Evaluating the role of nitrate reductase and the manipulation of the culture conditions on the biogenesis of silver nanoparticles by the wild yeasts

Abstract

This study investigated the correlation between silver nanoparticles (AgNPs) production by yeast isolates, and the activity of nitrate reductase. It also evaluated the influence of different physical and chemical conditions on the growth of Wickerhamomyces onychis (W. onychis) and AgNPs formation. The NO2− concentration of each sample was determined. The result showed that although all the yeasts are capable of synthesizing AgNPs, only eight produced the enzyme nitrate reductase. The relationship between the synthesis of silver nanoparticles and the nitrate reductase enzyme exhibited a statistically insignificant negative association. The development of W. onychis and the synthesis of AgNPs were significantly affected by variations in the incubation period, pH, temperature, concentrations of NaCl, and concentrations of various metals. The most effective medium for W. onychis growth was YPD medium, while PDB medium was optimal for AgNPs synthesis. The optimal period for the AgNPs production and yeast growth was seven days. The pH level of the media clearly influenced the synthemperature for the formation of AgNPs and the growth of cells was 30°. The optimal conditions for yeast growth and nanoparticles production were determined to be pH 8, 30°C, the absence of sodium chloride, 2 ppm of calcium chloride (CaCl2) and magnesium sulfate (MgSO4), 1 ppm of potassium dihydrogen phosphate (KH2PO4), 1.5 ppm of iron chloride (FeCl3), and 1 ppm of cobalt chloride (CoCl2).These results contribute to a better understanding of the potential for quick and inexpensive biosynthesis of metal nanoparticles in the future.