The objectives of this study were to obtain scientific data on the impact that interactions between water stress (water activity (a_w); 0.97, 0.95, 0.92), temperature (34, 37 °C) and CO₂ exposure (350, 650, 1000 ppm) may have on the growth, gene expression of biosynthetic genes (aflD,aflR), and phenotypic aflatoxin B₁ (AFB₁) production by a type strain ofAspergillus flavus on a conducive medium. The study showed that while aw affected growth there was no statistically significant effect of temperature or CO₂ exposure. The effect of these interacting factors onaflD andaflR gene expression showed that at 34 °C there was maximum relative expression ofaflD under the control conditions (34 °C, 350 ppm) with a decrease in expression with elevated CO₂ and water stress. ForaflR expression at 34 °C, there was a significant increase in expression, but only at 0.92 a_w and 650 ppm CO₂. However, at 37 °C, there was a significant increase in expression of bothaflD andaflR at 0.95 and 0.92 a_w and 650 and 1000 ppm CO₂. There was an associated increase in AFB₁ in these treatments. In contrast, at 34 °C there were no significant differences for interacting treatments. This is the first study to examine these three-way interacting climatic factors on growth and mycotoxin production by a strain ofA. flavus. This provides data that are necessary to help predict the real impacts of climate change on mycotoxigenic fungi.

This study was conducted to evaluate the antimicrobial activities and cytotoxicity of both crude extracts of Scenedesmus obliquus and their fractions. In vitro cytotoxicity assay against human hepatocellular carcinoma (HepG2), colon cancer (HCT116) and breast cancer (MCF7) cell line was monitored. The highest inhibition was observed using diethyl ether crude extract (DEE) recording between 12.5 and 19.5 mm inhibition zone against all tested bacteria and between 8.7 and 18.3 mm against tested fungi. The highest anticancer effect of DEE was observed at IC50 against HCT116 and HepG2 cell lines using just 24.6 and 42.8 μg ml-1, respectively. While, high concentration, 93.8 μg ml-1, was required to exhibit its effect against MCF7. Column chromatography technique was used to separate DEE crude extract to its main components using 7 different mobile phases. Fractions F1 and F7 were the highest fractions that had antimicrobial activity against tested bacteria and fungi. High IC50 > 80 μg ml-1 were required to exhibit anticancer activity at IC50 against the tested cancer cell lines. The main compounds responsible for the bioactivity were identified using GC-MS, nonadecane and butylated hydroxytoluene in F1 and 9-octadecadienoic acid and quercetin 7,3',4'-trimethoxy in F7 were identified. The current study highlights the potential use of S. Obliquus extract and their fractions as a source of antimicrobial and anticancer compounds.

Chitosan, bio-polyaminosacharide, is derived from chitin. Two sources (shrimp wastes and fungus biomass) were used to produce chitosan. And then the chitosan was produced in the nano-form followed by characterization by transmission electron microscopy. The images obtained clearly showed that the size of nano-chitosan ranged between 7 and 13 and 3-6 nm with spherical shape for shrimp and fungal sources, respectively. The antimicrobial activities of the tested concentrations of chitosan and nano-chitosan were examined and found to have high activity against the tested pathogens. The evaluation of the toxicity of the tested concentrations of the produced chitosan and its nano-size were performed using brine shrimp and rat bioassay. Toxicity examination of chitosan and their nano derivatives is an essential procedure to assess the possibility of using these concentrations as food ingredient. Nine groups of rats were treated with either chitosan or nano-chitosan of both sources at 100 and 200 mg kg-1 bw. Adding chitosan in the diet of all groups showed no significant changes in both the blood biochemical and oxidative stress parameters when compared with control group. The histopathology of liver, kidney and stomach confirmed the results of the previous parameters. No signs of inflammation, fibrosis or cirrhosis were found in examined organs. It is concluded that chitosan and nano-chitosan of shrimp and Rhizopus stolonifer had high antimicrobial activity and are not toxic in the same time and it can be used as food ingredients.