Penicillium polonicum-mediated green synthesis of silver nanoparticles: Unveiling antimicrobial and seed germination advancements

Abstract

Silver nanoparticles (AgNPs), widely recognized for their nanoscale geometric size and unique properties, such as large specific surface area, high permeability, and high safety, were synthesized using the endophytic fungus Penicillium polonicum PG21 through a green approach. Four key synthesis factors-48 h, 45 °C, pH 9.0, and 80 mM AgNPs concentration-were optimized. Characterization via ultraviolet-visible spectroscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction revealed the AgNPs as approximately 3-25 nm spherical particles with numerous functional groups ensuring stability. AgNPs were tested against various fungal and bacterial plant pathogens, including Botrytis cinerea (EB-1), Alternaria alternata (EB-2, EB-3), Fusarium solani (RG-1), Williamsia serinedens (SL-1), Sphingopyxis macrogoltabida (SL-2), Bacillus velezensis (SL-3), and Pseudomonas mediterranea (SL-4), causing agricultural challenges. PG21-synthesized AgNPs exhibited inhibition rates against all tested fungi, with 60 μg/mL AgNPs demonstrating optimal inhibition rates. Notably, EB-1 experienced a significant growth inhibition, reaching an inhibition rate reached of 74.22 ± 1.54%. Conversely, RG-1 exhibited the smallest inhibitory effect at 48.13 ± 0.92%. The effect of AgNPs on safflower seed germination and growth revealed notable increases in shoot length, fresh weight, stem length, and number of lateral roots-1.4, 1.4, 1.33, and 10.67 times higher than the control, respectively, at an AgNPs concentration of 80 μg/mL. In conclusion, green-synthesized AgNPs demonstrate pathogen toxicity, showcasing potential applications in disease management for industrial crops and promoting plant growth.

Keywords: Antimicrobial activity; Fungus; Green synthesis; Seed germination; Silver nanoparticles.

Fig. 1

Identification of endophytic fungus PG21 (a) colony morphology, (b) Mycelium and spore morphology, and (c) phylogenetic tree.

Fig. 2

UV–vis absorption spectra of AgNPs synthesized at different conditions (a) temperature, (b) pH, (c) AgNO3 concentrations, and (d) reaction time.

Fig. 3

Characterization of the AgNPs synthesized by Penicillium polonicum PG21 (a) Colour change of the reaction, (b) UV–vis absorption spectrum, (c) TEM image, (d)XRD pattern, and (e) FTIR spectra.

Fig. 4

Influence of varied AgNP concentrations on Safflower seed growth (a) Stem length, (b) Number of lateral roots, (c) Fresh weight, and (d) Bud length Asterisk indicates statistical significance between AgNPs treatments and control. (P10: 10 μg/mL; P20: 20 μg/mL; P40: 40 μg/mL; P80: 80 μg/mL; P160: 160 μg/mL). *, p < 0.05; **, p < 0.01; ***, p < 0.001; ****, p < 0.0001.