Browsing by Author "Souza, Carla"
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- Antimicrobial potential of formulations, incorporating spent yeast derived from synthetic biotechnology, against Pseudomonas spp.Publication . Deuchande, Teresa; Fundo, Joana; Rodrigues, Daniela; Souza, Carla; Pintado, Manuela; Amaro, Ana L.Yeasts are currently used as cell factories for the sustainable production of high value biomolecules for applications in the pharmaceutical and cosmetic sectors. However, the production of such molecules through fermentation, conducted in bioreactors and making use of genetically engineered yeast strains, generates a number of waste-streams, with spent yeast as the second main by-product of fermentation processes, representing more than 20% of the total waste produced. Since this by-product is rich in several molecules including proteins, vitamins and several minerals, being also a natural source of glucans and mannoproteins with known bioactivities, it is of interest to develop valorization strategies for these residues. In this work, spent yeast was autolysed and a set of formulations, incorporating the resulting supernatant and pellet at different concentrations, were tested as potential antimicrobial solutions to prevent diseases in plants and fungi caused by Pseudomonas spp. The formulations were initially tested against P. aeruginosa and then against strains affecting cultivated mushrooms (Agaricus bisporus), P. tolaasi, and P. agarici; and a number of P. syringae strains responsible for plant diseases including the pathovars actinidifoliorium, tomato, pisi, syringae and atrofaciens. It has been recently shown that spent yeast hydrolysates possess antimicrobial activity against Salmonella enterica, Aeromonas salmonicida, Bacillus cereus and Bacillus subtilis (Martin et al. 2021), suggesting that spent yeast extracts may have potential antimicrobial effect against a range of microorganisms. To date, there are no studies showing the potential of spent yeast extracts against Pseudomonas strains. The results showed that the supernatant of the autolyzed yeast at 0.1% inhibited the growth of P. aeruginosa by about 20% and P. tolaasii by 10% but increased the growth of P. agarici by up to 34%. The combination of supernatant with lactose also slightly increased P. tolaasii growth inhibition (12%) but it reduced the inhibitory effect of supernatant against P. aeruginosa. With regard to plant pathogens, the formulations containing 0.1% and 0.3% of pellet inhibited by 25% the growth P. syringae pv. actinidifoliorium, the bacterium responsible for kiwi canker, but for all the other pathovars, the inclusion of spent yeast extracts in the formulation induced bacterial growth. Among all the tested formulations, the ones including supernatant and pellet at low concentrations were the most promising leading to slight growth inhibition of some environmental Pseudomonas spp.
- Impact of novel clean label ham formulations on the human gut microbiotaPublication . Carvalho, Teresa Bento de; Barbosa, Joana Bastos; Carvalho, Nelson Mota de; Souza, Carla; Costa, Célia; Komora, Norton; Azevedo, Alexandra; Madureira, Ana Raquel; Teixeira, PaulaIntroduction: The influence of diet on the human gut microbiota has been the subject of much debate, particularly in relation to innovative products that are still considered novel. Dietary habits have a fundamental impact on the human gut microbiota, which explains the variations observed between individuals and over the course of a lifetime. The aim of this study was to evaluate the effect of four clean label ham formulations (Table 1) (without sodium nitrite and with natural nitrate sources combined with the addition of nitrate reducing cultures) on the human gut microbiota of potential consumers after in vitro digestion, according to the INFOGEST protocol, and colonic fermentation. Methods: DNA extraction from the stored pellets was carried out using the Invitrogen PureLink™ Microbiome DNA Purification Kit. 16S rRNA gene sequence data was processed with QIIME2 by Novogene UK; Quantification of fermentation metabolites, short-chained fatty acids and branched- chained fatty acids, by high-performance liquid chromatography (HPLC) from supernatant. The impact of each novel formulation and for a faecal inoculum control (Inoc) on the gut microbiota profile and fermentation metabolites (i.e., SCFAs) was assessed by next-generation sequencing (NGS) and high-performance liquid chromatography (HPLC), respectively. Results and discussion: Higher concentration of SCFA (Acetate + Butyrate + Propionate) after 48 h colonic fermentation were found for: D (65.96 mM) > A (63.36 mM) > E (59.35 mM) > C (58.64 mM) > B (57.22 mM) > Inoc (16.20 mM); Lowest SCFA concentrations were found for the inoculum control (Inoc), as expected, due to the lack of nutrients to promote bacterial fermentation over time. The most abundant phylum present were Bacillota and Pseudomonadota for all samples (A, B, C, D, E and Inoc) and all time points (0h, 24h and 48h); Higher relative abundance of Pseudomonadota was observed for all samples when compared to the inoculum control (Inoc); After fermentation, relative abundance of Bacteroidota is higher for the ham control sample (added sodium nitrite) than for the samples that are formulated with natural plant nitrate coupled with starter cultures. Conclusions: There were no discernible variations in SCFA levels or microbial populations during colonic fermentation between the new formulations and the conventional ham, indicating that the suggested clean label approach produced encouraging outcomes; Additional investigation should provide light on the endogenous production of volatile and non-volatile chemicals (nitrosamines) in vitro, their effects on the microbiota in the human gut, and any potential toxicity to human intestinal epithelial cells.