Study On Strain Screening And Bacteriostasis Avtivity Of A Novel Lactobacillin-producing Strain

A novel lactobacillin-producing strain was screened and isolated from pickle samples. A kind of new preliminary isolation way of bacterium producing antibiotic substance was used:culturing bacterium by Ep tubes and isolation bacterium by paper disk test.The strain was identified as Lactobacillus helveticus,by testing physiological- biochemical and morphologic characteristics.We name it HF08.Fermentation conditions for lactobacillin production have been established: 2% glucose as carbon source,1% peptone and 0.5% yeast extract as nitrogen source,initial pH5.5,culture medium volumes for 250ml in 250ml steady shake,seeds age for 72h,inocution 1% and culture temperature 37℃ for 48h.The bacteriostasis avtivity can then reach 141U/mL.The inhibitory activity of the fermenter totally lost after treatment with proteinase K. This kind of lactobacillin substance has very high heat stability and active range of pH(3.5～6.0). The inhibitory activity was stimulated by 0.002mol/L K+ and Mn2+ but inhibited by Fe2+,Cu2+ and Ca2+ while Na+and Mg2+ had few effect.The plasmid was isolated from the cell of HF08.The experiment of plasmid elimination confirmed that the plasmid has some relation to the ability of its bacteriostasis ability. The strains HF08 were immobilized with alginate.The bacteriostasis ability reduced,but the stability was slightly improved.The fed –batch condition can last three cycles.