This study evaluated the efficacy of glycone (myricitrin, hesperidin and phloridzin) and aglycone flavonoids (myricetin, hesperetin and phloretin) in inhibiting biofilm formation by Staphylococcus aureus RN4220 and S. aureus SA1199B that overexpress the msrA and norA efflux protein genes, respectively. The minimum inhibitory concentration (MIC) and minimum biofilm inhibitory concentration (MBIC - defined as the lowest concentration that resulted in ≥50% inhibition of biofilm formation) of flavonoids were determined using microdilution in broth procedures. The flavonoids showed MIC >1024 μg/mL against S. aureus RN4220 and S. aureus SA1199B; however, these compounds at lower concentrations (1-256 μg/mL) showed inhibitory effects on biofilm formation by these strains. Aglycone flavonoids showed lower MBIC values than their respective glycone forms. The lowest MBIC values (1 and 4 μg/mL) were observed against S. aureus RN4220. Myricetin, hesperetin and phloretin exhibited biofilm formation inhibition >70% for S. aureus RN4220, and lower biofilm formation inhibition against S. aureus SA1199B. These results indicate that sub-MICs of the tested flavonoids inhibit biofilm formation by S. aureus strains that overexpress efflux protein genes. These effects are more strongly established by aglycone flavonoids.

Cherry tomato (Lycopersicon esculentum Mill) fruits are susceptible to contamination by Aspergillus flavus, which may cause the development of fruit rot and significant postharvest losses. Currently there are significant drawbacks for the use of synthetic fungicides to control pathogenic fungi in tomato fruits, and it has increased the interest in exploring new alternatives to control the occurrence of fungal infections in these fruits. This study evaluated the efficacy of chitosan (CHI) from Mucor circinelloides in combination with carvacrol (CAR) in inhibiting A. flavus in laboratory media and as a coating on cherry tomato fruits (25°C, 12 days and 12°C, 24 days). During a period of storage, the effect of coatings composed of CHI and CAR on autochthonous microflora, as well as on some quality characteristics of the fruits such as weight loss, color, firmness, soluble solids, and titratable acidity was evaluated. CHI and CAR displayed MIC valuesof 7.5 mg/mL and 10 μL/mL, respectively, against A. flavus. The combined application of CHI (7.5 or 3.75 mg/mL) and CAR (5 or 2.5 μL/mL) strongly inhibited the mycelial growth and spore germination of A. flavus. The coating composed of CHI (3.75 mg/mL) and CAR (2.5 or 1.25 μL/mL) inhibited the growth of A. flavus in artificially contaminated fruits, as well as the native fungal microflora of the fruits stored at room or low temperature. The application of the tested coatings preserved the quality of cherry tomato fruits as measured by some physicochemical attributes. From this, composite coatings containing CHI and CAR offer a promising alternative to control postharvest infection caused by A. flavus or native fungal microflora in fresh cherry tomato fruits without negatively affecting their quality over storage.

Aims To investigate the probiotic potential of yeasts isolated from naturally fermented Brazilian table olives. Methods and Results Eighteen yeast strains were tested in terms of: safety; survival of gastrointestinal and digestion conditions; antimicrobial activity; cellular hydrophobicity; autoaggregation ability and adhesion to epithelial cells; coaggregation and inhibition of pathogenic bacteria adhesion. Six yeasts showed favourable results for all probiotic attributes: Saccharomyces cerevisiae CCMA 1746, Pichia guilliermondii CCMA 1753, Candida orthopsilosis CCMA 1748, Candida tropicalis CCMA 1751, Meyerozyma caribbica CCMA 1758 and Debaryomyces hansenii CCMA 1761. These yeasts demonstrated resistance to 37°C, pH 2·0 and bile salts, and survived in vitro digestion (≥106 CFU per ml). Furthermore, the yeasts exhibited a hydrophobic cell surface (42·5–92·2%), autoaggregation capacity (41·0–91·0%) and adhesion to Caco‐2 (62·0–82·8%) and HT‐29 (57·6–87·3%) epithelial cell lines. Also, the strains showed antimicrobial activity against Salmonella Enteritidis as well as the ability to coaggregate and reduce the adhesion of this pathogen to intestinal cells. Conclusions Autochthonous yeasts from naturally fermented Brazilian table olives have probiotic properties, with potential for development of new probiotic food products. Significance and Impact of Study These data are important and contribute to the knowledge of new potential probiotic yeasts capable of surviving gastrointestinal tract conditions and inhibiting pathogenic bacteria.

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