Mycotoxigenic fungi have attracted special attention due to their threat to food security and toxicity to human health. Aqueous extract of Zingiber officinale Roscoe was used as reducing and capping agent for the synthesis of silver (AgNPs), copper (CuNPs), and zinc oxide (ZnONPs) nanoparticles. UV-Visible spectra of the AgNPs, CuNPs, and ZnONPs showed absorption peaks at λ_max 416 nm, 472 nm, and 372 nm, respectively. Zeta potential of AgNPs, CuNPs, and ZnONPs were −30.9, −30.4 and −18.4 mV, respectively. ZnONPs showed the highest activity against Aspergillus awamori ZUJQ 965830.1 (ZOI 20.9 mm and MIC 24.7 µg/mL). TEM micrographs of ZnONPs-treated A. awamori showed cracks and pits in the cell wall, liquefaction of the cytoplasmic content, making it less electron-dense. The sporulation and ochratoxin A production of A. awamori was inhibited by ZnONPs in a concentration-dependent pattern. The inhibition percentage of OTA were 45.6, 84.78 and 95.65% for 10, 15, 20 of ZnONPs/mL, respectively.

The biosorption of cadmium(II) on live and dead biomass of Saccharomyces cerevisiaewas investigated with respect to the adsorption conditions. The biosorption mechanism was investigated by energy dispersive X-ray analysis (EDAX) and transmission electron microscope (TEM). The effects of the biosorbent dose, initial metal ion concentration, initial pH and contact time were studied. The optimum conditions for cadmium(II) biosorption were found to be 3 g/L, 250 mg/L and 6.0, respectively, for biosorbent dose, initial metal ion concentration and initial pH. Cadmium(II) biosorption by dead cells was a fast process. Under these conditions, the maximum biosorption capacity of the dead biomass was obtained to be 55 mg/g, while that of live biomass was 36 mg/g. TEM observations indicated the presence of cadmium (II) deposits intracellularly and extracellularly. EDAX examinations showed that cadmium(II) was exchanged with the element (aluminum) present on the surface of native cells of S. cerevisiae, thereby suggesting the occurrence of bioadsorption, ion exchange and complexation. Cadmium(II) biosorption capacity on dead cells was enhanced by ethanol treatment and alginate immobilization. Overall, the results showed that the ethanol-treated, alginate-immobilized biomass was capable of removing cadmium(II) from wastewater samples. Key words: Biosorption, Saccharomyces cerevisiae, cadmium(II), immobilization, chemical treatment.

THE PRESENT study aimed to assess the biosorption capacity of live, autoclaved and dried biomass of Yarrowia lipolytica AUMC 9256 for cadmium (Cd(II)) Minimum inhibitory concentration 500mg/L proved great tolerance of Y lipolytica AUMC 9256 to Cd(II). The time course growth in the presence of different concentrations of Cd(II) was studied. For live, autoclaved and dried biomass, maximum uptake capacities accomplished at pH 5.0, initial metal ion concentration 400mg/L, biomass dosage lg/L, and contact time 20min for autoclaved and dried biomass and 240min for live cells. The potential of Y lipolytica to produce cadmium nanoparticles was determined by UV-Visible spectroscopy measurements and transmission electron microscopy examinations. Moreover, to identify the possible mechanisms of Cd(II) uptake, TEM examinations, Fourier Transform Infrared spectroscopy, Energy dispersive X-ray microanalysis, and X-ray powder diffraction analyses were carried out. The potential implementation of dried Y lipolytica biosorbent for heavy metal removal from different water samples was successfully accomplished using the multistage microcolumn technique. Accordingly, Y lipolytica AUMC 9256 can be considered as a very promising potential to bioremediate Cd(II) ions and biosynthesis of Cd NPs.

This the first study describing the rapid extracellular synthesis of copper nanoparticles during the bioremediation of copper by living, autoclaved and dried biomass of Yarrowia lipolytica AUMC 9256. The time course growth in the presence of different concentrations of Cu(II) was studied. The minimum inhibitory concentration value of Y.lipolytica AUMC 9256 for Cu(II) was 1900 mg/l. The cellular localization of bioaccumulated copper ions was assessed. Maximum uptake capacities were accomplished at pH 6.0, initial metal ion concentration 450 mg/l, biomass dosage 1 g/l and contact time 180 min for live cells, 90 min for autoclaved and 30 min for dried biomass. Copper nanoparticles were characterized by UV-Visible spectrophotometer and transmission electron microscopy. They were all spherical in shape with an average size of 32.85 nm (live), 22.34 nm (autoclaved) and 15.62 nm (dried). The occurrence of extracellular complexation, precipitation, adsorption onto cell wall, and sequestration of needle-, rod-shaped precipitates within central large vacuole during Cu(II) uptake by live biomass were found out by transmission electron microscopy. Fourier Transform Infrared spectroscopy confirmed that mannans, phosphorus, P=S stretching, C-S stretching, M-O and ring deformation were more included in Cu(II) uptake by dried biomass. Energy dispersive X-ray microanalysis confirmed the presence of high-intensity characteristic peaks of Cu(II) and a sharp reduction of atomic % of phosphorus and potassium on the cell wall. X-ray powder diffraction patterns of Cu(II)-loaded biomass confirmed their crystalline nature. The removal of copper from ceramic industry wastewater was carried out by dried biomass effectively.