Síntese verde de nanopartículas de prata por microrganismos filamentosos (fungos e actinomicetos) isolados da caatinga e avaliação das propriedades biológicas aplicadas à agropecuária

Abstract

Metallic nanoparticles (MNPs) have aroused significant interest within the scientific community in recent years due to their wide range of applications across various scientific fields. The present study aimed to synthesize silver nanoparticles using filamentous fungi and Actinomycetes (Genus Streptomyces), and to characterize them regarding their physicochemical nature, as well as to evaluate their biological potential. Brief, for the production and extracellular biosynthesis of silver nanoparticles (AgNPs), the fungi Aspergillus tamarii, Mucor subtilissimus, Aspergillus terreus, and 4 strains of Actinomycetes (Streptomyces sp. DPUA 1542, S. sp. DPUA 1557, S. malasyensis DPUA 1571, S. parvulus DPUA 1573) were utilized. Following green synthesis, the AgNPs were characterized using UV-Vis spectrophotometry, FTIR spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), and Zeta potential, as well as the evaluation of acaricidal and termiticidal activity. The results obtained regarding the synthesis of AgNPs demonstrated that the tested filamentous fungi were not capable of producing AgNPs. However, two of the Streptomyces strains (Streptomyces sp. DPUA 1542 and Streptomyces sp. DPUA 1557) exhibited significant production, and these were utilized for characterization assays. The strain Streptomyces sp. DPUA 1542 (cultivated in ISP-2 medium) obtained AgNPs with alterations in the Surface Plasmon Resonance (SPR) property in the region near the 420nm length. Meanwhile, the AgNPs derived from Streptomyces sp. DPUA 1557, using soy flour, showed SPR variation in the region near the 400nm length. Zeta potential analysis revealed peaks of -26.46 mV (for AgNPs from Streptomyces sp. DPUA 1557) and -26.9 mV (for AgNPs from Streptomyces sp. DPUA 1542), indicating a good state of particle stability. When subjected to biological assays aimed at evaluating acaricidal and termiticidal activity, the nanoparticles showed no effect against the Dermacetor nitens tick. However, excellent results were observed, with 100% efficacy when tested against the termite Nasutitermes corniger, particularly when associated with the aqueous extract of Cassia grandis, a plant widely found in the Pernambuco hinterland. The synthesis processes used showed high reproducibility and are in accordance with the principles of green chemistry and sustainability, presenting themselves as a low-cost and biocompatible alternative in AgNPs synthesis.