Bacteriostatic And Functional Properties Of Lactic Acid Bacteria And Their Effects On Intestinal Microbial Flora In Mice

In order to screen out lactic acid bacteria strains with good bacteriostatic effects,91 strains were isolated and purified from the commercially available yoghurt by the flat-line drawing method,and their functional characteristics were simulated artificial gastrointestinal fluid,drug resistance,and growth characteristics,Cell surface hydrophobicity,cell self-aggregation and copolymerization characteristics were evaluated in order to screen out potential high-adhesion lactic acid bacteria strains that are resistant to acid and bile salts and have low drug resistance.1.Screening of lactic acid bacteria with highly effective antibacterial and adhesion propertiesThe agar diffusion method was used to perform inhibition zone tests on 91 strains of bacteria.The results showed that the strains Y3,Y9,LC4,W5,W6,W8,YY4,CY3,CY7,CY9,M2,M3,M8,Q7,Q10,YX3 showed Good antibacterial properties.The survival rates of strains Y3,Y9,and M3 in simulated artificial gastric juice(pH3.0)after 3 h showed a positive increase with high survival rates.Tolerance of strain CY9 to artificial intestinal juice showed the best survival rate,reaching 93.20%.According to gastrointestinal fluid test strains Y3,Y9,LC4,W5,W6,W8,YY4,CY3,CY7,CY9,M2,M3,M8,Q7,Q10,YX3 were selected.Resistance tests were continued on the strains.The strains Y9 and M3 showed more or moderate sensitivity to antibiotics.From the situation of the growth curve,it can be known that these 14 strains basically entered the logarithmic growth phase at the second hour,and stabilized at about 14-16h,entered the stable phase,and ended the logarithmic phase.These 14 strains were screened through three aspects,such as cell surface hydrophobicity,self-aggregation rate of lactic acid bacteria,and the co-aggregation rate of lactic acid bacteria and salmonella,to identify lactic acid bacteria strains with high adhesion characteristics,in order to enable them to colonize in the intestine,and Good use of its probiotic effect.Among them,strain Y9 had the highest surface hydrophobicity,which was 54.83%±1.14%,Strains CY8 and W8 had the highest self-aggregation ability,which were 37.46%and 37.25%,respectively.The two strains with the highest co-aggregation rates were YX3 and CY7,which were 23.13%and 22.28%.respectively.In summary,the results show that strains Y9 and M3 show good results in gastrointestinal fluid tolerance,weak drug resistance,growth characteristics,and indicators related to adhesion.16S rDNA sequence analysis was performed on these two strains to identify their species.The results showed that both strains were Lactobacillus casei.2.Effects of Lactic Acid Bacteria on the Structure and Composition of Microbiota in the Intestine of MiceLactobacillus strains Y9 and M3 were screened for adhesion with Caco-2 cells(human cloned colon adenocarcinoma cells)to select strains with higher adhesion.The adhesion index of strain Y9 was 9.53 bacteria/cell,and the adhesion index of strain M3 was 12 bacteria/cell,indicating that strain M3 was the final lactic acid bacteria strain with high efficiency,antibacterial and high adhesion properties.To observe the effect of probiotic lactic acid bacteria on the composition of micro-ecological flora in the intestine of mice by intragastric strain M3,and record the changes in daily body weight and daily food intake of mice from intragastric administration.The group started gavage of Salmonella.It can be seen that the body weight of the mice in the treatment group and the control group is slowly decreasing,while the body weight of the mice in the normal group is slowly increasing.On the 21st day,the treatment group started gavage of Lactobacillus casei M3,and it was found that the mice in the treatment group began to increase in weight,and the growth rate was faster than that in the normal group.After the gavage of Salmonella started on the 14th day,the daily food intake of the mice decreased.During the recovery of gavage of lactic acid bacteria,the daily food intake began to increase significantly.After the mice were dissected,the feces of the mice were collected and subjected to high-throughput sequencing to assess the changes in their microbial composition;according to the Alpha diversity analysis,the community diversity of the treatment group was greater than that of the control group,indicating that lactic acid bacteria M3 will increase intestinal bacteria Group abundance.According to the component diagram of the intestinal flora structure of mice at the genus level,the Bacteroides treatment group that may cause colitis accounts for less than the control group,while the beneficial bacteria treatment such as Akkermansia that reduces the incidence of colitis and prevents obesity The abundance of the group is significantly higher than that of the control group,so cheese lactic acid bacteria M3 can intervene in the intestine of mice,so that the structure of its microbiome can be changed to improve the intestinal flora.