Fast-growing psychrobacter sp. LC7 and application thereof

Abstract

The invention provides fast-growing psychrobacter LC7 and application thereof, and belongs to the technical field of aquatic feed. The preservation number of the fast-growing psychrobacter cell LC7 provided by the invention is CCTCC (China Center for Type Culture Collection) M 20252777, and the fast-growing psychrobacter cell LC7 is preserved in the China Center for Type Culture Collection on December 4, 2025. The fast-growing psychrobacter LC7 can significantly improve the expression quantity of genes related to intestinal development of the larimichthys crocea juveniles, significantly improve the activity of enzymes related to intestinal development, digestive absorption and immune functions of the larimichthys crocea juveniles, and improve the weight and specific growth rate of the larimichthys crocea juveniles. The fast-growing psychrobacter LC7 can promote the intestinal development of the larimichthys crocea juveniles, improve the digestion and absorption capacity and improve the immunocompetence, thereby improving the survival and growth of the larimichthys crocea juveniles.

Description

Technical Field

[0001] This invention relates to the field of aquatic feed technology, and in particular to a fast-growing psychrophilic bacterium LC7 and its applications. Background Technology

[0002] Gut microbiota play a crucial biological role in the early development of fish, serving as an important regulatory factor influencing host intestinal development, digestive physiology, and immune system maturation. The initial colonization process of the gut microbiota not only determines the stability of the subsequent microecological structure but also profoundly impacts the host's developmental trajectory. Studies have shown that early colonized microorganisms can compensate for the underdeveloped digestive enzyme system in juvenile fish by producing various exogenous enzymes and metabolites, regulating intestinal epithelial cell proliferation and differentiation, and activating the host's mucosal immune recognition system. Therefore, optimizing the gut microbiota structure during the early development of fish can effectively improve the intestinal health of juvenile fish and promote their healthy growth.

[0003] In recent years, with the continuous increase in the farming density of large yellow croaker and the ongoing shift towards efficient and intensive production methods, the industry has placed higher demands on the supply of healthy and stable seedlings. However, during the artificial breeding and early rearing stages, large yellow croaker fry have a weak ability to resist external changes, resulting in a persistently high mortality rate. Therefore, it is urgent to take measures to promote the healthy development of the fry's intestines, increase the level of endogenous digestive enzymes, improve the intestinal immune barrier, and reduce mortality and morbidity, thereby creating favorable conditions for the green and sustainable development of the large yellow croaker industry. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a fast-growing psychrophilic bacterium LC7 and its application. The fast-growing psychrophilic bacterium LC7 provided by this invention can promote the intestinal development of juvenile large yellow croaker, improve digestive and absorptive capacity, enhance immunity, and thus improve the survival and growth of juvenile large yellow croaker.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A fast-growing psychrophilic bacillus ( Psychrobacter celer The fast-growing psychrophilic bacillus LC7, with accession number CCTCC NO: M 20252777, was deposited at the China Center for Type Culture Collection on December 4, 2025.

[0006] In some embodiments, the depositary address of the fast-growing psychrophilic bacillus LC7 is Wuhan University, Wuhan, China.

[0007] In some embodiments, the 16S rDNA sequence of the fast-growing psychrophilic bacillus LC7 is shown in Seq_1.

[0008] Specifically, the nucleotide sequence of Seq_1 is as follows:

[0009] The present invention also provides a microecological preparation, including the fast-growing psychrophilic bacillus LC7 described in the above technical solution.

[0010] In some embodiments, the viable count of fast-growing psychrophilic bacillus LC7 in the probiotic preparation is preferably 1×10⁻⁶. 6 cfu / g ~1×10 8 cfu / g.

[0011] The present invention also provides the application of the fast-growing psychrophilic bacillus LC7 described in the above technical solution or the microecological preparation described in the above technical solution in improving the growth performance of juvenile large yellow croaker.

[0012] In some implementations, the improvement of growth performance of juvenile large yellow croaker preferably includes, but is not limited to, increasing the weight and a specific growth rate of juvenile large yellow croaker.

[0013] The present invention also provides the application of the fast-growing psychrophilic bacillus LC7 described in the above technical solution or the microecological preparation described in the above technical solution in improving the intestinal health of juvenile large yellow croaker.

[0014] In some embodiments, the improvement of intestinal health in juvenile large yellow croaker preferably includes, but is not limited to, significantly increasing the expression levels of genes related to intestinal development in juvenile large yellow croaker, and significantly increasing the activity of enzymes related to intestinal development, digestion and absorption, and immune function in juvenile large yellow croaker.

[0015] In some embodiments, the genes related to intestinal development in juvenile large yellow croaker are pcna and occup; the enzymes related to intestinal development, digestion and absorption, and immune function in juvenile large yellow croaker are alkaline phosphatase, leucine aminopeptidase, trypsin, amylase, brush border ATPase, brush border creatine kinase, lipase, intestinal inducible nitric oxide, acid phosphatase, nitric oxide synthase, and lysozyme. Among these, alkaline phosphatase and leucine aminopeptidase are related to intestinal development; trypsin, amylase, brush border ATPase, brush border creatine kinase, and lipase are related to digestion and absorption; and inducible nitric oxide, acid phosphatase, nitric oxide synthase, and lysozyme are related to immune function.

[0016] The present invention also provides the application of the fast-growing psychrophilic bacillus LC7 described in the above technical solution or the microecological preparation described in the above technical solution in the preparation of feed for juvenile large yellow croaker.

[0017] The present invention also provides a feed for juvenile large yellow croaker, comprising the fast-growing psychrophilic bacillus LC7 described in the above technical solution or the microecological preparation described in the above technical solution.

[0018] In some embodiments, the viable count of fast-growing psychrophilic bacillus LC7 in the feed for juvenile large yellow croaker is preferably 1×10⁻⁶.6 cfu / g ~1×10 8 cfu / g.

[0019] Beneficial technical effects: This invention provides a fast-growing psychrophilic bacterium LC7 and its applications. The fast-growing psychrophilic bacterium described in this invention ( Psychrobacter celer The accession number for LC7 is CCTCC M 20252777, and it was deposited at the China Center for Type Culture Collection on December 4, 2025. The fast-growing psychrophilic bacterium LC7 significantly increases the expression levels of genes related to intestinal development in large yellow croaker juveniles, significantly increases the activity of enzymes related to intestinal development, digestion and absorption, and immune function in large yellow croaker juveniles, and increases the weight and specific growth rate of large yellow croaker juveniles. LC7 can improve the survival and growth of large yellow croaker juveniles by promoting intestinal development, improving digestive and absorptive capacity, and enhancing immunity. Attached Figure Description

[0020] Figure 1 The results show the survival rate of juvenile large yellow croaker after testing the fast-growing psychrophilic bacillus LC7. Figure 2 The results of the test on the growth performance of large yellow croaker juveniles using fast-growing psychrophilic bacillus LC7; among them, Figure 2 A represents final body weight. Figure 2 B represents a specific growth rate; the same letter indicates... p >0.05, the difference is not significant, the same applies below; Figure 3 Results of detection of enzymes and genes related to intestinal development in juvenile large yellow croaker by fast-growing psychrophilic bacterium LC7; Figure 3 A is alkaline phosphatase. Figure 3 B is leucine aminopeptidase. Figure 3 C represents the relative expression level of pcna mRNA. Figure 3 D represents the relative expression level of odc mRNA; Figure 4 The results of detecting digestive and absorptive enzymes in the intestinal tract of juvenile large yellow croaker are presented as follows: LC7 of fast-growing psychrophilic bacteria. Figure 4 A is trypsin. Figure 4 B is lipase. Figure 4 C stands for amylase. Figure 4 D is Na + -K + -ATPase; Figure 4 E is creatine kinase; Figure 5 The results show the detection of immune-related enzymes and nitric oxide content in the intestine of juvenile large yellow croaker by fast-growing psychrophilic bacterium LC7; Figure 5 A represents the nitric oxide content. Figure 5 B represents total nitric oxide synthase. Figure 5C is an inducible nitric oxide synthase. Figure 5 D represents acid phosphatase; Figure 5 E stands for lysozyme; Figure 6 This is a schematic diagram of the 16S rDNA gene phylogenetic tree of the fast-growing psychrophilic bacterium LC7. Detailed Implementation

[0021] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments. Unless otherwise specified, the materials, reagents, etc., used in the embodiments and experimental examples of the present invention can be obtained commercially; unless otherwise specified, the methods used in the embodiments and experimental examples of the present invention are conventional methods.

[0022] Example 1: Isolation and molecular identification of fast-growing psychrophilic bacillus LC7.

[0023] Fresh intestinal samples from large yellow croaker were collected under aseptic conditions. The intestinal contents were squeezed out, and the intestines were rinsed thoroughly with sterile PBS. The intestinal samples were placed in a sterile homogenizer, and an equal volume of sterile PBS was added for homogenization. The resulting intestinal homogenate was serially diluted 1:10 using sterile PBS. 100 μL of each concentration gradient was evenly spread onto LB nutrient agar and incubated at 28°C. After single colonies grew on the plates, they were streaked to purify the strain. The purified single colonies were then transferred to LB broth and incubated for 18 h at 28°C and 200 rpm. The bacterial genomic DNA was extracted from the culture, and the 16S rDNA sequence was amplified using universal 16S rDNA primers 27F (AGAGTTTGATCCTGGCTCAG, Seq_2) and 1492R (GGTTACCTTGTTACGACTT, Seq_3). PCR reaction system: PremixSTAR Max DNA Polymerase 12.5 μL, DNA template 2 μL, ddH2O 8.5 μL, Forward primer 1 μL, Rever seprimer 1 μL. PCR program: 98℃ 10s, 55℃ 15s, 72℃ 1.5min, 35 cycles; 72℃ 10min. PCR products were sent to Sangon Biotech (Shanghai) Co., Ltd. for sequencing. The obtained 16S rDNA sequence (Seq_1) was compared on the NCBI website and preliminarily identified as *Acute-growing psychrophilic bacillus*. Psychrobacter celer It was numbered LC7. The phylogenetic tree is as follows: Figure 6 As shown.

[0024] The fast-growing psychrophilic bacillus LC7 was deposited at the China Center for Type Culture Collection on December 4, 2025, with accession number CCTCC NO: M 20252777.

[0025] Example 2: Physiological and biochemical identification of fast-growing psychrophilic bacillus LC7 Strain LC7 was Gram-negative, coccobacillus-shaped, and formed single, smooth, round, milky-white colonies on LB agar. Physiological and biochemical parameters of strain LC7 were determined using microbial reaction tubes (purchased from Hangzhou Binhe Microbial Reagent Co., Ltd.). Strain LC7 can utilize glucose, lactose, fructose, arabinose, galactose, xylose, glycerol, sodium pyruvate, and acetate. The main physiological and biochemical characteristics are shown in Table 1. Based on the morphological, physiological, and biochemical results, and the above-mentioned 16S rDNA phylogenetic tree results, strain LC7 of this invention can be confirmed as a fast-growing psychrophilic bacterium (…). Psychrobacter celer ).

[0026] Table 1. Physiological and biochemical characteristics of strain LC7 Note: + indicates positive, – indicates negative.

[0027] Example 3: Preparation of freeze-dried LC7 fast-growing psychrophilic bacillus powder The preserved fast-growing psychrophilic bacillus strain LC7 was inoculated onto LB nutrient agar solid medium and activated at 28°C for 48-72 hours. Typical single colonies were picked and inoculated into a seed culture medium containing: 10 g / L casein peptone, 5 g / L yeast extract, and 10 mL / L 60% sodium lactate solution (i.e., 1% v / v). For preparing solid plates, 15 g / L agar powder was added. The pH of this medium was adjusted to 7.0-7.2 before sterilization. After inoculation, the culture was incubated at 28°C and 200 rpm for 24-36 hours to obtain the activated seed culture.

[0028] The above seed culture was inoculated into a fermentation medium at an inoculation rate of 5%–10% by volume. The fermentation medium consisted of the following components: 54.3 g / L glucose, 17.6 g / L yeast extract, 30 g / L corn steep liquor powder, 2.7 g / L potassium dihydrogen phosphate, 2 g / L ammonium sulfate, and 3.5 g / L glycine; the pH was controlled at 7.0. Fermentation was carried out at 28°C, with a fermenter rotation speed of 200 rpm, an aeration rate of 1:0.85, and a fermentation cycle of 42 hours.

[0029] After fermentation, the fermentation broth was centrifuged at 12,000 rpm using a tubular centrifuge to collect the wet bacterial cells. Subsequently, the resulting bacterial sludge was uniformly mixed with a pre-cooled lyophilization protectant solution at a mass ratio of 1:1 (w / w). The lyophilization protectant was prepared by dissolving the following components in water in the following mass-volume percentages: 8% skim milk powder, 6% trehalose, 2% fructose, 0.7% glycine, and 0.1% L-cysteine ​​hydrochloride.

[0030] The uniformly mixed bacterial suspension was pre-frozen and then placed in a vacuum freeze dryer. The pre-freezing temperature did not exceed -40℃. During the sublimation drying stage, the vacuum degree was controlled at 10Pa~30Pa, and the partition temperature was gradually increased from a low temperature to below 10℃. During the desorption drying stage, the partition temperature was gradually increased to 25℃~30℃. After sublimation drying and desorption drying, the finally dried bacterial powder was obtained. The freeze-dried bacterial cake was then pulverized at low temperature to obtain a free-flowing powder product.

[0031] Example 4: Preparation of feed for juvenile large yellow croaker containing the fast-growing psychrophilic bacterium LC7 The basic feed for juvenile large yellow croaker used in this embodiment of the invention contains the following components by weight percentage (as shown in Table 2): white fish meal 45.00%, krill meal 22.00%, yeast extract 3.50%, squid viscera powder 3.00%, high-gluten flour 5.00%, α-carbohydrate... Starch 2.90%, Sodium alginate 2.00%, Multivitamins 1.50%, Multiminerals 1.00%, L ascorbic acid 2 The ingredients are: 0.20% phosphate ester, 2.00% calcium dihydrogen phosphate, 0.05% mold inhibitor, 0.05% antioxidant, 0.20% choline chloride, 6.50% fish oil, and 5.00% soybean lecithin. All raw materials are screened through a 120-mesh sieve and then mixed in a progressively larger quantity order. Different live bacterial counts of fast-growing psychrophilic bacillus LC7 powder are diluted with an equal volume of sterile ultrapure water to prepare suspensions containing different live bacterial counts. These suspensions are then added to the basal feed and mixed thoroughly to achieve a concentration of 1×10⁻⁶. 6 cfu / g ~1×10 8 CFU / g. The control group feed consisted of a basal feed with an equal volume of microcrystalline cellulose added. Finally, the feed was extruded into thin strips using an axial single-screw spherical extruder, and then made into micro-particles with a particle size of up to 1 mm using a rounding machine. The resulting micro-particles were air-dried indoors and stored in a refrigerator at 4°C.

[0032] Table 2 Basic Feed Formulation Note: 1Multivitamins (mg / kg): Retinaldehyde acetate, 32; α-Tocopherol, 240; Menaquinone, 10; Vitamin B1, 25; Pyridoxine hydrochloride, 20; Vitamin B12, 10; Riboflavin, 45; Pantothenic acid, 60; Vitamin D3, 5; Folic acid, 20; Niacin, 200; Biotin, 60; Inositol, 800; Microcrystalline cellulose, 13473.

[0033] 2 Multiple minerals: MgSO4·7H2O, 1200; FeSO4·H2O, 80; ZnSO4·H2O, 50; CuSO4·5H2O, 10; MnSO4·H2O, 45; CoCl2·6H2O, 50; Na2SeO3, 20; H2CaIO4, 60; zeolite powder, 13485.

[0034] Example 5: Effect of the application of fast-growing psychrophilic bacillus LC7 in feed for juvenile large yellow croaker Four hundred and twenty thousand juvenile large yellow croakers with an initial body weight of 4.68 ± 0.26 mg were randomly divided into four groups, with three replicates per group and three replicates per group. A feeding and growth experiment was conducted for 30 days. The culture water temperature was 23℃–26℃, pH 7.8–8.2, and salinity 22‰–24‰. The experimental groups were fed a diet supplemented with 1×10⁻⁶ tbsp. 6 cfu / g, 1×10 7 cfu / g, 1×10 8 The diet consisted of cfu / g fast-growing psychrophilic bacillus LC7; the control group was fed only a basal diet plus microcrystalline cellulose; all four groups were fed seven times a day, always to satiety, at 05:30, 08:30, 10:30, 13:30, 15:30, 17:30, and 23:00. Weights and counts were taken at the beginning and end of the rearing period to calculate the specific growth rate and survival rate of the large yellow croaker juveniles. The calculation methods for the specific growth rate and survival rate are as follows: Specific growth rate = [Ln(final body weight (mg)) - Ln(initial body weight (mg))] × 100 / (number of days of rearing (d)); Survival rate = (Number of juvenile fish surviving in the culture tank at the end of the experiment / Number of juvenile fish in the culture tank at the beginning of the experiment) × 100%.

[0035] The intestines of juvenile large yellow croakers from each group were collected and subjected to the following tests: The expression levels of intestinal development-related genes were determined using quantitative q-PCR. ChamQ Universal SYBR qPCR Master Mix (Novozymes Biotechnology Co., Ltd.) was used to detect the mRNA expression levels of the following genes: Proliferating cell nuclear antigen (pcna) and Ornithine decarboxylase (odc), using beta-nucleotide analogues (BNA). actin (β) Actin was used as an internal reference gene. A q-type gene was designed based on the nucleotide sequence of the large yellow croaker. PCR primers (Table 3).

[0036] Table 3 q-PCR primer sequences For the extraction of intestinal brush border membrane, firstly, intestinal segments were homogenized in 2 mL of a mixture containing 50 mmol / L mannitol and 2 mmol / L Tris (volume ratio 1:1). Then, 1 mL of 0.1 mol / L CaCl2 solution was added to the homogenate. Next, the mixture was centrifuged at 9000 × g for 10 min, and the supernatant was collected. Then, the supernatant was centrifuged at 34000 × g for 20 min, and the supernatant was discarded. Finally, the resulting precipitate rich in intestinal brush border membrane was resuspended in 1 mL of a solution of 0.1 mol / L KCl and 5 mmol / L Tris. The method effectively separates the intestinal brush border membrane using a mixed solution of Hepes (pH=7.5) and 1 mmol / L DTT (volume ratio 1:1:1).

[0037] Leucine aminopeptidase (LAP) activity utilizes leucine The assay was performed using p-nitroaniline as a substrate. The specific procedure was as follows: In a centrifuge tube, first add 1.5 mL of phosphate buffer (20 mmol / L, pH=7.2), then add 100 μL of leucine. 100 μL of preheated sample (30°C) was added last to the p-nitroaniline substrate solution. After the reaction started, the absorbance of the released p-nitroaniline was measured at 405 nm using a spectrophotometer. The absorbance was determined based on the molar absorptivity of p-nitroaniline (8800 L·mol⁻¹). 1 ·cm 1 The rate of hydrolysis of the substrate is calculated, thus reflecting the enzyme activity.

[0038] alkaline phosphatase, lipase, α Amylase, trypsin, Na+ K + – The determination of ATPase, creatine kinase, acid phosphatase, nitric oxide content, nitric oxide synthase, and lysozyme content were all performed using commercially available kits purchased from Nanjing Jiancheng Bioengineering Institute; the kit names are as follows: Alkaline phosphatase (ALP / AKP) Assay Kit (Microplate Method) (A059) 2 2) Lipase Assay Kit (Microplate Method) (A054) 2 1) α Amylase (AMS) test kit (starch) Iodine colorimetric method (C016) 1 1) Trypsin Assay Kit (UV Colorimetric Method) (A080) 2 2) Trace amounts of Na + -K + -ATPase (for tissue and general cell assays) kit (A070) 2 2) Creatine kinase (CK) assay kit (colorimetric method), acid phosphatase (ACP) assay kit (microplate method) (A060) 2 2) Nitric Oxide (NO) Assay Kit (Enzymatic Method) Colorimetric Method (A012) 1 2) Nitric oxide synthase (NOS) typing kit (colorimetric method) (A014) 1 2) and lysozyme (LZM) test kit (A050) 1 1).

[0039] Experimental data will be statistically analyzed using one-way ANOVA in SPSS 20.0. After significant differences are identified, Tukey's multiple comparisons will be performed at a significance level of [missing data]. P <0.05. The experimental data are expressed as mean ± standard error (mean ± SEM, n = 3).

[0040] In terms of survival rate and growth performance, 1×10 6 cfu / g group, 1×10 7 cfu / g group, 1×10 8 The survival rate of juvenile large yellow croaker in the CFU / g group showed an upward trend, although it was not statistically significant. P >0.05), but 1×10 8The survival rate in the CFU / g group was 4.31% higher than that in the control group (reference). Figure 1 (As shown). In addition, 1×10 7 cfu / g group, 1×10 8 The final body weight and specific growth rate of large yellow croaker fry in the cfu / g group were significantly higher than those in the control group. P <0.05). Among them, 1×10 7 cfu / g group, 1×10 8 The final body weight of juvenile large yellow croaker in the CFU / g group was 7.47% and 8.86% higher than that in the control group, respectively, and the specific growth rate was 2.08% and 2.45% higher than that in the control group, respectively (refer to...). Figure 2 A and Figure 2 (as shown in B).

[0041] The increased activity of alkaline phosphatase and leucine aminopeptidase in the brush border of the intestine of juvenile large yellow croaker indicates the establishment of the brush border digestive mechanism and the gradual maturation of the intestine. For the intestinal development function of juvenile large yellow croaker, 1×10 6 cfu / g group, 1×10 7 cfu / g group, 1×10 8 The activities of alkaline phosphatase and leucine aminopeptidase in the cfu / g group of juvenile large yellow croaker were significantly higher than those in the control group. P <0.05). Among them, 1×10 6 cfu / g group, 1×10 7 cfu / g group, 1×10 8 The alkaline phosphatase activity in the CFU / g group of juvenile large yellow croaker increased by 43.97%, 110.81%, and 195.62% respectively compared to the control group, and the leucine aminopeptidase activity increased by 22.72%, 38.46%, and 64.97% respectively compared to the control group (refer to...). Figure 3 A and Figure 3 (As shown in B). 1×10 8 Genes related to intestinal development in large yellow croaker juveniles in the CFU / G group ( PCNA and odc Both were significantly higher than the control group. P <0.05), PCNA and odc Compared with the control group, the rates were increased by 226.67% and 51.68% respectively (refer to...). Figure 3 C and Figure 3 (as shown in D).

[0042] Large yellow croaker juvenile intestinal lipase, α Amylase, trypsin, Na + K +An increase in ATPase and creatine kinase activity indicates an enhanced ability of the intestines to digest feed and absorb functional substances. For the digestive and absorptive function of juvenile large yellow croaker, 1×10 7 cfu / g group, 1×10 8 The intestinal trypsin activity, amylase activity, ATPase activity, and creatine kinase activity of large yellow croaker juveniles in the cfu / g group were all significantly higher than those in the control group. P <0.05). Among them, 1×10 7 cfu / g group, 1×10 8 Compared with the control group, the CFU / g group showed increases in trypsin activity of 32.30% and 45.16%, respectively; amylase activity of 19.03% and 33.01%, respectively; ATPase activity of 39.89% and 66.95%, respectively; and creatine kinase activity of 140.91% and 402.56%, respectively (refer to...). Figure 4 A, Figure 4 C Figure 4 D、 Figure 4 (As shown in E). 1×10 8 The intestinal lipase activity of large yellow croaker juveniles in the cfu / g group was significantly higher than that in the control group. P <0.05), which is 100.60% higher than the control group (refer to...). Figure 4 (as shown in B).

[0043] Increased levels of nitric oxide, nitric oxide synthase, and lysozyme in the intestines of juvenile large yellow croaker indicate improved intestinal immunity. For the intestinal immune function of juvenile large yellow croaker, 1×10 6 cfu / g group, 1×10 7 cfu / g group, 1×10 8 The CFU / g group significantly increased the intestinal inducible nitric oxide and acid phosphatase activities in juvenile large yellow croaker. P <0.05), among which, the activities of inducible nitric oxide were increased by 9.49%, 89.62%, and 105.65% respectively compared with the control group, and the activities of acid phosphatase were increased by 10.92%, 18.20%, and 34.81% respectively compared with the control group (refer to...). Figure 5 C and Figure 5 (As shown in D). 1×10 7 cfu / g group, 1×10 8 The CFU / g group significantly increased the content of nitric oxide, total nitric oxide synthase activity, and lysozyme activity in the intestine of juvenile large yellow croaker. P<0.05), among which, the content of nitric oxide increased by 33.94% and 69.67% respectively compared with the control group, the total nitric oxide synthase activity increased by 134.77% and 155.56% respectively compared with the control group, and the lysozyme activity increased by 58.35% and 93.19% respectively compared with the control group (refer to...). Figure 5 A, Figure 5 B. Figure 5 As shown in E.

[0044] In summary, adding fast-growing psychrophilic bacillus LC7 to feed can effectively promote intestinal development in juvenile large yellow croaker, improve digestion and absorption, enhance immunity, and improve the survival and growth of juvenile large yellow croaker.

[0045] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fast-growing psychrophilic bacillus ( Psychrobacter celer LC7, characterized in that, The fast-growing psychrophilic bacillus LC7 has the accession number CCTCC NO: M 20252777 and was deposited at the China Center for Type Culture Collection on December 4, 2025.

2. A microecological preparation, characterized in that, Includes the fast-growing psychrophilic bacillus LC7 as described in claim 1.

3. The microecological preparation according to claim 2, characterized in that, The viable count of fast-growing psychrophilic bacillus LC7 in the probiotic preparation was 1×10⁻⁶. 6 cfu / g ~1×10 8 cfu / g.

4. The application of the fast-growing psychrophilic bacillus LC7 as described in claim 1 or the microecological preparation as described in any one of claims 2 to 3 in improving the growth performance of juvenile large yellow croaker.

5. The application according to claim 4, characterized in that, The improvement of growth performance of juvenile large yellow croaker includes, but is not limited to, increasing the weight and specific growth rate of juvenile large yellow croaker.

6. The application of the fast-growing psychrophilic bacillus LC7 as described in claim 1 or the microecological preparation as described in any one of claims 2 to 3 in improving the intestinal health of juvenile large yellow croaker.

7. The application according to claim 6, characterized in that, The improvement of intestinal health in juvenile large yellow croaker includes, but is not limited to, significantly increasing the expression levels of genes related to intestinal development in juvenile large yellow croaker, and significantly increasing the activity of enzymes related to intestinal development, digestion and absorption, and immune function in juvenile large yellow croaker.

8. The application according to claim 7, characterized in that, The genes related to intestinal development of juvenile large yellow croaker are pcna and occ. The enzymes related to intestinal development, digestion and absorption, and immune function of juvenile large yellow croaker are alkaline phosphatase, leucine aminopeptidase, trypsin, amylase, brush border ATPase, brush border creatine kinase, lipase activity, intestinal inducible nitric oxide, acid phosphatase, nitric oxide synthase activity, and lysozyme.

9. The use of the fast-growing psychrophilic bacillus LC7 as described in claim 1 or the microecological preparation as described in any one of claims 2 to 3 in the preparation of feed for juvenile large yellow croaker.

10. A feed for juvenile large yellow croaker, characterized in that, Includes the fast-growing psychrophilic bacillus LC7 as described in claim 1 or the microecological preparation as described in any one of claims 2 to 3.

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