Characteristics Of Bacteriocin Produced By Enterococcus Faecalis TRS5 And Fermentation Conditions For Its Production

Bacteriocins are antibacterial peptides with antibacterial activity synthesized from ribosomes,it has an autoimmunity to the cell itself.Enterococcus is widely found in foods,The bacteriocin produced by Enterococcus can effectively inhibit Listeria growth or toxicity and it has been used as a bio-preservative in foods.So far,relatively little research has been done on the factors affected of different production of bacteriocins by Enterococcus.Therefore,We studied the probiotic characteristics of E.faeciumTRS5,a bacterin-producing bacteria,and the features of bacteriocin produced by E.faecalisTRS5.At the same time,we optimized the fermentation conditions of E.faecalisTRS5 which affect its bacteriocin producing.The main results are as follows:1.Compared with Lactobacillus rhamnosusLGG,E.faeciumTRS5 had better acid resistance and bile salt resistance.Drug sensitivity test showed that E.faeciumTRS5 had excellent bacteriostasis on tetracycline,piperacillin and other antibiotics.Hemolysis test confirmed that E.faeciumTRS5 was not hemolytic.Nine common virulence genes were not detected by PCR.In growth dynamic experiment,when culture time reached 3h,bacteria growth entered logarithmic growth phase.After 15 h of culture,the bacterial growth entered a stable period and remained basically unchanged after reaching the maximum yield.2.Bacteriocin produced by E.faeciumTRS5 had strong inhibitory effects on most tested bacteria,including Salmonella,Shigella,Staphylococcus aureus and Bacillus subtilis,especially L.monocytogenes.Bacteriocins had good thermal stability within 80?,but lose activity at 100?;between pH 5 and10 E.faeciumTRS5 still had high activity,especially in alkaline conditions.It still had certain antibacterial activity.When pH was at8,it had the strongest antibacterial activity.PCR amplification and sequencing demonstrated that E.faeciumTRS5 harbored enterocin P and L50-like structural genes.3.Antibacterial test was conducted by using the agar diffusion method.Optimal culture condition and medium composition of producing bacteriocin were studied by single-facter-experiment and ortho-experiment design.The results showed that the optimal culture condition for bacteriocin production by E.faeciumTRS5 was at 37?,pH=6.0,with aninoculum concentration of 1%.The optimal carbon source of the culture medium was glucose,the optimal nitrogen source was tryptone and the optimal growth factor was Beef Extract.The optimum dosage of stimulator Tween-80 was 0.2%.The optimum medium composition was as follows: 1.5%glucose,1.5%tryptone,1.5% Beef Extract,0.2% Tween-80,0.2% dipotassium phosphate,0.5% sodium acetate,0.2%triammonium citrate,0.058% magnesium sulfate,and0.025% manganese sulfate,distilled water 1000 mL.Under these conditions,the bacteriocin production of E.faeciumTRS5 was significantly increased with the efficacy value reaching 715AU/ml.