The Probiotic Properties Of Lactococcus And Its Application In Fermented Milk

Probiotics are considered to be microorganisms symbiotic with the host,which can produce many biological functions when reached a certain amount and have a positive effect on health.Therefore,In this study,lactic acid bacteria were first isolated and purified from6 types of milk and dairy products produced by herdsmen’s families in Balinyou Banner,Chifeng City,Inner Mongolia.Then we screened lactococcus with probiotic properties and identified the species.Finally,it was applied to fermented milk to provide strain resources for the future development and utilization of probiotics.the results of the study are as following:(1)A total of 64 strains of lactic acid bacteria were isolated and screened from 6 types of milk and dairy product samples produced by herdsmen’s families in Balinyou Banner,Chifeng City,Inner Mongolia,including 43 strains of Lactococcus and 21 strains of Lactobacillus.(2)43 strains of Lactococcus were tested by acid tolerance(p H2.0 and p H2.5)test and bile salt tolerance(0.3% W/V)test,and four strains with strong tolerance were screened,which were strains 3-4,6-1,6-3 and 14-5-1,respectively.The survival rate of the patients was 52.85%,62.84%,54.47% and 83.17%,respectively.(3)According to the antioxidant test,the DPPH free radical scavenging rate and reducing ability of cell suspension and cell-free extract of strain 14-5-1 were the strongest,that is,DPPH free radical scavenging rate was 54% and 33%,and reducing ability was 135%and 123%,respectively.In addition,according to the antibacterial activity test and hydrophobicity test,the antibacterial activity and hydrophobicity of strain 14-5-1fermentation broth were the strongest.It had inhibitory activity against Escherichia coli,Staphylococcus aureus and Aspergillus oryzae with a hydrophobic rate of 47.39%.Therefore,strain 14-5-1 was identified as the target strain.And it was identified by the sugar fermentation test and molecular biology test,and the 16 S r DNA gene sequence length of strain 14-5-1 was 1495 bp,which was 100% homologous with Pediococcus acidilactici R10,and the strain 14-5-1 is consistent with the results of the saccharide fermentation test of Pediococcus acidilactici.Therefore,strain 14-5-1 was identified as Pediococcus acidilactici.(4)According to the application study of strain 14-5-1 in fermented milk,the optimal fermentation conditions of fermented milk were as follows: inoculation amount of 5%(V/V),sugar addition amount of 6.5%,fermentation temperature of 42℃ and fermentation time of8 h.The fermented milk had suitable acidity(titrated acidity 92°T),smooth texture,the highest viable bacteria count of 8.92 lg(CFU/m L),high hardness and high sensory score during 28 d storage period;It was found that the coliform group(1 CFU/m L)of fermented milk did not exceed the national standard,and staphylococcus aureus and yeast were not detected,which met the quality index of fermented milk.In conclusion,the results of this study provide the basis and experimental material for the study of probiotic properties and application of Pediococcus acidilactici 14-5-1.