Anti-listeria activity of newly isolated lactic acid bacteria from fermented foods and their application to smoked salmon(Coho)

Abstract

The objective of this study was to evaluate the anti-listeria activities of lactic acid bacteria (LAB) isolated from Korean fermented foods and to assess the effect of fermentate (cells and cell-free supernatant [CFS]), CFS or cells in controlling L. monocytogenes on smoked salmon, packaged either in vacuum- and air-packaging. One L. lactis (CJNU3001) strain and two Enterococcus faecium (CJNU2524 and CJNU2008) strains appeared to have higher anti-listeria activity than the other 15 LAB strains. They also exhibited anti-listeria activity against 24 L. monocytogenes strains of various serotypes. CJNU3001 had greater anti-listeria activity in brain heat infusion broth than the two E. faecium strains. No anti-listeria activity was observed when the partially purified proteinaceous compounds of all three LAB strains were treated with proteinase K, revealing that their anti-listeria activities might be due to bacteriocins. Amplification and sequence analysis of the nisin gene confirmed that CJNU3001 was a nisin Z producer. The treatment of fermentate and CFS of CNJU3001 on smoked salmon inoculated with L. monocytogenes at 6.0 log CFU/g inhibited the growth of the pathogen during storage. On the other hand, about 2.0 log reduction was achieved immediately after treatment of the fermentate and CFS of CNJU3001 when L. monocytogenes was inoculated at 5.0 log CFU/g, regardless of storage temperature and packaging type. The treatment using only CJNU3001 cells was not effective in controlling L. monocytogenes on smoked salmon, regardless of inoculation level of the pathogen. The fermentate and CFS treatment of CJNU3001 did not cause any color change of vacuum-packed smoked salmon. Thus, this study suggests that CJNU3001 fermentate and CFS as biopreservatives could be used to control the growth of L. monocytogenes on smoked salmon without causing color change.