Study on Bacteriostatic Characteristics of Lactobacillus plantarum LV02 and Optimization of Fermentation Medium

  Objective  Bacteriostatic property of Lactobacillus plantarum LV02 bacteriocin produced on an optimized fermentation medium was determined.

  Method  Based on a single-factor design, the PB and the steepest ascent experiments were conducted to locate the center point of the step length and direction of the influencing factors for a CCD test. Subsequently, effects of different media on the bacteriostatic property and OD₆₀₀ of the cultured L. plantarum LV02 were evaluated for formulation optimization. The Oxford cup method was employed to determine the bacteriostatic capacity and stability under application conditions of the resulting LV02 bacteriocin produced on the optimized medium.

  Result  The optimized formula for the LV02 fermentation medium in 1 L of water constituted 34.07 g of glucose, 18.12 g of yeast extract, 2 g of dipotassium hydrogen phosphate, 0.16 g of manganese sulfate, 5 g of sodium acetate, 0.20 g of magnesium sulfate, 1 g of ammonium citrate, 1 mL of Tween 80, and 50 mL of carrot juice. On the optimized medium, LV02 grew to yield a 12% increase on OD₆₀₀ and bacteriocin with a 26% increase on the diameter of inhibition zone against Escherichia coli YS. For the crude LV02 bacteriocin extraction, 80% saturation concentration of ammonium sulfate was used. The antibacterial LV02 bacteriocin was stable under 100 ℃ for 120 m and pH 3.0～7.5.

  Conclusion  L. plantarum LV02 cultured on the optimized fermentation medium was bacteriostatic against E. coli YS. The fermentation produced bacteriocin with desirable stabilities to heat, acid, and slight alkaline condition and was considered promising for the development of an antibacterial agent.