Loading...
5 results
Search Results
Now showing 1 - 5 of 5
- 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.
- Microbial contamination of main contact surfaces of automated teller machines from metropolitan Area of PortoPublication . Barbosa, Joana Inês Bastos; Albano, Helena da Conceição Pereira; Silva, Fabiana Ferreira; Teixeira, Paula Cristina MaiaAutomated Teller Machines (ATM) are likely to be contaminated with various microorganisms because of their contact with the hands of many users daily. The main objective of this study was to investigate ATMs as a potential source of bacterial contamination. This study was conducted in the Metropolitan Area of Porto, in which 50 swab samples were cultured on selective media. Some isolates were identified based on colonial, morphological and biochemical characteristics. Susceptibility to several antibiotics was also evaluated for each isolated organism. Most contaminated ATMs had high numbers of Enterobacteriaceae and Enterococci. Staphylococci and Enterobacteriaceae were the most prevalent bacteria found. The recovered bacterial isolates varied in their antibiotic resistance pattern; Staphylococcus spp. demonstrated the most resistant profiles. With this pioneering study in Portugal, it was demonstrated that although ATMs in metropolitan area of Porto were not highly contaminated, some potentially pathogenic bacteria were present and resistant to some commonly used antibiotics.
- Screening of bacteriocinogenic lactic acid bacteria and their characterization as potential probioticsPublication . Pinto, Ana; Barbosa, Joana; Albano, Helena; Isidro, Joana; Teixeira, PaulaProbiotics are living microorganisms used as nutritional additives that confer health benefits on the host. Their use in food products is very attractive, especially if they could also inhibit important foodborne athogens. In this study, antimicrobial activity against several foodborne pathogens was screened for 280 lactic acid bacteria (LAB) isolated from di erent food products and the probiotic characteristics of bacteriocinogenic isolates were evaluated. Seven out of 280 LAB isolates were selected due to their bacteriocinogenic properties and identified by 16S rRNA gene sequence analysis as Pediococcus pentosaceus (n = 6) and Lactobacillus plantarum (n = 1). Virulence factors and antibiotic resistances were not detected for any of the isolates. Except for L. plantarum R23, all the isolates were able to survive through the simulated gastrointestinal tract conditions. Only P. pentosaceus CFF4 was able to adhere to Caco-2 cells after the simulated gastrointestinal tract passage. In conclusion, even though in vivo studies should be performed, P. pentosaceus CFF4, which was also able to inhibit the growth of foodborne pathogens in vitro, seems to be a potential probiotic to be used in the food industry.
- Data fusion of UPLC data, NIR spectra and physicochemical parameters with chemometrics as an alternative to evaluating kombucha fermentationPublication . Barbosa, Cosme Damião; Baqueta, Michel Rocha; Santos, Wildon César Rodrigues; Gomes, Dhionne; Alvarenga, Verônica O.; Teixeira, Paula; Lacerda, Inayara Cristina Alves; Albano, Helena; Rosas, Carlos Augusto; Valderrama, PatríciaKombucha consumption has become popular due to health benefits and sensorial properties. Different analytical techniques were associated with unsupervised chemometrics to evaluate kombucha fermentation using a low-level data fusion strategy. Kombucha was prepared from green and black teas (Camellia sinensis). The samples were analyzed by ultra-performance liquid chromatography (UPLC), portable near-infrared spectroscopy (NIR), and physicochemical analyses (ethanol, pH, total reducing sugars, and total titratable acidity). Also, the bioactive phenolic compounds were evaluated in the fermented samples. The merged results were analyzed by principal component analysis (PCA). The PCA was applied to discriminate substrate for kombucha production and the fermentation time. Although the fermentation behavior was similar for both substrates, the kombucha showed quantitative differences in physicochemical parameters. They also showed differences in bioactive compounds for each kombucha. Data fusion strategy was more effective to differentiate the two types of kombucha than single analysis. The portable NIR can be a reliable and robust analysis for fermentation monitoring. Moreover, the results can be used as a base to further studies and mainly to help in which substrate composition is better to be produced on an industrial scale.
- Non meat-based alheiras - a safer novel trend?Publication . Azevedo, Inês; Barbosa, Joana; Albano, Helena; Teixeira, PaulaIn response to nutritional and health concerns, the food industry has begun to offer a wider variety of products that reflect changing consumer preferences. In addition to traditional alheiras, made with pork and/or poultry meats, other varieties of alheiras (“innovative”) made from codfish, mushrooms, tofu, soy and vegetables were launched on the Portuguese market. The objective of this study was the characterisation of these products, giving particular attention to their microbiological and chemical safety. Therefore, fourteen different products were analysed. Enterobacteriaceae, Enterococcus, lactic acid bacteria, yeasts and moulds, were the prevalent microbiota of “innovative” alheiras. Sulphite reducing Clostridium spores, Escherichia coli, Listeria monocytogenes, Salmonella spp. or Staphylococcus aureus were not detected in any sample. No differences were observed between traditional and “innovative” alheiras concerning pH and water activity values while nitrites, nitrates and biogenic amines were found to be within accepted limits for these kinds of products. In terms of organic acids, lactic acid was found in all analysed samples while malic and succinic acid seemed to be predominant only in “innovative” alheiras. In conclusion, unlike traditional alheiras which often contain pathogenic agents, no harmful organisms nor chemical hazards were found in these new products, even though produced by the same companies.