Biosynthesis and characterization of silver nanoparticles from Punica granatum (pomegranate) peel waste and its application to inhibit foodborne pathogens.

Polyphenolics have been predicted to effectively develop antimicrobial agents for the food industry as food additives and promote human health. This study aims to synthesize pomegranate peel extract (PPE) with silver nanoparticles (AgNPs) against eight foodborne pathogens. Multispectroscopic analysis of UV-vis spectroscopy, Zeta potential, Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) analysis were used to characterize the interaction between PPE and AgNPs. Eight foodborne pathogenic strains (six bacterial and two fungal strains) Bacillus subtilis ATCC 6633, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 8379, Klebsiella pneumoniae ATCC 00607, Salmonella typhi DSM 17058, Shigella sonnei DSM 5570, Aspergillus flavus ATCC 9643, and Rhizopus oryzae ATCC 96382 were used to test the inhibitory potential of PPW-AgNPs. The reaction colour of PPE-AgNPs from yellow to brown indicated that the nanoparticles were successfully formed. The UV absorption of PPE-AgNPs was detected at 440 nm of 0.9 SPR. SEM image of PPE-AgNPs exhibited spherical shapes with a zeta potential of - 20.1 mV. PPE-AgNPs showed high antimicrobial activity against all tested strains. The highest inhibition activity of PPE-AgNPs was recorded for the B. subtilis strain followed by K. pneumonia, while the highest resistance was noticed for R. oryzae. The components of pomegranate peel were analyzed using gas chromatography-mass spectrometry (GC-MS). The major constituents of pomegranate peel is phenol (51.1%), followed by Isocitronellol (19.41%) and 1-Propanol, 2-(2-hydroxypropyl)- (16.05%). PPE is key in the simple, eco-friendly green synthesis of extracellular stable AgNPs as an alternative source for harmful chemical disinfectants.

Chitosan-stabilized selenium nanoparticles attenuate acrylamide-induced brain injury in rats.

Acrylamide (ACR) is produced during food processing and has been shown to cause health problems. Selenium, especially in its nanoscale, is an important trace element in human nutrition. Chitosan-stabilized selenium nanoparticles (Ch-SeNPs) stability and its protective potential against ACR-induced injury in rats were evaluated. Ch-SeNPs displayed high radical-scavenging activity and reducing power that were not significantly changed for 60 days at 4°C. The transmission electron microscopy images and dynamic light scattering results demonstrated high stability of Ch-SeNPs during storage. ACR (20 mg kg-1  day-1 ) led to elevate the level of malondialdehyde, dopamine and noradrenaline in blood serum, and cerebral cortex. Ch-SeNPs (0.2 mg kg-1  day-1 ) displayed more protection against ACR-induced damages comparing to Na2 SeO3 . More than 90% of the glutathione pool in the brain tissue was in reduced form. Correlation coefficient analysis demonstrated the attenuating effect of Ch-SeNPs against ACR-induced brain-injury and hormone imbalance. Administrating Ch-SeNPs 15 days before ACR-treatment is required for obtaining the best protection. PRACTICAL APPLICATIONS: Ch-SeNPs used in the present study characterized by its high storage stability for two months without losing its antioxidant potential. After conducting toxicity tests, it is suggested to supplement some foods with Ch-SeNPs because of its high antioxidant potential and significant protection ability against the oxidative stress damages in living organisms. These advantages may nominate the Ch-SeNPs for several industrial applications in the field of food processing and protection.

Molecular characterization of black Aspergillus species from onion and their potential for ochratoxin A and fumonisin B2 production.

Onion bulbs can become contaminated with various molds during the storage period, the most important causal agents being black aspergilli (Aspergillus section Nigri). Taxonomic studies have revealed that this group of Aspergillus contains many species that cannot be reliably identified using standard morphological methods. Therefore, it is necessary to define the fungus causing this problem in the onion exactly, especially since some species assigned to section Nigri are well known as ochratoxin and/or fumonisin producers. Sixty fungal isolates belonging to 10 fungal genera were isolated from 40 onion samples originated from the Taif region in Saudi Arabia. Black aspergilli were detected in 37 onion samples. Using primer pairs (awaspec and Cmd6) designed based on partial calmodulin gene sequence data, 37 isolates were identified as A. welwitschiae. The ochratoxin A and fumonisin B2 contents of the onion samples were examined. No ochratoxins were detected in the collected samples, while fumonisin B2 was detected in 37.5% of the onion samples. Eighteen of 37 isolates of Aspergillus welwitschiae were recognized as potential producers for fumonisin B2. Multiplex polymerase chain reactions designed to detect biosynthetic genes of fumonisins confirmed these results.

Arrest of cell cycle by inhibition of ribonucleotide reductase induces accumulation of NAD+ by Mn2+-supplemented growth of Corynebacterium ammoniagenes.

Cell division of the wild type strain Corynebacterium (formerly Brevibacterium) ammoniagenes ATCC 6872 which requires 1 microM Mn2+ for balanced growth was inhibited by addition of 20 mM hydroxyurea (HU) or 10 mM p-methoxyphenol (MP) to a Mn2+-supplemented fermentation medium at an appropriate time. Scanning electron microscopy (SEM) showed a restricted elongation characteristic of arrest of the cell cycle in coryneform bacteria. The cultures treated with HU or MP had, respectively, a fourfold or sixfold enhanced accumulation of NAD+ by a salvage biosynthetic pathway. An assay of nucleotide-permeable cells for ribonucleotide reductase activity using [3H-CDP] as substrate revealed a pre-early and complete decline of DNA precursor biosynthesis not found in the untreated control. Overproduction of NAD+ is an alternative to the conventional fermentation process using Mn2+ deficiency. A simple model is presented to discuss the metabolic regulation of the new process based on the presence of a manganese ribonucleotide reductase (Mn-RNR) in the producing strain.