Twenty-three strains of Leuconostoc species and 45 strains of Weissella species inhibiting the growth of Lactobacillus sakei, one of the most populous lactic acid bacteria in over-ripened kimchi, were isolated from kimchi in our previous study. Among these hetero-fermentative 68 strains, Leuconostoc mesenteroides CK0128, Weissella cibaria CK0633, and W. cibaria KK0797 exhibited a relatively high survival rate in MRS medium, which was adjusted to pH 4.3 using an acid mixture consisting of acetic and lactic acids, and produced a large amount of exopolysaccharides. The culture supernatants of 3 strains were fractionated by a molecular weight cutter and lyophilized. The fractions with a molecular weight smaller than 3,000 Da showed antagonistic activity against Staphylococcus aureus and Lb. sakei. The anti-bacterial substances were very stable to heat treatments ($121^{circ}C$, 15 min) and active at acidic conditions below pH 5. ${alpha}$-Amylase, lipase, and proteolytic enzymes (proteinase K and pepsin) did not affect their activities. These non-proteinaceous anti-bacterial substances inhibited the growth of several food pathogens.