The widespread and indiscriminate use of broad-spectrum antibiotics leads to microbial resistance, which causes major problems in the treatment of infectious diseases. However, advances in nanotechnology have opened up new domains for the synthesis and use of nanoparticles against multidrug-resistant pathogens. The traditional approaches for nanoparticle synthesis are not only expensive, laborious, and hazardous but also have various limitations. Therefore, new biological approaches are being designed to synthesize economical and environmentally friendly nanoparticles with enhanced antimicrobial activity. The current study focuses on the isolation, identification, and screening of metallotolerant fungal strains for the production of silver nanoparticles, using antimicrobial activity analysis and the characterization of biologically synthesized silver nanoparticles by X-ray diffraction (XRD) spectroscopy, energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). In total, 11 fungal isolates were isolated and screened for the synthesis of AgNPs, while the Penicillium notatum (K1) strain was found to be the most potent, demonstrating biosynthetic ability. The biologically synthesized silver nanoparticles showed excellent antibacterial activity against the bacteria Escherichia coli (ATCC10536), Bacillus subtilis, Staphylococcus aureus (ATCC9144), Pseudomonas aeruginosa (ATCC10145), Enterococcus faecalis, and Listeria innocua (ATCC13932). Furthermore, three major diffraction peaks in the XRD characterization, located at the 2θ values of 28.4, 34.8, 38.2, 44, 64, and 77°, confirmed the presence of AgNPs, while elemental composition analysis via EDX and spherical surface topology with a scanning electron microscope indicated that its pure crystalline nature was entirely composed of silver. Thus, the current study indicates the enhanced antibacterial capability of mycologically synthesized AgNPs, which could be used to counter multidrug-resistant pathogens.
The widespread use of antibiotics has resulted in the emergence of multidrug-resistant bacteria. Therefore, it is essential to explore alternative strategies to effectively combat medically significant resistant pathogens. In recent years, nanoparticles (NPs) have emerged as a promising alternative source of antimicrobial agents. While nanoscale particles were traditionally synthesized using chemical techniques, the development of metallic NPs using biological methods has garnered attention. This current study focuses on the synthesis of iron NPs (Fe NPs) using metal-tolerant fungal strains, as numerous microorganisms serve as environmentally safe and durable precursors to produce persistent and bi-functional NPs. The study involved the isolation and evaluation of ten fungal strains that are resistant to heavy metals to determine their ability to produce Fe NPs. The biologically synthesized Fe NPs were characterized using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy techniques. The XRD results indicated the presence of Fe in nanopowder form, displaying a series of reflection angles (2θ) at 65° and 75° indicating the existence of cubic planes. EDX analysis revealed the presence of ferrous and ferric elements, along with zero-valent Fe NPs. Micrographs of the surface topology displayed spherical aggregation of the synthesized NPs. Furthermore, the Fe NPs exhibited promising antibacterial potential against selected bacterial strains, including Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Cronobacter sakazakii, Listeria innocua, and Enterococcus fecalis. This study demonstrates that the biological synthesis of metallic NPs is environmentally safe, and Fe NPs produced through mycological means could be utilized to combat antibiotic-resistant pathogenic strains.
The objective of the current research was to identify and evaluate the possibility of production of pectinase, also known as pectin degrading enzymes, from indigenous bacterial strains. Qualitative screening of isolated bacterial strains showed that among 29 bacterial strains, 5 have maximum enzymatic activity. The highest pectinase producing strains were quantitatively analyzed for enzyme production. SH7 strain was found as highest pectinase producer (0.77 IU/mL) that was further analyzed to molecular level by amplification of 16s rRNA. It was found 100% similar with other reported strains of Bacillus thuringiensis. Medium optimization was performed to optimize fermentation conditions for maximum enzyme yield. An experimental design containing 12 experimental runs was designed by Plackett–Burman design (PBD). Maximum pectinase activity was obtained at 45°C after 24 h when the growth medium was supplemented with 2.5% nitrogen, 5.0% substrate, MgSO4 as metal ion, 1% inoculum size, and pH was adjusted to 6. Factorial regression analysis of the PBD design was performed and the overall design was also found significant in terms of R square value. In PBD, the most significant factors for production were temperature, pH, metal ion concentration, and nitrogen source. Central composite design (CCD) design consisting of 26 experimental runs was employed to optimize these four significant factors. The overall model summary showed maximum pectinase activity (19.2 IU/mL) at 37°C temperature, 0.08 NaCl, 1.7% nitrogen source, and pH 8.4. In CCD, NaCl, nitrogen source, and pH were also reported as significant factors by the Pareto chart, probability plots, and 3D interactions.
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