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In vitro assessment of safety and probiotic potential characteristics of Lactobacillus strains isolated from water buffalo mozzarella cheese
(Annals of Microbiology, 2017-02-28) Todorov, Svetoslav Dimitrov; Casarotti, Sabrina Neves; Carneiro, Bruno Moreira; Nero, Luis Augusto; Rahal, Paula; Penna, Ana Lúcia Barretto
The aim of this study was to evaluate the safety and probiotic potential characteristics of ten Lactobacillus spp. strains (Lactobacillus fermentum SJRP30, Lactobacillus casei SJRP37, SJRP66, SJRP141, SJRP145, SJRP146, and SJRP169, and Lactobacillus delbrueckii subsp. bulgaricus SJRP50, SJRP76, and SJRP149) that had previously been isolated from water buffalo mozzarella cheese. The safety of the strains was analyzed based on mucin degradation, hemolytic activity, resistance to antibiotics and the presence of genes encoding virulence factors. The in vitro tests concerning probiotic potential included survival under simulated gastrointestinal (GI) tract conditions, intestinal epithelial cell adhesion, the presence of genes encoding adhesion, aggregation and colonization factors, antimicrobial activity, and the production of the β-galactosidase enzyme. Although all strains presented resistance to several antibiotics, the resistance was limited to antibiotics to which the strains had intrinsic resistance. Furthermore, the strains presented a limited spread of genes encoding virulence factors and resistance to antibiotics, and none of the strains presented hemolytic or mucin degradation activity. The L. delbrueckii subsp. bulgaricus strains showed the lowest survival rate after exposure to simulated GI tract conditions, whereas all of the L. casei and L. fermentum strains showed good survivability. None of the tested lactobacilli strains presented bile salt hydrolase (BSH) activity, and only L. casei SJRP145 did not produce the β-galactosidase enzyme. The strains showed varied levels of adhesion to Caco-2 cells. None of the cell-free supernatants inhibited the growth of pathogenic target microorganisms. Overall, L. fermentum SJRP30 and L. casei SJRP145 and SJRP146 were revealed to be safe and to possess similar or superior probiotic characteristics compared to the reference strain L. rhamnosus GG (ATCC 53103).
Characterization of bacteriocins produced by strains of Pediococcus pentosaceus isolated from Minas cheese
(Annals of Microbiology, 2018-05-18) Nero, Luis Augusto; Gutiérrez-Cortés, Carolina; Suarez, Héctor; Buitrago, Gustavo; Todorov, Svetoslav Dimitrov
Interest in obtaining bacteriocin-producing strains of lactic acid bacteria (LAB) from different sources has been increasing in recent years due to their multiple applications in health and food industries. This study focused on the isolation and characterization of metabolically active populations of bacteriocinogenic LAB and the evaluation of their antimicrobial substances as well as of some nutritional requirements of them. One hundred and fifty colonies of LAB from artisanal cheeses produced in Minas Gerais state (Brazil) were isolated and screened for their antimicrobial activity. According to their activity against Listeria monocytogenes, ten strains were selected and subsequently identified using biochemical and molecular techniques including 16s rRNA amplification and sequencing as Enterococcus faecalis, Lactobacillus spp., and Pediococcus pentosaceus. Antimicrobial substances produced by four of the selected strains, P. pentosaceus 63, P. pentosaceus 145, P. pentosaceus 146, and P. pentosaceus 147, were biochemically characterized, and presented sensitivity to proteolytic enzymes (suggesting their proteinaceous nature) and to extreme pH. Antimicrobial activity showed stability after treatment with lipase, catalase, α-amylase, and chemicals. Growth kinetics of the P. pentosaceus selected showed maximal bacteriocin production at 37 °C during the end of the exponential growth phase (25,600 AU/mL) and stable production during 24 h of incubation. Dextrose, maltose, and a mixture of peptone, meat extract, and yeast extract increased bacteriocin production. This study demonstrated that dairy products provide a good alternative for obtaining LAB, with the ability to produce antimicrobial substances such as bacteriocins that have potential use as biopreservatives in food.
Technology and safety assessment for lactic acid bacteria isolated from traditional Bulgarian fermented meat product “lukanka”
(Brazilian Journal of Microbiology, 2017-05-11) Todorov, Svetoslav Dimitrov; Nero, Luis Augusto; Ivanova, Iskra Vitanova; Stojanovski, Saso; Iliev, Ilia; Moncheva, Penka
The present work discusses the technological and new selection criteria that should be included for selecting lactic acid bacteria for production of fermented meat. Lactic acid bacteria isolated from Bulgarian traditional fermented “lulanka” salami was studied regarding some positive technological parameters (growth at different temperature, pH, and proteolytic activity). The presence of genes related to the virulence factors, production of biogenic amines, and vancomycin resistance were presented in low frequency in the studied lactic acid bacteria. On the other hand, production of antimicrobial peptides and high spread of bacteriocin genes were broadly presented. Very strong activity against L. monocytogenes was detected in some of the studied lactic acid bacteria. In addition, the studied strains did not present any antimicrobial activity against tested closely related bacteria such as Lactobacillus spp., Lactococcus spp., Enterococcus spp. or Pediococcus spp. To our knowledge this is the first study on the safety and antimicrobial properties of lactic acid bacteria isolated from Bulgarian lukanka obtained by spontaneous fermentation.

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