Introduction: Bacteriocins are ribosomal-synthesized peptides with antimicrobial activity, produced by different groups of bacteria, including lactic acid bacteria (LAB). Most of the produced by LAB bacteriocins can be described with rather broad spectra of inhibition and they offer suggested applications in food preservation and pharmaceutical sector. An iconic example for bacteriocins is nisin, produced by different strains of Lactococcus spp., however, to our best of knowledge this is the first report on strains of Lactococcus lactis isolated from kimchi, producer of nisin.
Aim: The goal of this study was to explore bacteriocinogenic properties for LAB isolated from kimchi.
Methods: Different LAB were isolated from kimchi, obtained from the region of Pohang, Korea and identified based on physiological, biochemical, and molecular methods. The promising isolate (Lactococcus lactis subsp. lactis 431) was evaluated for production of bacteriocin, including stability in presence of enzymes, chemicals, pH and temperatures. Adherence properties for the expressed bacteriocins by Lactococcus lactis subsp. lactis 431 were evaluated at presence of selected chemicals, pH and temperatures. The presence of bacteriocin genes in strain 431 was investigated and analyzed. Growth of Lactococcus lactis subsp. lactis 431 in different pH values and presence of ox-bile was explored. Safety properties for Lactococcus lactis subsp. lactis 431 were evaluated.
Results: Selected isolate 431 was identified as Lactococcus lactis subsp. lactis based on biochemical, physiological, and biomolecular 16S rRNA gene sequencing. The bacterial effect of bacteriocin produced by strain 431 on Listeria spp. and Staphylococcus spp., has been shown for actively growing and stationary cells. Similar growth and bacteriocin production were observed when Lactococcus lactis subsp. lactis 431 was cultured in MRS at 30oC or 37oC. The presence of nisin operon with some point mutations on the genomic DNA was recorded based on the performed PCR reactions targeting different genes associated with nisin expression. Good growth for strain 431 was recorded in MRS broth with pH 5.0 to 9.0 and in absence of oxbile or concentration below 0.8%. Lactococcus lactis subsp. lactis 431 was shown that can be considered as safe for human and animals application based on negative reaction for production of biogenic amines, lipolytic, proteolytic and γ-hemolytic activity and susceptibility to different antibiotics and growth not affected by different commercial drugs.
Significance: Lactococcus lactis subsp. lactis 431 shows to have potential beneficial properties: production of nisin, be safe and suitable to GIT environment.
Acknowledgment: Handong Global University, FAPESP (Grant 2013/07914-8) and Centre for Research and Development in Agrifood Systems and Sustainability, funded by FCT (UIDB/05937/2020 and UIDP/05937/2020), Fundação para a Ciência e a Tecnologia, Portugal for providing financial support.
