Detoxification of Mycotoxin Patulin by the Yeast Kluyveromyces marxianus YG-4 in Apple Juice.

Patulin (PAT) is a mycotoxin produced by Penicillium species, which often contaminates fruit and fruit-derived products, posing a threat to human health and food safety. This work aims to investigate the detoxification of PAT by Kluyveromyces marxianus YG-4 (K. marxianus YG-4) and its application in apple juice. The results revealed that the detoxification effect of K. marxianus YG-4 on PAT includes adsorption and degradation. The adsorption binding sites were polysaccharides, proteins, and some lipids on the cell wall of K. marxianus YG-4, and the adsorption groups were hydroxyl groups, amino acid side chains, carboxyl groups, and ester groups, which were combined through strong forces (ion interactions, electrostatic interactions, and hydrogen bonding) and not easily eluted. The degradation active substance was an intracellular enzyme, and the degradation product was desoxypatulinic acid (DPA) without cytotoxicity. K. marxianus YG-4 can also effectively adsorb and degrade PAT in apple juice. The contents of organic acids and polyphenols significantly increased after detoxification, significantly improving the quality of apple juice. The detoxification ability of K. marxianus YG-4 toward PAT would be a novel approach for the elimination of PAT contamination.

Tibetan kefir grains fermentation alters physicochemical properties and improves antioxidant activities of Lycium barbarum pulp polysaccharides.

There is a lack of research on how Tibetan kefir grains fermentation alters the physicochemical properties and biological activity of Lycium barbarum pulp polysaccharides, despite some reports that fermentation can affect the structure and activity of plant polysaccharides. This study demonstrated that, through fermentation, the molecular weight of polysaccharides decreased from 25.33 to 15.11 kg/mol while the contents of total sugar and uronic acid increased by 19.11% and 40.38%, respectively. Furthermore, after fermentation, the polysaccharides exhibited an uneven and rough surface along with a reduced number of branched chains and triple helix structures. Tibetan kefir grains fermentation enhanced the antioxidant activity of polysaccharides, which may be attributed to an increase in arabinose, galactose, and uronic acid content and a decrease in polysaccharide molecular weight. This research offers an alternative viewpoint on the potential application of Tibetan kefir grains-fermented Lycium barbarum pulp polysaccharides in functional foods.

Strategy for Avoiding Alicyclobacillus acidocaldarius Contamination of Apple Juice by Adding Magnetosomes/Antibacterial Peptide Composites.

The survival of Alicyclobacillus acidocaldarius (A. acidocaldarius) in fruit juice after pasteurization results in high economic losses due to unpalatability. The present work addressed this issue by inhibiting the growth of A. acidocaldarius in apple juice by the addition of MN@IDR-1018 composites formed of innate defense regulator 1018 (IDR-1018) antibacterial peptides that are coupled on the surfaces of magnetosomes (MN) via amidation reactions. MN@IDR-1018 was demonstrated to provide excellent antibacterial activity against A. acidoterrestris with a minimum inhibitory concentration of 100 µg mL-1, which led to cell death via membrane dissolution and rupture. In addition, this concentration of MN@IDR-1018 was proved to present low toxicity in mice and had no discernible effect on the color, flavor, and aroma of apple juice. This enables the active material to be extracted from the apple juice by the application of a magnetic field, thereby avoiding the development of antibiotic resistance.

New insights into the alleviating role of Melaleuca alternifolia oil on metabolites pathway disorder of grapes caused by Aspergillus niger, verified by corresponding key genes expression.

Grape berries are susceptible to Aspergillus niger (A. niger) infection during storage, leading to a significant reduction in its nutritional quality. However, most alternations in nutrient contents and related gene expression during fungal infection or treated with antimycotics remain unexplored. This work aimed to monitor and verify the metabolic changes in berries caused by A. niger or Melaleuca alternifolia oil (MAO) by using UHPLC-ESI-MS2 and Quantitative Real-time PCR (RT-qPCR). Results showed that sucrose, glucose, fructose, trans-resveratrol and pterostilbene levels were down and pentose phosphate pathway, glycolysis pathway and phenylpropanoid pathway were significantly down-regulated compared with healthy berries due to A. niger infection, all of which were alleviated by MAO treated. A. niger also induced down-regulation of key genes expression associated with metabolic pathways and magnitude of down-regulation was reduced by MAO. These results provide a theoretical basis for MAO used to control the risk of A. niger-mediated diseases.

Determination of metabolites of Geotrichum citri-aurantii treated with peppermint oil using liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry.

Sour rot is a leading disease of citrus fruit caused by the postharvest pathogen Geotrichum citri-aurantii. It has been reported that essential oils can be used as substitutes for synthetic fungicides to control the pathogen. In this study, changes in metabolites and antifungal effects of G. citri-aurantii treated with peppermint oil (PO) were investigated. The inhibition rate of the mycelial growth increased as the PO concentration increased, and 6 µl PO/disk resulted in a radial growth inhibition of 79.2%. The electrical conductivity of G. citri-aurantii treated with PO increased compared to the control. By comparing the metabolic profiles of treated and untreated G. citri-aurantii cells, a total of 53 distinct metabolites 9 were up-regulated and 44 were down-regulated were found, including 16 lipid metabolites, 6 carbohydrate metabolites, 2 amino acid metabolites, 5 alcohols, 2 glycoside metabolites, and 3 ketone metabolites, etc, and these metabolites are involved in 25 major metabolic pathways. PRACTICAL APPLICATIONS: Chemical fungicides can effectively control G. citri-aurantii during fruit postharvest period. However, synthetic chemical fungicides have gradually led to buildup of resistance of fungil, which seriously causes the frequent of food-borne diseases. PO extracted from natural plants can be used as natural additive in many foods due to their antioxidant, antibacterial, and antifungal properties. Therefore, PO can be considered as a promising bacteriostatic agent for the defense of G. citri-aurantii during fruit postharvest period.