Browsing by Autor "Audisio, M Carina"

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Application of spray-dried bacteriocins as cheese biopreservatives.
(2025) Lenz, Romina M; Guitián, M Virginia; Villalva, Fernando J; Goncalvez de Oliveira, Enzo; Soria, M Cecilia; Audisio, M Carina; Ibarguren, Carolina
Listeria monocytogenes can contaminate refrigerated ready-to-eat foods, such as cheeses. Enterocins, with a strong listericidal effect, constitute a natural alternative to control this pathogen in food. To optimize their antimicrobial action in food matrices, bacteriocins can be immobilised in edible coatings through spray drying technology which allows the large-scale production of microcapsules of bioactive molecules. The aim of this work was to evaluate the antimicrobial effectiveness of Enterococcus avium DSMZ17511 bacteriocins, obtained in a low-cost culture broth (HS-L), spray-dried assaying different thermoprotective materials (maltodextrin, cheese whey and brea gum), and incorporated into agar-based active coatings applied on goat cheese pieces artificially contaminated with L. monocytogenes 99/287. The bacteriocin solution (BS) powders, labelled HS-L BS, maintained the antimicrobial activity even after 90 days of storage, with titres up to 128,000 UA/g, with the least thermoprotective effect exerted by brea gum (64,000-32,000 UA/g). An increase in antimicrobial titre was observed for all bacteriocin powders after 3 months, despite storage conditions; probably due to a release effect from the encapsulated bacteriocin or a combined release and gradual dehydration effect of the encapsulating matrix. Also, the dried products stored at 25 °C hydrated easily, while refrigeration or freezing did not affect the powders texture. For coatings applied on fresh goat cheese, only a difference of 0.5 log cfu/mL was observed between the viability of L. monocytogenes in the contaminated active-coated cheese and the control without coating. Instead, for the commercial goat cheese, with a drier matrix, the viability values stood 1.0 log cfu/mL below the control uncoated cheeses for up to 10 days. These spray dried bacteriocin powders provide an alternative for their application as food biopreservatives, since stable dehydrated products were obtained, with prolonged antimicrobial activity, and with verified inhibitory action in a food matrix.
Biocontrol of Sclerotinia sclerotiorum (Lib.) de Bary on common bean by native lipopeptide-producer Bacillus strains.
(2018) Sabaté, Daniela C; Brandan, Carolina Pérez; Petroselli, Gabriela; Erra-Balsells, Rosa; Audisio, M Carina
Bacillus sp. B19, Bacillus sp. P12 and B. amyloliquefaciens B14 were isolated from soils of Salta province, and PGPR properties on the common bean (Phaseolus vulgaris L.) cv. Alubia and antagonistic activity against Sclerotinia sclerotiorum were studied. It was determined that B19 and P12 increased crop germination potential (GP) from the common bean by 14.5% compared to control seeds; these strains also increased root length (10.4 and 15%, respectively) and stem length (20.2 and 30%, respectively) compared to the control; however, as for the B14 strain, no increases in growth parameters were detected. In addition, all the treatments that combined two bacilli: B14 + B19, B14 + P12 and B19 + P12, generated beneficial effects on GP and seedling growth compared to control seeds, but not compared to a single inoculant. B19 and P12 strains synthesized auxins at concentrations of 5.71 and 4.90 mg/mL, respectively, and it was qualitatively determined that they synthesize siderophores. In addition, previous studies have determined that B14 produces auxins in a concentration of 10.10 mg/mL, and qualitatively synthesizes siderophores. The phytosanitary state of the white bean cv. Alubia control seeds revealed bacterial contamination in 87% of all the evaluated seeds and different fungi such as Cladosporium sp., Fusarium sp., and Rhizopus sp. Bean seeds treated with B14, B19 or P12 showed no growth of contaminating bacteria or of pathogenic fungi; in fact, bacilli inoculum development was observed in all seeds. Additionally, B19, P12 and B14 strains inhibited in vitro the development of 9 native S. sclerotiorum strains isolated from the Salta region, with FI ranging between 60 and 100%. The three Bacillus strains synthesized different isoforms of the lipopeptides: surfactin, iturin, and fengycin in the presence of S. sclerotiorum, as determined by MALDI-TOF. In the in vivo trials, when common bean seeds were grown in soils contaminated with S. sclerotiorum, an incidence of 100% was determined when the seeds were not treated with any Bacillus. Seeds treated with the chemical fungicide and sown in S. sclerotiorum-infested soil did not produce seed emergence, while the inoculation of the seeds with B14 + P12, B14 + B19 or B19 + P12 reduced the effect of the pathogen by 46, 43 and 25%, respectively. Disease progression in B14 + P12 and B14 + B19 treatments was significantly lower than in the remaining treatments, with an AUDPC of 873.75 and 1071, respectively.
Inhibition of Bacillus cereus Strains by Antimicrobial Metabolites from Lactobacillus johnsonii CRL1647 and Enterococcus faecium SM21.
(2014) Soria, M Cecilia; Audisio, M Carina
Bacillus cereus is an endospore-forming, Gram-positive bacterium able to cause foodborne diseases. Lactic acid bacteria (LAB) are known for their ability to synthesize organic acids and bacteriocins, but the potential of these compounds against B. cereus has been scarcely documented in food models. The present study has examined the effect of the metabolites produced by Lactobacillus johnsonii CRL1647 and Enterococcus faecium SM21 on the viability of select B. cereus strains. Furthermore, the effect of E. faecium SM21 metabolites against B. cereus strains has also been investigated on a rice food model. L. johnsonii CRL1647 produced 128 mmol/L of lactic acid, 38 mmol/L of acetic acid and 0.3 mmol/L of phenyl-lactic acid. These organic acids reduced the number of vegetative cells and spores of the B. cereus strains tested. However, the antagonistic effect disappeared at pH 6.5. On the other hand, E. faecium SM21 produced only lactic and acetic acid (24.5 and 12.2 mmol/L, respectively) and was able to inhibit both vegetative cells and spores of the B. cereus strains, at a final fermentation pH of 5.0 and at pH 6.5. This would indicate the action of other metabolites, different from organic acids, present in the cell-free supernatant. On cooked rice grains, the E. faecium SM21 bacteriocin(s) were tested against two B. cereus strains. Both of them were significantly affected within the first 4 h of contact; whereas B. cereus BAC1 cells recovered after 24 h, the effect on B. cereus 1 remained up to the end of the assay. The LAB studied may thus be considered to define future strategies for biological control of B. cereus.
Response of sensitive and resistant Listeria monocytogenes strains against bacteriocins produced by different Enterococcus spp. strains.
(2022) Ibarguren, Carolina; Guitián, M Virginia; Lenz, Romina M; Cecilia, Soria M; Audisio, M Carina
Listeria monocytogenes is a relevant foodborne pathogen causing invasive listeriosis in humans, a disease with high mortality rates. Its ubiquity and growth characteristics enable this pathogen to survive harsh food processing environments. The addition of bacteriocins, antimicrobial peptides ribosomally synthesized by certain bacteria, appears as a natural alternative to control this pathogen in food. However, the emergence of L. monocytogenes strains resistant to the inhibitory action of bacteriocins has been detected. In order to analyse the development of this resistance, different properties of L. monocytogenes strains susceptible to bacteriocins (strains 01/155, 99/287 and 99/267) and their respective resistant isolates (strains 01/155B6R, 99/287B6R, 99/286C1R, 99/287 Mo1R, 99/287 M1bR, 99/287 M2dR, 99/267B6R), were compared in this work. Differences were analysed in: a) growth of the pathogen strains in direct contact with bacteriocin solution, in co-cultures with the producing strain, or with different sugars; b) response to antibiotics typically used against listeriosis; c) changes in cell morphology, observed by transmission or scanning electron microscopy; d) expression of mobility and haemolysin activity, two of L. monocytogenes main virulence factors; and e) biofilm formation ability. For all the isolates, the acquired resistance was permanent and crossed between the different bacteriocins under study. An inhibitory effect was observed for resistant strains only when they were grown in mixed culture with any of the bacteriocin-producing strains, with an acidified medium as additional growth stress. In all cases, the decrease in viability was lower for resistant strains and followed a particular profile for each strain. The variation of sugar substrate influenced resistant variants growth ability, with a more pronounced difference in the medium supplemented with glucose. Susceptibility to antibiotics was similar or higher for resistant variants, while neither the mobility nor the haemolytic activity presented differences among resistant or susceptible strains. Finally, the resistant variants showed a greater capacity to form biofilms, although this effect was reversed when grown in the presence of bacteriocins. Each resistant isolate had a particular behaviour pattern, and the acquisition of resistance appeared to be strain and bacteriocin dependent. These results contribute to the knowledge of L. monocytogenes bacteriocin-resistance development, which is essential to favour the use of these peptides as biopreservatives.