BIOSYNTHESIS OF NANOPARTICLES FROM LOW-VALUE AGRO-WASTE AND THEIR POTENTIAL AS BIOCIDES IN PAINT INDUSTRY

Abstract

ABSTRACT Paint contains organic materials which can serve as both carbon and energy sources for microorganisms, therefore susceptible to microbial attack during storage and after application on a surface. The resistance of paint spoilage microbes to conventional biocides necessitates the development of improved and more effective biocides. Nanomaterials have recorded broad-spectrum antimicrobial properties. This study investigated the biocidal efficacy of biogenic nanosilver (AgNPs) and nanotitania (TiNPs) as potential biocides for the paint industry. The nanosilver and nanotitania were synthesized by adding aqueous extract of banana peel to silver nitrate (AgNO3) and titanium iv oxide (TiO2), respectively. The biogenic nanoparticles were characterized using Ultraviolet-visible spectrophotometry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR) while Gas Chromatography-Mass Spectrometry (GC-MS) was used to profile metabolites present in the banana peel. Paint microbes were isolated from two samples of in-can paints and fifteen painted walls observed for visible discolorations in Abeokuta and characterized using morphological, biochemical, and molecular methods. The biocidal efficacy of the biogenic nanoparticles against the isolates was investigated. Bioactive compounds revealed by GC-MS were docked against biomarkers present in susceptible isolates using iGEMDOCK software. The results were analyzed using one-way Analysis of Variance while treatment means were separated by Duncan Multiple Range Test at 0.05 level of significance. Results showed that Ultraviolet-visible spectrophotometry recorded surface plasmon resonance at 475 and 260 nm for AgNPs and TiNPs, respectively. The SEM revealed polydispersed AgNPs and TiNPs having average sizes of 83.48 and 96.4nm, respectively. The EDX confirmed the presence of silver and titanium with carbon and oxygen showing that both nanoparticles are biogenic. The intensity of XRD peaks reflected that both nanoparticles are crystalline with AgNPs similar to that of face centered cubic structure of silver, while 2Ɵ at peak around 25° confirmed TiO2 anatase structure. The FT-IR analysis showed the presence of carboxylic acids and esters, confirming n-Hexadecanoic acid and methyl ester as revealed by GC-MS. The susceptible isolates identified by molecular method were Pseudomonas aeruginosa FUNAAB WAS01, Kosakonia cowanii FUNAAB WAS02, and Aspergillus aculeatus FUNAAB WAS03 with Kosakonia cowanii being a novel bacterium implicated in paint deterioration. At concentrations 4 - 125µg/ml, the nanoparticles exhibited biocidal efficacy against the three paint isolates. The TiNPs inhibited growth of Pseudomonas aeruginosa with zone of inhibition of 20 mm diameter while conventional biocide recorded no zone of inhibition. Docking analysis revealed that n – Hexadecanoic acid has a relatively high negative binding energy of 88, 80, and 73 kcal against Pseudomonas aeruginosa FUNAAB WAS01, Kosakonia cowanii FUNAAB WAS02, and Aspergillus aculeatus FUNAAB WAS03. The study suggested that biogenic nanosilver and nanotitania are effective biocides against microbes implicated in paint degradation.