A strain of Lactobacillus argenteus and its application in vegetable fermentation

Abstract

The invention discloses a strain of Lactobacillus argentoratensis and its application in vegetable fermentation, belonging to the technical field of microbial fermentation. The Lactobacillus argentoratensis has been deposited in the General Microbiological Center of China Microbiological Culture Collection Administration Committee, with a deposit number of CGMCC No. 28711. The invention separates a strain of Lactobacillus argentoratensis GXUN74705, artificially inoculates the strain into a mustard fermentation system, significantly reduces the pH value of the fermentation system, and significantly inhibits the synthesis of nitrite during the mustard fermentation process, thereby improving the safety of the product; the strain also accelerates the utilization of glucose in the mustard fermentation system, shortens the mustard fermentation time; and also obtains a mustard product with a better taste quality than traditional natural fermentation, and has good application prospects in mustard fermentation.

Description

Technical Field

[0001] The invention relates to the technical field of microbial fermentation, in particular to a strain of Lactobacillus argenteus and application thereof in vegetable fermentation. Background Art

[0002] Fermented vegetable foods are a type of vegetable processed products that are deeply loved by the Chinese people. They contain high levels of probiotics, vitamins and minerals, and have the effects of promoting weight loss, antioxidant, anti-cancer activity and lowering cholesterol, making fermented vegetable foods increasingly popular among people.

[0003] A certain amount of nitrite will be produced during the traditional vegetable fermentation process. If a large amount of food containing nitrite is consumed for a long time, the acidic environment of the human gastrointestinal tract will convert nitrite into nitrosamines, which have strong carcinogenic and teratogenic effects. Therefore, inhibiting the synthesis of nitrite during vegetable fermentation and reducing the nitrite content in vegetable fermented foods are urgent issues to be solved. In addition, the traditional vegetable fermentation process is complex and difficult to control, the product is greatly affected by external factors, the quality is unstable, and different vegetables have different fermentation times, which seriously affects the quality of vegetable fermented products.

[0004] At present, the methods for reducing the nitrite content in vegetable fermented foods and improving the quality of vegetable fermented products mainly include artificial inoculation and fermentation during the vegetable fermentation production process. Lactic acid bacteria are present in almost all vegetable fermented foods. They can produce a variety of organic acids by fermenting reducing sugars and other raw materials, thereby reducing the pH value of the food. High concentrations of acid inhibit the growth of bacteria and molds, thereby improving the shelf life and safety of the food. Therefore, artificial inoculation of lactic acid bacteria for vegetable fermentation can accelerate the reproduction of beneficial microorganisms, inhibit the synthesis of nitrite, promote the fermentation process, improve the quality of the product, and improve the safety of the product. For this reason, it is very necessary to develop new, safe and reliable vegetable fermentation agents. Summary of the invention

[0005] The purpose of the present invention is to provide a strain of Lactobacillus argenteus and application thereof in vegetable fermentation, so as to solve the problems existing in the above-mentioned prior art. The Lactobacillus argenteus provided by the present invention not only reduces the pH value of the mustard fermentation system and inhibits the synthesis of nitrite during the mustard fermentation process, but also accelerates the utilization of glucose in the mustard fermentation system, shortens the fermentation time, and improves the taste quality of the mustard fermented product, and has good application prospects in mustard fermentation.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a strain of Lactobacillus argentoratensis GXUN74705, which was deposited in the General Microbiology Center of China National Culture Collection Administration on October 23, 2023, with the deposit address at No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and the deposit number is CGMCC No. 28711.

[0008] The invention also provides a mustard starter, comprising the Lactobacillus argenteus GXUN74705.

[0009] The present invention also provides an application of the Lactobacillus argenteus GXUN74705 or the mustard fermentation agent in reducing the pH value of a mustard fermentation system.

[0010] Furthermore, the Lactobacillus argenteus GXUN74705 is inoculated into mustard in the form of a strain or a bacterial liquid for fermentation to reduce the pH value of the mustard fermentation system.

[0011] The present invention also provides an application of the Lactobacillus argenteus GXUN74705 or the mustard starter culture in reducing the nitrite content of fermented mustard.

[0012] Furthermore, the Lactobacillus argenteus GXUN74705 is inoculated into mustard in the form of a strain or a bacterial liquid for fermentation to inhibit nitrite synthesis during the fermentation process.

[0013] The present invention also provides an application of the Lactobacillus argenteus GXUN74705 or the mustard starter culture in shortening the fermentation time of pickled mustard.

[0014] Furthermore, the Lactobacillus argenteus GXUN74705 is inoculated into mustard in the form of a strain or a bacterial liquid for fermentation, thereby accelerating the utilization rate of glucose in the fermentation system and shortening the fermentation time of pickled mustard.

[0015] Furthermore, in terms of volume percentage, the inoculation amount of the Lactobacillus argenteus GXUN74705 is 6%.

[0016] The present invention discloses the following technical effects:

[0017] The present invention isolates a strain of Lactobacillus argentoratensis GXUN74705, which is artificially inoculated into a mustard fermentation system, thereby reducing the pH value of the mustard fermentation system, reducing the acidity of the fermented mustard, inhibiting the synthesis of nitrite, accelerating the utilization of glucose in the mustard fermentation process, shortening the fermentation time, and improving the quality of the mustard fermented product. The Lactobacillus argentoratensis provided by the present invention not only reduces the pH value of the mustard fermentation system, inhibits the synthesis of nitrite in the mustard fermentation process, but also accelerates the utilization of glucose in the mustard fermentation system, shortens the fermentation time, and improves the quality of the mustard fermented product, and has good application prospects in mustard fermentation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 is the phylogenetic tree of strain GXUN74705;

[0020] Figure 2 is the Gram staining image of strain GXUN74705;

[0021] Figure 3 This is a diagram showing the acid production effect of strain GXUN74705;

[0022] Figure 4 The fermentation diagrams of mustard with natural fermentation (A) and artificial inoculation of GXUN74705 (B) in Example 2;

[0023] Figure 5 This is a pH value detection diagram in the mustard fermentation system of natural fermentation and artificial inoculation of GXUN74705 in Example 2;

[0024] Figure 6 This is a graph showing the detection of nitrite content in the mustard fermentation system with natural fermentation and artificial inoculation of GXUN74705 in Example 2;

[0025] Figure 7 This is a graph showing the glucose content in the mustard fermentation system with natural fermentation and artificial inoculation of GXUN74705 in Example 2. DETAILED DESCRIPTION

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0028] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0029] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0030] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0031] The present invention provides a strain of Lactobacillus argentoratensis isolated from traditional fermented sauerkraut juice in Guangxi. The strain is named Lactiplantibacillus argentoratensis GXUN74705, and the deposit unit is the General Microbiological Center of China National Committee for the Preservation of Microbiological Cultures, and the deposit number is CGMCC No.28711. The strain is easy to culture, has a strong acid production ability, and significantly inhibits the synthesis of nitrite during mustard fermentation. It can be used as a mustard fermentation strain in the mustard fermentation industry. The Lactobacillus argentoratensis isolated by the present invention is artificially inoculated into mustard for fermentation. The pH value of the fermentation system is significantly lower than that of the natural fermentation system, which significantly inhibits the synthesis of nitrite during mustard fermentation, improves the safety of the product, and the strain also accelerates the utilization of glucose in the mustard fermentation system and shortens the mustard fermentation time; at the same time, a mustard fermentation product with better taste quality than traditional natural fermentation is also obtained. The specific research is as follows:

[0032] Example 1 Isolation, identification and preservation of strains

[0033] In this example, a strain was isolated and identified from pickled cabbage juice purchased from Luowen Farmers' Market in Xixiangtang District, Nanning City, Guangxi Zhuang Autonomous Region, and named GXUN74705. 16S rDNA sequencing was performed on it and a phylogenetic tree, Gram staining and acid production capacity were constructed.

[0034] The sequence obtained by 16S rDNA sequencing was compared with the 16S-based ID on the Ezbiocloud website, and it was found that its homology with Lactiplantibacillus argentoratensis was 100%. The neighbor-joining method (NJ method) was used to construct a phylogenetic tree for the sequence, as shown in Figure 2. Figure 1 As shown, strain GXUN74705 is most closely related to Lactiplantibacillus argentoratensis, from which it can be judged that the taxonomic status of strain GXUN74705 belongs to Lactiplantibacillus argentoratensis.

[0035] like Figure 2 As shown, the strain GXUN74705 was proved to be a Gram-positive bacterium by Gram staining.

[0036] like Figure 3 As shown, strain GXUN74705 was tested for its ability to survive in CaCO 3 -MRS solid medium, the size of the transparent zone, found that the strain has the ability to produce acid, and the acid production performance is good.

[0037] The above-mentioned strain GXUN74705 was identified as Lactiplantibacillus argentoratensis and was deposited in the General Microbiology Center of China Culture Collection Administration on October 23, 2023. The deposit address is No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, and the deposit number is CGMCC No. 28711.

[0038] Example 2 Pickled mustard greens

[0039] (I) Preparation of fermentation agent

[0040] (1) Streak Lactobacillus argenteus GXUN74705 on MRS solid medium and culture at 30°C for 48 h to obtain a single colony. Pick a single colony and inoculate it into MRS broth medium. Shake and culture at 30°C and 180 r / min until OD 600 =1.0 as seed solution.

[0041] (2) The seed liquid was transferred to 120 mL of MRS broth medium at a 2% (V / V) inoculum, and cultured at 30°C and 180 r / min for 24 h to obtain a bacterial solution. The bacterial solution was centrifuged at 8000 rpm for 10 min, the supernatant was removed, the bacteria were washed three times with saline, and then mixed with 50 mL of saline.

[0042] (ii) Pickling mustard greens and fermenting them naturally (see Figure 4 A) and artificial inoculation fermentation (see Figure 4 Middle B)

[0043] (1) Dried mustard greens (about 500 g) one day in advance;

[0044] (2) The night before, prepare 2L of water for washing rice, boil it and let it cool;

[0045] (3) Boil a pot of water, add peppercorns, blanch the mustard greens in boiling water until soft, and put them into the rice washing water prepared in advance;

[0046] (4) Sprinkle 3% (W / V) salt and 2% (W / V) brown sugar into mustard greens, mix well, and allow natural fermentation to proceed, serving as the control group;

[0047] Another batch of mustard was treated according to (1)-(4) above and inoculated with the above GXUN74705 fermentation agent at a 6% (V / V) inoculation rate for artificial inoculation and fermentation, which served as the experimental group;

[0048] (5) The rice washing water should cover the mustard greens. Press down with a heavy object, seal the jar, and start pickling.

[0049] (III) Detection of indicators during the fermentation process

[0050] 1. Determination of pH in mustard fermentation system

[0051] 10 mL of mustard fermentation broth samples were taken from the control group and the experimental group on days 0, 1, 3, 5, 7, 11, 15, 19 and 23 of inoculation; the pH was measured and recorded using a portable pH measuring instrument.

[0052] like Figure 5 As shown, in the mustard fermentation system artificially inoculated with strain GXUN74705, the pH value of the fermentation system was significantly lower than that of the natural fermentation system during the fermentation process.

[0053] 2 Determination of nitrite content in mustard fermentation system

[0054] 0.5 mL of mustard fermentation broth samples were taken from the control group and the experimental group on days 0, 1, 3, 5, 7, 11, 15, 19, and 23 of inoculation;

[0055] The nitrite content is measured by colorimetry based on the principle that nitrite can react with a color developer to generate a light red azo compound.

[0056] like Figure 6 As shown, the strain GXUN74705 was inoculated into freshly pickled mustard at an inoculation rate of 6% (V / V). At 1 day, 3 days, 5 days, 7 days, 11 days, 15 days, 19 days and 23 days after inoculation, the nitrite content in the fermentation system was extremely low and basically undetectable. However, in the natural fermentation (control group), different amounts of nitrite were synthesized in the fermentation system at 3 days, 5 days, 7 days, 11 days, 15 days and 19 days after fermentation. Among them, the nitrite content in the fermentation system reached about 308.6 μmol / L at 3 days of fermentation, and it was basically undetectable until 23 days later.

[0057] 3 Determination of glucose content in mustard fermentation system

[0058] 10 μL of mustard fermentation broth samples were taken from the control group and the experimental group on days 0, 1, 3, 5, 7, 11, 15, 19, and 23 of inoculation;

[0059] Through the glucose oxidase method, the glucose in the fermentation broth is acted upon by glucose oxidase to generate gluconic acid and hydrogen peroxide. The latter, under the action of peroxidase, couples and condenses the reduced 4-aminoantipyrine with phenol to form quinone compounds that can be measured by a spectrophotometer to detect the glucose content.

[0060] like Figure 7As shown, the strain GXUN74705 was inoculated into fresh pickled mustard at a 6% (V / V) inoculation rate. After 5 days of inoculation, the glucose in the fermentation system was basically completely consumed; while the glucose in the fermentation system was basically completely consumed after 7 days of natural fermentation (control group). It can be inferred that when fermenting mustard, artificial inoculation of strain GXUN74705 accelerated the utilization of glucose and shortened the fermentation time.

[0061] Example 3 Determination of Taste Quality of Fermented Mustard Products

[0062] The Lactobacillus argenteus was inoculated into mustard at an inoculation rate of 6% (V / V) for fermentation. After 20 days of fermentation, 10 well-trained experts evaluated the mustard fermentation products of natural fermentation and artificial inoculation of strain GXUN74705 in a standard room (without interference, noise, visual stimulation and other environmental factors). The evaluation was mainly conducted through the evaluation of the color, odor, hardness, crispness, juiciness, sourness, astringency and overall quality of the fermented mustard products. The evaluation criteria were as follows: Color evaluation: 10 points for turquoise or yellow-green, and 0 point for brown; Odor evaluation: 10 points for an unpleasant taste, 0 point for obvious sourness and a light fragrance; Hardness evaluation: 10 points for a product that needs to be crushed by hand with force, and 0 point for being too soft; Crispness evaluation: 10 points for a crisp sound when chewed, and 0 point for being too soft; Juiciness evaluation: 10 points for juice flowing out when chewed, and 0 point for being very dry and without moisture; Sourness evaluation: 10 points for obvious sourness, and 0 point for no sourness; Astringency evaluation: 10 points for obvious astringency, and 0 point for no astringency; Overall quality: 10 points for being very satisfied with the overall evaluation of the sauerkraut, and 0 point for being dissatisfied.

[0063] The results showed (see Table 1) that the strain GXUN74705 was inoculated into freshly pickled mustard at a 6% (V / V) inoculation rate. After 20 days of fermentation, 10 well-trained experts evaluated and found that the overall quality evaluation of the control group was 4 points, and the overall quality evaluation of the fermented mustard inoculated with the strain GXUN74705 was 6.4 points. The taste quality of the product was better than that of traditional naturally fermented mustard products.

[0064] Table 1 Evaluation of taste quality of fermented mustard

[0065]

[0066] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A strain of Lactiplantibacillus argentoratensis GXUN74705, characterized in that: It was deposited at the General Microbiology Center of China Microorganism Culture Collection Administration on October 23, 2023, with the deposit address at No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, and the deposit number is CGMCC No.28711.

2. A mustard fermentation agent, characterized in that: It comprises the Lactobacillus argenteus GXUN74705 described in claim 1.

3. Use of the Lactobacillus argenteus GXUN74705 according to claim 1 or the mustard starter culture according to claim 2 in lowering the pH value of a mustard fermentation system.

4. The use according to claim 3, characterized in that: The Lactobacillus argenteus GXUN74705 is inoculated into mustard in the form of a strain or a bacterial liquid for fermentation to reduce the pH value of the mustard fermentation system.

5. Use of the Lactobacillus argenteus GXUN74705 according to claim 1 or the mustard starter culture according to claim 2 in reducing the nitrite content of fermented mustard.

6. The use according to claim 5, characterized in that: The Lactobacillus argenteus GXUN74705 is inoculated into mustard in the form of a strain or a bacterial liquid for fermentation to inhibit nitrite synthesis during the fermentation process.

7. Use of the Lactobacillus argenteus GXUN74705 according to claim 1 or the mustard starter culture according to claim 2 in shortening the fermentation time of pickled mustard.

8. The use according to claim 7, characterized in that: The Lactobacillus argenteus GXUN74705 is inoculated into mustard in the form of a strain or a bacterial liquid for fermentation, thereby accelerating the utilization rate of glucose in the fermentation system and shortening the fermentation time of pickled mustard.

9. The use according to claim 8, characterized in that: In terms of volume percentage, the inoculation amount of the Lactobacillus argenteus GXUN74705 is 6%.

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