CN117089487A - Lactobacillus paracasei DT33 and application thereof in preparation of products with functions of micro-plastic adsorption, removal and defecation promotion - Google Patents

Abstract

The invention relates to the technical field of microorganisms, in particular to lactobacillus paracasei DT33 and application thereof in preparing products with functions of micro-plastic adsorption, removal and defecation promotion. The lactobacillus paracasei DT33 can produce various SCFAs with high yield, has better acid resistance, bile salt resistance and safety, and can be developed into edible probiotics; the strain has the function of promoting defecation, and can improve intestinal health and immunity; in addition, the strain can adsorb the microplastic, accelerate the discharge of the microplastic, reduce the oxidative damage caused by the accumulation of the microplastic, and provide great benefits for the intestinal health of human bodies and animals.

Description

Lactobacillus paracasei DT33 and application thereof in preparation of products with functions of micro-plastic adsorption, removal and defecation promotion

Technical Field

The invention relates to the technical field of microorganisms, in particular to lactobacillus paracasei DT33 and application thereof in preparing products with functions of micro-plastic adsorption, removal and defecation promotion.

Background

Short Chain Fatty Acids (SCFA) are a class of organic acids produced by fermentation of enterobacteria consisting of 1-6 carbon atoms, wherein acetate, propionate and butyrate are present in the highest amounts, and the total amounts exceed 95% of the SCFA content. SCFA, one of the important metabolites produced by the intestinal flora, plays an important role in regulating human health.

Specifically, SCFA can provide energy for intestinal flora and intestinal epithelial cells, promote proliferation and differentiation of the epithelial cells, and regulate expression of the tight junction protein, thereby enhancing intestinal barrier effect, maintaining structural stability of the intestinal flora and normal physiological functions of intestinal tract; in addition, SCFA exert a function of reducing inflammatory responses in intestinal mucosa by activating G protein-coupled receptors in intestinal epithelial cells and immune cells or inhibiting histone deacetylase activity, and reducing the production of inflammatory factors such as IL-6, IL-8, IL-10, TNF- α, and the like. Therefore, the obtained probiotics capable of efficiently producing SCFA has important significance in the aspects of maintaining normal functions of human intestinal tracts, regulating human immune systems and the like.

On the other hand, probiotics are increasingly widely used for regulating intestinal health, and various researches show that by utilizing probiotics such as streptococcus thermophilus, bifidobacterium lactis, lactobacillus casei and the like, defecation can be safely and effectively promoted, constipation can be relieved, and the discovery of new probiotics capable of promoting defecation is one of research hotspots in the field.

In addition, microplastic contamination has also become a serious environmental problem and also constitutes a potential threat to human health. Microplastic refers to tiny particles with the particle diameter smaller than 5mm, which are decomposed by physical, chemical and biological actions of plastic products discarded into the environment, and the materials of the microplastic comprise Polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET) and the like. Microplastic exists widely in air, water and soil, and can be ingested by plankton, fish, birds and the like, and finally enters human bodies through food chains. It is estimated that the micro-plastic intake of a human body can reach 5g per week, and micro-plastic exists in human feces, blood, lung tissues and placenta. Although there is no direct evidence to date that microplastic is damaging to human health, numerous studies have demonstrated that microplastic can cause damage to the digestive, respiratory, immune, nervous and reproductive systems of rodents, aquatic organisms, that microplastic accumulated in tissues cannot be cleared, can cause a substantial increase in reactive oxygen species, and thus cause oxidative stress, causing toxic effects. Therefore, the micro plastic in the human body is discharged, the content of the micro plastic is reduced, and the method has important significance for the long-term health of the human body.

At present, no method can remove the micro plastics of the human body, and only a few reports on the use of biological methods can reduce the pollution of plastics in the environment and water body. For example, some bacteria and fungi are able to degrade plastics by secreting cutinases, proteases, esterases, lipases, etc., breaking down polymers into monomers or oligomers; in addition, some bacteria have the ability to capture microplastic, they can adhere to the surface of the microplastic and create a viscous biofilm, and such a viscous matrix can capture free microplastic, causing the microplastic organisms to aggregate, thereby effecting separation and removal of the microplastic.

However, the existing bacteria or fungi capable of degrading or adsorbing the microplastic are non-edible strains, and the bacteria or fungi are difficult to withstand the gastrointestinal tract environment, so that the bacteria or fungi are difficult to apply to the removal of the microplastic of a human body. In order to reduce the accumulation of microplastic in humans and to reduce the health damage to humans caused by microplastic, there is a need in the art to develop probiotics that are resistant to the gastrointestinal environment and adsorb and scavenge microplastic.

Disclosure of Invention

In order to solve the technical problems, the invention provides lactobacillus paracasei (Lacticaseibacillus paracasei) DT33 which can produce various SCFAs in high yield, promote defecation, improve immunity and adsorb microplastic. The strain is separated from French cheese, has good acid resistance and bile salt resistance, and can promote defecation and regulate immunity after being planted in organisms. The strain can effectively adsorb the microplastic, accelerate the discharge of the microplastic, reduce the oxidative damage caused by the accumulation of the microplastic and promote the intestinal health. In addition, the strain has good safety and can be developed into edible probiotics. Based on this, the present invention proposes the following summary.

First, the present invention provides a lactobacillus paracasei, which is lactobacillus paracasei (Lacticaseibacillus paracasei) DT33.

The strain was deposited in the cantonese province microorganism strain collection at month 05 of 2023. Deposit unit address: guangzhou city first middle road No. 100 college No. 59 building 5; postal code: 510070, classification naming: lacticaseibacillus paracasei with accession number GDMCC No. 63622.

Morphological features of lactobacillus paracasei DT33 include: gram staining is positive, rod-shaped under the light mirror, circular at both ends, and can exist in pairs or chains. After 24h incubation in MRS solid medium, milky white colonies were formed that were round, convex in the middle, smooth in the edges and bright in the surface.

The physiological characteristics of lactobacillus paracasei DT33 include: lactobacillus paracasei DT33 can grow in an acidic or bile salt-containing culture medium, and can promote defecation and regulate immunity after being transplanted into an animal body. The strain can effectively adsorb the microplastic, has an antioxidation effect, and can reduce the oxidative damage caused by the microplastic.

Lactobacillus paracasei is widely present in the human intestinal tract and has a broad and long history of use in food fermentation, particularly dairy fermentation. Lactobacillus paracasei has been listed in a list of species useful for food, in the list of european union microbial species safety Qualification (QPS) promulgated by the European Food Security Agency (EFSA), and GRAS (generally recognised as safe) certification by the united states Food and Drug Administration (FDA) has also been obtained, and is widely used in various probiotic foods and dietary supplements worldwide. In addition, genome study data, mouse experiments and human clinical experiments all demonstrated the safety of lactobacillus paracasei.

Preferably, lactobacillus paracasei DT33 is cultivated with MRS medium.

Preferably, the MRS medium comprises the following components:

10g/L of casein enzyme digest, 10g/L of beef extract powder, 4g/L of yeast extract powder, 2g/L of triammonium citrate, 5g/L of sodium acetate, 0.2g/L of magnesium sulfate, 0.05g/L of manganese sulfate, 20g/L of glucose, 2g/L of dipotassium hydrogen phosphate and 1g/L of tween 80. Preferably, ph=5.7±0.2.

Preferably, the culture temperature is 37℃anaerobic culture.

Preferably, the incubation time is 24 hours.

Further, the invention provides a microbial agent, which comprises the lactobacillus paracasei DT33.

Further, the invention provides a reagent or a kit, which comprises the lactobacillus paracasei DT33 or the microbial agent.

Preferably, the reagent or kit is used to adsorb, scavenge or detect microplastic in an environment.

Further, the invention provides a food, which comprises the lactobacillus paracasei DT33 or the microbial agent.

The lactobacillus paracasei provided by the invention is used as probiotics to be added into food, so that defecation can be promoted, intestinal health and immune state can be improved, and microplastic in the body can be effectively removed.

Further, the invention provides a feed or feed additive, which comprises the lactobacillus paracasei DT33 or the microbial agent.

The feed or feed additive can promote animal defecation, improve animal intestinal health and immune state, effectively remove microplastic in animal body, and promote animal healthy growth and development.

Further, the invention provides a medicine, which comprises the lactobacillus paracasei DT33 or the microbial agent.

The medicine of the invention can promote defecation, adsorb microplastic or accelerate microplastic removal, resist acid or bile salt, promote high yield of short chain fatty acid, improve immune function, reduce oxidative damage or intestinal inflammation, and has antioxidant effect.

Preferably, the medicine further comprises pharmaceutically acceptable auxiliary materials.

Preferably, the auxiliary materials comprise a filler, an excipient, a lubricant, a wetting agent and a diluent.

In a specific implementation process, the preparation type of the medicine comprises, but is not limited to, powder, granules, capsules, tablets and oral liquid.

Further, the invention provides application of the lactobacillus paracasei DT33 or the microbial agent in adsorbing, removing or detecting microplastic in the environment.

Preferably, the environment comprises air, water, soil environment.

Further, the invention provides application of the lactobacillus paracasei DT33 or the microbial agent in preparing medicines; the medicine has the functions of at least one of the following aspects:

(1) Promoting defecation;

(2) Adsorbing or accelerating the removal of the microplastic;

(3) Acid or bile salt resistant;

(4) Producing short chain fatty acids;

(5) Improving immune function;

(6) Reducing oxidative damage or intestinal inflammation;

(7) Oxidation resistance.

Further, the invention provides the use of lactobacillus paracasei DT33 as described above or the microbial agent as described above for the preparation of a product for promoting the discharge of micro plastics.

Further, the invention provides application of the lactobacillus paracasei DT33 or the microbial inoculum in preparing a product for adsorbing micro-plastics.

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

the lactobacillus paracasei DT33 can produce various SCFAs with high yield, has better acid resistance, bile salt resistance and safety, and can be developed into edible probiotics; the strain has the function of promoting defecation, and can improve intestinal health and immunity; in addition, the strain can adsorb the microplastic, accelerate the discharge of the microplastic and reduce the oxidative damage caused by the accumulation of the microplastic, thereby providing great benefits for the intestinal health of human bodies and animals.

Drawings

FIG. 1 is a colony morphology of Lactobacillus paracasei DT33 on MRS medium.

FIG. 2 is a microscopic image of Lactobacillus paracasei DT33.

FIG. 3 is a statistical graph of the survival rate of Lactobacillus paracasei DT33 in acidic medium; the statistical analysis method is t test, ns represents p value greater than 0.05, data are from three repeated experiments, and error bars represent standard deviation.

FIG. 4 is a statistical plot of the survival rate of Lactobacillus paracasei DT33 in bile salt-containing medium; the statistical analysis method is t test, ns represents p value greater than 0.05, data are from three repeated experiments, and error bars represent standard deviation.

FIG. 5 is a graph showing the concentration statistics of acetic acid in Lactobacillus paracasei DT33 fermentation broth; the data were from three replicates, error bars represent standard deviations, statistical analysis was t test, and p values were less than 0.001.

FIG. 6 is a graph showing the effect of determining the transfer rate of activated carbon after the Lactobacillus paracasei DT33 was colonized.

Fig. 7 is a statistical plot of TNF- α content in ileum tissue after colonization with lactobacillus paracasei DT33, error bars indicating standard deviations, statistical analysis method t test, p values less than 0.001.

FIG. 8 is a photograph showing the adsorption and aggregation of Lactobacillus paracasei DT33 with PS fluorescent microspheres in solution.

Fig. 9 is a graph of lactobacillus paracasei DT33 versus PS fluorescent microsphere adsorption in solution, error bars represent standard deviations, data from three replicates, statistical analysis method t test, p less than 0.0001.

FIG. 10 is an electron microscope image of the adsorption of Lactobacillus paracasei DT33 and PS fluorescent microspheres at 50000 Xmagnification.

FIG. 11 is a statistical plot of the clearance of Lactobacillus paracasei DT33 against DPPH, error bars represent standard deviations, data from three replicates.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The examples are not intended to identify the particular technology or conditions, and are either conventional or are carried out according to the technology or conditions described in the literature in this field or are carried out according to the product specifications. The reagents and instruments used, etc. are not identified to the manufacturer and are conventional products available for purchase by regular vendors.

The trace element solution and the vitamin solution in the culture medium formula for simulating the intestinal environment in vitro are purchased from Coolaber company, the product number of the trace element solution is SL0120, and the product number of the vitamin solution is SL0110.

Example 1 isolation and characterization of Lactobacillus paracasei DT33

1. Isolation and identification of Lactobacillus paracasei DT33

1.1 sample Source

The strain lactobacillus paracasei (Lacticaseibacillus paracasei) DT33 used in this example was isolated from french cheese.

1.2 preparation of Medium

The culture medium used for sample isolation and strain selection was MRS medium, and the culture medium used for culturing Lactobacillus paracasei DT33 was MRS medium. The composition of MRS culture medium is shown in Table 1, and final pH of MRS culture medium is 5.7+ -0.2; adding 1.5% agar to obtain MRS solid culture medium.

TABLE 1MRS Medium formulation

1.3 isolation of strains

Placing 1g of French cheese sample into 10mL of MRS liquid culture medium prepared in step 1.2, uniformly mixing, culturing at 36 ℃ for 24h, sucking 1mL of enrichment liquid in an ultra-clean bench, performing ten-fold gradient dilution, and selecting 10 ^-4 、10 ^-5 、10 ^-6 、10 ^-7 Four bacterial solutions with dilution gradient of 100 mu L are coated on a culture dish containing sterile MRS solid culture medium, and are subjected to static culture at 36 ℃ for 48-72 hours under anaerobic condition until obvious single colonies are formed, a high-throughput automatic platform is used for automatically picking typical bacterial colonies from the culture dish to be cultured in the MRS liquid culture medium, and the strain obtained by separation is subjected to 16S rRNA sequencing to determine species information.

2. Identification of Lactobacillus paracasei DT33

2.1 colony characterization

After culturing lactobacillus paracasei DT33 in MRS solid medium for 24 hours, a milky white colony with round shape, convex middle, smooth edge and bright surface was formed, see fig. 1.

2.2 morphology under microscope

Lactobacillus paracasei DT33 colony smear: gram staining is positive, rod-like under the mirror, circular at both ends, and can exist in pairs or chains, see figure 2.

2.3 16S rRNA identification

Identification unit: optimum Trinitum Prinsepiae SpA.

The identification sequence is shown as SEQ ID No. 1.

Identification result: the sequencing result is compared with NCBI database, and the comparison result is combined with physiological and biochemical result to determine that the strain is lactobacillus paracasei (Lacticaseibacillus paracasei).

EXAMPLE 2 acid resistance detection of Lactobacillus paracasei DT33

The overall pH condition in the gastric environment of the human body is strongly acidic, so the acid resistance of the strain is an important index for evaluating whether the strain can survive and colonize in the gastric acid environment. The commercialized strain lactobacillus rhamnosus Lactobacillus rhamnosus GG (LGG) is a probiotic which is widely used at present and has strong acid resistance.

The acid resistance of lactobacillus paracasei DT33 was verified in this example using MRS medium at ph=2.5. The method comprises the following specific steps:

1mL of the bacterial liquid was centrifuged at 4000rpm for 10min, the supernatant was discarded, and then 1mL of PBS was added for washing once, and after centrifugation at 4000rpm for 10min, the pellet was resuspended in MRS medium at pH=2.5. Incubate for 3h at 37℃and sample at 0h and 3h, respectively. After centrifugation, the samples were resuspended in PBS and diluted in a gradient, and the diluted samples were plated on MRS agar plates and subjected to colony counting after anaerobic incubation at 37℃for 16 h. The survival rate calculation formula is: acid-resistant survival (%) =c1/c0×100% (c0:0 h count; c1:3h count). The control strain is lactobacillus rhamnosus LGG.

After 3 hours of culture in acid medium, the control strain lactobacillus rhamnosus LGG has a survival rate of 84.56%, the lactobacillus paracasei DT33 has a survival rate of 87.78% (fig. 3), which is equivalent to the acid resistance of the control strain, indicating that the strain has strong acid resistance and can survive in stomach environment.

EXAMPLE 3 Lactobacillus paracasei DT33 bile salt resistance assay

After entering the intestine through the stomach, the bacteria are killed by the high concentration of bile salts in the small intestine. The residence time of the food in the small intestine is generally 1 to 4 hours.

This example demonstrates the cholate resistance of lactobacillus paracasei DT33 strain using 0.1% cholate-MRS medium. The method comprises the following specific steps:

lactobacillus paracasei DT33 bacterial liquid is inoculated in a 96 deep well plate containing MRS culture medium, and is subjected to anaerobic culture at 37 ℃ for 24 hours. 300. Mu.L of the cultured bacterial liquid was centrifuged at 4000rpm for 10min, the supernatant was discarded, 600. Mu.L of MRS medium containing 0.1% bile salt was added, and the mixture was resuspended. The control group was taken 100. Mu.L of the resuspension, and 20. Mu.L of MTT (thiazole blue) solution was added; the treatment group was taken as 100. Mu.L of the resuspension, incubated at 37℃for 4h, and then 20. Mu.L of MTT solution was added. After adding MTT solution, the reaction was carried out at 37℃for 4 hours in the absence of light, and after the completion of the reaction, the reaction was centrifuged at 4000rpm for 10 minutes, and the supernatant was discarded. 100 mu L of DMSO solution is added into each hole, and the mixture is incubated for 10min under shaking at 37 ℃ to completely dissolve and mix the blue-violet formazan generated by the reaction. After mixing, absorbance at 570nm was measured by using an enzyme-labeled instrument, and survival rate was calculated. Survival = A1/a0×100% (A1: absorbance at 570nm for treatment group solutions, A0: absorbance at 570nm for control group solutions). The viability of the control strain lactobacillus rhamnosus LGG was determined in the same way.

After 4 hours of incubation with 0.1% bile salt-MRS medium, the survival rate of the control strain Lactobacillus rhamnosus LGG was 101.5% and the survival rate of Lactobacillus paracasei DT33 was 97.28% (FIG. 4). This indicates that lactobacillus paracasei DT33 is comparable to the control strain lactobacillus rhamnosus LGG for bile salt tolerance and survives in the small intestine.

Example 4 detection of the ability of Lactobacillus paracasei DT33 to produce SCFA

To better verify the ability of lactobacillus paracasei DT33 to produce SCFA in vivo, this example used in vitro simulated intestinal environment media, the media formulation is shown in table 2. Lactobacillus paracasei DT33 was inoculated into the medium and cultured anaerobically at 37℃for 24 hours. The culture broth was centrifuged at 4000rpm for 10min, the supernatant was filtered through a 0.22 μm aqueous filter and then placed in a liquid phase vial, and the content of SCFA in the supernatant was measured by HPLC. The control strain is another lactobacillus paracasei strain screened in the same batch screening experiment.

As can be seen from fig. 5, the acetic acid content in the lactobacillus paracasei DT33 broth was significantly higher than the control strain. In addition, the content of acrylic acid in the supernatant of lactobacillus paracasei DT33 fermentation broth was also measured in this example and was 0.038mg/mL. Thus, lactobacillus paracasei DT33 is a high yield SCFA strain isolated this time. Since the glucose content of the in vitro simulated intestinal environment culture medium used in this example is significantly lower than that of the conventional microorganism culture medium, such as MRS culture medium, the content of acetic acid and propionic acid produced by Lactobacillus paracasei DT33 is relatively low, and higher yields of acetic acid and propionic acid can be expected by using the conventional microorganism culture medium.

Table 2 in vitro simulated intestinal environment media formulation

Example 5 Lactobacillus paracasei DT33 promotes excretion in mice

Male C57 mice of 6 weeks of age, which were adaptively bred for one week, were randomly divided into two groups, the experimental group mice (6) were gavaged with Lactobacillus paracasei DT33, and the control group mice were gavaged with Lactobacillus rhamnosus LGG, a commercial strain. The number of days of gastric lavage is 7 days, and the dosage of gastric lavage is 10 ⁹ CFU/day. After 24 hours of last gastric lavage of the probiotics, all mice were perfused with 2ml of 5% activated carbon. After 20min of gavage with activated carbon, the mice were sacrificed, the abdominal cavity was dissected, the intestines from the pylorus to the ileocecum were removed, placed on paper, and the activated carbon delivery site was determined with the intestines remaining sufficiently relaxed. After the measurement is completed, colon tissue is taken and stored at-80 ℃ for ELISA detection.

As can be seen from fig. 6, lactobacillus paracasei DT33, which is a strain of lactobacillus paracasei, accelerates the transfer rate of activated carbon and better promotes excretion of mice, as compared to lactobacillus rhamnosus LGG, which is a strain of lactobacillus paracasei.

Example 6 Lactobacillus paracasei DT33 reduces intestinal inflammation in mice

The ileum tissue samples preserved in example 5 were taken for ELISA detection analysis.

The results are shown in FIG. 7, and the Lactobacillus paracasei DT33 significantly reduced the level of tumor necrosis factor (TNF-. Alpha.) compared to Lactobacillus rhamnosus LGG, which indicates that Lactobacillus paracasei DT33 has a better effect of reducing intestinal inflammation than Lactobacillus rhamnosus LGG.

EXAMPLE 7 measurement of the effect of Lactobacillus paracasei DT33 on adsorbing microplastic

Lactobacillus paracasei DT33 was inoculated into MRS medium and cultured anaerobically at 37℃for 24 hours. The cultured bacterial solution was centrifuged at 4000rpm for 10min, the supernatant was discarded, and 450. Mu.L of sterile PBS buffer was added for washing 2 times. Then PBS is added for resuspension, and the concentration of bacterial liquid is adjusted to be 1 multiplied by 10 ⁹ CFU/mL. The experimental group takes 100 mu L to 1.5mL EP tube of lactobacillus paracasei DT33 bacterial suspension, 900 mu L of PS fluorescent microsphere working solution (0.16 mg/mL, particle size 0.1 mu m, sile company) is added and mixed evenly, and the mixture is placed in a shaking table to shake and incubate for 4 hours under the conditions of 37 ℃ and 800rpm. The blank group was incubated with 100. Mu.L PBS and 900. Mu.L PS fluorescent microsphere working solution in a 1.5mL EP tube. The bacterial liquid control group was incubated with 100. Mu.L of Lactobacillus paracasei DT33 bacterial suspension and 900. Mu.L of PBS in a 1.5mL EP tube. After the incubation, taking the incubation liquid for observation and photographing. Taking the incubation liquid of the experimental group and the blank control group, centrifuging at 2000rpm for 10min, taking 100uL of supernatant, and measuring the fluorescence intensity by using an enzyme-labeling instrument. The parameters of the enzyme label instrument are as follows: excitation wavelength, 494nm; detection wavelength, 518nm. And calculating the adsorption rate according to the fluorescence intensity value. The control strain was another Lactobacillus paracasei strain obtained in the same batch screening experiment, and the adsorption rate of the control strain was determined in the same manner. The adsorption rate calculation formula is: adsorption (%) = (A1-A2) ×100/a1×100% (A1: fluorescence value of the blank group, A2: fluorescence value of the lactobacillus paracasei group). Taking the precipitate after centrifugation, fixing the precipitate at 4 ℃ by glutaraldehyde overnight, dehydrating the precipitate by ethanol gradient, and observing the precipitate by an electron microscope after drying.

As can be seen from fig. 8, PS fluorescent microspheres did not self-aggregate in the blank group; in the bacterial liquid control group, lactobacillus paracasei DT33 does not self-coagulate; in the experimental group, lactobacillus paracasei DT33 and PS fluorescent microspheres showed specific adsorption and flocculation.

As can be seen from FIG. 9, the adsorption rate of the control strain is 15.33%, the adsorption capacity of the microplastic is poor, while the adsorption rate of Lactobacillus paracasei DT33 reaches 72.53%, and the microplastic adsorption capacity is very strong. This indicates that lactobacillus paracasei DT33 has strain specificity for the adsorption effect of the microplastic.

As can be seen from FIG. 10, under the observation of an electron microscope, spherical PS fluorescent microspheres were adsorbed on the surface of the rod-shaped Lactobacillus paracasei DT33.

EXAMPLE 8 measurement of antioxidant Capacity of Lactobacillus paracasei DT33

Lactobacillus paracasei DT33 was inoculated into MRS medium and cultured anaerobically at 37℃for 24 hours. Centrifuging the cultured bacterial liquid at 4000rpm for 10min, discarding supernatant, adding 450 μl of sterile PBS buffer, washing for 2 times, and adjusting bacterial liquid concentration to 1×10 ⁹ CFU/mL. Experimental groups 500. Mu.L of the bacterial suspension were taken and 500. Mu.L of 0.2 mmoL/L1, 1-diphenyl-2-trinitrophenylhydrazine (DPPH) ethanol solution was added. The antioxidant vitamin C (Vc) was used as a positive control and 500. Mu.L of 3. Mu.g/mL vitamin solution was added to 500. Mu.L of 0.2mmoL/L DPPH ethanol solution. The control group was taken from 500. Mu.L of PBS and 500. Mu.L of 0.2mmoL/L DPPH ethanol solution was added. 500. Mu.L of the bacterial suspension was taken from the blank and 500. Mu.L of absolute ethanol solution was added. Mixing, and shaking in a shaking table at 30deg.C for 30min. After the completion of the shaking, the reaction mixture was centrifuged at 4000rpm for 10 minutes, and 100. Mu.L of the supernatant was subjected to absorbance measurement at 517nm by using a microplate reader. DPPH radical scavenging was calculated. The calculation formula is as follows: DPPH clearance (%) = [1- (As-A0)/Ai]X 100% (As: experimental; A0: blank; ai: control).

As can be seen from fig. 11, the antioxidant vitamin C has a removal rate of 60.90% for DPPH, and similar to vitamin C, lactobacillus paracasei DT33 has a certain antioxidant capacity, and a removal rate of 42.63% for DPPH. Thus, lactobacillus paracasei DT33 is colonized to reduce the oxidative damage of the host by the microplastic.

In conclusion, the lactobacillus paracasei DT33 is obtained through separation and screening. The strain can resist acid and bile salt, has the capability of colonization in stomach and small intestine, and can be applied to development of edible probiotics. The lactobacillus paracasei DT33 has high SCFA yield, can increase the intestinal tract transportation rate of mice after being planted into the bodies of the mice, promote the defecation of the mice, reduce the inflammatory factor level of the intestinal tracts of the mice, and has the protection capability on the intestinal tracts. The strain has strong capacity of adsorbing microplastic, and experimental data also prove that the strain has antioxidant capacity. Thus, the lactobacillus paracasei DT33 is a strain suitable for the digestive tract environment, and has wide application prospect in the aspects of promoting host defecation, reducing intestinal inflammation, adsorbing microplastic, accelerating the discharge of the microplastic and reducing the oxidative damage caused by the microplastic.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A strain of Lactobacillus paracasei, characterized in that it is Lactobacillus paracasei (Lacticaseibacillus paracasei) DT33 with accession number GDMCC No. 63622.

2. A microbial agent comprising the lactobacillus paracasei of claim 1.

3. A reagent or kit comprising the lactobacillus paracasei of claim 1 or the microbial agent of claim 2.

4. A reagent or kit according to claim 3, wherein the reagent or kit is for adsorbing, removing or detecting micro plastics in an environment.

5. A food product comprising the lactobacillus paracasei of claim 1 or the microbial agent of claim 2.

6. A pharmaceutical product comprising the lactobacillus paracasei of claim 1 or the microbial agent of claim 2.

7. Use of lactobacillus paracasei according to claim 1 or the microbial agent according to claim 2 for adsorbing, removing or detecting micro-plastics in an environment.

8. Use of the lactobacillus paracasei of claim 1 or the microbial agent of claim 2 in the preparation of a medicament; the medicine has the functions of at least one of the following aspects:

(1) Promoting defecation;

(2) Adsorbing or accelerating the removal of the microplastic;

(3) Acid or bile salt resistant;

(4) Producing short chain fatty acids;

(5) Improving immune function;

(6) Reducing oxidative damage or intestinal inflammation;

(7) Oxidation resistance.

9. Use of lactobacillus paracasei according to claim 1 or a microbial agent according to claim 2 for the preparation of a product for promoting the discharge of micro-plastics.

10. Use of lactobacillus paracasei according to claim 1 or the microbial agent according to claim 2 for the preparation of a product for adsorbing micro plastics.