Determination of the Antibacterial Constituents Produced by Lactobacilli against a Periodontal Pathogen: Sodium Lactate and a Low Molecular Weight Substance

Background and objectives: Probiotics are living bacteria which can improve the balance of microbiota. There are many recent studies on the effects of probiotics, including oral health promotion and the prevention of oral diseases. However, the mechanisms that underlie the activity of probiotic bacteria against periodontal pathogens have not been clearly elucidated. The purpose of this study was to examine the effects of lactic acid bacteria as probiotics in the prevention and treatment of periodontal disease. Material and Methods: The growth inhibitory effects of the culture supernatants of 50 strains of lactobacilli on the periodontal pathogen Porphyromonas gingivalis ATCC33277 were examined. To obtain a substance with antibacterial properties under neutral pH conditions, each culture supernatant was neutralized and purified by gel filtration column chromatography and reverse-phase HPLC. The molecular weight of purified substances was analyzed with LC-MS. Results: The results showed that two strains of Lactobacillus plantarum 122 (derived from the oral cavity) and L. fermentum ALAL020 (derived from fermented soy milk food products) had strong growth inhibition effects. The major antibacterial substance produced by L. plantarum 122 was thought to be sodium lactate. On the other hand, the molecular weight of the major antibacterial substance produced by L. fermentum ALAL020 we purified was 226.131 Da. An LC-MS analysis revealed that it had the following composition: C11H18O3N2. Conclusion: The antibacterial substance of L. plantarum 122 against P. gingivalis was sodium lactate, and that of L. fermentum ALAL020 we purified was a novel low molecular substance. This antibacterial substance has a possibility for using periodontal disease prevention.