Abstract
Biosynthesis of green nanomaterials using microorganisms is considered clean, eco-friendly and viable, instead of the physical or chemical methods. This study aimed in the biosynthesis of copper nanoparticles (CuNPs) exploiting Egyptian local bacterial isolates. Sixteen copper-resistant isolates out of 160 bacterial isolates; were captured from various plant rhizospheres including; chamomile, hibiscus, neem, iris, and pea, beside samples collected from the Sharm El-Sheikh seawater. Among the 16 copper-resistant isolates, one promising isolate I108 was chosen which synthesized CuNPs of diameter about 87.1 nm, showed UV absorbance of 0.54 at 580 nm, with a concentration of 12.21 mg l. This isolate was characterized by phenotypic and genotypic features. Based on 16S rRNA gene analysis and compared with the sequences presented in NCBI GenBank, the phylogeny positions assessment confirmed that it belonged to Genus Pseudomonas, and was closely related to Pseudomonas silesiensis strain A3 (98% similarity). For the bacterial synthesis of CuNPs, optimization of the P. silesinsis strain A3 cell-free supernatant was carried out using seven agro-industrial residues, added to the basal medium as different carbon sources. Results showed that 2% blackstrap sugar cane molasses was the most efficient carbon source for CuNPs biosynthesis, when incubated for at 30°C for 24 h using shaking speed of 120 rpm. The biosynthesized CuNPs has a size of 66.12 nm at a concentration of 19.2 mg l, and maximum surface plasmon peak (SPR) of 0.85.
Highlights
Nanoparticles (NPs) gained a lot of attention from scientists owing to their size, which occur between the size of their original materials and their structures at the nano size
After 24 to 48 h of incubation, the highest SPR peaks are recorded in the ranges from 0.64 to 0.66. This indicates the good dispersion and non-agglomeration of the CuNPs, owing to the capping agents that exist in the cell-free extract. These results are in agreement with those obtained by Tiwari et al, (2016), that CuNPs synthesis was taking place within 36 h of incubation by Bacillus cereus SWSD1 and after that period the particles size did not increase due to its non-agglomeration
Of the 106 isolates recovered from different Egyptian ecosystems, only single copper resistant isolate I108 is chosen and identified as P. silesiensis strain A3 based on the phenotypic and genotypic properties
Summary
Nanoparticles (NPs) gained a lot of attention from scientists owing to their size, which occur between the size of their original materials and their structures at the nano size. Mangesh et al, (2018) stated that large energy requirements are met by the specific oxidation reduction enzymes and protein molecules for metal reduction, these proteins possess catalytic and metal-binding properties. This is in addition to their hydrophobic lipid molecules which play a promising role as capping agents, and serve to stabilize the NP through preventing their oxidation. Din et al, (2017) reported that microbial methods have achieved perspectives through their strain selection, optimization of cultivation conditions including; nutritional factors, pH, temperature, incubation time, metal ion concentration, and volume of the biological material to be used in large-scale and commercial applications
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