The Making of Fragile Agro-ecosystems Productive, Adaptive and Sustainable: Multifunctional Agro-pastoralism

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Exploring the role of Autochthonous lactic acid Bacteria in enhancing quality and safety of Alheira

Publication . Fernandes, Nathália; Cadavez, Vasco; Gonzales-Barron, Ursula

The alheira is a traditional meat sausage produced in the Portuguese region of Trás-os-Montes. Lactic Acid Bacteria (LAB) are the dominant microorganisms in alheira and can endow it with various technological properties. This study aimed: 1) Isolate and identify LAB from artisanally produced alheiras from the Trás-os-Montes region; 2) Study their phenotypic characteristics and in vitro antimicrobial activity; and 3) Differentiate and associate the phenotypic characteristics of the LAB with 16S ribosomal gene sequencing data. Sixty-two LAB isolates were identified and Enterococcus (E.) faecium corresponded to 32.3% of isolates, followed by Leuconostoc (L.) mesenteroides (19.4%) and Latilactobacillus (Lb.) sakei (17.7%), aligning with previous research on traditional Portuguese fermented meat sausages. The phenotypic analysis of LAB isolates indicated diverse acidification capacities, proteolytic activities, and inhibitory effects against foodborne pathogens Listeria (L.) monocytogenes, Salmonella (S.) Typhimurium and Staphylococcus (S.) aureus. LAB play an essential role as biological control agents, generating metabolites with antimicrobial properties, including organic acids, proteases, peptidases and bacteriocins. Overall, lactobacilli displayed high inhibition activity ((inhibition zone radius higher than 10 mm) against the pathogens S. aureus, L. monocytogenes and S. Typhimurium. The mechanisms of pathogenic microorganism inhibition remain to be clarified and will be the subject of future studies. However, these results reveal the significant diversity of LAB found in artisanally produced alheiras, as well as their contribution to the microbiological safety and organoleptic characteristics of alheiras.

2024Master thesis

Open access

A Meta-Analysis on the In Vitro Antagonistic Effects of Lactic Acid Bacteria from Dairy Products on Foodborne Pathogens

Publication . Loforte, Yara; Fernandes, Nathália; Almeida, André Martinho de; Cadavez, Vasco; Gonzales-Barron, Ursula

Raw milk and traditional fermented foods such as artisanal cheese represent a natural source of lactic acid bacteria (LAB). They can produce antimicrobial compounds, such as bacteriocins and lactic acid, which may be exploited in dairy biopreservation. This study aimed to conduct a systematic review and meta-analysis to synthesize the inhibition diameter (ID) of LAB against L. monocytogenes, S. aureus, and Salmonella spp. Literature electronic searches were performed on PubMed, Scopus, and Web of Science, to identify articles that reported data on in-vitro antimicrobial activity by LAB isolated from dairy foods. A total of 1665 papers were retrieved, and 20 primary studies were selected according to the selection criteria, of which 397 observations were extracted. Random-effects meta-regression models were employed to describe the effects of LAB genus, pathogen concentration, susceptibility method, incubation time, inoculation volume, agar type and pH on the IDs for L. monocytogens, S. aureus, and Salmonella spp. L. monocytogens was the most susceptible pathogen (p < 0.05) to the LAB effects, followed by S. aureus and Salmonella spp. As a whole, LAB from the Lacticaseibacillus genus were the most effective (p < 0.05) in inhibiting L. monocytogens (21.49 ± 2.654 mm), followed by S. aureus (21.06 ± 2.056 mm). Salmonella spp. presented higher (p < 0.05) susceptibility to Lactobacillus genus (19.93 ± 2.456 mm). From the results, a general trend could be observed for the well-diffusion method to produce higher (p < 0.05) ID estimates than the spot and disk methods (30.73 ± 2.530 mm vs. 21.98 ± 1.309 mm vs. 13.39 ± 1.403 mm for L. monocytogenes; 22.37 ± 1.073 mm vs. 14.91 ± 2.312 mm vs. 20.30 ± 2.319 mm for Salmonella spp.), respectively. Among the tested moderators, the pathogen’s inoculum concentration, the in vitro susceptibility assay itself, incubation time and inoculation volume on agar are determinant parameters to be looked at when designing a robust and reproducible experimental plan. The in vitro results reinforced that LAB can be useful in controlling the development of pathogenic bacteria frequently found in the dairy industry.

2025Review

Open access