Investigação de diferentes condições de cultivo de Beauveria bassiana para micossíntese de nanopartículas de prata

Abstract

The investigation of metallic nanoparticles (MNPs) has been growing widely in areas of direct contact with humans. However, there is still little information about its biocompatibility and toxicity. Thus, there is a search for less toxic synthesis methods, without the use of solvents and production of chemical residues such as biological synthesis that uses biological materials such as the fungus to obtain silver nanoparticles (AgNPs), this method being called mycosynthesis. Depending on the culture conditions, different metabolites can be produced by the fungi and, thus, interfere in different ways in the formation of nanoparticles. In this context, the present work aimed to subject the fungus Beauveria bassiana to different cultivation conditions in order to obtain different metabolites to verify their effects on the AgNPs mycosynthesis. For this, the variables luminosity, agitation, pH and nutrients were evaluated. The conditions with the best potential for reduction were selected through the redox potential (ORP). In order to detect the produced metabolites, the mycelial filtrates of the selected conditions were submitted to analysis in high performance liquid chromatography (HPLC). Soon after, the cell filtrates obtained directly from the cultures (Filtrate 1) and mycelium filtrates (Filtrate 2) were used to perform mycosynthesis, being tested at natural pH and pH 9.5, obtaining 40 ways to synthesize AgNPs. Then, the colloidal suspension was characterized by Ultra-Violet spectrophotometry in the visible region (UV-Vis) and dynamic light scattering (DLS). As a result, 10 conditions were selected with the best potential for reduction. Referring to the identification, 19 peaks were detected, which together with the results of the cultivation behavior indicate the presence of metabolites such as amino acids, fatty acids and organic bases such as biogenic amines. In the case of mycosynthesis, 17 conditions of mycosynthesis were identified that promoted the formation of AgNPs. Regarding the characterization of the colloidal suspension, it was observed the band that represents the SPR of the silver that occurred between 350 - 485 nm. From the DLS, mean sizes between 32 - 452 nm were found, with polydispersity indices (PDI) between 0.316 - 0.830. Thus, the best synthesis conditions were NP10 (F2 at pH = 9.5, polydispersion index (PDI) = 0.461 and Zeta potential = - 31 mV) and NP18 (F2 at natural pH, PDI = 0.397 and Zeta potential = - 28 mV). Thus, we conclude that B. bassiana was able to produce different substances in relation to the selected culture conditions which enabled the mycosynthesis of AgNPs, being considered the best synthesis conditions NP10 and NP18. As perspectives it is expected to perform the characterization of the solid material through Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) to compare with the literature and demonstrate advantages and disadvantages of selected conditions, and evaluate antimicrobial activity of AgNPs obtained from the best selected synthetic conditions.