Document Type : Original Article
MICROBIOLOGY DEPARTMENT, MEDICAL SCHOOL, IRAN MEDICAL UNIVERSITY, TEHRAN, IRAN
Introduction: Selected probiotic lactobacilli have inhibitory effect and therefore may be use as biological preservative, so, the aim of this study was to present some data on isolation, growth, antimicrobial activity, effect of pH, heat, and sensitivity to proteolytic enzymes of lactobacillus.
Material and Methods: Isolation of lactic acid bacteria from sausage was done by using 1g of samples in MRS medium. Each isolate of lactobacillus species was identified by biochemical tests and comparison of their sugar fermentation pattern. Antibacterial activities was done by an agar spot, well diffusion and blank disk method. Stability of antibacterial activity was measured in boiling water and autoclaving for 15 min. Enzyme sensitivity of supernatant fluid and concentrated cell free culture after treatment with a-amylase, lysozyme and trypsin was determined.
Results: The isolated bacteria were Lacto. plantarum, Lacto delbruekii, Lacto. acidophilus, Lacto. brevis. The isolated bacteria had strong activity against indicator strains. The antibacterial activity was stable at 100?C for 10 minutes and at 56?C for 30 minutes, but activity was lost after autoclaving. The maximum production of bacterocin was obtained at 25-30°C at pH 6.5.
Discussion: If Lactobacilli that are used to induce sausage fermentation have antimicrobial activity with heat stable bacteriocin, these bacteria may be considered to be a healthy probiotic diet. Lactobacilli originally isolated from meat products are the best candidates as probiotic bacteria to improve the microbiological safety of these foods.