Biological capacities of seven Chilean ferns.

Sticherus squamulosus, Hymenophyllum dentatum, Blechnum microphyllum, Polypodium Feuillei, Blechnum chilense, Lophosoria quadripinnata, and Lissopimpla excelsa are native fern species found in southern Chile and are often used in traditional medicine. However, their bioactive properties have not been confirmed. In this study, ethanolic extracts of ferns exhibited significant antibacterial capacity against human pathogens. H. dentatum and S. squamulosus were selected for further analysis owing to their antimicrobial and antioxidant capacities. The entire H. dentatum extract exhibited fungistatic and fungicidal capacity on Botrytis cinerea and Penicillium digitatum, with minimum inhibitory concentration values of 1.56 mg/mL and 6.25 mg/mL and minimum fungicidal concentration values of 6.25 mg/mL and 12.5 mg/mL, respectively. The S. squamulosus extract presented the highest rutin content (222.5 µg/g fern). In addition, the ethanolic extract of H. dentatum inhibited 91% of DPPH radicals. Therefore, both types of ferns can be used in the food industry.

Synthesis and Evaluation of Antifungal and Antibacterial Abilities of Carbon Nanotubes Grafted to Poly(2-hydroxyethyl methacrylate) Nanocomposites.

Developing nanomaterials with the capacity to restrict the growth of bacteria and fungus is of current interest. In this study, nanocomposites of poly(2-hydroxyethyl methacrylate) (PHEMA) and carbon nanotubes (CNTs) functionalized with primary amine, hydroxyl, and carboxyl groups were prepared and characterized. An analysis by Fourier-transform infrared (FT-IR) spectroscopy showed that PHEMA chains were grafted to the functionalized CNTs. X-ray photoelectron spectroscopy suggested that the grafting reaction was viable. The morphology of the prepared nanocomposites studied by field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) showed significant changes with respect to the observed for pure PHEMA. The thermal behavior of the nanocomposites studied by differential scanning calorimetry (DSC) revealed that the functionalized CNTs strongly affect the mobility of the PHEMA chains. Tests carried out by thermogravimetric analysis (TGA) were used to calculate the degree of grafting of the PHEMA chains. The ability of the prepared nanocomposites to inhibit the growth of the fungus Candida albicans and the bacteria Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli was evaluated. A reduced antifungal and antibacterial capacity of the prepared nanocomposites was determined.

Characterization of kefir yeasts with antifungal capacity against Aspergillus species.

Kefir is a fermented probiotic drink obtained by placing kefir granules in a suitable substrate. The kefir granules are a consortium of bacteria and yeasts embedded in a exopolysaccharide matrix. The aim of this research was the isolation and identification of yeasts from kefir of different origin, the evaluation of their antifungal capacity against Aspergillus spp., and the characterization of virulence related traits. Using RFLP of ITS1/ITS4 region, D1/D2 region sequencing, and RAPD techniques, 20 kefir isolates were identified as Geotrichum candidum, Pichia kudriavzevii, Pichia membranifaciens, Saccharomyces cerevisiae, and Candida ethanolica. Their antifungal capacity was evaluated by their conidia germination reduction, which allowed the selection of eight isolates with high to moderate conidia germination reduction against Aspergillus flavus and Aspergillus parasiticus. Furthermore, these selected isolates showed growth inhibition on contact in the dual culture assay for both Aspergillus species and 3 of them-belonging to S. cerevisiae and P. kudriavzevii species-generated volatile organic compounds which significantly affected the growth of both fungi. For the evaluation of virulence-related traits, growth at high temperatures, enzymatic activities, and the adhesion to Caco-2 cells were analyzed. The isolates did not present more than one positive virulence-related trait simultaneously. In particular, it is important to highlight that the adhesion capacity to the model of intestinal barrier was extremely low for all of them. According to the results obtained, further studies would be of interest for the possible use of these promising yeasts as biocontrol agents against fungi in food.

Thyme essential oil loaded microspheres for fish fungal infection: microstructure, in vitro dynamic release and antifungal activity.

AIMS: Evaluate the effect of varying the droplet size of microspheres charged with thyme essential oil (TEO-MS) on their swelling (Sw), release rate (%RR) and in vitro antifungal activity against Saprolegnia sp. METHODS: TEO-MS obtained by ionic gelation were characterised through SEM microscopy and X-ray microtomography. Their Sw and RR% were evaluated at simulated fish-gastrointestinal conditions using gravimetric and spectrophotometric techniques. RESULTS: For all evaluated droplet sizes (p ≥ 0.05), TEO was heterogeneously distributed inside of the MS and TEO-MS experimented agglomeration and sphericity loss after the drying process. Under gastric conditions, the acid pH (2.9) limited the Sw (50-100%) of TEO-MS, generating a low RR% (14-18%). Contrary, the slightly alkaline intestinal pH (8.1) favoured the Sw (∼3.2 to 3.8 times) and therefore the RR% (42-63%). CONCLUSIONS: TEO-MS (5-100 mg/mL) presented antifungal capacity onto Saprolegnia sp. after the simulated fish digestion, being the small droplet size once the most effective.