ESB - Dissertações de Mestrado / Master Dissertations
Permanent URI for this collection
Browse
Browsing ESB - Dissertações de Mestrado / Master Dissertations by advisor "Albano, Helena da Conceição Pereira"
Now showing 1 - 1 of 1
Results Per Page
Sort Options
- Probiotic potential of leuconostoc lactis rk18 isolated from fermented food and its bacteriocinogenic activity against foodborne pathogensPublication . Oliveira, Mónica Raquel Brás; Teixeira, Paula Cristina Maia; Albano, Helena da Conceição Pereira; Barbosa, Joana Inês BastosFermentation is one of the oldest techniques for the production of foods. Lactic acid bacteria (LAB) have been progressively used in food industry since, besides improving nutritional and technological features, they also contribute to the safety of food products. Consequently, this work aimed to isolate lactic acid bacteria from several food products and to evaluate their potential antimicrobial activity and probiotic characteristics. From 202 LAB isolated from 20 fermented food products, only three isolates were selected and identified as Enterococcus faecium RS7 (fermented shrimp), Enterococcus faecium P12 (pork sausage) and Leuconostoc lactis RK18 (khmer fermented rice fresh noodles) based on their antimicrobial activity against Enterococcus faecalis and Listeria monocytogenes strains. These selected isolates were further tested for probiotic characteristics. Despite the beneficial characteristics apparently presented by the three isolates due to their antimicrobial activity, only Ln. lactis RK18 met the safety requirement and therefore it was the only isolate selected for further tests. Leuconostoc lactis RK18 did not present any of the virulence factors nor virulence genes tested (with exception of aggregation substance protein gene asa1), and it was also susceptible to all antibiotics recommended by European Food Safety Authority. Regarding beneficial characteristics, it was found that anti-listerial activity of Ln. lactis RK18 was due to the production of a Class IIa bacteriocin (<6.5 kDa in size), which remained stable at average temperatures (30 ºC to 80 ºC) and at pH values ranging from 4 to 6, and although susceptible to some detergents, it showed greatly resistance to several enzymes. Despite being very sensitive to acidic environments, when incorporated into a complex food matrix such as alheira, Ln. lactis RK18 was able to survive through simulated gastrointestinal tract (GIT) conditions and also to adhere (but not invade) to human colon adenocarcinoma cell lines Caco-2 in vitro. Even though exposure to GIT conditions had influenced the adhesion ability of Ln. lactis RK18 cells, this potential probiotic and merely 10% of its treated cell-free supernatant, were able to prevent the ability of L. monocytogenes CEP 104794 to adhere and invade Caco-2 cells. Overall, Ln. lactis RK18 appeared to be a safe strain, with no risk to human health, which harbored important features to be successfully considered as a potential biopreservative and probiotic culture. Nevertheless, further experiments should be performed for the validation of its application in the food industry.