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- Evaluation of a bacteriocinogenic Lactobacillus plantarum strain on the microbiological characteristics of “Alheira de Vitela”Publication . Macieira, Ariana; Albano, Helena; Pinto, Miguel; Linheiro, Raquel; Barbosa, Joana; Teixeira, PaulaLactic Acid Bacteria (LAB) and their bacteriocins can be successfully used as natural preservatives in meat products. This work aimed to investigate the effect of fresh and lyophilized starter cultures of an autochthonous bacteriocinogenic LAB strain (Lactobacillus plantarum ST153Ch: bac + culture) on the microbiological characteristics of “Alheira”, a traditional Portuguese smoked product. “Alheira” with the addition of fresh or lyophilized culture (ca. 108 cfu/g) and “Alheira” control (no bacteriocinogenic culture added) were produced by an industrial meat company. The antilisterial activity of this culture in this food matrix was investigated, with some samples being inoculated with Listeria monocytogenes (ca. 105 cfu/g). Detection of L. monocytogenes, Salmonella spp., sulphite reducing clostridia, Yersinia enterocolitica and enumeration of L. monocytogenes, Staphylococcus aureus, Bacillus cereus, Escherichia coli, Enterobacteriaceae, lactic acid bacteria, yeasts and moulds were performed immediately after production and at 3, 7, 15, 21, 28, 60 and 90 days of storage at 4 ℃, according to ISO methodologies. Also, a 16S rRNA Gene Analysis was performed of the microbial communities of “Alheira” with and without the lyophilized bacteriocinogenic culture. Pathogenic and indicator organisms were not detected or were below acceptable levels in all samples. LAB counts increased during storage and reached similar values after 15 days (ca. 1010 cfu/g) in all samples. There was a clear trend for a higher reduction of L. monocytogenes in the presence of the bioprotective culture, more pronounced during the initial 15 days of storage. From the analysis of the microbial communities of samples of “Alheiras” at different stages of fermentation, Leuconostocaceae and Lactobacillaceae predominated in all the samples and Lactobacillus was the genus more prevalent in “Alheiras” after 60 days of storage with the addition of bacteriocinogenic culture.
- 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.
- 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.