| Manchu sour tea,also known as "bean juice",is a distinctive summer drink for the Manchu people.It has the functions of invigorating the spleen,moistening the intestine and reducing inflammation,generating fluid and relieving thirst,assisting digestion and eliminating fatigue,etc.Lactic acid bacteria is the absolute dominant bacteria in the fermentation process of sour tea.However,there is no report on the research and application of lactic acid bacteria in Manchu acid tea.In this study,4 strains of Lactiplantibacillus plantarum A-1,A-2,B-1,B-2 and 1 strain of Swiss Lactobacillus helveticus M-1 isolated from Manchu sour tea are used as test strains.A series of tests were conducted to evaluate the safety,growth and probiotic properties,aiming at screening the safe strains with potential probiotic properties,and providing reference for the application of lactic acid bacteria resources in Manchu sour tea in probiotic products.The test results are as follows:1.Safety evaluation of lactic acid bacteriaThe 5 strains of lactic acid bacteria in this study had no nitrate reductase activity,amino acid decarboxylase activity,and hemolytic activity,and were sensitive to most antibiotics.A series of safety evaluation tests showed that all 5 strains of lactic acid bacteria had basic safety.2.Growth characteristics evaluation of lactic acid bacteriaIn this experiment,the logarithmic growth stage of the 5 strains was 4-12 h,and each strain had strong growth activity and good acid production ability,and grew well at 37℃and Na Cl concentration ≤6%.When Na Cl concentration was 8%,strains A-2,B-1 and B-2 were still tolerant to Na Cl,and had good tolerance to Na Cl.3.Evaluation of probiotic properties of lactic acid bacteria(1)All 5 strains could tolerate 0.3%(w/v)bile salt environment.(2)After being treated in artificial gastric juice for 3 h,the survival rates of strains A-1,A-2,B-1,B-2 and M-1 were 76.24%,68.36%,45.08%,81.26% and 51.17%,respectively,indicating that strains A-1,A-2 and B-2 had good tolerance,all of which were above 65%.(3)After being treated in artificial intestinal solution for 8 h,the survival rates of strains A-1,A-2,B-1,B-2 and M-1 were 73.88%,64.71%,45.68%,75.44% and 57.16%,respectively,indicating that strains A-1,A-2 and B-2 had good tolerance,all of which were more than 60%.(4)In the test of hydrophobic ability,the hydrophobic rates of strain A-1,A-2,B-1,B-2 and M-1 were 38.49%,46.03%,42.76%,47.13% and 33.32%,respectively,indicating that strain B-2 had the strongest hydrophobic ability,followed by A-2.(5)In the test of self-coagulation ability,the hydrophobic rates of strain A-1,A-2,B-1,B-2 and M-1 were 49.42%,64.07%,55.72%,61.75% and 44.93%,respectively,indicating that strain A-2 had the strongest hydrophobic ability,followed by B-2.(6)In the co-aggregation ability test,strains A-2 and B-2 had better co-aggregation ability with Staphylococcus aureus,Escherichia coli and Salmonella.(7)Bacteriostatic ability test,strains A-2,B-1,B-2 had better bacteriostatic ability against Staphylococcus aureus,Escherichia coli and salmonella(bacteriostatic zone >10mm).(8)In the test of antioxidant capacity,the antioxidant capacity of strain A-2 and B-2 was better,and the DPPH clearance rate of fermentation supernatant of strain A-2 was the highest,which was 46.37%.The scavenging rate of hydroxyl radical in cell suspension of strain A-2 was the highest(60.09%).The scavenging rate of superoxide anion radical in the supernatant of strain B-2 fermentation was the highest,which was28.71%.(9)In the cholesterol degradation ability test,the degradation rates of strain A-1,A-2,B-1,B-2 and M-1 were 45.57%,47.01%,45.19%,47.85% and 35.47%,respectively,indicating that strain B-2 had the strongest degradation ability,which was actually A-2.Based on the results of all evaluation tests,strains A-2 and B-2 were identified as the best potential beneficial strains,which had great potential in the development and application of probiotics. |
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