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The biosynthesis of nanoparticles (NPs) has been proposed due to its fast, clean, safe, and cost-effective production and being efficient alternative to conventional physicochemical methods. This study aimed to isolate and identify aquatic yeast strains for their potential to form Zinc oxide nanoparticles (ZnONPs). A yeast strain, NS02, with high tolerance against zinc ion (5.25 mM) was isolated using the enrichment technique and was selected as efficient candidate for the biosynthesis of ZnONPs under cell-free extract (CFE) strategy. The preliminary evaluation on the formation of ZnONPs was performed by visual observation and UV-visible absorption spectra of the biosynthesized ZnONPs. The morphology, size and elemental distribution of the nanoparticles were determined by Field emission scanning electron microscopy (FESEM) equipped with energy-dispersive X-ray (EDX). X-ray diffractometer (XRD) was used to identify the crystalline phase of the ZnONPs. Antibacterial activity of ZnONPs against pathogenic bacteria isolated from the clinical specimens was investigated using agar well diffusion method. The isolate NS02 was characterized based on their morphological properties and amplification the ITS-5.8S-ITS2 rDNA regions. The present study pioneered the capabilities of the native aquatic strain Rhodotorula pacifica for the extracellular synthesis of ZnONPs with CFE strategy. The biosynthesized ZnONPs had a growth inhibitory effect all tested clinical isolates due to their nanometric size and well-defined dispersity. This investigation is attempted to indicate the novel microbial sources of aquatic yeasts as biological plant in the synthesis of ZnONPs with antimicrobial activity under cell-free extract strategy.
 

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Heavy metal contamination (HMs) of water and soil is the most serious problem caused by industrial and mining processes and other human activities. Mycoremediation is a biotechnological method that employs fungi to remove toxic contaminants from the environment in an efficient and cost-effective manner. Pleurotus species are considered to be the most popular and widely cultivated species worldwide, and this may be due to their low production cost and high yield. It has been indicated that Pleurotus species may improve plant growth in metal-contaminated soils through enhancing nutrition uptake or by alleviating toxicity of the metals. In this experiment, the fungus was grown in vitro in liquid and solid media for 3 weeks on five different concentrations (0, 15, 30, 45, 60 ppm) of five heavy metals (Cd, Zn, Ni, Pb, Mn) as sulphate and the effect of these metal on radial growth, biomass production and metal content of fungal biomass were determined. Based on the results, this fungus showed a great variety of tolerance against the metals, as that growth parameters were increased in the case of two metals contamination (Zn and Mn) and inhibition of growth was observed even at the low concentrations of nickel, cadmium and lead (15 mg/liter). The amount of metal accumulation in the fungal mycelium also increased with the increase of the metal concentration in the culture medium. In this research, for the first time, the growth parameters and the amount of accumulation of heavy metals in axenic conditions have been investigated and described.