Lactolisterin BU-producer Lactococcus lactis subsp. lactis BGBU1-4: Biocontrol of Listeria monocytogenes and Staphylocococcus aureus in fresh soft cheese and effect on immunological response of rats

In last two decades, there has been a strong trend in the application of lactic acid bacteria as adjunctive cultures to control growth of spoilage and pathogenic bacteria in food. One of the most important properties that contribute to the application of these bacteria is the production of antimicrobial molecules. Lactococcus lactis subsp. lactis BGBU1-4, isolated from traditional brined cheese, produces thermostable bacteriocin named lactolisterin BU, with broad spectrum of activity against spoilage bacteria and foodborne pathogens. In this study, effect of strain BGBU1-4, as adjunct culture, on the numbers of Listeria monocytogenes ATCC19111 and Staphylococcus aureus LMM322 in artificially contaminated Quark-type, soft acid coagulated cheese, was examined. In addition, we analyzed influence of BGBU1-4 on chemical and sensory properties of the cheese, as well as immunological response of Albino oxford rats fed with Quark-type of cheese made using BGBU1-4 as adjunct culture. Results of this study revealed antibacterial potential of strain BGBU1-4 against L. monocytogenes ATCC19111 and S. aureus LMM322 in Quark-type cheese during 21 days of storage at 4 degrees C. Also, it was noticed the ability of BGBU1-4 to control the spontaneously grown yeasts and molds. Chemical composition and pH values of cheese containing BGBU1-4 were unchanged in comparison to control. The sensory quality scores showed that there was difference between cheese with and without adjunct culture in terms of flavor and oral texture, while for the odor and appearance no differences between two cheese variants were scored. Results of the immunological response of Albino rats fed with Quark-type cheese containing BGBU1-4 indicate absence of systematic inflammation. However, increased pro-inflammatory cytokines content (IL-1 beta, IL-6, IL-17) in intestine of rats fed with cheese containing BGBU1-4, concomitantly with unchanged anti-inflammatory cytokines suggests disruption of gut homeostasis and inflammation in this tissue. The changes caused by BGBU1-4 are reversible, system returns into homeostasis seven days after cessation of feeding with cheese containing BGBU1-4