Recently, the use of probiotics to prevent oral diseases is on focus. However, the probiotic mechanism against periodontal pathogens has not been elucidated. For clarification, we analyzed the characteristics of the active components in the culture supernatant produced by Lactobacillus fermentum ALAL020 (Lf020), which has antibacterial activity against Porphyromonas gingivalis.
The culture supernatant of Lf020 was heated to 37 °C, 60 °C, 100 °C and 121 °C for 15 minutes to compare the antibacterial temperature sensitivity against the P. gingivalis type strain. We also compared the antimicrobial susceptibility to other P. gingivalis strains and the inhibitory effect of trypsin-like enzyme (gingipain) activity. Further, we have already reported that the antibacterial components include a cyclic-dipeptide (2016 IADR). Here a synthesized dipeptide was used to test the antibacterial activity against P. gingivalis and Prevotella intermedia as well as the gingipain inhibitory test.
The antibacterial activity of the culture supernatant of Lf020 against P. gingivalis was reduced to half by temperature treatment at 37 ° C or higher, but not further even when the temperature was raised. The antibacterial test results with several strains of P. gingivalis showed differences in susceptibility. The gingipain inhibitory test suppressed all P. gingivalis strains by the Lf020 culture supernatant. The synthetic dipeptide showed antibacterial activity at 5 mg/ml against P. gingivalis and P. intermedia, but did not have an inhibitory effect on gingipain activity.
The culture supernatant of Lf020 was thermostable and effective against all strains of P. gingivalis, but there were differences in sensitivity. The synthetic dipeptide showed antibacterial activity at the same concentration as the natural antibacterial dipeptide purified from the culture supernatant of Lf020, but gingipain inhibition was not observed. Therefore, it is likely that other substances suppress P. ginigvalis in the culture supernatant of Lf020.