using hemp skin is characterized in that: the method comprises the following steps:

(1) pretreating hemp skin to obtain pretreated hemp fibers;

(2) carrying out degumming treatment on the hemp fibers pretreated in the step (1) by using pectinase and hemicellulase to obtain degummed hemp fibers;

(3) crushing the hemp fibers degummed in the step (2), and sieving to obtain hemp fiber powder;

(4) carrying out bio-enzyme treatment on the hemp fiber powder in the step (3) to obtain hemp skin nanofiber solution;

(5) and (4) carrying out ultrasonic treatment on the hemp skin nanofiber solution obtained in the step (4), centrifuging, and carrying out freeze drying on the supernatant to obtain the hemp skin nanofiber.

2. The method of preparing nanocellulose from hemp bark according to claim 1, wherein: the step (1) is specifically as follows: pretreating hemp skin with 0.2-0.8wt% sodium hydroxide at bath ratio of 1:15-1:30(kg/L), treatment temperature of 50-60 deg.C, and treatment time of 6-8 hr, and washing the treated hemp skin with water to neutrality.

3. The method of preparing nanocellulose from hemp bark according to claim 1, wherein: the step (2) is specifically as follows: degumming the pretreated hemp fiber with 0.5-1.5wt% of pectinase and 0.2-0.8wt% of hemicellulase at pH 2.5-6.0 and 20-55 deg.C for 24h, boiling in boiling water for 10min, inactivating enzyme, washing with water, and drying.

4. The method of preparing nanocellulose from hemp bark according to claim 1, wherein: the 80-mesh sieve is used for sieving in the step (3).

5. The method of preparing nanocellulose from hemp bark according to claim 1, wherein: the step (4) is specifically as follows: treating hemp fiber powder with biological enzyme with concentration of 0.05-0.3mg/mL at pH of 4.0-5.5 and pH of 1:20-1:50 (kg/L) at 30-60 deg.C for 24-30 hr.

6. The method of preparing nanocellulose from hemp bark according to claim 1, wherein: the biological enzyme in the step (4) is cellulase or endoglucanase.

7. The method of preparing nanocellulose from hemp bark according to claim 1, wherein: the ultrasonic treatment conditions in the step (5) are as follows: the ultrasonic power is 500-900W, and the treatment time is 8-15 min.

8. The method of preparing nanocellulose from hemp bark according to claim 1, wherein: the freeze-drying conditions in the step (5) are as follows: the vacuum degree is 20Pa, and the temperature is-85 ℃; the time is 48 h.

Technical Field

The invention belongs to the technical field of fiber industry, and particularly relates to a method for preparing nano cellulose by using hemp skin.

Background

Cannabis Sativa, also known as hemp, species of Cannabis (Cannabis Sativa L) belonging to the family Cannabiaceae (Cannabiaceae) of the order Urticales (Urticales) of the Magnoliaceae class (Magnoopsida), annual herbaceous plants, one of the earliest crops of bast fibers utilized in human cultivation. China is the country with the largest planting area of industrial hemp, accounts for about half of the world, and the yield accounts for 25% of the total yield of raw hemp of industrial hemp all over the world. The hemp planting has low requirements on climate and soil, rapid growth, strong capability of resisting diseases and insect pests, no need of insecticide and fertilizer during the planting period, no soil pollution and good environmental ecology. Hemp is used as a raw material for fiber products, clothing, ropes, sails, grease, paper and medical supplies. The main chemical components of the hemp skin are cellulose, hemicellulose, pectin, lignin and lipid wax, and compared with other bast fibers, the hemp fiber has higher content of the gelatin, especially the pectin and the hemicellulose have higher content than other bast fibers, which causes that the extraction of the hemp cellulose is more difficult than other bast fibers.

The method for preparing nano-cellulose by taking cellulose fiber as a raw material mainly comprises a chemical method, a mechanical physical method and a biological method, and the methods respectively have advantages and disadvantages. Chemical methods, such as: the method for preparing nano-cellulose (CN 111793139A) by hydrolyzing organic acid has the advantages that the application of the prepared nano-cellulose is limited by the toxicity problem of the organic acid; oxidation or ionic processes, such as: a method for preparing nano-cellulose by multi-site oxidation and application thereof (CN 106758492A), the method needs expensive reaction reagent and is difficult to separate from the prepared nano-cellulose; physical methods, such as: the method for preparing microfibrillated nanocellulose by refined and dried ramie (CN 103938477A) needs to consume higher energy by adopting an ultra-fine refiner to continuously and circularly grind repeatedly. The biological enzyme method can prepare the nano-cellulose under mild conditions, is more environment-friendly, and the nano-cellulose prepared by the biological enzyme method cannot damage the structure of the nano-cellulose.

Disclosure of Invention

In order to solve the problems, the invention discloses a method for preparing nano cellulose by using hemp skin, which mainly adopts a combination of a biological enzyme method and pretreatment, wherein the biological enzyme method is an environment-friendly method, and the prepared hemp nano cellulose has the advantages of no damage to the structure, better performance and capability of being used for food packaging, nano paper, food additives, health care products, cosmetics and the like.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for preparing nano cellulose by using hemp skin comprises the following steps:

(1) pretreating hemp skin to obtain pretreated hemp fibers;

(2) carrying out degumming treatment on the hemp fibers pretreated in the step (1) by using pectinase and hemicellulase to obtain degummed hemp fibers;

(3) crushing the hemp fibers degummed in the step (2), and sieving to obtain hemp fiber powder;

(4) carrying out bio-enzyme treatment on the hemp fiber powder in the step (3) to obtain hemp skin nanofiber solution;

(5) and (4) carrying out ultrasonic treatment on the hemp skin nanofiber solution obtained in the step (4), centrifuging, and carrying out freeze drying on the supernatant to obtain the hemp skin nanofiber.

Preferably, the step (1) is specifically: pretreating hemp skin with 0.2-0.8wt% sodium hydroxide at bath ratio of 1:15(kg/L), treatment temperature of 50-60 deg.C for 6-8 hr, and washing the treated hemp skin with water to neutrality.

Preferably, the step (2) is specifically: degumming the pretreated hemp fiber with 0.5-1.5wt% of pectinase and 0.2-0.8wt% of hemicellulase at pH 2.5-6.0 and 20-55 deg.C for 24h, boiling in boiling water for 10min, inactivating enzyme, washing with water, and drying.

Preferably, an 80-mesh sieve is used for the sieving in the step (3).

Preferably, the step (4) is specifically: treating hemp fiber powder with biological enzyme with concentration of 0.05-0.3mg/mL at bath ratio of 1:30, pH of 4.0-5.5, treatment temperature of 30-60 deg.C and treatment time of 24-30 h.

Preferably, the biological enzyme in the step (4) is cellulase or endoglucanase.

Preferably, the ultrasonic treatment conditions in the step (5) are as follows: the ultrasonic power is 500-900W, and the treatment time is 8-15 min.

Preferably, the lyophilization conditions in the step (5) are as follows: the vacuum degree is 20Pa, and the temperature is-85 ℃; the time is 48 h.

The invention has the following beneficial effects:

(1) the method for preparing the nano cellulose adopts a biological enzyme method, is an environment-friendly method, has no damage to the structure of the prepared hemp nano cellulose, has better performance, and can be used for food packaging, nano paper, food additives, health care products, cosmetics and the like;

(2) the method pretreats the hemp skin, adopts a lower bath ratio (1:15-1:30(kg/L)) and a lower concentration of sodium hydroxide (0.2-0.8 wt%), greatly reduces chemical reagents compared with the conventional method, greatly reduces the generated waste water, and is more environment-friendly;

(3) the invention adopts biological enzymes such as cellulase or endoglucanase and the like to prepare nano-cellulose by ultrasonic waves, utilizes the biological enzymes to act on an amorphous area in the cellulose, randomly hydrolyzes 1, 4-beta-glucosyl bonds, cuts long-chain cellulose molecules into short molecules, generates a large amount of micromolecule cellulose with non-reducing ends, and then utilizes the cavitation action of the ultrasonic waves to generate shock waves to enable the fibers to form smaller particles, and can explode the original non-nano-level cellulose into nano-level, reduce the size of the nano-cellulose and improve the yield of the nano-cellulose, wherein the particle diameter of the prepared nano-cellulose is less than 300nm, the particle diameter uniformity is good, the nano-cellulose preparation yield is more than 30 percent, the nano-cellulose solution has good stability and good light transmittance.

Drawings

The invention is further illustrated with reference to the following figures and examples.

FIG. 1 is a particle size distribution diagram of nanocellulose prepared in example 3;

fig. 2 is the tyndall phenomenon of the aqueous solution of nanocellulose prepared in example 3.

Detailed Description

The present invention will now be described in further detail with reference to examples.

The source of the sodium hydroxide used in step (1) of the present invention is not particularly limited, and any commercially available product conventionally used in the art may be used. The raw materials in the embodiment of the invention are produced by chemical reagents Limited of Kemi Europe in Tianjin.

The source of the pectinase and hemicellulase used in step (2) of the present invention is not particularly limited, and any commercially available product that is conventional in the art may be used. The pectinase in the embodiment of the invention is purchased from Novoxin biotechnology limited, and the enzyme activity is 5000U/g; the hemicellulase is purchased from Souchhama bioengineering GmbH, and the enzyme activity is 20000U/g.

The source of the cellulase or endoglucanase used in step (4) of the present invention is not particularly limited, and any commercially available product conventionally used in the art may be used. The cellulase in the embodiment of the invention is purchased from Shanghai-sourced leaf biotechnology limited, and the enzyme activity is 50000U/g.

In the present invention, the bath ratio is a ratio of the mass of the hemp fiber to the volume of the treatment liquid.

Example 1

(1) Pretreating hemp skin with 0.2 wt% sodium hydroxide at 50 deg.C for 6 hr at a bath ratio of 1:15(kg/L), and washing the hemp skin to neutrality;

(2) treating the hemp fiber obtained in the step (1) with pectinase with the concentration of 1.5wt% and hemicellulase with the concentration of 0.2 wt%, wherein the pH value is 5.0, the treatment temperature is 55 ℃, the treatment time is 24 hours, the hemp fiber after enzyme degumming treatment is added into boiling water to be boiled for 10min, the enzyme is inactivated, and then the hemp fiber is washed with water and dried;

(3) crushing the hemp fibers degummed in the step (2), and sieving the crushed hemp fibers with a 80-mesh sieve to obtain hemp fiber powder;

(4) treating the hemp fiber powder in the step (3) with cellulase with the concentration of 0.05mg/mL, wherein the bath ratio is 1:30(kg/L), the pH value is 5.5, the treatment temperature is 45 ℃, and the treatment time is 30 hours, so as to obtain hemp skin nanofiber solution;

(5) performing ultrasonic treatment on the hemp skin nanofiber solution obtained in the step (4), wherein the ultrasonic power is 700W, the treatment time is 10min, then centrifuging, and freeze-drying the supernatant, wherein the freeze-drying conditions are as follows: the vacuum degree is 20Pa, and the temperature is-85 ℃; the time is 48 h.

Example 2

(1) Pretreating hemp skin with 0.8wt% sodium hydroxide at bath ratio of 1:15(kg/L), treatment temperature of 60 deg.C for 6 hr, and washing the treated hemp skin with water to neutrality;

(2) treating the hemp fiber obtained in the step (1) with pectinase with the concentration of 0.5 wt% and hemicellulase with the concentration of 0.8wt%, wherein the pH value is 6.0, the treatment temperature is 30 ℃, the treatment time is 24 hours, the hemp fiber after enzyme degumming treatment is added into boiling water to be boiled for 10min, the enzyme is inactivated, and then the hemp fiber is washed with water and dried;

(3) crushing the hemp fibers degummed in the step (2), and sieving the crushed hemp fibers with a 80-mesh sieve to obtain hemp fiber powder;

(4) treating the hemp fiber powder in the step (3) with cellulase with the concentration of 0.3mg/mL, wherein the bath ratio is 1:30(kg/L), the pH value is 4.0, the treatment temperature is 30 ℃, and the treatment time is 30 hours, so as to obtain hemp skin nanofiber solution;

(5) performing ultrasonic treatment on the hemp skin nanofiber solution obtained in the step (4), wherein the ultrasonic power is 500W, the treatment time is 15min, then centrifuging, and freeze-drying the supernatant, wherein the freeze-drying conditions are as follows: the vacuum degree is 20Pa, and the temperature is-85 ℃; the time is 48 h.

Example 3

(1) Pretreating hemp skin with 0.6 wt% sodium hydroxide at 50 deg.C for 8 hr at a bath ratio of 1:20(kg/L), and washing the hemp skin to neutrality;

(2) treating the hemp fiber obtained in the step (1) with pectinase with the concentration of 1.2 wt% and hemicellulase with the concentration of 0.6 wt%, wherein the pH value is 4.5, the treatment temperature is 50 ℃, the treatment time is 24 hours, the hemp fiber after enzyme degumming treatment is added into boiling water to be boiled for 10min, the enzyme is inactivated, and then the hemp fiber is washed with water and dried;

(3) crushing the hemp fibers degummed in the step (2), and sieving the crushed hemp fibers with a 80-mesh sieve to obtain hemp fiber powder;

(4) treating the hemp fiber powder in the step (3) with cellulase with the concentration of 0.2mg/mL, wherein the bath ratio is 1:50(kg/L), the pH value is 4.8, the treatment temperature is 50 ℃, and the treatment time is 24 hours, so as to obtain hemp skin nanofiber solution;

(5) performing ultrasonic treatment on the hemp skin nanofiber solution obtained in the step (4), wherein the ultrasonic power is 900W, the treatment time is 10min, then centrifuging, and freeze-drying the supernatant, wherein the freeze-drying conditions are as follows: the vacuum degree is 20Pa, and the temperature is-85 ℃; the time is 48 h.

The particle size distribution of the prepared nano-cellulose is shown in figure 1, and the Tyndall phenomenon after the prepared nano-cellulose is prepared into a solution is shown in figure 2, which shows that the obtained nano-cellulose has smaller particle size and uniform particle size distribution, and the sol is obtained after the nano-cellulose is dissolved in water.

Example 4

(1) Pretreating hemp skin with 0.5 wt% sodium hydroxide at bath ratio of 1:15(kg/L), treatment temperature of 60 deg.C for 7 hr, and washing the treated hemp skin with water to neutrality;

(2) treating the hemp fiber obtained in the step (1) with pectinase with the concentration of 1.0 wt% and hemicellulase with the concentration of 0.8wt%, wherein the pH value is 3.0, the treatment temperature is 50 ℃, the treatment time is 24 hours, the hemp fiber after enzyme degumming treatment is added into boiling water to be boiled for 10min, the enzyme is inactivated, and then the hemp fiber is washed with water and dried;

(3) crushing the hemp fibers degummed in the step (2), and sieving the crushed hemp fibers with a 80-mesh sieve to obtain hemp fiber powder;

(4) treating the hemp fiber powder in the step (3) with cellulase with the concentration of 0.1mg/mL, wherein the bath ratio is 1:20(kg/L), the pH value is 4.5, the treatment temperature is 60 ℃, and the treatment time is 24 hours, so as to obtain hemp skin nanofiber solution;

(5) and (3) carrying out ultrasonic treatment on the hemp skin nanofiber solution obtained in the step (4), wherein the ultrasonic power is 900W, the treatment time is 8min, then centrifuging, and freeze-drying the supernatant, wherein the freeze-drying conditions are as follows: the vacuum degree is 20Pa, and the temperature is-85 ℃; the time is 48 h.

Example 5

(1) Pretreating hemp skin with 0.6 wt% sodium hydroxide at bath ratio of 1:30(kg/L), treatment temperature of 60 deg.C for 6 hr, and washing the treated hemp skin with water to neutrality;

(2) treating the hemp fiber obtained in the step (1) with pectinase with the concentration of 1.0 wt% and hemicellulase with the concentration of 0.5 wt%, wherein the pH value is 4.5, the treatment temperature is 45 ℃, the treatment time is 24 hours, the hemp fiber after enzyme degumming treatment is added into boiling water to be boiled for 10min, the enzyme is inactivated, and then the hemp fiber is washed with water and dried;

(3) crushing the hemp fibers degummed in the step (2), and sieving the crushed hemp fibers with a 80-mesh sieve to obtain hemp fiber powder;

(4) treating the hemp fiber powder in the step (3) with cellulase with the concentration of 0.2mg/mL, wherein the bath ratio is 1:30(kg/L), the pH value is 5.0, the treatment temperature is 60 ℃, and the treatment time is 30 hours, so as to obtain hemp skin nanofiber solution;

(5) performing ultrasonic treatment on the hemp skin nanofiber solution obtained in the step (4), wherein the ultrasonic power is 500W, the treatment time is 10min, then centrifuging, and freeze-drying the supernatant, wherein the freeze-drying conditions are as follows: the vacuum degree is 20Pa, and the temperature is-85 ℃; the time is 48 h.

Comparative example 1

The concentration of sodium hydroxide in step (2) was 0.1 wt% as compared with example 1, and the other steps were the same as in example 1.

Comparative example 2

The concentration of sodium hydroxide in step (1) was 1.0 wt% as compared with example 2, and the other was the same as in example 2.

Comparative example 3

The concentration of pectinase in step (2) was 0.3 wt% as compared to example 2, otherwise as in example 2.

Comparative example 4

The concentration of pectinase in step (2) was 2.0 wt% as compared to example 1, otherwise the same as in example 1.

Comparative example 5

The concentration of hemicellulase in step (2) was 0.1 wt% compared to example 1, otherwise the same as in example 1.

Comparative example 6

The concentration of hemicellulase in step (2) was 1.2 wt% compared to example 2, otherwise the same as in example 2.

Comparative example 7

The concentration of cellulase in step (4) was 0.4mg/mL as compared with example 2, and the procedure was otherwise the same as in example 2.

Comparative example 8

The pH in step (4) was 3.0 as compared with example 2, and the rest was the same as in example 2.

Comparative example 9

The pH in step (4) was 6.0 as compared with example 1, and the procedure was otherwise the same as in example 1.

Comparative example 10

The pH in step (2) was 2.0 as compared with example 4, and the other steps were the same as in example 4.

Comparative example 11

The pH in step (4) was 6.5 as compared with example 2, and the other steps were the same as in example 2.

The test results of the nanocelluloses prepared in examples 1 to 5 and comparative examples 1 to 11 are shown in table 1.

TABLE 1

The particle diameters in table 1 are particle diameter values of the maximum distribution intensity;

the yield calculation method in table 1 is:

the total yield calculation method in table 1 is:

the stability test method in table 1 is:

dissolving the nano-cellulose freeze-dried powder (0.05 wt%) by using deionized water, storing 10mL of the solution in a glass sample bottle, standing at room temperature for 15 days, and observing the appearance change of the nano-cellulose solution.

In the comparative example 1, the concentration of sodium hydroxide in the step (2) is low, glue impurities in hemp skin fibers cannot be effectively removed, a shielding effect is generated on the action of cellulase in the step (4), the catalytic efficiency of the cellulase is further influenced, the particle size of the nano-cellulose in the comparative example 1 is larger than that in the example 1, and the preparation rate is lower than that in the example 1; comparative example 2 the concentration of sodium hydroxide in step (1) is higher, the fiber structure is damaged, the fiber loss is higher, more monosaccharide is generated during the action of cellulase in step (4), and the preparation rate and the total preparation rate of nano-cellulose are reduced; in the comparative example 3, the concentration of the pectinase in the step (2) is lower, the glue impurities in the hemp peel are not hydrolyzed sufficiently, the shielding effect is generated on the action of the cellulase in the step (4), the catalytic efficiency of the cellulase is further influenced, and the nano cellulose in the comparative example 3 has larger particle size than that in the example 2 and lower preparation rate; in the step (2) of the comparative example 4, the pectinase concentration is higher, the pectin removal amount is higher, hemp fibers are separated into single fibers, the fiber loss is large, the preparation yield and the total preparation rate are influenced, the enzyme concentration is high, and the cost is higher; in the comparative example 5, the concentration of the hemicellulase in the step (2) is lower, the hydrolysis of glue impurities in the hemp peel is insufficient, the effect of the cellulase in the step (4) is shielded, the catalytic efficiency of the cellulase is further influenced, and the nano cellulose in the comparative example 5 has larger particle size than that in the example 1 and lower preparation rate; comparative example 6 the concentration of hemicellulase is high, the removal amount of hemicellulose in the fibers is high, hemp fibers are separated into single fibers, the fiber loss is large, the total production yield is influenced, the enzyme concentration is high, and the cost is high; comparative example 7 the concentration of cellulase is high, more nano-cellulose with smaller particle size is hydrolyzed into monosaccharide, the particle size is increased, and the preparation rate is reduced; comparative example 8 too low a pH greatly reduced the hydrolysis efficiency of cellulase, resulting in increased particle size and reduced yield; the pH value of the comparative example 9 is not in the proper range of the cellulase, so that the hydrolysis efficiency of the cellulase is reduced, the particle size is increased, and the preparation rate is reduced; the pH value which is too low in the comparative example 10 reduces the efficiency of pectinase and hemicellulase in the step (2), glue impurities in hemp skin fibers cannot be effectively removed, a shielding effect is generated on the action of cellulase in the step (4), the catalytic efficiency of the cellulase is further influenced, the particle size is increased, and the preparation rate is reduced; comparative example 11 pH was out of the appropriate range for cellulase in step (4), decreasing the hydrolysis efficiency of cellulase, resulting in an increase in particle size and a decrease in production yield as compared to example 2.

In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.