Optimization of extraction and evaluation of antioxidants from mestruz (Coronopus didymus) leaves in fish feedAuthor: Alex Zefanias Baloi
Advisor: Dra. Vilásia Guimarães Martins
Abstract
The development of new methods for synthesizing silver nanoparticles (AgNP) that are more environmentally friendly has received considerable attention in recent years, with green synthesis—especially biological approaches—leading these new strategies. Microalgae are fast-growing photosynthetic organisms that produce a wide range of compounds capable of reducing ionic silver into AgNP, making them a lower-impact alternative. AgNP are mainly applied as antimicrobial agents, representing an alternative to the use of antibiotics due to the already well-established antimicrobial properties of silver. Therefore, in this study, AgNP were synthesized for the first time using dissolved organic matter (DOM) collected by a foam fractionator (skimmer) from the culture of Nannochloropsis oceanica, acting as both reducing and stabilizing agent in the synthesis process, which was monitored using UV-Vis absorbance spectra. The AgNP produced were evaluated by Transmission Electron Microscopy, showing average sizes ranging from 11.89 ± 6.33 to 27.55 ± 8.41 nm. Analysis using the Litesizer revealed a hydrodynamic diameter of 263.82 ± 4.89 nm, a polydispersity index of 0.178, and a zeta potential of -20.41 ± 0.32 mV. The DOM was also evaluated by Fourier Transform Infrared Spectroscopy (FTIR), in addition to microbiological assays for Minimum Inhibitory Concentration (MIC) against Acinetobacter baumannii, Pseudomonas aeruginosa, Vibrio coralliilyticus, and Staphylococcus aureus, as well as growth kinetics and biofilm assays (inhibition and disruption) on A. baumannii, demonstrating that the use of DOM is a viable approach, resulting in a high value-added biotechnological product.