Screening and Production of Antibacterial from Lactobacillus plantarum NS(9) Isolated from Nile Tilapia Bekasam

Lactic acid bacteria has been used as biopreservatif becouse produce a number of antibacterial substances are safety and has inhibitory activity against enteropatogenic bacteria. The aims of this study were to screen of antibacterial compounds produced by Lactobacillus plantarum NS (9) and to produce their antibacterial compounds. The research was devided into two stages. In the first stage was L. plantarum NS (9) inoculated at 37°C, for 24 hours in semi-anaerobic conditions. The cell-free supertnatant was given three treatment, ie not neutralized (A), neutralized (pH 7) (N), and precipitated with ammonium sulfate 50% (P). This three supernatant was assayed their antibacterial activity against E. coli, S. typhimurium ATCC 14028, S. aureus, B. cereus and L. monocytogenes using the agar well diffusion method. In the second stage, production of antibacterial compound was L. plantarum NS (9) inoculated at 37°C, for 24 hours in semi-anaerobic conditions. The Dencity Optical, value pH, acid total and antibacterial activity were measured every three hours during growth of bacteria. The results of the antibacterial screening showed that L. plantarum NS (9) produced inhibitory zone againts the five indicator bacteria from a supernatant, whereas N and P supernatant were not produced inhibitory zone. This result indicated that inhibition activity of L. plantarum (NS 9) was caused by the lower pH of supernatant. The antibacterial compouds were produced at 6 hours of incubation and were increased to simultaneously with increasing of bacteria growth. The highest antibacterial activity against E. coli, B. cereus and L.monocytogenes were produced at the end of the exponential growth phase (12 -15 hours incubation) while against S. aureus and S. typhimurium ATCC 14028 at 21 and 24 hour of incubation, respectively. The antibacterial activity also was increased to simultaniously with increasing of acid total (1.350 to 4.050%) and decreasing of pH value (6-4) during growth of bacteria.