Abstract: Nutrient broth media containing different concentrations of sodium lactate (0, 0.2, 0.5, 1.0, 1.5 g/100 mL and 2.0 g/100 mL; consequent pH 4.0－6.2) were used to culture Pseudomonas aeruginosa constantly at 25 ℃ to examine the inhibitory effect of sodium lactate on bacterial growth. In the proper pH range, sodium lactate showed outstanding antibacterial activity. At a medium pH level lower than the critical inhibitory pH, the antibacterial effect of sodium lactate was directly proportional to the corresponding concentration. At a medium pH of 4.8, sodium lactate exhibited the highest antibacterial activity at 2.0 g/100 mL, followed by 1.0 g/100 mL; the antibacterial activity was the weakest at 0.5 g/100 mL. At a constant sodium lactate concentration, the antibacterial activity was inversely proportional to medium pH.

Key words: preservative, Pseudomonas aeruginosa, sodium lactate, pH