Preliminary Application,Isolation And Purification Of Bacteriocin Produced By Enterococcus Faecium BZ2

In order to obtain bacteriocin,a natural preservative with antimicrobial ability,the bacteriocin was produced by Enterococcus faecium BZ2(E.faecium BZ2)was purified by ethyl acetate gradient precipitation and Sephadex G-75 gel chromatography,E.faecium BZ2 was previously isolated from the Koumiss samples collected from Xilingol,Inner Mongolia,and the effects of crude bacteriocin extract from E.faecium BZ2 on fresh keeping of chilled pork and mutton were examined.The results were as follows:The potency of the crude extract of bacteriocin from E.faecium BZ2 was obtained by the ethyl acetate gradient precipitation method was 144869 AU/mg,which the volume ratio of Cell-Free supernatant to ethyl acetate was 1:3,and the protein content was 7.264 mg/m L.The crude extract was moderately purified by gel chromatography Sephadex G-75,the optimum separation conditions were the sample quantity was 0.7 mL and the flow rate was 1.0 mL/min,Under this conditions,the antimicrobial titer of the moderately purified bacteriocin was 1382745 AU/mg.There were two proteins in the crude extracted bacteriocin through Tris-Tricine-SDS-PAGE gel electrophoresis,whose molecular weight were between 70-80 kDa.After 30 min treatment at 105 ℃ The crude extract of bacteriocin produced by E.faecium BZ2 still had antibacterial activity against Listeria monocytogenes in the pH range from 2.0 to 7.0,which had antibacterial activity against gram-positive bacteria and gram-negative bacteria which was choiced.When the amount of crude extract of bacteriocin was 200 mg/mL,the fresh-keeping period of pork was prolonged 5 days and that of mutton was extended 7 days compared with the control group.In the crude extracted bacteriocin group,the pH value,TVB-N value and total colony were all lower than those of Nisin addition group with the same titer,indicated that the effect of crude extracted bacteriocin from E.faecium BZ2 was slightly better than Nisin.The crude bacteriocin produced by E.faecium BZ2 had antibacterial and fresh keeping effect on both chilled pork and mutton.The pH value,TVB-N value,and total colony during storage period all increased,but magnitudes of above three indicators were not completely synchronized during the storage period.