Partial characterization of lacticin NK24, a newly identified bacteriocin of Lactococcus lactis NK24 isolated from Jeot-gal

Strain NK24 was isolated from Jeot-gal and identified as a bacteriocin prod ucer, which has bactericidal activity against Leuconostoc mesenteroides KCC M 11324. Strain NK24 was identified tentatively as Lactococcus lactis by th e API test. The activity of lacticin NK24, named tentatively as the bacteri ocin produced by L. lactis NK24, was defected during the mid-log growth pha se, reached a maximum during the early stationary phase, and decreased afte r the late stationary phase. Lacticin NK24 showed a relatively broad spectr um of activity against non-pathogenic and pathogenic micro-organisms as ass essed using the spot-on-lawn method. Its antimicrobial activity on sensitiv e indicator cells was completely destroyed by protease IX or protease XIV T he inhibitory activities of lacticin NK24 were defected during treatments u p to 100 degreesC for 30 min. Lacticin NK24 was very stable over a pH range of 2.0-9.0 and to all organic solvents examined it demonstrated a typical bactericidal mode of inhibition against L. mesenteroides KCCM 11324. The ap parent molecular mass of lacticin NK24 was estimated to be in the region of 3-3.5 kDa, which was determined by the direct detection of bactericidal ac tivity after SDS-PAGE. (C) 2001 Academic Press.