Characteristics of the antibacterial substances produced by Lactobacillus casei subsp. and Streptococcus faecium

Lactobacillus casei subsp. 및 Streptococcus faecium이 생산한 항균성물질의 성상

Antibacterial substances produced by Lactobacillus casei subsp. and Streptococcus faecium were examined for its antibacterial effects against some pathogenic bacteria. They were partially purified with ammonium sulfate precipitation, methanol-acetone extraction, G-50 gel filtration and examined its characteristics. When L casei subsp. and Str faecium were cultivated in MRS broth, stationary phase of L casei is until 24 hours and Str faecium is 20 hours. pH change of the cultured medium was both decreased after 12 hours and then constant at pH 4.5~4.6 after 28 hours. MRS broth culture fluids of L casei subsp. and Str faecium appeared the antibacterial effects by the spot-on-the-lawn method against ETEC, Sal pullorum and Sta aureus. Culture filtrates of L casei subsp. and Str faecium also appeared the antibacterial effects by the disc diffusion method. Culture filtrates of L casei sub. rhamnosus 7469 produced 0.032M of lactic acid and 0.01M of acetic acid. Str faecium 27273 also produced 0.027M of lactic acid and 0.01M of acetic acid. Protein concentrations of culture filtrates produced by L casei sub rhamnosus 7469 and Str faecium 27273 was $495{\mu}g/m{\ell}$ and $594{\mu}g/m{\ell}$, respectively. Antibacterial substances which are partially purified by ammonum sulfate precipitation, methanol-acetone extraction and G-50 gel filtration inhibit the growth of ETEC, Sal pullorum and Sta aureus. Characteristics of purified antibacterial substances was examined. Its molecular weight was about 31Kd, stabilized at $100^{\circ}C/20min.$ and some of proteolytic enzyme treatment.