Effect of garlic extract (GE) and diallyldisulfide (DADS) which is a principal component of antibacterial activity in GE on the growth of Escherichia coli were investigated.
1) GE or DADS inhibited the growth during 24 hr incubation. But GE in low concentration. promoted the growth after 48 hr incubation, whereas DADS did not. Cysteine reduced this inhibition.
2) By heating GE for 5 mmn. in boiling water bath, the inhibitory activity was reduced, but the promotive factor was not destroyed.
3) Growth rate on the incubation at 25 °C was slower than that at 37 °C, and inhibitory effect of GE at 25 °C was more active than that at 37V °C.
4) GE and lactic or acetic acid inhibited the growth synergistically.
5) Increasing the concentration of GE or DADS in the medium extended the lag phase of the bacteria in shaking culture.
6) Both GE and DADS showed bactericidal action on the bacteria.
7) It was presumed that the inhibitory factor in GE was reduced during the incubation, but the promotive factor presented in GE was kept or activated, then the growth promotion by GE was observed in later stage of the cultivation.