Abstract
Soil humic precursors could be considered the most active and mobile fraction and are highly significant to a series of biochemical processes in all types of soil. The microbial biosynthesized humic precursors attracted increasing attention on green synthesis of nanocomposite compounds realized between biopolymers and metal nanoparticles. Silver nanoparticles are the most used engineered nanocomposite serving as antimicrobial agents. In the present study we used aqueous solution of humic precursors synthesized by four microbial consortia (C1-C4) and selected on the basis of high quantities of exometabolites with structural similarities to soil humic acid fraction. The humic precursors were used as capping agents of silver nanoparticles in the nanocompozite synthesis. Biosynthesized humic precursors act as reductive and stabilizative agents of nanoparticles which are found between 5-300nm in size and with spherical preponderant shape. The presence of humus precursors and the biosynthesized silver nanoparticles was confirmed by FTIR and UV-Vis. At a given precursor concentration, the efficiency of nanocomposite synthesis increased with particle concentration and time of reaction, property which can be attributed to the high reduction capacity of humic precursors. The induced antimicrobial effect of exposure to nanocomposites differs due to the size, time of preparation and stability. Stabilization of nanocomposite by specific metal-ligand bonds was obtained in the solution for three months without any precipitate. The antimicrobial effect of nanocomposites was estimated under laboratory agar well diffusion tests against mycotoxigenic soil fungal isolate Aspergillus niger (A27). The green synthesis of nanocomposite material with the best antimicrobial effect against test fungus was realized by microbial consortium C3and C4.
Highlights
Silver (Ag) has a strong toxicity to a broad spectrum of microorganisms
Research has been carried out to assess the influence of biopolymers as humic precursors from to four microbial consortia (C1-C4) as a silver reducing and capping agents for synthesis of nanocomposite materials as new efficient antimicrobial agents
Since biopolymers were biosynthesized by microbial consortia C1-C4, the composition and reactivity were different from one to another
Summary
Silver (Ag) has a strong toxicity to a broad spectrum of microorganisms. Due to their antimicrobial properties, silver nanoparticles (AgNPs) were obtained by nanotechnologies involving reducing agents of chemical or biological nature (Sarsar et al, 2014; Elbeshehy et al, 2015; Khodashenas and Ghorbani, 2015) and used in biomedical applications, food preservation and other ecological disinfection processes (Prabhu and Poulose, 2012; Matei et al, 2015). Nanocomposites made from humic precursors biosynthesized by microbial consortia and silver nanoparticles attempt to capitalize matrix characteristics for obtaining antimicrobial nanocomposites and selecting efficient consortia. Research has been carried out to assess the influence of biopolymers as humic precursors from to four microbial consortia (C1-C4) as a silver reducing and capping agents for synthesis of nanocomposite materials as new efficient antimicrobial agents
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