Study On Bacteriocin-like Substance Fermentation By Immobilized Bacillus Subtilis LL18-4

A novel bacteriocin-like producing strain was screened and isolated from mature alcohol distillery grain and yellow water samples. The strain was identified as Bacillus subtilis by physiological-biochemical testing, and morphologic Characteristics. The 16S rDNA gene of the strain were amplified by PCR,and sequenced. It was named LL18-4.Immobilized cells has many advantages over free-cell cultures, including higher productivity as a result of high cell densities, long-term operational stability, improved process control, protection against contamination, and improved plasmid stability. The attempts were made to produce bacteriocin-like substance by immobilized cells of Bacillus subtilis LL18-4 entrapped in calcium alginate beads.The results showed that the immobilized cell beads were intact for 216hr under 3% of calcium alginate in 2% CaCl₂ solution.The physical stability of beads was improved .and the following fermentation conditions were the best for Immobilized cell to produce bacteriocin-like substance of the highest activity:culture temperature at 37℃,pH 6.5,1% inoculation quantity, incubated 72h culture time and valence as 334.2u/ mL. the concentration of bacteriocin-like produced during the third cycles increased to 260.9u/ mL. Primary study of biological properties of such strain indicated that such strain partial sensitive to proteinase K. This kind of bacteriocin-like substance has high heat stability. Bacteriostasis activity pH ranged between 4.5 to 8.5.BLS producing strains were determined under conditions eliminating the effects of organic acids and hy- drogen peroxide. As a result, this inhibitory spectrum was obtained by the well-diffusion assay. It exhibited a broad spectrum of antimicrobial activity including against various plant pathogenic fungi. The bacteriostasis activity substance would be a kind of protein.The fermentation results are desirable, and it shows an abroad prospect of applications.This bacteriocin-like substance might be useful as a natural preservative.