CN113817205A - Photocatalytic polylactic acid antibacterial film and preparation method and application thereof - Google Patents

Photocatalytic polylactic acid antibacterial film and preparation method and application thereof Download PDF

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CN113817205A
CN113817205A CN202111149405.8A CN202111149405A CN113817205A CN 113817205 A CN113817205 A CN 113817205A CN 202111149405 A CN202111149405 A CN 202111149405A CN 113817205 A CN113817205 A CN 113817205A
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film
polylactic acid
photocatalytic
pla
ala
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王敬敬
陈璐
赵勇
刘海泉
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Shanghai Ocean University
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Shanghai Ocean University
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/12—Chemical modification
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
    • A01N37/00—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom having three bonds to hetero atoms with at the most two bonds to halogen, e.g. carboxylic acids
    • A01N37/42—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom having three bonds to hetero atoms with at the most two bonds to halogen, e.g. carboxylic acids containing within the same carbon skeleton a carboxylic group or a thio analogue, or a derivative thereof, and a carbon atom having only two bonds to hetero atoms with at the most one bond to halogen, e.g. keto-carboxylic acids
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
    • A01N59/00—Biocides, pest repellants or attractants, or plant growth regulators containing elements or inorganic compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
    • B65D65/38—Packaging materials of special type or form
    • B65D65/46—Applications of disintegrable, dissolvable or edible materials
    • B65D65/466—Bio- or photodegradable packaging materials
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/12—Chemical modification
    • C08J7/123—Treatment by wave energy or particle radiation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/12—Chemical modification
    • C08J7/14—Chemical modification with acids, their salts or anhydrides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
    • Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics

Abstract

The invention provides a photocatalytic polylactic acid antibacterial film and a preparation method and application thereof, the invention utilizes a low-temperature plasma technology to modify the surface of a polylactic acid material, so that a large number of active carboxyl groups are generated on the surface of the polylactic acid material, on the basis, the carboxyl groups on the surface of the polylactic acid film are innovatively subjected to covalent reaction with a photosensitizer, and the photocatalytic PLA antibacterial film is prepared by combining blue LED light irradiation; the invention organically integrates and innovates the photodynamic technology, the low-temperature plasma technology and the food packaging material, develops the packaging film material with the high-efficiency sterilization function, is a breakthrough of the food packaging industry, and provides new theoretical ideas and innovative practices for developing functional food packaging film materials in the future; the antibacterial film is used as a green food packaging material for efficiently killing common pathogenic bacteria and putrefying bacteria in food, and the novel packaging films are further used for packaging food such as salmon, so that the shelf life of the food is greatly prolonged.

Description

Photocatalytic polylactic acid antibacterial film and preparation method and application thereof
Technical Field
The invention belongs to the technical field of green degradable sterilization food packaging films, particularly relates to a photocatalytic polylactic acid (PLA) antibacterial film, and a preparation method and application thereof, and particularly relates to a food packaging film with photodynamic sterilization effect, which is prepared by covalently coupling a PLA film and a photosensitizer by using low-temperature plasma.
Background
The antibacterial active package is a leading edge and a hot spot of research and development in the field of food and materials at present, and the PLA and the copolymer thereof have an important position in the field of food packaging material research and development. PLA is a biopolymer material synthesized from plant resources, has good processability, safety, biocompatibility and biodegradability, and has been approved by the U.S. Food and Drug Administration (FDA) as a raw material for developing food packaging films (Zhanshi Ping, Wangtao, Wanjing chang, etc. the synthesis and modification research of biomedical materials PLA advances [ J ] the chemical industry advances, 2020,39(01): 199-. PLA has no toxic or side effect on human bodies, is a high polymer material with development prospect, can not cause environmental pollution after being abandoned, is very suitable for replacing the traditional non-degradable food packaging material and preparing a novel green sustainable packaging base material. However, PLA is a biological inert substance, has poor natural hydrophilicity, has no active structure in a molecular chain segment, and has no antibacterial property (Lilihua, Meta, Lililihong and the like, plasma graft polymerization PVP of a PLA film and surface property research [ J ]. the report of Chinese biomedical engineering, 2006,25(5):618 and 622.), and the defects limit the application of the PLA in the field of food antibacterial active packaging.
Photodynamic sterilization (PDI) is a novel non-thermal sterilization method that is effective in killing bacteria and fungi. Light, photosensitizer and oxygen are the necessary conditions that constitute PDI sterilization technology. At present, most researches are carried out on constructing a PDI technical system by using natural curcumin as a photosensitizer so as to kill various microorganisms. Curcumin produces Reactive Oxygen Species (ROS) including singlet oxygen, hydrogen peroxide, hydroxyl, etc. under blue light (455-460nm) irradiation, and attacks cells to cause their death. A large number of researches prove that the curcumin-mediated PDI technology can effectively kill Listeria monocytogenes (Huangjiaming, Chenbowen, Li Hui et al, curcumin-mediated photodynamic inactivation enhances the antibacterial effect on mixed Listeria monocytogenes and biofilms [ C ]. The sixteenth annual meeting and the tenth middle American food industry forum high-level, 2019:2) of the Chinese food science and technology society and staphylococcus aureus (Tytao, Gaoying, Sunkang, etc.. the curcumin photodynamic therapy researches on methicillin-resistant staphylococcus aureus and biofilms thereof [ J ]. the journal of China Experimental surgery, 2019,36(6): 1092-. In addition, curcumin widely used in a PDI system is insoluble in water and common organic solvents, has poor physicochemical stability, is very easy to oxidize, is easy to decompose under visible light, and seriously influences the activity of PDI, and the defects limit the practical application of curcumin in the food antibacterial packaging industry.
In order to obtain a PLA packaging material with antibacterial activity, a solvent casting method is adopted in research, and lemon essential oil and nano TiO are added into a PLA solution2And nano Ag particles, the PLA-based nano composite membrane prepared can effectively inhibit the growth and the propagation of microorganisms on the surface of the cooled pork, and the inhibition rates of Escherichia coli and staphylococcus aureus respectively reach 99.20 +/-3.56% (-2Log CFU) and 99.92 +/-3.14% (-3Log CFU) (Zenglilkwan, Mengginging, Xueshan and the like]Packaging engineering, 2018,39(21): 96-101.). In addition, the PLA/chitosan composite membrane prepared by the electrostatic spinning technology has good antibacterial effect on escherichia coli and staphylococcus aureus, and especially when the mass ratio of the chitosan to the PLA is more than 1:10, the antibacterial rate of the composite membrane on two bacteria can reach more than 90% (-1Log CFU) (Jiang rock, Qin Jing Wen, Wang hongbo chitosan/PLA composite nanofiber preparation and antibacterial performance research [ J]Material report, 2012,26(18):74-76+ 80.).
Besides blending PLA and antibacterial materials, researchers have attempted to modify the surface of PLA film by hydrophilic modification, such as compounding, chemical grafting, etc., and covalently bond the modified surface active groups with antibacterial agents to obtain the antibacterial activity of the packaging film. For example, Mazuwei et al modified PLA by carbodiimide condensation chemistry to generate carboxyl groups on the surface, covalently grafted type I collagen onto the PLA membrane surface via the introduced carboxyl groups, and obtained a stable collagen coating (Mazuwei, highly abundant, Gong Yihong, etc.. chemical grafting and coating of collagen onto poly-L-lactic acid (PLLA) and its effect of promoting chondrocyte growth [ J ]. advanced college Chemicals, 2004(04): 749-752.).
The process of modifying PLA by a chemical method is complex, and a large amount of organic reagents are used in the whole reaction process, so that the molecular weight and the mechanical strength of the material are greatly reduced, the environment is greatly harmed, and the biocompatibility of the PLA material is badly influenced. More importantly, the antibacterial efficacy of the composite membrane prepared by the methods is generally not ideal enough, only 1-2Log CFU harmful bacteria can be reduced, and the urgent demand of consumers on efficient antibacterial packaging materials cannot be met.
Disclosure of Invention
Aiming at the defect of insufficient bacteriostatic ability of the PLA packaging material in the prior art, the invention mainly aims to provide a preparation method of a photocatalytic PLA antibacterial film, namely, a green antibacterial food packaging material for efficiently killing pathogenic bacteria and putrefying bacteria in food based on the combination of a plasma treatment technology and a photodynamic sterilization technology.
The second purpose of the invention is to provide the photocatalytic PLA antibacterial film.
The third purpose of the invention is to provide the application of the photocatalytic PLA antibacterial film.
In order to achieve the above primary object, the solution of the present invention is:
a preparation method of a photocatalytic PLA antibacterial film comprises the following steps:
(1) preparing a PLA film by adopting an extrusion-casting method;
(2) carrying out low-temperature plasma treatment on the PLA film to obtain a treated PLA film;
(3) dissolving 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide in a 2-morpholine ethanesulfonic acid buffer solution to obtain a conjugated solution, and soaking the treated PLA film in the conjugated solution for activation to obtain an activated PLA film;
(4) dissolving a photosensitizer in deionized water to obtain a photosensitizer solution, immersing the activated PLA film in the photosensitizer solution for covalent coupling, and then washing and drying to obtain the photocatalytic PLA antibacterial film.
As a preferred embodiment of the present invention, in step (1), the temperatures of the sections of the extrusion device in the extrusion casting method are 130-.
As a preferred embodiment of the present invention, in the step (2), the processing parameters of the low-temperature plasma are: the speed is 8cm/s, the working current is 5-7A, and the treatment time is 10-30 s.
The low-temperature plasma treatment technology can quickly and efficiently initiate physical or chemical changes which cannot be or are difficult to realize in conventional reactions, endow the surface of the membrane material with various excellent properties, does not change the properties of a base material, and is an important method for expanding the application range of the polymer membrane material. The advantages of low-temperature plasma modification are embodied in particular as follows: (1) endowing the surface of the modified material with various excellent performances; (2) the material surface modification layer has extremely thin thickness and basically unchanged integral property; (3) can endow some materials with properties which are not possessed by the materials, such as antibacterial property and the like. After low temperature plasma treatment, the surface of the PLA film is endowed with a large number of active carboxyl groups, and the carboxyl groups provide a large number of active sites for covalent bonding of the PLA film and the bacteriostatic agent.
As a preferred embodiment of the present invention, in step (3), the oscillating speed during the activation process is 180-200rpm, the temperature is 30-40 ℃, and the time is 2-4 h.
As a preferred embodiment of the present invention, in the step (4), the photosensitizer is 5-aminolevulinic acid (5-ALA); the oscillation speed in the covalent coupling process is 180-.
Among them, 5-ALA is a precursor substance of endogenous porphyrin of bacteria, and most bacteria utilize ALA in the heme biosynthetic pathway to produce porphyrin. Compared with curcumin, 5-ALA has stable physicochemical property, is not easy to be oxidized, is safe and nontoxic, has stronger PDI activity, and is allowed to be used in the field of food industry. Under the excitation of blue light (wavelength 450-480nm), porphyrin absorbs light energy and generates a photodynamic chemical reaction to generate ROS, thereby generating toxic effect on bacterial cells. Light Emitting Diodes (LEDs) have been widely used in daily life due to their excellent characteristics of stable performance, safety, low energy consumption, low cost, etc., and are ideal light sources for exciting photosensitizers to undergo photodynamic reactions.
As a preferred embodiment of the present invention, in the step (4), the drying temperature is 25-35 ℃ and the drying time is 12-24 h.
In order to achieve the second objective, the solution of the invention is:
a photocatalytic PLA antibacterial film is obtained by the preparation method.
In order to achieve the third object, the solution of the invention is:
an application of the photocatalytic PLA antibacterial film as a food packaging film.
As a preferred embodiment of the invention, bacterial suspensions of Listeria monocytogenes, Vibrio parahaemolyticus and Shewanella putrefies are respectively inoculated on a photocatalytic PLA antibacterial membrane, incubated in dark for 60min and placed under a blue LED lamp for irradiation; and then shearing the photocatalytic PLA antibacterial film, homogenizing, diluting with sterile normal saline, coating the diluent, culturing for 24-48h, and calculating the number of colonies.
As a preferred embodiment of the invention, the wavelength range of the blue LED lamp is 455-460 nm; the irradiation time is 10-30 min.
As a preferred embodiment of the present invention, the light energy density is 10.0-60.0mW/cm2。
Due to the adoption of the scheme, the invention has the beneficial effects that:
the method modifies the PLA film by using a low-temperature plasma technology to generate active carboxyl groups on the surface of the PLA film, and covalently couples photosensitizer 5-ALA to the surface of the PLA film through carboxyl to prepare a green packaging material with PDI antibacterial activity; modifying the polluted bacteria liquid on the PLA film by illumination by taking a blue LED as a light source, and finding that gram-positive pathogenic bacteria, gram-negative pathogenic bacteria and putrefying bacteria are greatly killed; the salmon packaged by the photocatalytic PLA antibacterial film is illuminated by a blue LED for 30min (100.8J/cm)2) Then, 4Log CFU/mL (99.99%) of food-borne pathogenic bacteria and spoilage bacteria on the surface of the food are killed, dripping water loss, pH value and change of Malondialdehyde (MDA) values of the food during storage are obviously inhibited, and shelf life of the food is obviously prolonged; the PLA antibacterial film based on the photodynamic mediation has high sterilization efficiency, can be efficiently sterilized in a short processing time, is green, safe and degradable, is simple and convenient to use and operate, and can be used by directly placing a sample packaged by the modified PLA film on an operation table of a PDI system.
Drawings
Fig. 1 is a view of a salmon photodynamic sterilization device packaged by a photocatalytic PLA antibacterial film.
Fig. 2 is a graph of the scavenging efficiency of l. monocytoenes from films treated in examples of the invention and comparative examples.
Fig. 3 is a graph showing the removal efficiency of v.
Fig. 4 is a graph of the removal efficiency of s.putrefeaciens from the treated films of the examples of the present invention and comparative examples.
FIG. 5 is a graph showing the effect of PLA30/ALA membrane on the removal of biofilm in example 3 of the present invention and in comparative example 1.
Fig. 6 is a graph showing the removal efficiency of the treated film on the surface of salmon samples according to the examples of the present invention and the comparative examples.
Fig. 7 is a graph showing the removing efficiency of the treated film on the surface v. parahaemolyticus of the salmon sample in the example of the present invention and the comparative example.
Fig. 8 is a graph showing the removal efficiency of the treated films on the surface s.putrefeaciens of the salmon sample in the example of the present invention and the comparative example.
FIG. 9 is a graph showing the change in the number of colonies of salmon packaged with PLA30/ALA film and PE film in example 3 of the present invention within 5 days of storage.
FIG. 10 is a graph showing the change in drip loss of salmon packaged with PLA30/ALA film and PE film in example 3 of the present invention during 5 days of storage.
FIG. 11 is a graph showing the change of pH value of salmon packaged with PLA30/ALA film and PE film in example 3 of the present invention within 5 days of storage.
FIG. 12 is a graph showing the change in MDA value within 5 days of storage of salmon packaged with PLA30/ALA film and PE film in example 3 of the present invention.
Reference numerals: 1-LED lamp, 2-culture dish, 3-elevating platform and 4-LED photography lamp box.
Detailed Description
The invention provides a photocatalytic PLA (polylactic acid) antibacterial film as well as a preparation method and application thereof. On the basis of fully integrating the advantages of the photodynamic technology and the low-temperature plasma technology, the invention develops a green food packaging material for efficiently killing common pathogenic bacteria and putrefying bacteria in food by taking PLA as a film matrix, 5-ALA as a photosensitizer and blue LED as a light source, and further uses the novel packaging films for packaging the food such as salmon and the like, thereby greatly prolonging the shelf life of the food.
1. Materials:
1.1 bacterial species
Monocytogenes (ATCC19115, ATCC13932, ATCC7644, 4bLM) were isolated from raw pork in this laboratory. Parahaemolyticus (ATCC17802) was isolated from japanese "Shirasu" diet; parahaemolyticus (VPC17, VPC36, VPC47) was isolated from stool specimens of acute diarrhea in this laboratory. Putrefacesins (SP05, SP08) were isolated from samples of rotten fish heads in this laboratory.
1.2 media and reagents
Tryptic Soy Broth (TSB), brain Heart infusion agar (BHI), PALCAM agar medium, tryptone Soy agar medium (TSA), and ferric Sal medium were purchased from Beijing Luqiao technology, Inc.
PLA granules were purchased from jishun, zhejiang; ALA is purchased from shanghai ao probiotic science and technology ltd; 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride was purchased from Michelle chemical technology, Inc., Shanghai; n-hydroxysuccinimide was purchased from Michelle chemical technology, Inc., Shanghai; 2-Morpholinoethanesulfonic acid buffer was purchased from Michelle chemical technology, Inc., Shanghai; all chemicals were analytically pure.
1.3 instruments
An LSJ-20 plastic single screw extruder is available from Jinwo Seiko Co., Ltd, Zhejiang; the MB-200 plastic electronic processor is purchased from Shanghai, south China electronic device factory; 9272 constant temperature incubator isolated from water is purchased from Shanghai-Hengshi Co., Ltd; TGL16M desk-top high-speed refrigerated centrifuge was purchased from shanghai late-formed medical devices, ltd; the LED combined lamp box is purchased from Shenzhen Shang Tian photoelectricity Limited company.
2. The preparation method comprises the following steps:
the preparation method of the photocatalytic PLA antibacterial film comprises the following steps:
(1) preparation of PLA films
Preparing a PLA film by adopting an extrusion casting method: the temperatures of the 1 section, the 2 section, the 3 section, the 4 section, the 5 section, the 6 section and the 7 section in the area of the plastic extrusion device can be respectively set to be 130-;
wherein the temperatures of the 1-zone, 2-zone, 3-zone, 4-zone, 5-zone, 6-zone and 7-zone in the region of the plastic extrusion device are preferably 140 ℃, 160 ℃, 170 ℃, 175 ℃ and 170 ℃, respectively, the single screw speed is preferably 50rpm, and the average thickness of the PLA film is preferably 40 μm;
(2) low temperature plasma treatment of PLA films
Carrying out low-temperature plasma treatment on the prepared PLA film by adopting a plastic electronic processor to obtain a treated PLA film; the parameters of the plasma treatment were: the speed is 8cm/s, the working current is 5-7A, and the processing time is 10-30 s;
such as PLA10 film, PLA20 film and PLA30 film, are respectively prepared by low-temperature plasma treatment for 10s, 20s and 30 s; the parameters of the plasma treatment were: the speed is 8cm/s, and the working current is preferably 6A;
(3) covalently coupled photosensitizers
The covalent coupling of the photosensitizer is divided into three steps:
(3.1) preparing a conjugate solution: dissolving 0.1 mol/L1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and 0.02mol/L N-hydroxysuccinimide in 0.1 mol/L2-morpholine ethanesulfonic acid buffer solution, adjusting the pH value of the conjugate solution to 5.4, and soaking the PLA membrane treated in the step (2) in the conjugate solution for activation to obtain an activated PLA membrane; the oscillation speed in the activation process can be 180-200rpm, the temperature can be 30-40 ℃, and the time can be 2-4;
such as PLA10 film, PLA20 film and PLA30 film, are soaked in a conjugate solution for activation under the following conditions: the rotating speed is preferably 200rpm, the temperature is preferably 40 ℃, and the time is preferably 2 h;
(3.2), covalently coupled photosensitizer: dissolving a photosensitizer 5-ALA in deionized water to obtain a photosensitizer solution, wherein the concentration of the photosensitizer solution is 4 mg/mL; then immersing the activated PLA film into a photosensitizer solution for covalent coupling;
for example, the activated PLA10 film, PLA20 film and PLA30 film were immersed in 4mg/mL 5-ALA solution respectively, and the covalent coupling (i.e., grafting) conditions were as follows: the oscillation speed can be 180-200rpm, the temperature can be 30-40 ℃, and the time can be 4-6 h; wherein the oscillation speed is preferably 200rpm, the temperature is preferably 40 ℃, and the time is preferably 4 h;
(3.3), washing and drying: washing the PLA film coupled with the photosensitizer with deionized water for three times to remove the unbound photosensitizer, and then putting the prepared photocatalytic PLA antibacterial film into a forced air oven for drying.
Such as PLA10/ALA films, PLA20/ALA films and PLA30/ALA films, were rinsed three times with deionized water to remove unbound photosensitizer, and the prepared films were then placed in a forced air oven to dry, under the conditions: the drying temperature can be 25-35 ℃, and the drying time can be 12-24 h; wherein, the drying temperature is preferably 25 ℃, and the drying time is preferably 12 h.
3. Preparation of bacterial liquid
The photocatalytic PLA antibacterial film can be used as a food packaging film, and is particularly used for packaging salmon.
Gram-positive l.monocytogenes, gram-negative v.parahaemolyticus, and s.putrefaces represent food-borne pathogenic bacteria and spoilage bacteria, respectively. All strains were maintained at-80 ℃ in 25% glycerol, L.monocytogenes and V.parahaemolyticus were activated in BHI and TSB (3% NaCl, w/v) at 37 ℃ for 12h, and S.putrefaces in TSB for 12h, respectively. The obtained initial stable cell culture fluid was centrifuged for 5min (4 ℃, 4000rpm), and the cell was resuspended in 0.85% sterile physiological saline solution, and the cell concentration was adjusted to-8 Log CFU/mL.
Wherein the experimental strains are L.monocytogenes, V.parahaemolyticus and S.putrefeaciens with-8 log CFU/mL bacterial concentration, and the inoculated bacterial liquid is 100 mu L.
4. Assembly of a photodynamic device
Blue LED (455-220W) was purchased from Shenzhen (Guangtian photoelectricity, Inc., China). The LED system is surrounded by an LED photographing lamp box to prevent external light from entering. The distance between the LED light source and the PLA film was adjusted to 5.0 cm. The illumination energy of the blue LED may be 10.0-60.0mW/cm2Preferably 56.0mW/cm2Measured using an energy meter console (PM100D) equipped with a photodiode power sensor (S130C). Specifically, as shown in fig. 1, an LED lamp 1 is mounted at the top end of an LED photography lamp box 4, a lifting platform 3 is disposed at the center of the LED photography lamp box 4, a culture dish 2 is disposed on the upper surface of the lifting platform 3, the culture dish 2 faces the LED lamp 1, and a photocatalytic PLA antibacterial film inoculated with bacteria liquid is loaded in the culture dish 2.
The dose obtained for each sample was calculated using the following formula:
E＝Pt
where E is the dose (energy density) in J/cm2P is irradiance (power density) in units of W/cm2And t is time in units of s.
5. Photodynamic method for treating pathogenic bacteria and putrefying bacteria under pure culture condition
The photocatalytic PLA antibacterial film is cut into 2 multiplied by 2cm2The square membrane of (1) was inoculated with 100. mu.L of each of L.monocytogenes, V.parahaemolyticus and S.putrefeacens bacterial suspensions, and incubated in the dark for 60 min. The membrane dripped with the bacteria liquid is placed in a photodynamic lamp box and is irradiated for 10-30min by a blue LED lamp with the wavelength of 455-460 nm. Then, the membrane is cut into pieces and homogenized for 5min, diluted by 0.85% sterile physiological saline, the appropriate dilution is selected, 100 mu L of the dilution is taken for coating, the plate is cultured for 24-48h at 37 ℃, and the colony number is calculated. Each treatment was done in 3 replicates and each dilution was repeated 3 times.
In conclusion, the invention utilizes the low-temperature plasma technology to modify the surface of the PLA material, so that a large number of active carboxyl groups are generated on the surface of the PLA material, on the basis, the carboxyl groups on the surface of the PLA film and the photosensitizer 5-ALA are innovatively subjected to covalent reaction to prepare a novel packaging film material, and the novel packaging film material is combined with the light irradiation of a blue LED (455-460nm) to prepare the PLA food packaging film (namely, the photocatalysis PLA antibacterial film) with photodynamic bactericidal activity. The invention organically integrates and innovates the photodynamic technology, the low-temperature plasma technology and the food packaging material, develops the packaging film material with the high-efficiency sterilization function, is a breakthrough of the food packaging industry, and provides new theoretical ideas and innovative practices for developing functional food packaging film materials in the future.
The present invention will be further described with reference to the following examples.
Example 1:
the preparation method of the photocatalytic PLA10/ALA antibacterial film comprises the following steps:
(1) preparation of PLA films
Preparing a PLA film by adopting an extrusion casting method: temperatures of zone 1, zone 2, zone 3, zone 4, zone 5, zone 6 and zone 7 in the region of the plastic extrusion device were set to 140 ℃, 160 ℃, 170 ℃, 175 ℃ and 170 ℃, respectively, a single screw speed was 50rpm, and an average thickness of the PLA film was 40 μm.
(2) Low temperature plasma treatment of PLA films
Carrying out low-temperature plasma treatment on the prepared PLA film by adopting a plastic electronic processor; the plasma processing parameters were: the speed was 8cm/s, the working current was 6A, and the treatment time was 10s, to obtain a PLA10 film.
(3) Covalently coupled photosensitizers
The covalent coupling of the photosensitizer is divided into three steps:
(3.1) preparing a conjugate solution: dissolving 0.1 mol/L1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and 0.02mol/L N-hydroxysuccinimide in 0.1 mol/L2-morpholine ethanesulfonic acid buffer solution, adjusting the pH value of the conjugate solution to 5.4, soaking the PLA10 film obtained in the step (2) in the conjugate solution for activation, wherein the oscillation rotation speed of the activation is 200rpm, the temperature is 40 ℃, and the time is 2 hours, so as to obtain an activated PLA10 film;
(3.2), covalently coupled photosensitizer: immersing the activated PLA10 film into 4mg/mL 5-ALA solution for covalent coupling to obtain a PLA10/ALA film; the oscillation speed of covalent coupling is 200rpm, the temperature is 40 ℃, and the time is 4 h;
(3.3), washing and drying: the PLA10/ALA film was rinsed three times with deionized water to remove unbound 5-ALA, and then the prepared photocatalytic PLA10/ALA antibacterial film was dried in a forced air oven at 25 deg.C for 12 h.
Example 2:
the preparation method of the photocatalytic PLA20/ALA antibacterial film comprises the following steps:
(1) preparation of PLA films
Preparing a PLA film by adopting an extrusion casting method: temperatures of zone 1, zone 2, zone 3, zone 4, zone 5, zone 6 and zone 7 in the region of the plastic extrusion device were set to 140 ℃, 160 ℃, 170 ℃, 175 ℃ and 170 ℃, respectively, a single screw speed was 50rpm, and an average thickness of the PLA film was 45 μm.
(2) Low temperature plasma treatment of PLA films
Performing low-temperature plasma treatment on the prepared PLA film by adopting a plastic electronic processor, wherein the plasma treatment parameters are as follows: the speed was 8cm/s, the working current was 6A, and the treatment time was 20s, to obtain a PLA20 film.
(3) Covalently coupled photosensitizers
The covalent coupling of the photosensitizer is divided into three steps:
(3.1) preparing a conjugate solution: dissolving 0.1 mol/L1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and 0.02mol/L N-hydroxysuccinimide in 0.1 mol/L2-morpholine ethanesulfonic acid buffer solution, adjusting the pH value of the conjugate solution to 5.4, soaking the PLA20 film obtained in the step (2) in the conjugate solution for activation, wherein the oscillation rotation speed of the activation is 200rpm, the temperature is 40 ℃, and the time is 2 hours, so as to obtain an activated PLA20 film;
(3.2), covalently coupled photosensitizer: immersing the activated PLA20 film into 4mg/mL 5-ALA solution for covalent coupling to obtain a PLA20/ALA film; the oscillation speed of covalent coupling is 200rpm, the temperature is 40 ℃, and the time is 4 h;
(3.3), washing and drying: the PLA20/ALA film was rinsed three times with deionized water to remove unbound 5-ALA, and then the prepared photocatalytic PLA20/ALA antibacterial film was dried in a forced air oven at 25 deg.C for 12 h.
Example 3:
the preparation method of the photocatalytic PLA30/ALA antibacterial film comprises the following steps:
(1) preparation of PLA films
Preparing a PLA film by adopting an extrusion casting method: temperatures of zone 1, zone 2, zone 3, zone 4, zone 5, zone 6 and zone 7 in the region of the plastic extrusion device were set to 140 ℃, 160 ℃, 170 ℃, 175 ℃ and 170 ℃, respectively, a single screw speed was 50rpm, and an average thickness of the PLA film was 35 μm.
(2) Low temperature plasma treatment of PLA films
Carrying out low-temperature plasma treatment on the prepared PLA film by adopting a plastic electronic processor; the plasma processing parameters were: the speed was 8cm/s, the working current was 6A, and the treatment time was 30s, to obtain a PLA30 film.
(3) Covalently coupled photosensitizers
The covalent coupling of the photosensitizer is divided into three steps:
(3.1) preparing a conjugate solution: dissolving 0.1 mol/L1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and 0.02mol/L N-hydroxysuccinimide in 0.1 mol/L2-morpholine ethanesulfonic acid buffer solution, adjusting the pH value of the conjugate solution to 5.4, soaking the PLA30 film obtained in the step (2) in the conjugate solution for activation, wherein the oscillation rotation speed of the activation is 200rpm, the temperature is 40 ℃, and the time is 2 hours, so as to obtain an activated PLA30 film;
(3.2), covalently coupled photosensitizer: immersing the activated PLA30 film into 4mg/mL 5-ALA solution for covalent coupling to obtain a PLA30/ALA film; the oscillation speed of covalent coupling is 200rpm, the temperature is 40 ℃, and the time is 4 h;
(3.3), washing and drying: the PLA30/ALA film was rinsed three times with deionized water to remove unbound 5-ALA, and then the prepared photocatalytic PLA30/ALA antibacterial film was dried in a forced air oven at 25 deg.C for 12 h.
Comparative example 1:
the preparation method of the PLA film of this comparative example included the following steps:
preparing a PLA film by adopting an extrusion casting method: temperatures of zone 1, zone 2, zone 3, zone 4, zone 5, zone 6 and zone 7 in the region of the plastic extrusion device were set to 140 ℃, 160 ℃, 170 ℃, 175 ℃ and 170 ℃, respectively, a single screw speed was 50rpm, and an average thickness of the PLA film was 40 μm.
Comparative example 2:
the preparation method of the PLA/ALA film of this comparative example comprises the steps of:
(1) preparation of PLA films
Preparing a PLA film by adopting an extrusion casting method: temperatures of zone 1, zone 2, zone 3, zone 4, zone 5, zone 6 and zone 7 in the region of the plastic extrusion device were set to 140 ℃, 160 ℃, 170 ℃, 175 ℃ and 170 ℃, respectively, a single screw speed was 50rpm, and an average thickness of the PLA film was 45 μm.
(2) Covalently coupled photosensitizers
The covalent coupling of the photosensitizer is divided into three steps:
(2.1) preparing a conjugate solution: dissolving 0.1 mol/L1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and 0.02mol/L N-hydroxysuccinimide in 0.1 mol/L2-morpholine ethanesulfonic acid buffer solution, adjusting the pH value of the conjugated solution to 5.4, soaking the PLA film in the conjugated solution for activation, wherein the oscillation rotation speed of the activation is 200rpm, the temperature is 40 ℃, and the time is 2 hours, thus obtaining the activated PLA film;
(2.2), covalently coupled photosensitizer: immersing the activated PLA membrane into 4mg/mL 5-ALA solution for covalent coupling to obtain a PLA/ALA membrane; the oscillation speed of covalent coupling is 200rpm, the temperature is 40 ℃, and the time is 4 h;
(2.3), washing and drying: the PLA/ALA membrane was rinsed three times with deionized water to remove unbound 5-ALA, and then the prepared PLA/ALA membrane was placed in a forced air oven for drying at 25 deg.C for 12 h.
The products of the above examples and comparative examples were subjected to the following experiments.
< experiment 1>
Photodynamic method for treating biofilms
Respectively culturing L.monocytogenes, V.parahaemolyticus and S.putrefeaciens to logarithmic phase, and adjusting the thallus concentration to-8 Log CFU/mL. The PLA film of comparative example 1 and the PLA30/ALA film of example 3 were cut into 1X 1cm pieces2The square membrane of (4) was placed on the bottom of a 24-well plate, and 990. mu.L of BHI, TSB (3% NaCl, w/v) and TSB culture solution and 10. mu.L of bacterial suspension (-8Log CFU/mL) were added to the 24-well plate, respectively. The well plate was sealed with a sealing bag and placed in an incubator to culture the biofilm. Wherein L.monocytogenes is cultured at 37 ℃ for 48 hours, V.parahaemolyticus is cultured at 37 ℃ for 24 hours, and S.putrefaces is cultured at 25 ℃ for 24 hours.
And after the biofilm grows to be mature, treating PDI for 20-60 min. Excess culture medium was aspirated and washed 3 times with PBS buffer to remove planktonic bacteria. After adding 1mL of 4% glutaraldehyde fixing solution, freezing and fixing at 4 ℃ for 1 hour, the fixing solution was removed and washed 3 times with PBS buffer. Adding 200. mu.L SYBR Green I, shading and staining for 30min, washing with PBS, air drying, and observing the structure of the biofilm by Zeiss LSM710-NLO type CLSM.
< experiment 2>
Photodynamic method for treating salmon surface pathogenic bacteria and putrefying bacteria
Cutting Salmon into 2 × 2cm pieces2Square (3.0 ± 0.2g), uv-sterilized for 30min to remove microorganisms from the sample itself. After inoculating 100. mu.L of each of L.monocytogenes, V.parahaematolyticus and S.putrefaces bacterial suspensions to the surface of salmon, the PLA membrane of comparative example 1, the PLA/ALA membrane of comparative example 2, the PLA10/ALA membrane of example 1, the PLA20/ALA membrane of example 2 and the PLA30/ALA membrane of example 3 (5X 5 cm) were used respectively2) And (5) sealing and packaging the salmon sample. Incubating for 60min under dark condition, performing photodynamic treatment for 30min, cutting off the membrane, taking out the salmon sample, diluting with 0.85% sterile normal saline for 5 times, homogenizing for 15min, selecting appropriate dilution, coating 100 μ L of dilution, culturing the plate at 37 deg.C for 36h, and calculating colony count. Each treatment was done in 3 replicates and each dilution was repeated 3 times.
< experiment 3>
PLA film package storage salmon sample
Cutting Salmon into 2 × 2cm pieces2Square (3.0 ± 0.2g), uv-treated for 30min to kill the microbes of the sample itself. Using Polyethylene (PE) film and PLA30/ALA film of example 3 (5X 5 cm), respectively2) And (5) sealing and packaging the salmon. After incubation for 60min under dark condition, salmon is placed in a PDI lamp box at 25 ℃ for continuous illumination storage for 5 days, and the colony count, the water drop loss and the pH value of a sample are detected at the same time every day according to the change of MDA value.
1. Data analysis
Experimental data were processed and analyzed using OriginPro 9.1, SPSS17.0 software package (SPSS inc., Chicago, USA). The significance between the data was compared using the least significant difference method (LSD) (p ═ 0.05).
2. Results
2.1 PLA films prepared by different plasma treatment times and the bacteriostatic effect of the photodynamic treatment time on pathogenic bacteria and putrefying bacteria
The initial inoculum size of the three bacteria was-8 Log CFU/mL. Plasma treatment time produced PLA films covalently attached to ALA are shown in FIGS. 2-4Inactivation of L.monocytoenes, V.parahaemolyticus and S.putrefeacens by coupled PLA/ALA membranes after blue light irradiation. Three groups of negative controls were: PLA films had a light group, PLA/ALA films had a light group, and PLA30/ALA films had a no light group. The numbers of L.monocytogenes cells in the three negative control groups were 8.69, 8.70, and 8.58Log CFU/mL, respectively (FIG. 2). However, the bacterial suspension was dropped onto the PLA10/ALA membrane of example 1, the PLA20/ALA membrane of example 2 and the PLA30/ALA membrane of example 3 in combination at 33.6J/cm2、67.2J/cm2And 100.8J/cm2After the blue light irradiation (10min, 20min and 30min) treatment, the membrane shows obvious killing effect on gram-positive pathogenic bacteria. The L.monocytogenes cell number decreased from 6.95 to 4.91Log CFU/mL (P) when the plasma treatment time increased from 10min to 30min<0.05，100.8J/cm2). To further demonstrate the broad spectrum antibacterial properties of the modified PLA films, v. The removal effect is shown in fig. 3 and 4, and the removal efficiency of the composite membrane on v. The number of cells in the PLA membrane illuminated group of Parahaemolyticus was 8.76Log CFU/mL, and the number of cells in the PLA/ALA membrane illuminated group and the PLA30/ALA membrane non-illuminated group were 8.75Log CFU/mL and 8.56Log CFU/mL, respectively. The number of v. After 30min of blue light irradiation of PLA30/ALA membrane, the number of V.parahaemolyticus cells finally decreased to 3.98Log CFU/mL. Similar to v.parahaemolyticus, PLA30/ALA membrane showed great antibacterial efficiency against s.putrefeaciens after 30min blue light irradiation (reduced from 8.31Log CFU/mL to 4.19Log CFU/mL). The results show that the higher the ALA content covalently coupled to the PLA film surface, the better the bactericidal effect as the plasma treatment time was extended. In addition, the irradiation dose is another factor that affects the photodynamic sterilization effect. The photodynamic sterilization efficiency of the PLA film is in direct proportion to the plasma treatment time and the irradiation dose, and the PLA film which is modified by the plasma and covalently coupled with the ALA has stronger killing effect on pathogenic bacteria and putrefying bacteria ((>99.99％)。
2.2 Effect of PLA30/ALA Membrane on biofilm removal
As is clear from the above, the PLA30/ALA film of example 3 has the most excellent planktonic bacteria-inhibiting ability, and therefore, PLA30/ALA film was selected as an experimental group to investigate the biofilm-removing effects of the modified film on three kinds of bacteria, and the PLA film of comparative example 1 was selected as a control. The removal effect of PLA30/ALA membranes on biofilms formed by l.monocytogens, v.parahaemolyticus and s.putrefeaciens was observed by CLSM, and PDI treatment was performed for 20min, 40min and 60min after the biofilms were grown to maturity on the PLA membrane and PLA30/ALA membrane, respectively. As can be seen from FIG. 5, the biomass of the bacterial envelope formed on the surface of the PLA30/ALA film gradually decreased with the increase of the light treatment time, while the PLA film can still form a large amount of biofilm after being irradiated for 60 min. Thus, it is clear that the PLA30/ALA membrane has excellent ability to inhibit and remove biofilm formation by bacteria under PDI treatment conditions.
2.3 PLA/ALA film prepared by different plasma treatment time and bacteriostasis effect of photodynamic treatment time on salmon surface pathogenic bacteria and putrefying bacteria
Fig. 6 to 8 are the change of colony numbers of l.monocytoenes, v.parahaemolyticus and s.putrefeacens after packaging salmon samples with different PLA films and irradiation of blue light. The optimal irradiation dose for the photodynamic treatment of the three bacteria is 100.8J/cm according to the bacteriostasis effect of different plasma time2Therefore, in this experiment, salmon samples were packaged with the PLA film of comparative example 1, the PLA/ALA film of comparative example 2, the PLA10/ALA film of example 1, the PLA20/ALA film of example 2 and the PLA30/ALA film of example 3, respectively, and then packaged at 100.8J/cm2The samples were irradiated. After photodynamic treatment, the colony number of the control group is-7 Log CFU/g. The amount of L.monocytoenes was reduced after packaging the samples with PLA10/ALA film compared to the control group>90 percent. The amount of L.monocytoenes in the sample packaged with PLA30/ALA film was only 4.45Log CFU/g (about 99.9% reduction). As can be seen from fig. 7 and 8, the PLA film also showed a similar antibacterial tendency to l. Blue light irradiation for 30min (100.8J/cm)2) After that, v.parahaemolyticus and s.putrefeaci on the control film-packaged sampleens averaged 7.71Log CFU/g and 7.22Log CFU/g, respectively. The colony number of the surface of the salmon packaged by PLA10/ALA membrane, PLA20/ALA membrane and PLA30/ALA membrane is obviously reduced after being treated by PDI, V.parahaemolyticus cells are reduced from 6.05Log CFU/g to 3.82Log CFU/g, and S.putrefeasens cells are reduced from 6.29Log CFU/g to 4.09Log CFU/g. Therefore, the modified PLA film can effectively kill pathogenic bacteria and putrefying bacteria on the surface of the salmon>99.9%), exhibits excellent antibacterial properties.
2.4 microbiological analysis of Salmon packaged with PLA30/ALA film during storage
As shown by the bacteriostatic effect of different plasma time and the clearing effect of PLA30/ALA membrane on the biological envelope, the optimal condition for the photodynamic treatment of the salmon sample is 100.8J/cm of irradiation after the PLA30/ALA membrane is packaged2. In the storage experiment, the sample was wrapped with a conventional polyethylene wrap (PE) film purchased on the market as a control group. FIG. 9 is a change in the number of colonies after the salmon sample packaged with PE film and PLA30/ALA film was stored at 25 ℃ for 5 days. Neither the PE film nor PLA30/ALA film packaged salmon samples had microbial growth after photodynamic treatment on day 0. After 1 day of storage, the microorganisms on the surfaces of the salmon in the experimental group and the control group began to grow and propagate in a large amount, but the colony count of the PLA30/ALA membrane group was 4.02Log CFU/g, which is 99.9% less than that of the PE membrane (7.06Log CFU/g) in the control group, and thus it was found that the use of the PLA30/ALA membrane for packaging the salmon sample could effectively inhibit the growth of the microorganisms on the surfaces of the salmon. The colony count on the surface of the sample further increased with the increase of the storage time, and the total number of bacteria on the salmon packaged by the PLA30/ALA film is always less than that of the control group during the storage period. Notably, on day 3 of storage, the colony count on the surface of PLA30/ALA membrane-packaged salmon began to decrease, while the colony count of the control group began to decrease on day 4.
2.5 drip loss, pH and MDA changes during storage of Salmon
Fig. 10 is a plot of drip loss variation for salmon samples during storage. The drip loss of salmon samples continues to increase throughout storage due to the loss of water holding capacity as the sample's muscle fiber structure is destroyed during storage. The drip loss of the PLA30/ALA film and PE film packaged samples was 6.67% and 9.17% respectively on day 1 of storage, and reached 21.0% and 32.84% respectively after 5 days of storage. The PLA30/ALA film well maintains the water holding capacity of the muscle fiber of the salmon sample within 5 days of storage time, and delays the drip loss of the salmon.
Salmon initial pH was about 6.06 and the pH of the samples continued to rise during 5 days of storage (fig. 11). The pH of the samples packaged with PLA30/ALA films were below 6.5, which is 0.49 lower than the control. This shows that packaging salmon with PLA30/ALA film is effective in inhibiting the pH change of salmon during storage. This is due to the PLA30/ALA film inhibiting the proliferation of microorganisms during storage, thereby delaying the pH rise due to microbial activity.
Oxygen radicals act on unsaturated fatty acids of lipids to produce lipid peroxides which decompose into a complex series of compounds such as MDA, keto, hydroxyl, etc., and thus, measuring the level of MDA in a sample can reflect the degree of lipid oxidation during storage of salmon. Figure 12 is the MDA values for each set of samples during storage. On day 1, the MDA values for the samples packaged with PLA30/ALA film and PE film were 3.32n mol/mg and 3.35n mol/mg, respectively, with no significant difference. From day 2, a clear difference began to appear between the experimental group and the control group, with the content of PLA30/ALA membrane group being 4.20n mol/mg, while the content of MDA of PE membrane group reached 5.16n mol/mg. By the 5 th day of storage, the MDA values of PLA30/ALA film and PE film-packaged salmon were 5.75n mol/mg and 8.19n mol/mg, respectively. Therefore, the use of PLA30/ALA film for packaging salmon samples can inhibit lipid peroxidation to a certain extent and guarantee the quality of salmon during storage.
The analysis proves that the PLA film which is subjected to low-temperature plasma treatment and covalently grafted with the photosensitizer 5-ALA can effectively kill food-borne pathogenic bacteria and putrefying bacteria on the surfaces of foods under pure culture conditions under the irradiation of 455-460nm blue LED lamps, has excellent biological envelope resistance, and is a novel photodynamic PLA bacteriostatic packaging film which can effectively guarantee the safety of foods. The protection scope of the invention includes ALA, but is not limited to that ALA is covalently coupled with a packaging film material modified by a low-temperature plasma technology, so as to prepare a food packaging film with photodynamic antibacterial effect.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. It will be readily apparent to those skilled in the art that various modifications to these embodiments and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments. Those skilled in the art should appreciate that many modifications and variations are possible in light of the above teaching without departing from the scope of the invention.

Claims (10)

1. A preparation method of a photocatalytic polylactic acid antibacterial film is characterized by comprising the following steps: which comprises the following steps:
(1) preparing a polylactic acid film by adopting an extrusion casting method;
(2) carrying out low-temperature plasma treatment on the polylactic acid film to obtain a treated polylactic acid film;
(3) dissolving 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide in a 2-morpholine ethanesulfonic acid buffer solution to obtain a conjugated solution, and soaking the treated polylactic acid film in the conjugated solution for activation to obtain an activated polylactic acid film;
(4) dissolving a photosensitizer in deionized water to obtain a photosensitizer solution, immersing the activated polylactic acid film in the photosensitizer solution for covalent coupling, and then washing and drying to obtain the photocatalytic polylactic acid antibacterial film.
2. The method for preparing a photocatalytic antibacterial film of polylactic acid according to claim 1, wherein: in the step (1), the temperatures of the sections of the extrusion device in the extrusion casting method are 130-.
3. The method for preparing a photocatalytic antibacterial film of polylactic acid according to claim 1, wherein: in the step (2), the parameters of the low-temperature plasma treatment are as follows: the speed is 8cm/s, the working current is 5-7A, and the treatment time is 10-30 s.
4. The method for preparing a photocatalytic antibacterial film of polylactic acid according to claim 1, wherein: in the step (3), the oscillation speed is 180-200rpm in the activation process, the temperature is 30-40 ℃, and the time is 2-4 h.
5. The method for preparing a photocatalytic antibacterial film of polylactic acid according to claim 1, wherein: in the step (4), the photosensitizer is 5-aminolevulinic acid; the oscillation speed in the covalent coupling process is 180-200rpm, the temperature is 30-40 ℃, and the time is 4-6 h.
6. The method for preparing a photocatalytic antibacterial film of polylactic acid according to claim 1, wherein: in the step (4), the drying temperature is 25-35 ℃, and the drying time is 12-24 h.
7. A photocatalytic polylactic acid antibacterial film is characterized in that: which is obtained by the production method according to any one of claims 1 to 6.
8. Use of the photocatalytic polylactic acid antibacterial film according to claim 7 as a food packaging film.
9. Use according to claim 8, characterized in that: respectively inoculating bacterial suspensions of Listeria monocytoenes, Vibrio parahaemolyticus and Shewanella putrefensis to a photocatalytic polylactic acid antibacterial film, incubating in a dark place, and placing under a blue LED lamp for irradiation; and then shearing the photocatalytic polylactic acid antibacterial film, homogenizing, diluting with sterile normal saline, coating the diluent, culturing for 24-48h, and calculating the number of colonies.
10. Use according to claim 9, characterized in that: the wavelength range of the blue LED lamp is 455-460 nm;
preferably, the light energy density of the blue LED lamp is 10.0-60.0mW/cm2。
CN202111149405.8A 2021-09-29 2021-09-29 Photocatalytic polylactic acid antibacterial film and preparation method and application thereof Pending CN113817205A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115652610A (en) * 2022-11-16 2023-01-31 武汉纺织大学 Dual-antibacterial polypropylene non-woven fabric and preparation method thereof

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018117885A1 (en) * 2016-12-21 2018-06-28 S.C. Institutul De Cercetari Produse Auxiliare Organice S.A. Pla - based active and degradable biocomposites for food packaging
CN109517226A (en) * 2019-01-07 2019-03-26 福建农林大学 A kind of light power bacteria reducing preservative film for packaged instant jellyfish
CN110746630A (en) * 2019-11-15 2020-02-04 上海海洋大学 Grafted antibacterial degradable preservative film and preparation method and application thereof
CN113024892A (en) * 2021-03-24 2021-06-25 上海海洋大学 Cellulose-based membrane with photodynamic antibacterial activity, preparation and application thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018117885A1 (en) * 2016-12-21 2018-06-28 S.C. Institutul De Cercetari Produse Auxiliare Organice S.A. Pla - based active and degradable biocomposites for food packaging
CN109517226A (en) * 2019-01-07 2019-03-26 福建农林大学 A kind of light power bacteria reducing preservative film for packaged instant jellyfish
CN110746630A (en) * 2019-11-15 2020-02-04 上海海洋大学 Grafted antibacterial degradable preservative film and preparation method and application thereof
CN113024892A (en) * 2021-03-24 2021-06-25 上海海洋大学 Cellulose-based membrane with photodynamic antibacterial activity, preparation and application thereof

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
郑宝东等: "光动力技术研究进展及其在食品工业中的应用前景", 《食品与生物技术学报》 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115652610A (en) * 2022-11-16 2023-01-31 武汉纺织大学 Dual-antibacterial polypropylene non-woven fabric and preparation method thereof
CN115652610B (en) * 2022-11-16 2024-02-13 武汉纺织大学 Dual-antibacterial polypropylene non-woven fabric and preparation method thereof

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