Browsing by Author "Albano, Helena"
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- Ability of leuconostoc lactis RK18 to prevent adhesion and invasion of human intestinal cells by foodborne pathogen listeria monocytogenesPublication . Oliveira, Mónica; Barbosa, Joana; Albano, Helena; Teixeira, Paula
- Antilisterial activity of bacteriocinogenic Pediococcus acidilactici HA6111-2 and Lactobacillus plantarum ESB 202 grown under pH and osmotic stress conditionsPublication . Engelhardt, Tekla; Albano, Helena; Kisk, Gabriella; Mohácsi-Farkas, Csilla; Teixeira, PaulaBacteriocin producing lactic acid bacteria (LAB) cultures can be used as biopreservatives in fermented food products; thus the food industry is interested in stable cultures that produce bacteriocins consistently. Inhibtion of Listeria spp. by bacteriocinogenic Pediococcus acidilactici and Lactobacillus plantarum (both isolated from fermented meats) was investigated under conditions of stress induced by low pH and high salt concentrations. Listeria monocytogenes serogroup IIb (from cheese), L. monocytogenes serogroup IVb (from cheese), L. monocytogenes serogroup IIb (from ground beef) and Listeria innocua NCTC 11288 were used as target strains. P. acidilactici and Lb. plantarum demonstrated antilisterial activity under the stress conditions investigated (pH 3.5; pH 8.5; 7.5% NaCl). However, activity was dependent on the stress conditions applied and on the target organism. L. monocytogenes serogroup IIb (from ground beef) and L. innocua C 11288 were, respectively the most sensitive and the most resistant to the cell-free supernatants produced by the LAB investigated.
- Antilisterial activity of lactic acid bacteria isolated from "Alheiras" (traditional Portuguese fermented sausages)Publication . Albano, Helena; Oliveira, Márcia; Aroso, Ricardo; Cubero, Núria; Hogg, Tim; Teixeira, PaulaA total of 226 lactic acid bacteria (LAB) isolated from ‘‘Alheira’’, a traditional Portuguese fermented sausage, were screened for antagonistic activity against some pathogenic microorganisms, including Listeria monocytogenes. The objective was to isolate LAB with antibacterial activity from ‘‘Alheiras’’ and to select strains that could be used in ‘‘Alheira’’ production. Isolates displaying antibacterial activity against Listeria innocua and L. monocytogenes were investigated for the nature of the antibacterial compounds active against these microorganisms. Results showed that two LAB cultures retained activity in the supernatants after neutralization and catalase treatment. These two strains were both identified as Pediococcus pentosaceus. The final aim of this work was to test the antilisterial activity of these two strains during storage of ‘‘Alheira mass’’ (sterilized), at 4 C. The growth of L. innocua population was significantly suppressed in the paste of ‘‘Alheira’’ when the samples were co-inoculated with the LAB strains, in comparison with the paste only inoculated with L. innocua or co-inoculated with a bacteriocin negative strain of Ped. pentosaceus (ca. 1 · 107 CFU/g after 28 days of incubation).
- Antimicrobial potential of different propolis extractsPublication . Oliveira, Mónica; Teixeira, Helena; Barbosa, Joana; Albano, Helena; Teixeira, PaulaIntroduction: Propolis is a mixture of different types of beeswax and resins collected from plants by bees (Apis mellifera). The role of propolis in the hive is related to its mechanical properties and it is used to construct, adapt and protect the hive; its antimicrobial activity ensures an aseptic environment. Propolis is known for having antibacterial activity conferred by the presence of flavonoids, aromatic acids and esters in their composition and for the presence of ferulic and caffeic acids. Several authors reported that the activity of each chemical compound present in propolis is influenced by the extraction method. These compounds are quite soluble in ethanol, however, the extracts resulting from this solvent can only be used if the ethanol is food grade. Other solvents such as propylene glycol, glycerol and oils, as well as other techniques, have been tested and have shown promising results regarding their composition and biological activities. Discussion & Conclusions: Apparently, the solvent did not affect the pH value of the propolis extracts. Ethanol and PG allowed better extractions of the phenolic compounds presented in propolis, with similar concentration values. The antioxidant activities of all extracts were similar and their composition was identical, varying only in the content of flavonoid compounds. Caffeic acid, coumaric acid, ferulic acid, quercetin and kaempferol were identified by HPLC. Propolis extracted with ethanol and PG showed higher antimicrobial activity against several microorganisms. All propolis extracted with PG, at both temperatures, inhibited most of the microorganisms tested. However, at 50 ºC, 0.3125 μg/ml of propolis extract was enough to inhibit a large number of microorganisms. Propolis 1, extracted with PG at 50 ºC demonstrated quite promising results. As conclusion, although further tests are required, propolis extracted with PG, a compound that according to the United States FDA is Generally Recognized as Safe (GRAS), could be a promising product to be used in food industry to, for example, reduce the microbial loads of raw meats and avoid cross-contaminations.
- Antimicrobial potential of different propolis extractsPublication . Oliveira, Mónica; Teixeira, Helena; Barbosa, Joana; Albano, Helena; Teixeira, Paula
- Antimicrobial properties of oregano oil (Origanum vulgare) against Listeria monocytogenes in “alheira”Publication . Carvalho, Marta; Oliveira, Márcia; Albano, Helena; Teixeira, Paula
- Antimicrobial properties of oregano oil (origanum vulgare) against salmonella enteritidis, staphylococcus aureus and listeria monocytogenes in "alheira"Publication . Carvalho, Marta; Albano, Helena; Teixeira, Paula
- Are nurses uniforms a reservoir for Methicillin-resistant Staphylococcus aureus? Lessons to be learned from PortugalPublication . Fernandes, E.; Costa, P.; Graveto, J.; Santos, C.; Osório, N.; Alarico, S.; Albano, Helena
- Bioactive alternatives to mitigate foodborne pathogensPublication . Moreira, Inês Azevedo; Barbosa, Joana; Albano, Helena; Teixeira, Paula
- Characterization of a lactiplantibacillus plantarum r23 isolated from arugula by whole-genome sequencing and its bacteriocin production abilityPublication . Barbosa, Joana; Albano, Helena; Silva, Beatriz; Almeida, Maria Helena; Nogueira, Teresa; Teixeira, PaulaLactiplantibacillus plantarum is one of the lactic acid bacteria species most used as probiotics and starter cultures in food production. Bacteriocin-producers Lpb. plantarum are also promising natural food preservatives. This study aimed to characterize Lpb. plantarum R23 and its bacteriocins (R23 bacteriocins). The genome sequence of Lpb. plantarum R23 was obtained by whole-genome sequencing (WGS) in an Illumina NovaSeq platform. The activity of Lpb. plantarum R23-produced bacteriocin against two Listeria monocytogenes strains (L7946 and L7947) was evaluated, and its molecular size was determined by tricine-SDS-PAGE. No virulence or antibiotic resistance genes were detected. Four 100% identical proteins to the class II bacteriocins (Plantaricin E, Plantaricin F, Pedi-ocin PA-1 (Pediocin AcH), and Coagulin A) were found by WGS analysis. The small (<6.5 kDa) R23 bacteriocins were stable at different pH values (ranging from 2 to 8), temperatures (between 4 and 100 °C), detergents (all, except Triton X-100 and Triton X-114 at 0.01 g/mL), and enzymes (catalase and α-amylase), did not adsorb to the producer cells, had a bacteriostatic mode of action and their maximum activity (AU/mL = 12,800) against two L. monocytogenes strains occurred between 15 and 21 h of Lpb. plantarum R23 growth. Lactiplantibacillus plantarum R23 showed to be a promising bio-preservative culture because, besides being safe, it produces a stable bacteriocin or bacteriocins (har-bors genes encoding for the production of four) inhibiting pathogens as L. monocytogenes. Further studies in different food matrices are required to confirm this hypothesis and its suitability as a future starter culture.