Efficient continuous biosynthesis of silver nanoparticles by activated sludge micromycetes with enhanced tolerance to metal ion toxicity

The method for producing AgNPs by granules of activated sludge micromycetes with enhanced tolerance to metal ion toxicity − Penicillium glabrum, Fusarium nivale and Fusarium oxysporum has been developed; the optimum conditions for AgNP biosynthesis being found: the Ag+ ion concentration, duration of the contact of microbial cells with silver ions, a growth phase of microorganisms, medium composition, a рН value, mixing conditions, and also lighting intensity. The effect of Cl−, SO42− and HPO42− ions binding Ag+ ions was eliminated, that brought to significant increase of the yield of NPs. Under batch conditions, silver particles of 60-110 nanometers in size were formed with a 65% yield. It was established that the nanoparticles were covered with microbial cell membrane proteins composed up to 70% by weight of the NPs that prevented their aggregation. In addition, it was the first time stable AgNPs had been formed by continuous AgNP biosynthesis by living cells of F. oxysporum with an 80% yield for a long time.

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