Probiotics Of Lactobacillus From Inner Mongolia "Hurood" Cheese And Its Application In Fermented Milk

People pay more and more attention to the relationship between diet and health,and research and development of healthy and functional foods has become an important trend in current food science research.According to reports,intake of probiotics can enhance the body's immune system and regulate intestinal health.In order to exert its beneficial effects in the human body,probiotics must be able to tolerate the acidic environment in the stomach,resist the bile salts present in the small intestine,and then successfully reach the human intestinal tract,adhere and colonize the intestinal tract,and then exert its probiotic effect.Cheese is a good carrier for probiotics.The dense texture and relatively high fat content of cheese make it have a buffering effect in the gastrointestinal tract of a strongly acidic environment,and the relatively high p H of the cheese matrix passes the strong acidity of the probiotics through the stomach.Survival in the environment provides appropriate protection.In this article,I mainly used Lactobacillus strains isolated from "Hurood" cheese in Inner Mongolia as the research object.Measure the antioxidant activity(the ability to remove DPPH free radicals and hydroxyl free radicals)of Klebsiella pneumonia,Escherichia coli,Pseudomonas aeruginosa,Staphylococcus aurous and Salmonella typhii were measured to evaluate the probiotic characteristics of Lactobacillus.Secondly,phenotype,physiology and biochemistry and 16 S r DNA method was used to identify the strains.Finally,a potential Lactobacillus fine strain was selected as an auxiliary strain to be added to the fermented milk to evaluate its effect on the quality of the fermented milk.Below are key research findings.Four strains of KC96,LP88,NS24 and LP38 were selected from the laboratory-preserved strains of Lactobacillus.The strains were initially identified by phenotype,Gram staining,physiological and biochemical methods.All 4 strains were determined to be Lactobacillus.The commercial strains of Lactobacillus rhamnosus GG(L.rhamnosus GG)were used as controls to study the probiotic characteristics of four strains of Lactobacillus in vitro.The results showed that all 4 strains of Lactobacillus had better tolerance to simulated artificial gastric juice(p H 2.0 and p H 3.0,4 h treatment)and low concentrations of bile salts(0.1,0.3,0.5 g/m L,4 h treatment),especially Strain LP38 has the highest tolerance,with the number of viable bacteria reaching 5.01 log CFU/m L after 4 h of p H 2.0 treatment,and the number of viable bacteria reaching 7.97 log CFU/m L after 4 h of treatment with 0.5 g/m L bile salt concentration;strains LP38 and NS24 Paraxylene,vinyl acetate and chloroform show better adhesion and hydrophobicity,all 4 strains of Lactobacillus have a certain inhibitory effect on 5 pathogenic bacteria,of which the strain LP38 has the best antibacterial effect;Strain LP38 showed the highest DPPH free radical and hydroxyl free radical scavenging activity,and the scavenging rates could reach 45.12% and 66.66% at a concentration of 10 log CFU/m L.Antibiotic sensitivity test results showed that strain KC96 is resistant to all antibiotics,strain LP88 is sensitive to ampicillin and penicillin,strain NS24 is sensitive to ampicillin,penicillin,and tetracycline,and strain LP38 is sensitive to ampicillin and penicillin.In addition,we also found Four S-layer conserved protein motifs and necessary protein interaction networks were found in four Lactobacillus strains.In summary,the strain LP38 showed good probiotic characteristics.Therefore,16 S r DNA molecular biology and phylogenetic tree identification were performed on it,and the strain LP38 was finally determined to be Lactobacillus plantarum.L.plantarum LP38 was added to fermented milk in the form of accessory bacteria,and fermented milk was produced by co-fermentation with the production starter.The results showed that in the fermentation stage,compared with the control group,the addition of L.plantarum LP38 can accelerate the acidification of fermented milk and shorten the fermentation time;during refrigeration at 4 ?,the contents of lactic acid and citrate,as well as the water holding capacity and sensory evaluation scores were higher in the fermented milk containing L.plantarum LP38.