Abstract
We investigated the antimicrobial activity of several bacteriocins, which were produced by newly isolated lactic acid bacteria in koji extract medium supplemented with rice protein hydrolyzate (RPH), against strains of NBRC type culture and spoilage bacteria isolated from deteriorated sake. The partial sequences of the 16S rRNA gene of the spoilage bacteria isolated from sake showed a high similarity to those of Lactobacillus fructivorans, Lactobacillus hilgardii, and Lactobacillus paracasei, with 99.6-100% identity. Enterococcus durans C102901 (C102901), Lactococcus lactis subsp. lactis C101910 (C101910), and Lactococcus lactis subsp. lactis NBRC 12007 (NBRC 12007) grew well and produced bacteriocins with high activity in koji extract medium supplemented with RPH. When culture supernatants containing bacteriocins from C101910 and NBRC 12007 were added to the medium at a volume ratio of 10% (v/v), the growth of L. fructivorans NBRC 13954T was significantly inhibited and the viable cell concentration decreased below the detection limit (1.0×102 cells/ml) at 4 h. Further, by the addition of bacteriocin solutions from C102901, C101910, and NBRC 12007 to the medium at a volume ratio of 1% (v/v), the growth of L. hilgardii NBRC 15886T and H130 (closely related to L. hilgardii) isolated from putrid sake was bactericidally inhibited and the colony-forming units fell by more than three orders of magnitude within 4-12 h as compared with the initial cell concentration.
