Biosynthesis of silver nanoparticles by cell-free extract from Trichoderma reesei - study on the influence of growth media

Abstract Trichoderma reesei is a non-pathogenic microorganism able to reduce the toxic for the microorganism silver ions (Ag+) to non-toxic silver nanoparticles (AgNPs). The effect of components of the nutrient medium on which the biomass from T. reesei was obtained on the biosynthesis of AgNPs from Ag+ was monitored. Five media were studied. The main medium (1) contained glucose-2%, NH4Cl-0.1%, CO(NH2)2-0.3%, (NH4)2SO4-0.1%, KH2PO4-0.2%, (NH4)2SO4-0.14%, MgSO4.7H2O-0.03%, CaCl2.2H2O-0.04%. The other were medium 1+0.1% yeast extract (2), medium 1+0.1% corn steep liquor (3), medium 1+0.1% peptone (4), medium 1+0.1% casamino acids (5). After culturing the strain, the resulting biomass was subjected to aqueous extraction, and the cell-free extract - CFE (containing biologically active metabolites) was used for extracellular biotransformation (performed with 10% extracted biomass and 10 mM AgNO3) of Ag+ to AgNPs. The AgNPs formation was monitored by UV-Vis. The isolated nanoparticles were characterized by TEM, ICP-AES and FTIR-ATR. The slowest reduction rate of Ag+ was obtained with the CFE from biomass grown in medium 1 and the highest - with CFE from biomass grown in medium 3. Nearly mono disperse spherical AgNPs (2-6 nm) were synthesized with the aid of CFE of fungi cultivated in media 1 and 3. The AgNPs obtained with CFE from the other media were 4-11 nm.</jats:p

EXTRACELLULAR BIOSYNTHESIS OF SILVER NANOPARTICLES BY TRICHODERMA REESEI AND THEIR APPLICATION TO REMOVE XANTHOGENATE FROM WASTEWATER

Application of fungi in the biosynthesis of silver nanoparticles is a green and feasible alternative to chemical and physical methods used for AgNPs synthesis. The fungus Trichoderma reesei is a non-pathogenic and environmentally friendly microorganism capable to produce extracellular enzymes and metabolites in high scale. An extracellular biosynthesis of silver nanoparticles (AgNPs) from AgNO3 solution by using the cell-free extract of Trichoderma reesei biomass is presented in this study. Kinetics of the biotransformation is described by a second order reaction equation. Spherical or approximately spherical AgNPs that are well-dispersed and with a size between 3-4 and 15-17 nm have been produced at transformation degree of 30 % with respect to the initial silver ions concentration. The biosynthesized AgNPs show high stability against agglomeration even after storage for 60 days. Soluble xanthates, used in some industrial applications, are found toxic to aquatic biota even at low concentrations. The synthesized AgNPs are capable to immobilize potassium amyl xanthate from model wastewater. The pollutant adsorption is described by the Langmuir adsorption isotherm and the calculated maximum adsorption capacity is 4.67 mg/mg. The pollutant immobilization by AgNPs is much faster process and requires much less adsorbent (50 fold) in comparison with the activated carbon (chemical grade of purity)

PREPARATION OF SILVER NANOPARTICLES – NATURAL ZEOLITE COMPOSITE AND STUDY OF ITS ANTIBACTERIAL PROPERTIES

Composite consisting of natural zeolite and silver nanoparticles (AgNPs-zeolite) has been synthesized by ion exchange followed by a thermal treatment. The prepared material is characterized by BET, EDX, TEM and XPS. The antibacterial activity of the synthesized material has been studied against Е. coli. Results on the influence of the material\u27s doze and treatment time on the antimicrobial action of the composite are presented. The minimum inhibitory concentration is 10 mg AgNPs-zeolite/mL of culture medium containing E. coli (105 CFU/mL). Bactericidal activity has been observed after 300 minutes of treatment. The bactericidal action of the synthesized nanocomposite against E. coli is maintained after three repeated re-inoculations, and after the third inoculation it is 99.9%. Possible mechanism of the observed antimicrobial action is briefly discussed