CN115895053B

CN115895053B - Biodegradable membrane and preparation method and application thereof

Info

Publication number: CN115895053B
Application number: CN202210932673.5A
Authority: CN
Inventors: 吕永梅; 王冕; 张译文; 余晓红; 章晓洋; 柳晓晨; 商曰玲; 陈小冬
Original assignee: Yancheng Institute of Technology
Current assignee: Yancheng Institute of Technology
Priority date: 2022-08-04
Filing date: 2022-08-04
Publication date: 2024-03-26
Anticipated expiration: 2042-08-04
Also published as: CN115895053A

Abstract

The invention discloses a biodegradable film, a preparation method and application thereof, wherein the biodegradable film comprises the following raw materials in percentage by volume: 60-80% of fermented shrimp shell extract, 10-30% of water, 0.5-1% of film forming agent, 0-1% of plasticizer, 0-1% of surfactant and 0-10% of cross-linking agent; wherein the fermented shrimp shell extract is obtained by fermenting shrimp shell with light emitting bacillus which is LYM-1 of Photobacterium (photo bacterium sp.) with deposit number of GDMCC No.62616; the film forming agent is polyvinyl alcohol, the plasticizer is glycerin, the surfactant is Tween 20, and the crosslinking agent is boric acid, citric acid or glutaraldehyde. The degradable film has the use characteristics of traditional plastics, can achieve the aim of complete biodegradation without specific conditions, takes shrimp shells as raw materials, is environment-friendly, has high tensile strength, good flexibility and high elongation at break, and has the effects of heat preservation and moisture preservation on vegetable germination.

Description

Biodegradable film and preparation method and application thereof

Technical Field

The invention belongs to the technical field of mulching film materials, and particularly relates to a biodegradable film and a preparation method and application thereof.

Background

The mulching film has the functions of heat preservation, soil moisture preservation, yield increase and income increase, so that the mulching film is widely applied to agricultural production in China. In recent years, the use amount of agricultural mulching films in China is increased year by year, the level of 100 ten thousand tons/year is reached, and the agricultural mulching films in China become the country with the largest use amount of agricultural mulching films in the world. The main raw material of the traditional agricultural mulching film is polyethylene, the molecular weight is high, the structure is compact, the agricultural mulching film can be degraded in soil within hundreds of years, the thickness of the agricultural mulching film is generally less than 0.008mm, and the agricultural mulching film is difficult to implement and is difficult to recycle. Meanwhile, the residual film in the soil can influence the structure of the soil, so that the humus of the soil is deteriorated, and the number of microorganisms and the enzyme activity are reduced, thereby leading to the yield reduction of crops. Therefore, the white pollution brought by agricultural mulching films has become a hot spot for research and discussion of domestic and foreign experts and scholars, and the degradable films are a new research direction. Research on degradable films has been reported, and the main application materials include cellulose, protein, starch, etc. Cellulose degradable films are mainly mixed with polylactic acid (PLA), polyvinyl alcohol (PVA), modified starch and the like to ensure that the films have high mechanical strength, water resistance and other physical properties. Although these degradable mulching films have good mechanical properties and heat and moisture preservation effects, the cost of the degradable mulching films is relatively high, and the degradable mulching films are difficult to apply to large-scale agricultural production, and the preparation mode (usually chemical method) of the base materials needs to be improved. Therefore, the search for inexpensive raw materials for preparing the degradable agricultural mulching film becomes a development trend.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a biodegradable film, a preparation method and application thereof, which takes a shrimp shell which is an inexpensive byproduct as a raw material, prepares the film which has heat preservation, moisture preservation and water resistance and can be degraded by microorganisms and provide nutrition for plant growth in a green low-carbon mode, not only solves the problem that a plastic film is difficult to degrade, but also provides a novel method for treating the crayfish shell.

The invention is realized by the following technical scheme:

the biodegradable film comprises the following raw materials in percentage by volume: 60-80% of fermented shrimp shell extract, 10-30% of water, 0.5-1% of film forming agent, 0-1% of plasticizer, 0-1% of surfactant and 0-10% of cross-linking agent; wherein the fermented shrimp shell extract is obtained by fermenting shrimp shell with light-emitting bacillus which is LYM-1 of Photobacterium sp, and the preservation number is GDMCC No.62616; the film forming agent is polyvinyl alcohol, the plasticizer is glycerin, the surfactant is Tween 20, and the crosslinking agent is boric acid, citric acid or glutaraldehyde.

Preferably, the preparation comprises the following raw materials in percentage by volume: 60-80% of fermented shrimp shell extract, 10-30% of water, 0.5-1% of film forming agent, 0.1-1% of plasticizer, 0.01-1% of surfactant and 0.1-10% of cross-linking agent.

A method of preparing a biodegradable film comprising the steps of:

step 1) preparing a seed culture medium, inoculating luminous bacillus, performing activation culture to prepare a seed liquid, inoculating the seed liquid of the luminous bacillus into shrimp shells for fermentation, wherein the inoculation amount is 5%, determining fermentation time by measuring reducing sugar and total sugar content in fermentation liquid, and removing residues after fermentation is finished to obtain a fermented shrimp shell extracting solution;

step 2) adding water accounting for 10% -30% of the total volume and film forming agent accounting for 0.5% -1% of the total volume into a container for mixing, and heating to liquefy to obtain a mixed solution A;

step 3) adding 60-80% of the total volume of the fermented shrimp shell extract into the mixed solution A, stirring and mixing, and adding 0.2-1% of plasticizer and 0.01-1% of surfactant to obtain mixed solution B;

step 4) adding a cross-linking agent accounting for 0.1% -10% of the total volume into the mixed solution B, and stirring uniformly to obtain a mixed solution C;

and 5) pouring the mixed solution C into a mould to uniformly spread at the bottom of the mould, putting the mould into an oven for drying, taking out the mould after film formation, and putting the mould into a dryer for balancing for 48 hours to obtain the composite material.

Preferably, the conditions of the activation culture of step 1) are as follows: the temperature was 37℃for 12h and the pH was 7.0.

Preferably, the fermentation conditions of step 1) are as follows: the temperature is 25-40 ℃, the rotating speed is 150-220 rpm, the time is 3-10 d, and the pH is 6-8.

Preferably, the step 1) of removing the residue is performed as follows: the rotational speed is set to 8000rpm by adopting a refrigerated centrifuge, and the time is 10min.

Preferably, the heating in step 2) is carried out at a temperature of 90 ℃ for 20min.

Preferably, the cross-linking agent in step 4) is boric acid, citric acid or glutaraldehyde; when the cross-linking agent is boric acid, the addition amount of the cross-linking agent is 0.1-2% of the total volume of the mixed solution B; when the cross-linking agent is citric acid, the addition amount of the cross-linking agent is 0.2-10% of the total volume of the mixed solution B; when the cross-linking agent is glutaraldehyde, the addition amount of the cross-linking agent is 0.2-5% of the total volume of the mixed solution B.

Preferably, the temperature of the drying in the step 5) is 40-60 ℃ and the time is 24-96 h.

A biodegradable film is used for maintaining temperature and humidity during vegetable germination.

The beneficial effects of the invention are as follows:

(1) The process for preparing the biodegradable film realizes the high-value utilization of the shrimp shells of the catering wastes and solves the problems of difficult processing and environmental pollution caused by accumulation of the shrimp shells.

(2) The invention prepares the degradable mulching film which has heat preservation, moisture preservation and waterproof performance and can be degraded by microorganisms by taking the shrimp shell as a raw material and provides nutrition for plant growth, and solves the problems that the traditional mulching film is difficult to recover, difficult to degrade, residual affects soil fertility and the like.

Drawings

FIG. 1 is a graph showing the variation of the total sugar (a), reducing sugar (b) and polysaccharide (c) contents of the seed solution in example 1 during fermentation;

FIG. 2 is a morphological feature of a conventional PVA film and biodegradable films prepared in examples 2-10;

FIG. 3 is an infrared spectrum of a general PVA film and biodegradable films prepared in examples 2 to 10;

FIG. 4 is an infrared spectrum of a biodegradable film prepared in example 2, example 6, and example 7;

FIG. 5 is an infrared spectrum of a biodegradable film prepared in example 2, example 3, and example 8, which is a common PVA film;

FIG. 6 is an infrared spectrum of a biodegradable film prepared in example 2, example 4, and example 9;

FIG. 7 is an infrared spectrum of a biodegradable film prepared in example 2, example 5, and example 10, which is a common PVA film;

FIG. 8 is a scanning electron microscope image (dimensions 10 μm, 5 μm, 3 μm, 1 μm, respectively) of a normal PVA film (a) and biodegradable films prepared in example 6 (b), example 8 (c);

FIG. 9 shows the growth of chicken feather dish in example 11: (a) The growth under the light-shielding condition and the growth under the illumination condition are shown in (b).

Detailed Description

The invention will be further illustrated by the following drawings and specific examples, which are set forth in order to carry out the invention in light of the present teachings, and it should be understood that these teachings are presented solely for purposes of illustration and are not intended to limit the scope of the present teachings.

The strain provided by the invention and the raw materials and reagents used in the application of the strain can be purchased from the market.

The biodegradable film comprises the following raw materials in percentage by volume: 60-80% of fermented shrimp shell extract, 10-30% of water, 0.5-1% of film forming agent, 0-1% of plasticizer (preferably 0.1-1%), 0-1% of surfactant (preferably 0.01-1%), and 0-10% of cross-linking agent (preferably 0.1-10%); wherein the fermented shrimp shell extract is obtained by fermenting shrimp shell with light-emitting bacillus which is LYM-1 of Photobacterium sp, and the preservation number is GDMCC No.62616; the film forming agent is polyvinyl alcohol, the plasticizer is glycerin, the surfactant is Tween 20, and the crosslinking agent is boric acid, citric acid or glutaraldehyde.

Example 1 preparation of fermentation broths

1. Preparation of culture Medium

LB medium: yeast extract 5g/L, tryptone 10g/L, sodium chloride 10g/L, pH 7.0, and sterilization at 121 ℃ for 20min.

Fermentation medium: shrimp shell 30g/L, pH 7.0, and sterilizing at 121deg.C for 20min.

2. Preparation of seed liquid

The luminous bacillus stored in the ultralow temperature refrigerator at the temperature of minus 80 ℃ is picked up by an inoculating loop and inoculated on an LB flat plate, the LB flat plate is placed in an incubator at the temperature of 37 ℃ for 12 hours of activation culture, and the strong bacterial colony is picked up from the activated flat plate and cultured in an LB liquid culture medium to prepare seed liquid. At intervals, the OD was measured by taking a spot from the medium ₆₀₀ Value, to be OD ₆₀₀ Stopping culturing when the value reaches 0.6-0.8, and using for the next fermentation.

The luminous bacillus is luminous bacillus (Photobacterium sp.) LYM-1, is autonomously cultivated in the laboratory, is preserved in the microorganism strain collection center of Guangdong province, is located at building 5 of Mitsui No. 100 of Mitsui No. 59 of Xiuzhou district of Guangdong province, is classified and named as luminous bacillus (Photobacterium sp.), and has a preservation date of 2022, 7 months and 11 days and a preservation number of GDMCC No.62616.

3. Preparation of fermentation broths

(1) The seed solution was inoculated into a 250mL triangular flask containing 100mL of fermentation medium in an inoculum size of 5%, and fermented at 37℃for 10d at 180r/min, and the reducing sugar and total sugar content in the fermentation solution were periodically measured during the fermentation to determine the fermentation time.

(2) Determination of reducing sugar content: 2mg of glucose standard is weighed and added with 2mL of deionized water to prepare a glucose solution with the concentration of 1mg/mL as a standard solution, then 0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18 and 0.2mL of glucose standard solution are respectively moved by a pipette into a 1.5mL EP tube, 300 mu L of DNS reagent is added, boiling water is used for 5min, cooling is carried out to room temperature, water is supplemented to 1mL, supernatant is taken after centrifugation, absorbance is measured at the wavelength of 520nm, the concentration of glucose is taken as an abscissa, and the absorbance is taken as an ordinate, so that a standard curve of the glucose solution is obtained.

Substituting the measured absorbance into a regression equation of a glucose standard curve after measuring the absorbance of the fermentation broth, and calculating to obtain the content of reducing sugar in the fermentation broth:

in the above formula: x is the content of reducing sugar in the fermentation liquor; y is the absorbance of the sample; a is the slope of the regression equation; b is the intercept of the regression equation on the y-axis; c is the dilution of the sample.

(3) Determination of total sugar content: 2mg of glucose standard is weighed by adopting standard curve measurement, 2mL of deionized water is added to prepare 1mg/mL of glucose solution as standard solution, then 0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18 and 0.2mL of glucose standard solution are respectively moved by a pipette, in a 1.5mL EP tube, distilled water is supplemented to 0.2mL, 0.2mL of phenol (mass fraction is 5%) is added, 1mL of concentrated sulfuric acid is added, after uniform mixing, the reaction is carried out at room temperature for 30min, the absorbance of the solution is measured at the 490nm position of a characteristic absorption peak, and the absorbance is taken as an abscissa to obtain the standard curve of the glucose solution.

Transferring 0.2mL of the filtered fermentation liquor into a 1.5mL EP tube, wherein the rest steps are the same as the measurement method of the standard curve, substituting the measured absorbance into a regression equation of a glucose standard curve after measuring the absorbance, and calculating to obtain the total sugar content in the fermentation liquor:

in the above formula: x is the total sugar content in the fermentation broth; y is the absorbance of the sample; a is the slope of the regression equation; b is the intercept of the regression equation on the y-axis; c is the dilution of the sample.

(4) The polysaccharide content (total sugar-reducing sugar) in the fermentation broth is estimated initially by reducing sugar and total sugar content, and the fermentation broth on the day with the highest polysaccharide content is taken for the subsequent preparation of the biodegradable film.

As shown in FIG. 1 (a), the total sugar content of fermentation No. 7d in this example was the highest, and it was 0.583mg/mL; as shown in FIG. 1 (b), the maximum reducing sugar content at 6d of fermentation was 0.123mg/mL; as shown in FIG. 1 (c), the polysaccharide content at 7d of fermentation was the highest, 0.31mg/mL, so that the fermentation broth at 7d of fermentation was used for the preparation of the biodegradable film in the subsequent examples.

Example 2 treatment of fermentation broth, membrane production (biodegradable Membrane PF)

1. Fermentation broth separation and purification

The fermentation broth obtained in example 1 was filtered and centrifuged to obtain a supernatant. Concentrating the supernatant by rotary evaporation at 55 ℃ and then filtering the supernatant according to the following steps: ethanol=1:3, 95% ethanol was added, and the mixture was allowed to stand at 4℃for 12 hours, centrifuged at 4000r/min for 10min, and the precipitate was collected and dissolved in distilled water. Mixing polysaccharide solution with Sevage reagent (chloroform: n-butanol=4:1) at a volume ratio of 5:1, oscillating for 30min, centrifuging, collecting water phase, and repeating until all proteins are removed. Adding 3 times of anhydrous ethanol into the concentrated solution from which proteins are removed, standing at 4deg.C for 24h in a refrigerator, centrifuging at 8000r/min for 5min, discarding supernatant, adding ultrapure water into the obtained polysaccharide precipitate to dissolve to obtain uniform solution, and dialyzing in a dialysis bag after treatment overnight.

2. Concentrating the fermentation liquor, and making membrane (biodegradable film PF)

(1) Centrifuging the fermentation liquor prepared in the example 1 for 5min at 8000r/min to remove fermentation residues, concentrating by a rotary evaporator to make the polysaccharide content reach 2mg/mL, and dialyzing the concentrated fermentation liquor to remove small molecular impurities to obtain the fermented shrimp shell extract.

(2) Weighing a proper amount of polyvinyl alcohol 17-99, dissolving in distilled water, heating while stirring to accelerate the dissolution, and heating at 90 ℃ for 20min to obtain a uniform solution (polyvinyl alcohol solution) with the concentration of 2%. And (3) sucking the fermented shrimp shell extract with the total volume of 75%, uniformly stirring and mixing the fermented shrimp shell extract with a polyvinyl alcohol solution, pouring the obtained film-forming solution into a polystyrene film tool, drying the film-forming solution in a baking oven with the temperature of 50 ℃ for 48 hours, removing the film-forming solution after the film-forming solution is formed into a film, and balancing the film-forming solution in a dryer for 48 hours to obtain the biodegradable film PF, as shown in figure 2.

The biodegradable film PF prepared in this example has a certain light transmittance, as shown in FIG. 3 and FIG. 4, and the surface of the film and the Fourier transform infrared spectrum show that the biodegradable film PF has good compatibility with PVA molecules, and is 3336cm ^-1 The peaks at the points represent O-H stretching vibration, the shift to low wave numbers is obvious, the hydrogen bond between the polysaccharide and PVA in the fermentation broth is reduced, and the peaks of the film after the fermentation broth are added represent the O-H stretching vibration are obviously enlarged, which is caused by self-OH on the polysaccharide in the fermentation broth. The mechanical strength of the biodegradable film PF is 2.31+/-1.09 MPa, and is improved to a certain extent compared with the mechanical strength (2.01+/-0.78) of a single PVA film; the breaking elongation is changed from 5.31 plus or minus 2.17 percent of the pure PVA film to 4.86 plus or minus 1.86 percent; the water absorption is improved from 607.77 +/-23.12% of a single film to 659.11 +/-33.42%, because the hydroxyl groups in the polysaccharide are hydrophilic groups and act together with the hydroxyl groups in the PVA, so that the adsorption capacity to water molecules is stronger; the water solubility rate is changed from 33.42 +/-3.21% of a single membrane to 22.34+/-6.42%, the dissolution rate of the biodegradable film PF in water is reduced, and the biodegradable film PF can be kept complete in water.

EXAMPLE 3 preparation of biodegradable film PFC

The film forming step was substantially the same as in example 2, except that: citric acid was added to the film forming liquid in an amount of 0.2% by volume to prepare a biodegradable film PFC as shown in fig. 2.

The biodegradable film PFC prepared in this example has a certain light transmittance, as shown in FIG. 3 and FIG. 5, the film surface and the Fourier transform infrared spectrum show that the polysaccharide, citric acid and PVA molecules in the biodegradable film PFC have good compatibility and react, and most obviously, the film surface and the Fourier transform infrared spectrum are at 1715cm ^-1 Coalescence peaks were found, because citric acid reacted with polyvinyl alcohol and polysaccharides in the broth to form ester bonds, which play a great role in improving the water repellency of the film, consistent with the data below for improved water repellency. The mechanical strength of the biodegradable film PFC is 2.65+/-0.78 MPa, and compared with the mechanical strength (2.01+/-0.78) of a single PVA film, the mechanical strength of the biodegradable film PFC is improved to a certain extent; the elongation at break is changed from 5.31+/-2.17% of a pure PVA film to 118.18 +/-36.01%, and the ductility of the film is greatly improved; the water absorption is increased from 607.77 +/-23.12% to 619.21 +/-45.02% in a single film, probably due to the attractive force of the self-contained hydroxyl groups in citric acid on water molecules; the water solubility is changed from 33.42 +/-3.21% of a single film to 18.12+/-4.23%, the dissolution rate of the biodegradable film PFC in water is reduced, and the waterproof performance is greatly improved, because citric acid reacts with hydroxyl groups in polysaccharide and PVA to generate ester bonds, and the waterproof performance of the film is improved because the ester bonds are hydrophobic groups.

EXAMPLE 4 preparation of biodegradable film PFB

The film forming step was substantially the same as in example 2, except that: boric acid was added to the film-forming liquid in an amount of 0.05% by volume to prepare a biodegradable film PFB as shown in FIG. 2.

The biodegradable film PFB prepared in this example has a certain light transmittance, as shown in FIG. 3 and FIG. 6, the film surface and the Fourier transform infrared spectrum show that the polysaccharide, boric acid and PVA molecules in the biodegradable film PFB have good compatibility and react, and can be seen at 1731cm ^-1 Is considered to be the carbon of the borate group during the reaction of polyvinyl alcohol with boric acidStretching with oxygen to about 1640cm ^-1 The peak of (2) is related to the asymmetric deformation of the-OH water. The mechanical strength of the biodegradable film PFB is 2.12+/-0.57 MPa, and compared with the mechanical strength (2.01+/-0.78) of a single PVA film, the mechanical strength of the biodegradable film PFB is improved to a certain extent; the breaking elongation is changed from 5.31+/-2.17% of the pure PVA film to 6.21+/-3.12; the water absorption is changed from 607.77 +/-23.12% of a single film to 133.91 +/-19.18%, because the crosslinking action between boric acid, PVA and polysaccharide reduces the number of hydroxyl groups on the biodegradable film PFB, and the gaps between molecular structures and the binding force between water molecules are reduced; the water solubility rate was changed from 33.42 + -3.21% to 45.41+ -5.24% of the single film.

EXAMPLE 5 preparation of biodegradable film PFGa

The film forming step was substantially the same as in example 2, except that: glutaraldehyde of 0.2% of the total volume is added to the film forming solution to prepare a biodegradable film PFGa as shown in fig. 2.

The biodegradable film PFGa prepared in this example has a certain light transmittance, and as shown in FIG. 3 and FIG. 7, the film surface and the Fourier transform infrared spectrum show that the polysaccharide, glutaraldehyde and PVA molecules in the biodegradable film PFGa have good compatibility and react, and the reaction is carried out at 1550cm ^-1 (c=o) -ionized carbonyl and 1046cm ^-1 New peaks at. The mechanical strength of the biodegradable film PFGa is 3.01+/-0.82 MPa, compared with the mechanical strength (2.01+/-0.78) of a single PVA film, the mechanical strength of the biodegradable film PFGa is greatly improved, because aldehyde compounds can form a compact three-dimensional network structure with polyvinyl alcohol and hydroxyl groups in polysaccharide through acetalation reaction, and the mechanical strength of the biodegradable film PFGa is greatly improved; the elongation at break is changed from 5.31+/-2.17% of a pure PVA film to 91.39 +/-12.45%, and the ductility of the film is greatly improved; the water absorption is changed from 607.77 +/-23.12% of a single film to 712.36 +/-32.14%, which is probably because the hydroxyl on the biodegradable film PFGa is not on a plane any more due to the crosslinking action between glutaraldehyde, PVA and polysaccharide, but is in a three-dimensional structure, the contact area with water molecules is increased, the acting force on the water molecules is increased, and the water absorption performance is improved; the water solubility rate is changed from 33.42 +/-3.21% of a single film to 50.12+/-5.36％。

EXAMPLE 6 preparation of biodegradable film PFGl

The film forming step was substantially the same as in example 2, except that: glycerin was added to the film-forming liquid in an amount of 0.25% by volume to prepare a biodegradable film PFGl as shown in FIG. 2.

The biodegradable film PFGl prepared in this example has a certain light transmittance, and as shown in fig. 3, the surface of the film and the fourier transform infrared spectrum show that the polysaccharide, glycerol and PVA molecules in the biodegradable film PFGl have good compatibility. The mechanical strength of the biodegradable film PFGl is 3.38+/-1.18 MPa, and compared with the mechanical strength (2.01+/-0.78) of a single PVA film, the mechanical strength of the biodegradable film PFGl is greatly improved; the elongation at break is changed from 5.31+/-2.17% of a pure PVA film to 86.56+/-21.23%, and the ductility of the film is greatly improved; the water absorption is changed from 607.77 +/-23.12% of a single film to 216.34 +/-22.31%, and the difficulty of combining water molecules with a biodegradable film PFGl is probably increased due to the fact that a large number of hydroxyl groups in glycerol and hydroxyl groups in PVA and polysaccharide have intermolecular hydrogen bonds, so that the water absorption performance is poor; the water solubility is changed from 33.42 +/-3.21% of a single film to 29.24+/-7.12%, and the waterproof performance is improved to a certain extent.

EXAMPLE 7 preparation of biodegradable film PFGlT

The film forming step was substantially the same as in example 2, except that: the biodegradable film PFGlT was prepared by adding 0.25% by volume of glycerin and 0.01% by volume of Tween 20 to the film-forming liquid, as shown in FIG. 2.

The biodegradable film PFGlT prepared in the embodiment has certain light transmittance, and as shown in fig. 3 and 4, the surface of the film and the Fourier transform infrared spectrogram show that the polysaccharide, the glycerol, the Tween 20 and PVA molecules in the biodegradable film PFGlT have good compatibility with 2950-2910 cm ^-1 Corresponding to-CH ₂ -asymmetric and symmetric stretching modes of the group at 1094cm ^-1 The centered strip represents the vibration of the carbon oxygen stretched polyvinyl alcohol. The mechanical strength of the biodegradable film PFGlT is 3.66+/-1.32 MPa, and compared with the mechanical strength (2.01+/-0.78) of a single PVA film, the mechanical strength of the biodegradable film PFGlT is greatly improved; elongation at break was changed from 5.31.+ -. 2.17% of pure PVA film to 67.27+21.24%, the ductility of the film is greatly improved; the water absorption is changed from 607.77 +/-23.12% of a single film to 227.43 +/-33.12%, and probably because a great amount of hydroxyl groups in glycerol and hydroxyl groups in PVA and polysaccharide have intermolecular hydrogen bonds, the difficulty of combining water molecules and a biodegradable film PFGlT is increased, and the water absorption performance is poor; the water solubility is changed from 33.42 +/-3.21% of a single film to 28.71+/-6.54%, and the waterproof performance is improved to a certain extent.

EXAMPLE 8 preparation of biodegradable film PFCGl

The film forming step was substantially the same as in example 2, except that: the biodegradable film PFCGl was prepared by adding glycerol in an amount of 0.25% by volume and citric acid in an amount of 0.2% by volume to the film-forming liquid, as shown in FIG. 2.

The biodegradable film PFCGl prepared in this example has a certain light transmittance, and as shown in FIG. 3 and FIG. 5, the surface of the film and the Fourier transform infrared spectrogram show that the polysaccharide, citric acid, glycerol and PVA molecules in the biodegradable film PFCGl have good compatibility and react. The mechanical strength of the biodegradable film PFCGl is 3.49+/-0.84 MPa, and compared with the mechanical strength (2.01+/-0.78) of a single PVA film, the mechanical strength of the biodegradable film PFCGl is greatly improved; the elongation at break is changed from 5.31+/-2.17% of a pure PVA film to 135.49 +/-12.14%, and the ductility of the film is greatly improved; the water absorption is changed from 607.77 +/-23.12% of a single film to 204.16 +/-11.36%, and the water absorption performance is possibly deteriorated due to intermolecular hydrogen bonding effect formed by hydroxyl groups carried in citric acid and glycerol, so that the water resistance is improved; the water solubility is changed from 33.42 +/-3.21% of a single film to 20.47+/-3.87%, and the waterproof performance of the film is further improved.

EXAMPLE 9 preparation of biodegradable film PFBGl

The film forming step was substantially the same as in example 2, except that: the biodegradable film PFBGl was prepared by adding glycerin in an amount of 0.25% by volume and boric acid in an amount of 0.2% by volume to the film-forming liquid, as shown in FIG. 2.

The biodegradable film PFBGl prepared in this example has a certain light transmittance, as shown in fig. 3 and 6, and the surface of the film and the fourier transform infrared spectrogram show that the polysaccharide, boric acid, glycerol and PVA molecules in the biodegradable film PFBGl have good compatibility and react. The mechanical strength of the biodegradable film PFBGl is 3.52+/-0.72 MPa, and compared with the mechanical strength (2.01+/-0.78) of a single PVA film, the mechanical strength of the biodegradable film PFBGl is greatly improved; elongation at break was changed from 5.31±2.17% of pure PVA film to 62.51 ±13.62; the water absorption is changed from 607.77 +/-23.12% of a single film to 233.91 +/-19.18%, because the crosslinking action between boric acid, PVA and polysaccharide reduces the number of hydroxyl groups on the biodegradable film PFBGl, and the gaps between molecular structures and the binding force between water molecules are reduced; the water solubility rate was changed from 33.42 + -3.21% to 56.60+13.24% of the single film.

EXAMPLE 10 preparation of biodegradable film PFGlGa

The film forming step was substantially the same as in example 2, except that: the biodegradable film PFGaGl was prepared by adding 0.25% by volume of glycerin and 0.2% by volume of glutaraldehyde to the film forming liquid, as shown in fig. 2.

The biodegradable film PFGaGl prepared in this example has a certain light transmittance, and as shown in fig. 3 and 7, the surface of the film and the fourier transform infrared spectrum show that the polysaccharide, glutaraldehyde, glycerol and PVA molecules in the biodegradable film PFGaGl have good compatibility and react. The mechanical strength of the biodegradable film PFGaGl is 3.11+/-0.72 MPa, compared with the mechanical strength (2.01+/-0.78) of a single PVA film, the mechanical strength of the biodegradable film PFGaGl is greatly improved, because the aldehyde compound can form a compact three-dimensional network structure with the polyvinyl alcohol and the hydroxyl in the polysaccharide through acetalation reaction, and the mechanical strength of the biodegradable film PFGaGl is greatly improved; the elongation at break is changed from 5.31+/-2.17% of a pure PVA film to 111.59 +/-11.54%, and the ductility of the film is greatly improved; the water absorption is changed from 607.77 +/-23.12% of a single film to 234.61 +/-34.44%, so that the water resistance is improved; the water solubility rate was changed from 33.42 + -3.21% to 50.12+ -5.36% of the single film.

The scanning electron microscope of the 3 sample films in the above examples is shown in fig. 8, in which fig. 8 (a) is a normal PVA film (P), fig. 8 (b) is a biodegradable film (PFGl) prepared in example 6, and fig. 8 (c) is a biodegradable film (PFCGl) prepared in example 8, and the magnification is 10000 times, 20000 times, 40000 times, 80000 times in this order. Scanning electron microscope micrographs show: the PFGl film with only fermentation broth added is not firmly combined with PVA, the surface of the film is not smooth enough, and the color contrast caused by the difference of the film height in FIG. 8 (b) is obvious; the PFCGl film (fig. 8 (c)) with citric acid and glycerol added has a uniform color and a flat film surface, because citric acid serves as an intermediate reactant to link the polysaccharide to the polyvinyl alcohol.

EXAMPLE 11 use of biodegradable films

1. Taking chicken hair vegetable seeds with vitality after screening, planting the chicken hair vegetable seeds into a basin, covering the chicken hair vegetable seeds with the biodegradable film PFCGl prepared in the example 8, covering the chicken hair vegetable seeds with soil to form a solid around the chicken hair vegetable seeds, taking the chicken hair vegetable seeds as an experimental group, simultaneously taking several parallel groups of the experimental groups, selecting a blank group without covering the film, selecting a positive control group covered with a plastic film, putting the chicken hair vegetable seeds into a light-resistant constant-temperature incubator at 10 ℃, watering the chicken hair vegetable seeds once, and observing the germination condition of the chicken hair vegetable seeds.

The results are shown in FIG. 9 (a): under the light-shielding condition, plants without the cover film (blank groups) do not grow, because the temperature is low and the moisture volatilization does not accord with the germination condition of the plants; the biodegradable film (experimental group) and the plastic film (positive control group) are added for 7 days to sprout, the plants of the experimental group grow 2 plants, the plants of the positive control group grow 5 plants, and the total length and the diameter of the plants of the positive control group are better than those of the experimental group, but compared with the plastic film, the degradable film can be degraded, and the influence on the environment is reduced to the minimum in the manufacturing process and degradation products.

2. The experimental group, the blank group and the positive control group are placed in a constant temperature chamber with illumination at 10 ℃ and water is poured once, and the germination condition is observed.

The results are shown in FIG. 9 (b): under illumination conditions, plants without film (blank group) did not grow due to moisture evaporation; both biodegradable film-added (experimental group) and plastic film-added (positive control group) plants grew, but the plants of the experimental group were not as good as the plants of the positive control group, due to the poor light transmission of the biodegradable film compared to the plastic film.

In general, biodegradable films have certain water-retaining and heat-retaining properties, and are biodegradable compared to plastic films, and have great value in intensive research.

The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims

1. The biodegradable film is characterized by comprising the following raw materials in percentage by volume: 60-80% of fermented shrimp shell extract, 10-30% of water, 0.5-1% of film forming agent, 0-1% of plasticizer, 0-1% of surfactant and 0-10% of cross-linking agent; wherein the fermented shrimp shell extract is obtained by fermenting shrimp shell with light-emitting bacillus which is LYM-1 of Photobacterium sp, and the preservation number is GDMCC No.62616; the film forming agent is polyvinyl alcohol, the plasticizer is glycerin, the surfactant is Tween 20, and the crosslinking agent is boric acid, citric acid or glutaraldehyde.

2. A biodegradable film according to claim 1, characterized in that it comprises the following raw materials in percentage by volume: 60-80% of fermented shrimp shell extract, 10-30% of water, 0.5-1% of film forming agent, 0.1-1% of plasticizer, 0.01-1% of surfactant and 0.1-10% of cross-linking agent.

3. A method of producing a biodegradable film according to claim 1 or 2, comprising the steps of:

4. A method of preparing a biodegradable film according to claim 3, characterized in that the conditions of said activation culture of step 1) are as follows: the temperature was 37℃for 12h and the pH was 7.0.

5. A method of producing a biodegradable film according to claim 3, characterized in that the fermentation conditions of step 1) are as follows: the temperature is 25-40 ℃, the rotating speed is 150-220 rpm, the time is 3-10 d, and the pH is 6-8.

6. A method of producing a biodegradable film according to claim 3, characterized in that said step 1) of removing residues comprises the following operations: the rotational speed is set to 8000rpm by adopting a refrigerated centrifuge, and the time is 10min.

7. A method of producing a biodegradable film according to claim 3, characterized in that the heating temperature in step 2) is 90 ℃ for 20min.

8. A method of preparing a biodegradable film according to claim 3, characterized in that in step 4) the cross-linking agent is boric acid, citric acid or glutaraldehyde; when the cross-linking agent is boric acid, the addition amount of the cross-linking agent is 0.1-2% of the total volume of the mixed solution B; when the cross-linking agent is citric acid, the addition amount of the cross-linking agent is 0.2-10% of the total volume of the mixed solution B; when the cross-linking agent is glutaraldehyde, the addition amount of the cross-linking agent is 0.2-5% of the total volume of the mixed solution B.

9. A method of producing a biodegradable film according to claim 3, wherein said drying in step 5) is carried out at a temperature of 40 to 60 ℃ for a time of 24 to 96 hours.

10. A biodegradable film according to claim 1 or 2 for use in maintaining temperature and humidity during germination of vegetables.