The impact of antimicrobial food additives and sweeteners on the growth and metabolite production of gut bacteria.

Metabolic disorders caused by the imbalance of gut microbiota have been associated with the consumption of processed foods. Thus, this study aimed to evaluate the effects of antimicrobial food additives (benzoate, sorbate, nitrite, and bisulfite) and sweeteners (saccharin, stevia, sucralose, aspartame, and cyclamate) on the growth and metabolism of some gut and potentially probiotic bacterial species. The effects on the growth of Bifidobacterium longum, Enterococcus faecium, Lactobacillus acidophilus, and Lactococcus lactis subsp. lactis cultures were investigated using a turbidimetric test and by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). To evaluate the metabolic activity, the cultures were exposed to compounds with the highest antimicrobial activity, subjected to cultivation with inulin (1.5%), and analyzed by liquid chromatography for the production of short-chain fatty acids (acetate, propionate, and butyrate). The results showed that potassium sorbate (25 mg/mL), sodium bisulfite (0.7 mg/mL), sodium benzoate, and saccharin (5 mg/mL) presented greater antimicrobial activity against the studied species. L. lactis and L. acidophilus bacteria had reduced short-chain fatty acid production after exposure to saccharin and sorbate, and B. longum after exposure to sorbate, in comparison to controls (acetic acid reduction 1387 µg/mL and propionic 23 µg/mL p < 0.05).

Effect of supercritical CO2 fractionation of Tahiti lemon (Citrus latifolia Tanaka) essential oil on its antifungal activity against predominant molds from pan bread.

This study aimed to verify the in vitro antifungal activity of Tahiti lemon essential oil (LEO) and its fractions, obtained by supercritical CO2 fractionation, against Penicillium sumatrense and Aspergillus niger isolated from pan bread. For this, LEO was solubilized (20 MPa and 40 °C) and fractionated (10 MPa and 40 °C) in supercritical CO2, resulting in soluble (SF) and precipitated (PF) fractions. LEO, SF and PF volatile compounds were identified by gas chromatography coupled to mass spectrometry (GC-MS) and semiquantified by gas chromatography with a flame ionization detector (GC-FID). To evaluate the in vitro antifungal activity of the essential oils (LEO, SF and PF), the minimal inhibitory and fungicidal concentrations (MIC and MFC, respectively) were determined using the 96-well plate methodology. For this, pan breads ware prepared with no preservatives and stored for seven days at 25 °C, and their pH, water activity and moisture contents were determined. Then, two predominant species (Penicillium sumatrense and Aspergillus niger) were isolated from pan breads, characterized according to their morphological and molecular characteristics, and were used in the antifungal activity studies. LEO and its fractions presented monoterpenes, sesquiterpenes and their oxygenated derivatives in their composition. Specifically, limonene was the major component identified in the essential oils. SF showed greater antifungal potential than PF and LEO, showing that supercritical CO2 fractionation could improve the antifungal efficiency of LEO. The results suggest that LEO and its fractions may contribute to the inhibition of Aspergillus niger and Penicillium sumatrense growth in pan breads.

Aspergillus section Flavi diversity and the role of A. novoparasiticus in aflatoxin contamination in the sugarcane production chain.

The presence of Aspergillus section Flavi and aflatoxins in sugarcane as well as in by-products, such as molasses, sugar, yeast cream and dried yeast, collected from different fields and processing plants in São Paulo state, were investigated throughout the sugarcane production chain. A total of 246 samples was collected and analyzed and 226 isolates of Aspergillus section Flavi were isolated. Aspergillus section Flavi strains were found in sugarcane juice, milled sugarcane, stalk, soil and dried yeast samples. Among the isolates of Aspergillus section Flavi submitted to polyphasic identification (n = 57), Aspergillus novoparasiticus and Aspergillus arachidicola were predominantly found. A significant proportion of the isolates (84.5%) were found to have morphological and physiological characteristics of A. novoparasiticus. Most samples, with the exception of sugar, showed some aflatoxin contamination. The highest level was in dried yeast with an average of 2.55 µg/kg and maximum value of 10.19 µg/kg. This is the first report of contamination of sugarcane by A. novoparasiticus.

Biodiversity of mycobiota throughout the Brazil nut supply chain: From rainforest to consumer.

A total of 172 Brazil nut samples (114 in shell and 58 shelled) from the Amazon rainforest region and São Paulo state, Brazil was collected at different stages of the Brazil nut production chain: rainforest, street markets, processing plants and supermarkets. The mycobiota of the Brazil nut samples were evaluated and also compared in relation to water activity. A huge diversity of Aspergillus and Penicillium species were found, besides Eurotium spp., Zygomycetes and dematiaceous fungi. A polyphasic approach using morphological and physiological characteristics, as well as molecular and extrolite profiles, were studied to distinguish species among the more important toxigenic ones in Aspergillus section Flavi and A. section Nigri. Several metabolites and toxins were found in these two sections. Ochratoxin A (OTA) was found in 3% of A. niger and 100% of A. carbonarius. Production of aflatoxins B and G were found in all isolates of A. arachidicola, A. bombycis, A. nomius, A. pseudocaelatus and A. pseudonomius, while aflatoxin B was found in 38% of A. flavus and all isolates of A. pseudotamarii. Cyclopiazonic acid (CPA) was found in A. bertholletius (94%), A. tamarii (100%), A. caelatus (54%) and A. flavus (41%). Tenuazonic acid, a toxin commonly found in Alternaria species was produced by A. bertholletius (47%), A. caelatus (77%), A. nomius (55%), A. pseudonomius (75%), A. arachidicola (50%) and A. bombycis (100%). This work shows the changes of Brazil nut mycobiota and the potential of mycotoxin production from rainforest to consumer, considering the different environments which exist until the nuts are consumed.