Lactobacillus plantarum strain LT303 and application thereof

Abstract

The invention relates to the technical field of microorganisms, in particular to a lactobacillus plantarum strain LT303 and application thereof.The lactobacillus plantarum strain LT303 is separated from an acid material, and a fermentation product obtained after fermentation of the strain and leaf mustard has the antibacterial effect on salmonella enteritidis, staphylococcus aureus and / or listeria monocytogenes; the content of sweet amino acids, namely threonine, alanine, serine, glycine and proline, of the pickled Chinese cabbages prepared by fermentation of the strain LT303 is remarkably high, and the fermented pickled Chinese cabbages are the most sweet and fresh in taste and the most abundant in sweet amino acid content; besides, the texture of the pickled Chinese cabbages prepared by adding the mango juice, the pitaya juice and the siraitia grosvenorii juice is enhanced, and the content of sweet amino acids is more remarkably increased, so that the LT303 strain can be used for preparing the pickled Chinese cabbages which are more sweet in taste and more unique in flavor, fermentation liquor has the value of researching and developing antibacterial peptides, and new raw materials and thoughts are provided for increasing the additional value of products in the later period.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, and in particular to Lactobacillus plantarum strain LT303 and its applications. Background Technology

[0002] Sauerkraut, a traditional fermented vegetable product, enjoys a broad consumer base both domestically and internationally due to its unique flavor and certain health benefits. Its production primarily relies on natural lactic acid bacteria and other microorganisms attached to the surface of the raw materials, undergoing a lactic acid fermentation process under anaerobic conditions. While traditional natural fermentation methods can create a typical flavor, they suffer from problems such as unstable fermentation cycles, significant fluctuations in product quality, and uncontrollable flavor compound formation. With increasing consumer demands for food flavor, nutrition, and safety, and the rapid development of the functional food market, selecting superior fermentation strains and optimizing processes to specifically improve the taste, texture, and functional properties of sauerkraut has become an important research direction in this field.

[0003] Currently, research on fermented vegetables largely focuses on screening for lactic acid bacteria that produce acid rapidly and have strong tolerance, aiming to shorten the fermentation cycle and improve product stability. However, research on dedicated fermentation strains that can significantly enhance the content of characteristic flavor compounds (especially sweet amino acids) and impart additional functions (such as antibacterial activity) to the products remains relatively limited. Sweet amino acids (such as threonine, alanine, serine, glycine, and proline) are key components contributing to the sweet taste and rich flavor of fermented vegetables, and their content directly affects the product's acceptability and quality grade. Furthermore, the fermentation broth contains metabolites with antibacterial activity, providing potential resources for developing natural biopreservatives or functional peptides, which can significantly increase the added value of the product.

[0004] In terms of process improvement, adding exogenous nutrients or natural plant ingredients to promote the growth of starter cultures and enhance the texture and flavor of the product is a feasible strategy. Fruit juice is rich in vitamins, minerals, and various active ingredients, and existing studies have explored its potential as a fermentation aid substrate. However, its growth-promoting effect on specific lactic acid bacteria and its targeted impact on the taste, amino acid profile, and texture of the final product still require in-depth evaluation on a case-by-case basis.

[0005] Therefore, discovering new fermentation strains that can synergistically enhance the sensory quality and functional characteristics of sauerkraut, and developing corresponding fermentation processes that can further strengthen these advantages, is of great significance for innovating high-quality, high-value-added sauerkraut products and promoting the upgrading of traditional industries. Summary of the Invention

[0006] In view of the above, it is necessary to discover new fermentation strains that can synergistically improve the sensory quality and functional characteristics of sauerkraut, and to develop supporting fermentation processes that can further enhance these advantages, so as to achieve the goal of innovating high-quality, high-value-added sauerkraut products and promoting the upgrading of traditional industries.

[0007] To achieve the above objectives, this invention has screened out a new strain: Lactiplantibacillus plantarum LT303, its classification name is: Lactiplantibacillus plantarum The strain is classified and named as Lactobacillus plantarum in Chinese, with accession number GDMCC NO: 66635. It is deposited at the Guangdong Provincial Center for Microbial Culture Collection, located at the Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, on July 3, 2025.

[0008] The present invention also includes the Lactobacillus plantarum ( Lactiplantibacillus plantarum Sauerkraut fermentation broth of strain LT303.

[0009] The present invention also includes the Lactobacillus plantarum ( Lactiplantibacillus plantarum Application of strain LT303 in improving the sweet amino acid content of sauerkraut fermentation broth.

[0010] Furthermore, the sweet amino acid is threonine, alanine, serine, glycine, and / or proline.

[0011] This invention also includes the (NH4)2SO4 salting-out extract of the sauerkraut fermentation broth in inhibiting Salmonella enteritidis (NH4)2SO4. Salmonella enterica subsp. enterica serovar Enteritidis Staphylococcus aureus Staphylococcus aureus ) and / or Listeria monocytogenes ( Listeria monocytogenes Applications during growth.

[0012] Furthermore, the mass concentration of (NH4)2SO4 during salting out is 25% or 40%.

[0013] The present invention also includes the Lactobacillus plantarum ( Lactiplantibacillus plantarum Application of strain LT303 in the preparation of fruit-flavored sauerkraut.

[0014] Furthermore, the fruit is mango, dragon fruit, and / or monk fruit.

[0015] This invention also includes a method for preparing the fruit-flavored pickled mustard greens, the method comprising: washing whole mustard greens and placing them in a fermentation tank for pickling mustard greens; then, processing mango, dragon fruit, or monk fruit at a solid-liquid mass ratio of 5:1 with cell wall disruption, filtering the filtrate to obtain mango juice, dragon fruit juice, or monk fruit juice; adding the mango juice, dragon fruit juice, or monk fruit juice to the mustard greens in the fermentation tank; and inoculating with *Lactobacillus plantarum* at an inoculation rate of 2% by mass.Lactiplantibacillus plantarum The strain LT303 is obtained by pickling and fermenting for 15 days.

[0016] The present invention also includes the application of the aforementioned Lactobacillus plantarum ( Lactiplantibacillus plantarum A method for preparing (NH4)2SO4 salting-out extract from sauerkraut fermentation broth of strain LT303 is as follows: Sauerkraut fermentation broth is measured, centrifuged at room temperature, and the lower layer of impurities and bacterial sludge mixture is discarded. The upper clear liquid is retained. Then, the broth is concentrated to 1 / 10 of the original volume using a vacuum water bath rotary evaporator under a series of temperature gradients. A concentrated solution of 25% or 40% (NH4)2SO4 is added to the concentrated solution for salting-out. After salting-out, the solution is centrifuged in centrifuge tubes, and the supernatant is collected for secondary salting-out and centrifugation until no more precipitate appears.

[0017] The present invention has the following beneficial effects: The LT303 strain of the present invention is isolated from acidified material. This strain has no significant antibacterial effect on pathogens, but the fermentation product of this strain and mustard fermentation has an effect on Salmonella enteritidis (…). Salmonella enterica subsp. enterica serovar Enteritidis Staphylococcus aureus Staphylococcus aureus ) and Listeria monocytogenes ( Listeria monocytogenes The presence of antibacterial effects indicates that the fermentation broth of this strain of sauerkraut possesses the value for developing antimicrobial peptides. Furthermore, the content of sweet amino acids (threonine, alanine, serine, glycine, and proline) in sauerkraut fermented by strain LT303 is significantly higher than that in other experimental groups, indicating that sauerkraut fermented by strain LT303 has the sweetest and freshest taste, and the richest content of sweet amino acids. In addition, fruit juice enrichment experiments revealed that mango juice, dragon fruit juice, and monk fruit juice can effectively increase the viable cell count of strain LT303. Sauerkraut prepared using the addition of mango juice, dragon fruit juice, and monk fruit juice exhibits enhanced texture and a significantly increased content of sweet amino acids. This demonstrates that adding mango juice, dragon fruit juice, and monk fruit juice to sauerkraut fermented by strain LT303 can enhance the taste and texture of the sauerkraut, effectively enriching the sauerkraut product and increasing its value. Therefore, strain LT303 of this application can produce sauerkraut with a sweeter taste and more unique flavor, and the fermentation broth possesses the value for developing antimicrobial peptides, providing new raw materials and ideas for enhancing the added value of products in the future. Attached Figure Description

[0018] Figure 1 The image shows the plate growth of the *Lactobacillus plantarum* strains described in this application, where A represents strain LXC, B represents strain LT303, C represents strain LT304, and D represents strain LT400.

[0019] Figure 2The images show microscopic examination of the strains of *Lactobacillus plantarum* from this application, where A is strain LXC, B is strain LT303, C is strain LT304, and D is strain LT400.

[0020] Information on the preservation of biological materials.

[0021] The strain information deposited in this application is as follows: Lactiplantibacillus plantarum LXC, its classification name is: Lactiplantibacillus plantarum The strain is classified and named *Lactobacillus plantarum* in Chinese, with accession number GDMCCNO: 66634. It is deposited at the Guangdong Provincial Center for Microbial Culture Collection, located at the Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, on July 3, 2025.

[0022] The strain information deposited in this application is as follows: Lactiplantibacillus plantarum LT303, its classification name is: Lactiplantibacillus plantarum The strain is classified and named *Lactobacillus plantarum* in Chinese, with accession number GDMCCNO: 66635. It is deposited at the Guangdong Provincial Center for Microbial Culture Collection, located at the Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, on July 3, 2025.

[0023] The strain information deposited in this application is as follows: Lactiplantibacillus plantarum LT304, its classification name is: Lactiplantibacillus plantarum The strain is classified and named *Lactobacillus plantarum* in Chinese, with accession number GDMCCNO: 66636. It is deposited at the Guangdong Provincial Center for Microbial Culture Collection, located at the Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, on July 3, 2025.

[0024] The strain information deposited in this application is as follows: Lactiplantibacillus plantarum LT400, its classification name is: Lactiplantibacillus plantarum The strain is classified and named *Lactobacillus plantarum* in Chinese, with accession number GDMCCNO: 66637. It is deposited at the Guangdong Provincial Center for Microbial Culture Collection, located at the Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, on July 3, 2025. Detailed Implementation

[0025] All features disclosed in this specification, or steps in all methods or processes disclosed herein, may be combined in any way, except for mutually exclusive features and / or steps.

[0026] Unless otherwise stated, each feature disclosed in this specification (including any appended claims and abstract) is merely one example of a series of equivalent or similar features.

[0027] Example 1

[0028] This example uses *Lactobacillus plantarum* (… Lactiplantibacillus plantarum Isolation and identification of strains.

[0029] 1. Strain screening and isolation: Mother brine from market-prepared pickled cabbage, pickled cowpeas, and pickled bamboo shoots was added to MRS broth medium and incubated at 37 ℃ for 24 h for enrichment. 10 mL of the enriched strain was transferred to a sterile Erlenmeyer flask, 90 mL of physiological saline was added, and the mixture was shaken to mix thoroughly. The mixture was then serially diluted, and 100 µL was plated onto MRS agar plates containing calcium carbonate and incubated at 37 ℃ for 48 h. Stranding was performed multiple times on strains exhibiting calcium dissolution zones for purification. The strains were classified according to colony morphology, and after three generations of streaking isolation, pure strains were obtained and stored at -80 ℃.

[0030] 2. The strains in the enrichment solution were initially screened using MRS solid medium containing calcium carbonate. Stranding of strains exhibiting calcium dissolution zones was performed multiple times for purification, identifying suspected lactic acid bacteria. Morphological classification and Gram staining were then performed on the suspected strains. The results are shown in Table 1 and... Figure 1 , Figure 2 As shown.

[0031]

[0032] Note: "+" indicates a positive reaction; "-" indicates a negative reaction.

[0033] From Table 1 and Figure 1 visible: Figure 1 This is a plate image showing the growth of the *Lactobacillus plantarum* strain of this application. Figure 1 In the text, A represents strain LXC, whose colonies are round and raised, milky white, small, with neat edges, moist, and opaque. Figure 1 In the text, B represents strain LT303, whose colonies are round, milky white, with neat edges, and opaque. Figure 1 C in the text refers to strain LT304, whose colonies are round, milky white, with neat edges, moist, and opaque. Figure 1 In Table 1, D represents strain LT400, whose colonies are round, milky white, with neat edges, and opaque. As can be seen from Table 1, the colonies of strain XD are round, milky white, with neat edges, moist, and opaque; the colonies of strain XC2 are round, milky white, and opaque; and the colonies of strain SD are round, milky white, with neat edges, moist, and opaque.

[0034] From Table 1 and Figure 2 visible: Figure 2This is a microscopic image of the *Lactobacillus plantarum* strain described in this application. Figure 2 In this context, A represents strain LXC. Figure 2 B is strain LT303. Figure 2 C is strain LT304, Figure 2 D is strain LT400; from Figure 2 As can be seen in Table 1, strains LXC, LT303, LT304, and LT400 showed a purple Gram staining, indicating a positive result. Under the microscope, the strains were observed to be in pairs and rod-shaped. In addition, as shown in Table 1, strains XD, XC2, and SD also showed a Gram staining, and under the microscope, the strains were observed to be in pairs and rod-shaped.

[0035] 3. Molecular identification: The 16S rDNA sequences of strains LXC, LT303, LT304, LT400, XD, XC2, and SD listed in Table 1 were sequenced. The sequences were submitted to the National Center for Biotechnology Information (NCBI) database for BLAS homology comparison. The comparisons showed that these strains were homologous with... Lactiplantibacillus plantarum The homology reached 100%. Based on the morphological characteristics in Table 1, strains LXC, LT303, LT304, LT400, XD, XC2, and SD were identified as... Lactiplantibacillus plantarum .

[0036] Example 2

[0037] This example is a performance test, as detailed below:

[0038] 1. The activated bacterial strain was inoculated into MRS broth at a volume fraction of 2% and cultured at 37 ℃ for 24 h. The pH value of the fermentation broth was measured at regular intervals using a pH meter. The total acid content was determined according to GB 12456—2021 "National Food Safety Standard - Determination of Total Acid in Food". The results are shown in Table 2.

[0039]

[0040] Note: Different lowercase letters in the table indicate significant differences in the data within the same column. p<0.05 The same letter indicates that the differences in the same column are not significant. p>0.05 ), the same as in the table below.

[0041] Table 2 shows that among the seven *Lactobacillus plantarum* strains, strains LXC and LT304 had higher total acid content and stronger acid production capacity, followed by strain LT400. Strains XD and SD had the lowest total acid content, while strains LT303 and XC2 had relatively weak total acid content. In terms of pH, strain XD had the highest total acid content, followed by strain SD. After screening, the four strains with the highest total acid content—strains LXC, LT303, LT304, and LT400—were selected for sauerkraut fermentation experiments.

[0042] Example 3

[0043] This example describes the sauerkraut fermentation experiment using strains LXC, LT303, LT304, and LT400, as detailed below:

[0044] Four bacterial strains were inoculated into mustard greens for sauerkraut fermentation experiment and compared with CK (fermentation group without any bacterial strains) as control. After 20 days of fermentation, the total acid, color difference and texture index of the finished vegetables were measured. The specific results are shown in Tables 3 and 4.

[0045]

[0046] Table 3 shows that different strains have different effects on... The value has no effect. p>0.05 );exist Regarding values, there were no significant differences between CK, strain LXC, strain LT400, strain LT304, and strain LT303. p>0.05 However, strains LT304 and LT303 showed significant differences. p<0.05 );exist Regarding values, there were no significant differences between CK, strain LXC, strain LT303 and strain LT304, strain LT400. p>0.05 However, strains LT304 and LT400 showed significant differences. p<0.05 This indicates that strain LT303 reduces the brightness of sauerkraut, while strain LT304 increases the brightness of sauerkraut and alleviates the increase in yellowness.

[0047]

[0048] The effects of different bacterial strains on the texture of sauerkraut fermented with different strains on its quality were investigated in five aspects: hardness, elasticity, adhesiveness, cohesiveness, and chewiness. Table 4 shows that, in terms of hardness and chewiness, strains LXC and LT400 showed no significant differences compared to strains CK, LT303, and LT304. p>0.05 However, strains LXC and LT400 showed significant differences. p< 0.05In terms of hardness and chewiness, the order was LXC > CK > LT303 > LT304 > LT400. Strain LXC had a hardness of 535.60 g and a chewiness of 3.52 mJ, while strain LT400 had a hardness of 377.75 g and a chewiness of 2.30 mJ. Regarding elasticity, there was no significant difference among the five strains. p>0.05 In terms of adhesiveness, CK showed the highest level, with strains LT304 and LT400 showing significant differences from CK and LXC. Regarding cohesion, strain LT304 showed the highest level, with a significant difference from CK.

[0049] Example 4

[0050] This example demonstrates the testing of amino acid content in fermented sauerkraut.

[0051] Strains LXC, LT303, LT304, and LT400 were inoculated into mustard greens as experimental groups, while mustard greens without any added strains were used as the CK (control) group. The mustard greens in each group were fermented in a direct-inoculation fermenter for 20 days, and the content of sweet amino acids in the fermentation broth was tested. The test results are shown in Table 5.

[0052]

[0053] In sauerkraut products, the higher the content of sweet amino acids, the better the savory and sweet taste. In the above experimental results, we found that only threonine and serine were detected in the sauerkraut fermentation broth of the CK (control) group, while threonine, alanine, serine, and glycine were detected in the sauerkraut fermentation broth of strain LXC, threonine, alanine, serine, glycine, and proline were detected in the sauerkraut fermentation broth of strain LT303, threonine, alanine, serine, and glycine were detected in the sauerkraut fermentation broth of strain LT304, and threonine and alanine were detected in the sauerkraut fermentation broth of strain LT400. This indicates that the types of amino acids produced by the sauerkraut fermentation broth of different strains are also different due to their different metabolic capabilities. In terms of content, the content of sweet amino acids: threonine, alanine, serine, glycine, and proline in the sauerkraut fermentation broth of strain LT303 was significantly higher than that in other experimental groups. This indicates that the sauerkraut fermented by strain LT303 has the sweetest and freshest taste, and the richest content of sweet amino acids. Therefore, the research group selected strain LT303 for the next experiment.

[0054] Example 5

[0055] This embodiment tests the antibacterial effect of strain LT303 against common pathogenic bacteria.

[0056] 1. Determination of the inhibitory effect of the strain on pathogens: The inhibitory effect of strain LT303 on Salmonella enteritidis (Salmonella enteritidis) was determined using the perforated agar diffusion method. Salmonella enterica subsp. enterica serovar EnteritidisEscherichia coli ( Escherichia coli Staphylococcus aureus Staphylococcus aureus ) and Listeria monocytogenes ( Listeria monocytogenes The antibacterial activity of the inhibition zone was measured by measuring the diameter of the transparent zone (diameter of inhibition zone = measurement diameter - pore diameter), and the results are shown in Table 6.

[0057]

[0058] Note: “—” in the table indicates no inhibitory effect.

[0059] As shown in Table 6, strain LT303 had no inhibitory effect on the above four pathogens: Salmonella enteritidis, Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes, and had no antibacterial effect on other pathogens.

[0060] 2. Determination of the inhibitory effect of fermented sauerkraut broth on pathogens: A sample of sauerkraut fermentation broth was centrifuged at room temperature to remove the lower layer of impurities and bacterial sludge, retaining the supernatant. The broth was then concentrated using a vacuum water bath rotary evaporator at a series of temperature gradients until the volume was 1 / 10 of the original broth. (NH4)2SO4 solution was added to the concentrate for gradient salting out (salting out concentration gradients: 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, and 55%). After salting out, the centrifuge tubes were centrifuged, and the supernatant was subjected to a second salting out and centrifugation until no more precipitate appeared. The amount of precipitate from the gradient concentration salting out is shown in Table 7. Then, the precipitate samples were used for a filter paper disc antibacterial test. The specific method was as follows: a centrifuge tube with precipitate was taken, and the supernatant and precipitate were used as test samples. (NH4)2SO4 of the same concentration was used as a blank for the antibacterial test, and the size of the inhibition zone was observed. The results are shown in Table 8.

[0061]

[0062] As shown in Table 7, precipitates only formed in the sauerkraut fermentation broth at concentrations of 25% and 40%, with the highest salt precipitation at 25% concentration, followed by 40%. No precipitates formed at other concentrations.

[0063]

[0064] Note: The significance of different bacteria and different salting-out concentrations in the table was analyzed by grouping.

[0065] Table 8 shows that at a salting-out concentration of 25%, Salmonella enteritidis (… Salmonella enterica subsp. enterica serovar Enteritidis The supernatant and the inhibition zone of the precipitate were significantly different from those of the blank. p<0.05At a salting-out concentration of 40%, Salmonella enteritidis ( Salmonella enterica subsp. enterica serovar Enteritidis The inhibition zone of the supernatant was not significantly different from that of the blank. p>0.05 The precipitated inhibition zone was significantly different from the blank. p<0.05 The fermented sauerkraut broth is effective against Salmonella enteritidis (Salmonella enteritidis). Salmonella enterica subsp. enterica serovar Enteritidis It has antibacterial properties.

[0066] At salting-out concentrations of 25% and 40%, the supernatant and precipitate showed effects on Escherichia coli (Escherichia coli). Escherichia coli The inhibition zone of the sample was not significantly different from that of the control. p>0.05 This indicates that the fermentation broth of sauerkraut at two concentrations has an effect on Escherichia coli (Escherichia coli). Escherichia coli It has no antibacterial effect.

[0067] At a salting-out concentration of 25%, the supernatant showed resistance to Staphylococcus aureus (Staphylococcus aureus). Staphylococcus aureus No significant antibacterial effect. p<0.05 ), precipitation of Staphylococcus aureus ( Staphylococcus aureus Significant antibacterial effect ( p< 0.05 At a salting-out concentration of 40%, the supernatant and precipitate showed resistance to Staphylococcus aureus (Staphylococcus aureus). Staphylococcus aureus The inhibition zone of the sample was significantly different from that of the control. p<0.05 This indicates that precipitation at both concentrations is effective against Staphylococcus aureus (Staphylococcus aureus). Staphylococcus aureus It has antibacterial effects.

[0068] At salting-out concentrations of 25% and 40%, the supernatant and precipitate showed effects on Listeria monocytogenes (…). Listeria monocytogenes The inhibition zone of the sample was significantly different from that of the control group. p<0.05 ).

[0069] Therefore, in this embodiment, strain LT303 has no inhibitory effect on the above four pathogens, but after fermentation of sauerkraut, the fermentation broth has an inhibitory effect on Salmonella enteritidis (Salmonella enteritidis). Salmonella enterica subsp. enterica serovar Enteritidis Staphylococcus aureus Staphylococcus aureus ) and / or Listeria monocytogenes ( Listeria monocytogenes It has antibacterial effects against Escherichia coli (Escherichia coli). Escherichia coli It has no antibacterial effect.

[0070] Example 6

[0071] This example studies the fermentation effect of strain LT303 after the addition of flavoring substances.

[0072] In the fermentation process of sauerkraut, a single raw material is usually selected. However, Guangxi is rich in many fruits. If fruits and vegetables can be used to prepare fermented sauerkraut, the quality of sauerkraut can be further improved. However, if fruits are added directly to vegetables, the sugar content of the fruits is too high and they are easy to rot, resulting in a poor taste after fermentation. Therefore, we considered extracting some fruit juice and mixing it with vegetables for soaking and fermentation to study the feasibility of preparing fruit-flavored sauerkraut. Therefore, we selected local fruits in Guangxi (citrus, monk fruit, lychee, mango, dragon fruit, and banana) as auxiliary materials to ferment and produce fruit-flavored sauerkraut. The specific research plan is as follows.

[0073] Selected fruit juices active against strain LT303: Fresh monk fruit, peeled citrus, peeled and pitted lychee, peeled and pitted mango, peeled dragon fruit, and peeled banana were placed in a high-speed blender for blending (solid-liquid ratio of 5:1), filtered, and the filtrates were used to obtain monk fruit juice, citrus juice, lychee juice, mango juice, dragon fruit juice, and banana juice. These were added to liquid MRS medium at a 1:1 ratio to prepare experimental group culture media, with the liquid MRS medium as the control group. After fermentation with strain LT303 for 48 hours, the viable cell count of each experimental group was calculated using the plate count method. The specific results are shown in Table 9.

[0074]

[0075] As shown in Table 9, among the fruit juices, mango juice, dragon fruit juice, and monk fruit juice had significant effects on increasing the bacterial count of strain LT303. p <0.05 Other fruit juices did not enhance the growth of strain LT303, while citrus juice and lychee juice significantly inhibited its growth. p<0.05 This indicates that not all fruit juices are suitable for fermentation with strain LT303. Therefore, mango juice, dragon fruit juice, and monk fruit juice are preferred for preparing fruit-flavored sauerkraut. The specific scheme is as follows.

[0076] After washing the whole mustard greens, they were placed in a fermentation tank for pickling. Then, mango juice, dragon fruit juice, and monk fruit juice were mixed at a solid-liquid mass ratio of 5:1 and the mixture was broken down. The mixture was then filtered and the filtrate was added to the mustard greens. Strawberry strain LT303 was inoculated at a mass ratio of 2% and the mixture was pickled and fermented for 15 days to obtain fruit-flavored pickled vegetables. The mustard greens group that were inoculated with strain LT303 without adding fruit juice served as the control group. As we know from the previous study, strain LT303 can significantly improve the texture of pickled vegetables and the amino acid content of the fermentation liquid. Therefore, this example mainly tested the texture of different pickled vegetables and the amino acid content in the fermentation liquid. The results are shown in Tables 10 and 11.

[0077]

[0078] Note: Different lowercase letters in the table indicate significant differences in the data within the same column. p<0.05 The same letter indicates that the differences in the same column are not significant. p>0.05 ), the same as in the table below.

[0079] As shown in Table 10, the hardness, elasticity, adhesiveness, cohesiveness, and chewiness of the mango-pickled cabbage, dragon fruit-pickled cabbage, and monk fruit-pickled cabbage experimental groups were significantly higher than those of the control group-pickled cabbage in the fruit juice. p<0.05 This indicates that the addition of mango juice, dragon fruit juice, and monk fruit juice can increase the hardness and crispness of sauerkraut. This may be because the pectin in mango juice, dragon fruit juice, and monk fruit juice undergoes gelation with the fermentation of sauerkraut, thereby improving the texture of the sauerkraut.

[0080]

[0081] As shown in Table 11, compared with the control group-pickled cabbage, the experimental groups of mango-pickled cabbage, dragon fruit-pickled cabbage, and monk fruit-pickled cabbage showed significantly increased contents of threonine, alanine, serine, glycine, and proline in the fruit juice. p<0.05 This may be because mango juice, dragon fruit juice, and monk fruit juice increased the viable count of strain LT303, thereby increasing the content of sweet amino acids in the fermentation liquid, enhancing the sweetness of the sauerkraut, and improving its taste.

[0082] Therefore, in summary, the addition of mango juice, dragon fruit juice, and monk fruit juice can effectively enhance the sweetness of sauerkraut fermented by strain LT303 and increase its fruit aroma, indicating that the production of fruit-flavored sauerkraut can effectively enrich sauerkraut products and increase their value.

[0083] In summary, the *Lactobacillus plantarum* strain LT303 of this application has no significant inhibitory effect on pathogens, but this strain, together with the fermentation products of mustard fermentation, has an effect on *Salmonella enteritidis* (…). Salmonella enterica subsp. enterica serovar Enteritidis Staphylococcus aureus Staphylococcus aureus ) and / or Listeria monocytogenes ( Listeria monocytogenes The sauerkraut prepared by fermentation of strain LT303 has an antibacterial effect; and the contents of sweet amino acids such as threonine, alanine, serine, glycine and proline in the sauerkraut prepared by fermentation of strain LT303 are significantly higher than those in other experimental groups, indicating that the sauerkraut fermented by strain LT303 has the sweetest and freshest taste and the richest content of sweet amino acids; in addition, the juice enrichment test found that mango juice, dragon fruit juice and monk fruit juice can effectively increase the viable count of strain LT303. The sauerkraut prepared by adding mango juice, dragon fruit juice and monk fruit juice has a stronger texture. In addition, the content of sweet amino acids is significantly increased. This indicates that adding mango juice, dragon fruit juice and monk fruit juice to sauerkraut prepared by fermentation of strain LT303 can improve the taste and texture of sauerkraut, effectively enrich the sauerkraut product and increase the value of the product.

[0084] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A strain of Lactobacillus plantarum ( Lactiplantibacillus plantarum The strain LT303, with accession number GDMCC NO: 66635, is deposited at Guangdong Provincial Center for Microbial Culture Collection, located at the Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, on July 3, 2025.

2. Contains *Lactobacillus plantarum* as described in claim 1 ( Lactiplantibacillus plantarum Sauerkraut fermentation broth of strain LT303.

3. The *Lactobacillus plantarum* as described in claim 1 ( Lactiplantibacillus plantarum Application of strain LT303 in improving the sweet amino acid content of sauerkraut fermentation broth.

4. The application according to claim 3, characterized in that, The sweet amino acids are threonine, alanine, serine, glycine, and / or proline.

5. The (NH4)2SO4 salting-out extract of the sauerkraut fermentation broth as described in claim 2 inhibits Salmonella enteritidis (NH4)2SO4 salting-out extract. Salmonella enterica subsp. enterica serovar Enteritidis Staphylococcus aureus Staphylococcus aureus ) and / or Listeria monocytogenes ( Listeria monocytogenes Applications during growth.

6. The application according to claim 5, characterized in that, The mass concentration of (NH4)2SO4 during salting out is 25% or 40%.

7. The *Lactobacillus plantarum* as described in claim 1 ( Lactiplantibacillus plantarum Application of strain LT303 in the preparation of fruit-flavored sauerkraut.

8. The application as described in claim 7, characterized in that, The fruits mentioned are mango, dragon fruit, and / or monk fruit.

9. A method for preparing fruit-flavored sauerkraut as described in claim 8, characterized in that, The method is as follows: After washing the whole mustard greens, place them in a fermentation tank for pickling. Then, break down the cell walls of mango, dragon fruit, or monk fruit at a solid-liquid mass ratio of 5:1, filter the solution, and obtain mango juice, dragon fruit juice, or monk fruit juice. Add the mango juice, dragon fruit juice, or monk fruit juice to the mustard greens in the fermentation tank, and inoculate with *Lactobacillus plantarum* as described in claim 1 at an inoculation rate of 2% by mass. Lactiplantibacillus plantarum The strain LT303 is obtained by pickling and fermenting for 15 days.

10. Application of *Lactobacillus plantarum* as described in claim 2 ( Lactiplantibacillus plantarum A method for preparing (NH4)2SO4 salting-out extract from sauerkraut fermentation broth of strain LT303, characterized in that, The method is as follows: measure the sauerkraut fermentation broth, centrifuge it at room temperature to remove the lower impurities and bacterial sludge mixture, retain the upper clear liquid, and then concentrate it to 1 / 10 of the original volume using a vacuum water bath rotary evaporator under a series of temperature gradients to obtain a concentrated liquid. Then, add a (NH4)2SO4 solution with a mass concentration of 25% or 40% to the concentrated liquid for salting out. After salting out, centrifuge it in a centrifuge tube, take the supernatant for secondary salting out and centrifugation until no more precipitation occurs.

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