Lactobacillus farciminis SR2 and use thereof

Abstract

Disclosed are a lactobacillus farciminis SR2 and a use thereof. The present lactobacillus farciminis SR2 shows good tolerance under an acidic condition of pH = 3.0, has strong adaptability in 45 C° high-temperature and high salt (10% NaCl) environment, inhibits the growth of harmful bacteria such as escherichia coli, staphylococcus aureus, and salmonella, has high productivity of ferulic acid esterase, can significantly lower the pH level of rice straw silage feed, significantly increase the content of lactic acid, significantly reduce the content of ammonia nitrogen, significantly increase the content of dry matter and WSC, significantly reduce the content of NDF, ADF and cellulose, improve the fermentation quality of the rice straw silage feed, and the method can be widely applied to the field of rice straw fermentation feed preparation.

Description

A kind of Lactobacillus sausage SR2 and its application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on May 9, 2022, with application number CN202210500994.8 and invention name “A sausage Lactobacillus and its application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The invention belongs to the technical field of lactobacillus, and particularly relates to a Lactobacillus sausage SR2 and an application thereof. Background Art

[0003] my country is a major producer of herbivorous livestock, and the balanced supply of high-quality silage has become a bottleneck restricting the healthy development of the mutton industry. Therefore, fully utilizing and developing the vast potential of unconventional feed resources in agricultural areas has become a top priority. Comprehensive straw management has become a top priority, with prohibitions on straw burning and disposal and its comprehensive utilization becoming crucial for promoting ecological progress and efficient resource utilization. Given the current shortage of roughage resources facing my country's livestock industry, the rational and effective development and utilization of straw is a key direction for its development.

[0004] Rice straw comprises over 80% cell wall components. The unique structure of these cell walls (a hierarchical and condensed cellulose structure) limits its digestibility and utilization in animals. Furthermore, due to its hard, rough texture, low crude protein content, and the encapsulation of hemicellulose and cellulose by lignin, rice straw has a poor palatability and is difficult to maximize. Fermentation not only promotes the conversion of crude fiber in rice straw into carbohydrates, enhancing its nutritional value, but also improves its palatability. However, due to the low number of lactic acid bacteria naturally attached to rice straw stems and leaves, and the low soluble carbohydrate (WSC) content, it is difficult to produce high-quality silage from ensilage alone. In practice, secondary fermentation and mold are inevitable in silage, influenced by management conditions and weather. This moldy silage not only results in a loss of nutritional value but can also cause problems such as decreased milk production, diarrhea, miscarriage, and mastitis in livestock, impacting their performance. Therefore, identifying high-quality lactic acid bacteria agents is crucial.

[0005] Summary of the Invention

[0006] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0007] The invention provides a Lactobacillus sausage SR2, and the preservation number of the Lactobacillus sausage SR2 is CCTCC NO: M 2022416.

[0008] The present invention also provides application of the Lactobacillus sausage SR2 as a plant feed additive.

[0009] Preferably, the Lactobacillus sausage SR2 is used for plant feed silage.

[0010] Preferably, the Lactobacillus sausage SR2 can produce a high amount of feruloyl esterase.

[0011] Preferably, the Lactobacillus sausage SR2 increases the lactic acid content in plant feed, reduces the acetic acid content in plant feed, and reduces the ammoniacal nitrogen content.

[0012] Preferably, the Lactobacillus sausage SR2 inhibits the production of aerobic bacteria and yeast in silage.

[0013] Preferably, the Lactobacillus sausage SR2 significantly increases the dry matter and WSC contents, and significantly reduces the NDF, ADF, and cellulose contents.

[0014] Preferably, the plant feed comprises rice straw.

[0015] The present invention also provides the use of the Lactobacillus sausage SR2 in preparing an antibacterial preparation.

[0016] Preferably, the Lactobacillus sausage SR2 inhibits Escherichia coli, Salmonella and Staphylococcus aureus.

[0017] The present invention also provides an antibacterial preparation, the active ingredient of which includes the Lactobacillus sausage SR2 described in the above technical solution.

[0018] The beneficial effects of the present invention are as follows: the Lactobacillus sausage SR2 provided by the present invention exhibits good tolerance under acidic conditions (pH = 3.0), has strong adaptability in a high temperature of 45°C and a high salt (10% NaCl) environment, can inhibit the growth of harmful bacteria such as Escherichia coli, Staphylococcus aureus and Salmonella, and has the ability to produce high levels of ferulic acid esterase, can significantly reduce the pH of rice straw silage, significantly increase the lactic acid content, significantly reduce the ammonia nitrogen content, significantly increase the dry matter and WSC content, significantly reduce the NDF, ADF and cellulose content, improve the fermentation quality of rice straw silage, and can be widely used in the field of rice straw fermented feed preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly describes the drawings used in describing the embodiments. Obviously, the drawings described below represent only some embodiments of the present invention, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0020] Figure 1 is the FA standard curve;

[0021] Figure 2 shows the transparent zone screening of feruloyl esterase-producing strains, wherein a is a dilution coating diagram of lactic acid bacteria, and b is the transparent zone produced by the feruloyl esterase-producing strain on the plate;

[0022] Figure 3 is a morphological identification diagram, where a is the SR1 colony characteristics, b is the SR2 colony characteristics, c is the SR1 microscopic morphology (100×), and d is the SR2 microscopic morphology (100×);

[0023] FIG4 is a growth curve diagram of the SR1 strain;

[0024] FIG5 is a growth curve of the SR2 strain.

[0025] Biological Deposit Description

[0026] Lactobacillus farciminis SR2 was deposited in the China Center for Type Culture Collection (CCTCC), Wuhan University, Wuhan, China on April 14, 2022, with the deposit number CCTCC No: M 2022416. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0030] Example 1

[0031] Isolation and identification of Lactobacillus sausage:

[0032] 1. Separation method:

[0033] 1.1 Sample processing:

[0034] Select healthy Hu sheep, use a rumen catheter to collect gastric juice from the reserved hole in the stomach, place it in a sterile thermos, and quickly bring it back to the laboratory. On the clean bench, use sterile gauze to filter it, and then dilute it in a gradient manner.

[0035] 1.2 Initial Screening for Feruloyl Esterase-Producing Strains: Select three appropriate gradients and apply 100 μL of each dilution onto MRS medium plates using the three-point method. Spread evenly and incubate in an inverted, anaerobic manner at 37°C for 48 hours. Select colonies of varying morphology and repeatedly streak them onto MRS medium until a purified single colony is obtained. Use a sterile toothpick to pick a single colony and spot-spot it onto screening medium. Incubate at 30°C for 12-72 hours and observe for the appearance of a distinct clear zone on the plate. If a clear zone appears, the strain is preliminarily considered to have the ability to produce FAE. Furthermore, perform Gram staining and H2O2 enzyme tests on the screened strains to observe whether the strains appear as purple single cells under microscopic examination and whether the H2O2 enzyme reaction is negative. If these characteristics are met, the strain is considered a lactic acid bacterium.

[0036] 1.3 Rescreening of feruloyl esterase-producing strains:

[0037] (1) Preparation of FA standard curve: Take 6 100 mL volumetric flasks, number them from 1 to 5, add reagents according to Table 1, and make 3 parallels for each group.

[0038] Table 1 Preparation of FA standard curve

[0039]

[0040] After mixing according to the above steps, the mixture was filtered through a 0.22 μm membrane and subjected to high performance liquid chromatography (HPLC) determination. The measured values ​​were used to draw a standard curve for ferulic acid, as shown in Figure 1.

[0041] As shown in Figure 1, the functional equation of FA is y=58.225x-392.6, and the correlation coefficient between FA concentration (50-200 μg / mL) and peak area is R 2 =0.9980, which has a good linear relationship and can be used for the subsequent determination of FAE enzyme activity of strains.

[0042] (2) Preparation of fermentation broth: Transfer the FAE-producing lactic acid bacteria screened initially into MRS liquid culture medium, culture at 37°C overnight, wash 2-3 times with 90% sterile saline, and resuspend the cells in deionized water. Transfer the bacterial suspension to fresh enzyme-producing liquid culture medium at a 5% inoculum volume for fermentation, culture at 37°C for 48 hours, and measure the FAE activity of the screened lactic acid bacteria for reference in further screening. Centrifuge the test solution at 8000-12000 rpm / min for 5 minutes to obtain the supernatant fermentation broth.

[0043] (3) Enzyme activity determination: Take 2 test tubes, add reagents according to Table 2, and perform 3 parallel assays for each group.

[0044] Table 2 FAE activity determination table

[0045]

[0046] After completing the above steps, boil the mixture in a boiling water bath for 10 minutes, centrifuge at 8,000-12,000 rpm / min for 5 minutes, filter the supernatant, and perform HPLC analysis. Calculate the concentration of ferulic acid based on the standard curve. One enzyme activity unit (U) is defined as the amount of enzyme required to decompose FAE and produce 1 μmol of FA per minute. The calculation formula is:

[0047] Enzyme activity (mU / mL) = ferulic acid content in the reaction solution (μg) / ferulic acid molar mass × reaction time (min)

[0048] (4) HPLC chromatographic conditions:

[0049] C18 column: Synergi Hydro-RP80 (250×4.6mm 4um)

[0050] Mobile phase: A-methanol; B-1% glacial acetic acid (28:72)

[0051] Flow rate: 0.6 mL / min

[0052] Column temperature: 40°C

[0053] Detection wavelength: UV320nm

[0054] Injection volume: 10 μL.

[0055] Screening results of ferulic acid esterase-producing strains:

[0056] In this experiment, the rumen fluid of Hu sheep was treated and diluted and spread on MRS medium. After separation and purification, 156 lactic acid bacteria were obtained. The 156 lactic acid bacteria were respectively inoculated on screening plates with ethyl ferulate as the sole carbon source. After 12 hours of culture, it was found that only two strains numbered SR1 and SR2 produced large transparent circles. It can be preliminarily judged that strains SR1 and SR2 can utilize the carbon source ethyl ferulate and may have FAE activity. The diameters of the transparent circles of SR1 and SR2 were 8mm and 12mm respectively. Compared with strain SR1, the diameter of strain SR2 was larger, indicating that the strain had better performance in degrading ethyl ferulate. The specific transparent circle results are shown in Figure 2, where Figure 2a is the dilution coating diagram of lactic acid bacteria; Figure 2b is the transparent circle produced by the ferulic acid esterase-producing strain on the plate. In addition, based on the initial screening results of the clear zone, the fermentation broths of strains SR1 and SR2 were subjected to high-performance liquid chromatography according to step 1.3, revealing that both strains SR1 and SR2 had feruloyl esterase (FAE) activity, with strain SR2 having a higher enzyme activity than SR1, at 10.36 mU / mL. The results are shown in Table 3. As can be seen from Table 3, strain SR2 had a high feruloyl esterase activity of 10.36 mU / mL, higher than that of strain SR1, and higher than the enzyme activities of existing feruloyl esterases produced by Lactobacillus plantarum (enzyme activity 8.34 mU / mL), Pediococcus acidilactici (enzyme activity 5.12 mU / mL), and Lactobacillus brevis (enzyme activity 7.56 mU / mL).

[0057] Table 3 Clear zone size of strains and their enzyme activity determination

[0058]

[0059] 2. Identification of high-yielding ferulic acid esterase strains:

[0060] 2.1 Morphological identification

[0061] Take a loop of FAE-producing lactic acid bacteria and streak it on MRS medium, invert it at 37°C, and specifically, streak the strains SR1 and SR2 on MRS medium containing agar, culture them anaerobically at 37°C for 48 hours, and observe the shape, color, size, and edge characteristics of the colonies. At the same time, take a single colony and stain it with a Gram staining kit (Beijing Solebold Technology Co., Ltd.) to examine the bacterial morphology under a microscope. The results are shown in Figure 3. Specifically, the colony characteristics are shown in Figure 3 a and b. The results show that strain SR1 forms milky white, round, regular-edged, centrally raised, and glossy colonies on the plate. Strain SR2 is a milky white colony with a slightly raised center, but its edges are irregular and the surface is moist and flat. The smear staining results after 48 hours of culture are shown in Figure 3 c and d. The results show that both SR1 and SR2 are G+ short rods under microscopy.

[0062] 2.2 Growth curve determination:

[0063] Take a ring of lactic acid bacteria and inoculate it into MRS liquid culture medium, culture it at 37℃ for 48h; then take the bacterial suspension and inoculate it (according to 5% inoculation volume) into liquid culture medium, culture it at 37℃ for 0-24h, and measure its OD every two hours. 600 nm value and pH value, and draw the growth curve of the strain. The results are shown in Figures 4 and 5.

[0064] Figures 4 and 5 show that the pH of the culture medium gradually decreased as strain SR1 grew, likely due to the production of metabolites such as lactic acid during growth. The accumulation of lactic acid in the culture medium is related to the incubation time of strain SR1. Longer incubation times increase lactic acid production, leading to a continuous decrease in the pH of the culture medium and disrupting the growth and metabolism of the strain. Based on the OD values, strain SR1 grew slowly from 0 to 2 hours, entering a stagnant phase. From 2 to 16 hours, strain SR1 entered a logarithmic phase with the fastest growth rate. After 16 hours, it entered a plateau phase, with growth gradually stabilizing. After 24 hours, the final pH of strain SR1 was 3.94. Strain SR2 utilizes sugars to produce lactic acid during its growth, which continuously increases the acidity of the culture medium, causing damage to the bacteria and inhibiting their growth. Judging from the OD value and pH, the reproduction speed of strain SR2 accelerated after 2 hours and entered the logarithmic growth phase. At the same time, the acid production ability also increased accordingly, and the pH value dropped rapidly; after 18 hours, it gradually stabilized and the pH value slowly decreased. After 24 hours, the final pH of strain SR2 was 3.83.

[0065] 2.3 Growth characteristics identification:

[0066] 2.3.1 Acid resistance test:

[0067] A loop of lactic acid bacteria was inoculated into MRS liquid culture medium and cultured at 37°C for 48 h. The bacterial suspension was then inoculated (at 5% inoculum) into MRS liquid culture medium with different pH values ​​(3.5, 4, 4.5, 5, 5.5, 6, and 6.5), cultured at 37°C for 48 h, and the growth of the strains was visually observed. The results are shown in Table 4.

[0068] 2.3.2 Temperature resistance test:

[0069] A ring of lactic acid bacteria was inoculated into MRS liquid culture medium and cultured at 37°C for 48 h. Then, the bacterial suspension was inoculated (at 5% inoculum size) into MRS liquid culture medium and cultured at different temperatures (5°C, 25°C, 30°C, 37°C, and 45°C), wherein the culture was performed at 5°C and 15°C for 120 h, at 25°C and 35°C for 48 h, and at 45°C for 96 h. The results are shown in Table 4.

[0070] 2.3.3 Salt tolerance test of strains:

[0071] A loop of lactic acid bacteria was inoculated into MRS liquid culture medium and cultured at 37°C for 48 h. The bacterial suspension was then inoculated (at a 5% inoculum size) into MRS liquid culture medium containing 3%, 6.5%, 10%, and 15% salt concentrations and cultured at 37°C for 48 h. The growth of the strains was visually observed. The results are shown in Table 4.

[0072] Table 4 Growth of strains under different conditions

[0073]

[0074] Note: -, no growth; +, weak growth; ++, normal growth; +++, good growth.

[0075] Table 4 shows that at pH 2.0, both strains failed to grow. At pH 3.0, SR1 grew weakly, while SR2 grew moderately. At pH 4.0-7.0, both strains grew well. At 5°C, both strains failed to grow, but grew well at 25-37°C and only weakly at 45°C. Both strains grew in culture medium containing 3% to 10% NaCl, but failed to grow at a salt concentration of 15%. This indicates that strain SR1 can grow well in MRS culture medium at a pH of 4.0-7.0, 25-37°C, and a 3% salt concentration. Strain SR2 has a higher acid tolerance than SR1 and can grow well in MRS culture medium at a pH of 3.0-7.0, 25-37°C, and a 3% salt concentration.

[0076] 2.3.4 Biochemical identification:

[0077] Single colonies of lactic acid bacteria were picked for biochemical testing. Bacterial biochemical identification tubes purchased from Hangzhou Tianhe were used for determination. The instructions in the reaction tube kit were followed and the culture was continued for 2 to 3 days. The reaction of the strain was recorded and the type of strain was estimated based on the "Classification and Identification of Lactic Acid Bacteria and Experimental Methods". The results are shown in Table 5.

[0078] Table 5 Biochemical reactions of strains

[0079]

[0080] Note: +, positive; -, negative.

[0081] As shown in Table 5, the biochemical tube reactions of SR1 and SR2 with lactose, sucrose, maltose, and glucose all showed yellow, indicating positive results. Nitrate reduction and catalase tests were negative, with SR1 producing gas from glucose and SR2 producing ammonia from arginine. The biochemical tube reactions of SR1 with arabinose, ribose, mannitol, and sorbitol were negative, while those of SR2 were negative. These results are generally consistent with the physical and chemical test identification results of Lactobacillus rhamnosus and Lactobacillus salviae by Hu Bo, Zhang Defa, et al. Combined with Ling Daiwen's "Classification, Identification, and Experimental Methods of Lactic Acid Bacteria," we can preliminarily identify SR1 as Lactobacillus rhamnosus and SR2 as Lactobacillus salviae.

[0082] 2.3.5 Identification by 16S rDNA method:

[0083] 16SrDNA sequence identification was completed by Nanjing Qingke Biological Company.

[0084] The results of the 16S rDNA assay are as follows: PCR amplification of the genomic DNA of the test sample was performed using primers to generate PCR products. 5 μL of the product was subjected to gel electrophoresis, confirming the expected target fragment at approximately 1.5 kbp. The qualified PCR products were sent to Nanjing Qingke for sequencing. The sequence lengths of SR1 and SR2 were 1408 and 1478 bp, respectively. The original sequences of SR1 and SR2 were corrected and spliced ​​using DNAStar SeqMan software to obtain valid sequences. These sequences were submitted to NCBI and compared using BLAST software. The results showed that SR1 shared 98.78% homology with Lactobacillus rhamnosus, and SR2 shared 99.73% similarity with Lactobacillus farciminis, both consistent with the expected results. Based on the morphological, physicochemical characteristics and 16SrDNA information of strains SR1 and SR2, the strains SR1 and SR2 with ferulic acid esterase activity isolated from the rumen fluid of Hu sheep were identified as Lactobacillus rhamnosus and Lactobacillus sausage.

[0085] 2.3.6 Antibacterial test:

[0086] The frozen SR2 strain was inoculated into MRS medium and cultured at 37°C for 24 hours. The activated SR2 strain was subcultured twice. The activated SR2 strain was re-transferred into MRS liquid medium at a 3% inoculum volume and cultured for 24 hours. The bacterial liquid was centrifuged to obtain the supernatant. The bacteria (Escherichia coli, Staphylococcus aureus, Salmonella) were used as indicator bacteria, and nutrient agar medium was used as the culture medium for the indicator bacteria. The strains were activated and the indicator bacterial liquid was diluted with physiological saline to OD 600The absorbance is 0.1. Pour 10mL of autoclaved water agar into the culture dish to form the bottom. After solidification, place the sterilized Oxford cup on the agar paper, draw 1mL of indicator bacteria solution and add it to 100mL of nutrient broth culture medium kept at a constant temperature of 50±5℃, shake well, pour it into the solidified agar culture medium with the Oxford cup, pour 20mL into each culture dish, cool and solidify. Use tweezers to remove the Oxford cup, draw 200μL of SR2 bacterial liquid supernatant and inject it into the well, use MRS culture medium as blank control, put it in a 4℃ refrigerator for 2h, then put the culture dish in a 37℃ incubator for culture, observe the antibacterial effect of SR2 strain on indicator bacteria for 18h, and the results are shown in Table 6 below.

[0087] Table 6 SR2 antibacterial test results

[0088] Pathogens Escherichia coli Salmonella Staphylococcus aureus Inhibition zone (mm) 20.3±0.716.5±0.617.4±0.5

[0089] It can be seen from Table 6 that the Lactobacillus sausage SR2 of the present invention can inhibit Escherichia coli, Salmonella and Staphylococcus aureus.

[0090] In summary, compared with other bacteria, the feruloyl esterase activity of Lactobacillus SR2 was higher than that of Pediococcus acidilactici (4.32 mU / mL) and Lactobacillus brevis (7.56 mU / mL). Lactobacillus SR2 has a stronger tolerance to acidity. Microbial fermentation agents suitable for silage should have a consistent fermentation pathway, which can not only use sugar to increase acid production, but also have a certain acid resistance to reduce the pH value of silage to 4.0 as quickly as possible, thereby hindering the activity of harmful microorganisms and improving feed quality. Strain SR2 showed good tolerance under acidic conditions (pH = 3.0) and had strong adaptability in high temperature (45°C) and high salinity (10% NaCl) environments, had an antibacterial effect, and had the ability to produce feruloyl esterase.

[0091] Example 2

[0092] Effect of Lactobacillus sausage SR2 on the utilization of rice straw as feed:

[0093] Materials and methods

[0094] Test materials:

[0095] Test silage: de-spike japonica rice straw harvested from the experimental base of the Institute of Grain Crops, Jiangsu Academy of Agricultural Sciences in October 2021.

[0096] Test strains: Lactobacillus rhamnosus SR1 and Lactobacillus salivary SR2.

[0097] Preparation of bacterial agent: After activation, Lactobacillus rhamnosus SR1 and Lactobacillus sausage SR2 were transferred to MRS medium at a 5% inoculum volume and cultured at 37°C until the number of viable bacteria reached 10 8 cfu / mL, centrifuge at 10000 rpm for 2 min to remove the supernatant to obtain the bacteria, and dilute the bacteria to 10 with sterile saline. 8 cfu / mL.

[0098] Experimental Design:

[0099] Treatment group settings: The experiment set up three additives: Lactobacillus rhamnosus SR1 (R), Lactobacillus sausage SR2 (F), Lactobacillus rhamnosus SR1 and Lactobacillus sausage SR2 (RF), and a CK control group without additives was set up, for a total of four treatments. The addition amount of each group is shown in Table 7 below.

[0100] Table 7 Experimental design

[0101]

[0102] Silage preparation: Cut rice straw into 2-3 cm length, and add activated SR1 and SR2 strains at a rate of 5×10 5 Use a spray bottle to spray the cut rice straw with a spraying rate of 100 cfu / g of rice straw. For the CK group, spray an equal amount of water. Mix the raw materials with disposable gloves, place them into silage bags, and seal them with a vacuum sealer. Each bag weighs 300g. After 60 days of room temperature fermentation, remove the bags and sample them for quality testing. Separately, store the rice straw raw material at -20°C in a refrigerator for subsequent testing.

[0103] Sample determination: DM (dry matter), NDF (neutral detergent fiber), ADF (acid detergent fiber), CP (crude protein), WSC (soluble carbohydrates), in vitro digestibility (IVDMD), pH value, organic acids (lactic acid, acetic acid, propionic acid, butyric acid), and ammonia nitrogen content of the samples were determined.

[0104] Experimental results:

[0105] The fermentation quality analysis results of rice straw silage treated with different microbial agents are shown in Table 8:

[0106] Table 8 Fermentation quality analysis of rice straw silage after 60 days

[0107]

[0108]

[0109] Note: Different lowercase letters in the same column indicate significant differences (P < 0.05) between fermentation treatments with different strains. PA, propionic acid; AA, butyric acid. “---” indicates not detected.

[0110] As shown in Table 8, after 60 days of rice straw silage fermentation, the pH values ​​of all treatment groups were significantly lower than those of the control group (P<0.001), among which the pH value of rice straw treated in group F was the lowest (P<0.001).

[0111] Organic acids are important factors affecting feed fermentation quality. Compared with the CK group, the LA (lactic acid) content of the F and RF groups was significantly higher than that of the CK group (P < 0.001). Among them, the LA content of the F group was the highest, significantly higher than that of the RF group. The addition of Lactobacillus SR2 (F group) promoted the production of lactic acid. Compared with the CK, R, and RF treatment groups, the lactic acid content of the F group increased by 114.53%, 97.57%, and 10.36%, respectively. The addition of Lactobacillus SR2 had a greater impact on acetic acid (AA), significantly reducing the acetic acid content of the F and RF groups and increasing the lactic acid / acetic acid ratio.

[0112] The LA / AA (lactic acid / acetic acid) value reflects the homogenous fermentation of lactic acid bacteria in silage. Except for the R group, the LA / AA values ​​of the F and RF groups increased by 114.53% and 94.39% respectively compared with the CK group, significantly higher than the CK group. Among them, the LA / AA value of the F group was the highest.

[0113] The AN (ammonia nitrogen) content reflects the degree of protein breakdown in silage, and its level affects the feed value. Ammonia nitrogen is produced by the degradation of crude protein in the original silage by putrefactive microorganisms (such as Clostridium). A higher AN content indicates poorer fermentation efficiency. The AN content in the F and RF groups was 60.63% and 49.84% lower, respectively, than in the CK group. This suggests that the addition of Lactobacillus SR2 can effectively reduce the degradation of crude protein in rice straw by putrefactive microorganisms, thereby improving the quality of rice straw silage.

[0114] Microbial counts are also an important indicator for assessing feed fermentation quality. The number of lactic acid bacteria in the F and RF groups was significantly higher than that in the CK group (P<0.001). The number of aerobic bacteria in both the F and RF groups was significantly lower than that in the CK group (P<0.001), with the F group having the lowest number of aerobic bacteria. The number of yeasts in the F group was significantly lower than that in the other treatment groups (P<0.001), with no significant difference between the R, RF, and CK groups.

[0115] The nutritional quality analysis results of rice straw silage treated with different microbial agents are shown in Table 9:

[0116] Table 9 Nutritional quality analysis of rice straw silage after 60 days

[0117]

[0118]

[0119] Note: Different lowercase letters in the same row indicate significant differences after fermentation with different strains (P<0.05).

[0120] As shown in Table 9, except for the R group, the DM (dry matter) content of the F and RF groups was significantly higher than that of the CK group (P<0.001), and the DM content of the R group was no different from that of the CK group; the CP content of the F group was the highest, significantly higher than that of the CK and F groups.

[0121] WSC content reflects the consumption of sugars during the fermentation period. WSC content in F group and RF group increased by 42.67% and 27.7% respectively compared with CK group, and both were significantly higher than CK group (P=0.003).

[0122] Fiber levels directly affect animal feeding and digestion performance. Compared with the CK group, the NDF content of the F group was significantly lower (P = 0.006); the ADF content of the F group was the lowest, significantly lower than that of the CK and R groups. The cellulose content of the F group was the lowest, significantly lower than that of the CK and R groups. Although the IVDMD content did not differ significantly between the groups, the IVDMD content of the F group was the highest, increasing by 2.25% compared to the CK group. Studies have found that in a trial of adding ferulic acid-producing lactic acid bacteria to alfalfa silage, inoculation with ferulic acid esterase-producing lactic acid bacteria did not improve the fermentation quality and fiber degradation capacity of the silage. However, our study found that the NDF, ADF, and cellulose content of the rice straw feed supplemented with ferulic acid esterase-producing Lactobacillus SR2 (F group) decreased, while the carbohydrate content increased.

[0123] SR2 sequence:

[0124]

[0125] SR1 sequence:

[0126]

[0127] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A Lactobacillus farciminis SR2, characterized in that: the preservation number of the Lactobacillus farciminis SR2 is CCTCC NO: M 2022416.

2. Use of the Lactobacillus farciminis SR2 according to claim 1 as a plant feed additive.

3. According to the use described in claim 2, characterized in that: the Lactobacillus farciminis SR2 is used for ensiling plant feed.

4. According to the use described in claim 2 or 3, characterized in that: the Lactobacillus farciminis SR2 can highly produce ferulic acid esterase.

5. According to the use described in claim 3, characterized in that: the Lactobacillus farciminis SR2 increases the lactic acid content in plant feed, reduces the acetic acid content in plant feed, and reduces the ammonia nitrogen content.

6. According to the use described in claim 3, characterized in that: the Lactobacillus farciminis SR2 inhibits the production of aerobic bacteria and yeasts during ensiling.

7. According to the use described in claim 3, characterized in that: the Lactobacillus farciminis SR2 significantly increases the dry matter and soluble carbohydrate contents, and significantly reduces the neutral detergent fiber, acid detergent fiber, and cellulose contents.

8. According to the use described in claim 2 or 3, characterized in that: the plant feed includes rice straw.

9. Use of the Lactobacillus farciminis SR2 according to claim 1 in the preparation of an antibacterial preparation.

10. According to the use described in claim 9, characterized in that: the Lactobacillus farciminis SR2 inhibits Escherichia coli, Salmonella, and Staphylococcus aureus.

11. An antibacterial preparation, characterized in that, the active ingredient of the antibacterial preparation includes the Lactobacillus farciminis SR2 according to claim 1.

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