Screening Of Potential Probiotic Lactic Acid Bacteria And Its Application In Fermented Milk

For lactic acid bacteria strains with live properties,this study on acid horse milk samples from Mongolian pastoral areas 197 strains of lactic acid bacteria in acid,bile salt tolerance,resistance to simulate artificial the screening and identification of biological characteristics,such as gastrointestinal tract and the screening of the strain of the preparation of fermented milk,on the determination of antioxidant activity,inhibit the activity of ACE and adjust the research of intestinal flora in mice,for the future development and utilization to provide good strains of probiotics.The specific results are as follows:1.Screening and identification of potential probiotic lactic acid bacteria.(1)Twelve strains with strong acid resistance were selected through acid resistance(pH 2.0,pH 2.5,pH 3.0)and bile salt resistance tests for subsequent experiments.(2)In the simulated artificial gastrointestinal fluid test,12 strains showed different tolerances.After 3 hours of artificial gastric juice treatment,the survival rate was between 22.81%and 95.86%,and the survival rates of strain 2-32 and strain 2-33 were 80.64%and 95.86%,respectively.A total of 5 strains with a survival rate greater than 60%(2-7,2-13,2-20,2-32,2-33)were selected for simulated artificial intestinal fluid test(after 4 h and 8 h treatment)The viable counts of the five strains were maintained between 109 and 1010 CFU/mL,and the survival rate was all above 50%.Through the determination of the cell surface hydrophobic capacity,these 5 strains all have a certain adhesion capacity,of which strain 2-33 has the highest hydrophobic capacity 42.61%,and the remaining 4 strains were less than 10%,so strain 2-33 was selected The target strain.(3)The in vitro drug sensitivity test of 10 antibiotics revealed that strain 2-33 was resistant to norfloxacin,cefradine,gentamicin,vancomycin,and streptomycin;it was not sensitive;It was moderately sensitive;it was sensitive to tetracycline,chloramphenicol,erythromycin,and ampicillin.(4)Through the sugar fermentation test and the molecular identification of the 16S rDNA gene sequence,the strain 2-33 was identified as Lactobacillus plantarum,the gene sequence length obtained was 1432 bp,and the accession number was MN611708.2.Preparation of fermented milk with Lactobacillus plantarum 2-33 to determine its antioxidant activity and inhibition of ACE activity.(1)Through the determination of antioxidant capacity,the total antioxidant capacity of strain 2-33 fermented whey is 0.23 ± 0.01 mmol of ferrous sulfate,which is slightly lower than the antioxidant capacity of 0.03 mg/mL Vc solution;The reducing power was slightly lower than the reducing power of 0.1 mg/mL Vc solution,the absorbance value was 0.68±0.01;the ability to remove DPPH and O2-reaches 72.80±0.30%and 21.32 ±0.50%respectively;the ACE inhibition rate was 1.98±0.09%.3.Gastrointestinal Lactobacillus plantarum 2-33 fermented milk was used to determine the food utilization rate,organ index and intestinal flora of mice.(1)Through oral gavage of Lactobacillus plantarum 2-33 fermented milk,mice were found to have a total food intake.The low-dose fermented milk group(0.1 ml,1 ×109 CFU/mL)had a weekly food intake of 274.90 ± 18.95 g,which was significant higher than the control group,model group and high-dose group(0.3 mL,1 × 109 CFU/mL)(P<0.05);on the mouse liver index,the high-dose group was significantly higher than the control,model group and low-dose group(P<0.05);from the perspective of kidney index,the addition of Lactobacillus plantarum 2-33 fermented milk to gavage increased the kidney index of mice,the degree of improvement:high dose group>low dose group>model group>control group,high dose The difference between the group and the low-dose group was significant(P<0.05),and the low-dose group was significantly different from the model group and the control group(P<0.05);from the spleen index,Lactobacillus plantarum fermented milk increased the spleen of mice Index,the high-dose group was significantly higher than the control group,model group and low-dose group(P<0.05).(2)After 15 days of fermented milk by L.plantarum 2-33 fermented by gavage,the number of Lactobacillus and Bifidobacterium in the high-dose fermented milk group and the low-dose fermented milk group were significantly higher than the model group(P<0.01)The number of enterobacteria in the low-dose milk group and the high-dose group was significantly lower than that of the model group(P<0.05);the number of enterococci in the high-dose group of fermented milk was significantly lower than that of the model group(P<0.01),but there was no significant difference between the number of cocci and the model group(P>0.05);the number of Clostridium perfringens in the high-dose and low-dose fermented milk groups was significantly lower than that in the model group(P<0.01);therefore,Lactobacillus plantarum 2-33 fermented milk has obvious regulation effect on mice with intestinal flora imbalanced by antibiotic solution.The results of this study provide excellent strains for the development and utilization of probiotics and have good application prospects.