Study On Probiotic Properties Of Enterococcus Faecalis EF-ZA1107-06 And Its High Density Culture

Enterococcus is widely used in the food,feed and pharmaceutical industries.At present,the two enterococcus strains most widely used in the market are Enterococcus faecium SF68from Switzerland and Enterococcus faecalis Symbioflor 1 from Germany.However,there are few enterococcus developed independently in China.In this study,a strain of enterococcus isolated from the feces of 1-month-old infants in Guangzhou was studied.And the safety and probiotic performance(hydrophobicity,self-cohesion,artificial gastrointestinal tolerance,antibacterial activity,hypoglycemic activity,cholesterol-lowering ability and antioxidant activity)of strain were investigated,and cell models were established to evaluate the effect of the strain on oxidative stress and its antitumor activity.In addition,the culture conditions of the strain were optimized to obtain the maximum number of viable bacteria.The strain was identified as Enterococcus faecalis by molecular biology and named Enterococcus faecalis EF-ZA1107-06(EF-ZA1107-06 for short).The safety evaluation of the strains showed that the strains did not produce nitroreductase and amino decarboxylase,had no hemolytic activity,had moderate to high sensitivity to common antibiotics,did not contain plasmids,and had no acute toxicity to animals.In conclusion,EF-ZA1107-06 is a safe strain.Probiotic evaluation of EF-ZA1107-06 in vitro showed that the strain had a certain hydrophobicity and self-cohesion,which were(17.74±0.07)%,(96.0±1.7)%,and had a certain artificial gastrointestinal tolerance,and had antibacterial activity against common pathogenic bacteria;The maximum inhibitory rate of EF-ZA1107-06 against?-glucosidase was(21.57±0.15)%,and the maximum inhibitory rate against?-amylase was(57.7±0.43)%;EF-ZA1177-06 had the ability of disentanglement of conjugated bile salt co-precipitation,and the cholesterol clearance rate was(44.29±0.30)%.Moreover,the cholesterol clearance rate of growing cells and resting cells was higher than that of inactivated cells;The supernatant,lysate and suspension of the strain all had certain free radical scavenging ability,iron ion chelating ability,reducing activity and hydrogen peroxide tolerance.Cell models were established to evaluate the antioxidant activity and antitumor activity of EF-ZA1107-06.The oxidative damage model of Caco-2 cells was established by stimulating the cells with H₂O₂.The results showed that the supernatant,lysate and inactivated bacteria of EF-ZA1107-06 have a protective effect on oxidative stress damage of Caco-2 cells.The antitumor results showed that the inactivated bacteria of EF-ZA1107-06 had the best inhibitory effect on Hep G2 and MDA-MB-231 cells,and the highest inhibitory rate on Hep G2 cells was(59.96±0.95)%,which was equivalent to the level of the positive control5-Fu and the highest inhibition rate on MDA-MB-231 cells is(71.22±0.72)%,which was significantly higher than the level of 5-FU(50.64±0.63)%.In addition,the inactivated bacteria of EF-ZA1107-06 had an inhibitory effect on the cycle of Hep G2 and MDA-MB-231cells and also can induce early cell apoptosis.Study on characteristics of EF-ZA1107-06 and its high density culture.Characteristic studies showed that Enterococcus faecalis EF-ZA1107-06 had good acid tolerance.The optimal medium was 2.0%glucose,2.0%yeast powder,3.0%beef extract and 0.08%magnesium sulfate.After optimization,the viable bacteria count of EF-ZA1107-06 was increased by 7 times.