Background: Biosynthetic nanomaterials have recently received increasing attention because
they are non-toxic, clean, environmentally acceptable, safe, and biocompatible.
Objective: In the present study, cell-free culture filtrate of Aspergillus sp. was used for extracellular
synthesis of zinc oxide (ZnO) nanoparticles.
MethodS: Plackett-Burman and Taguchi designs were implemented to optimize conditions for maximum
ZnO nanoparticle production. In the Plackett-Burman design, 15 factors, representing different
carbon and nitrogen sources, were studied. For the Taguchi design, an L-27 (313) standard orthogonal
array was constructed to examine nine factors.
Results: The maximum yield of ZnO nanoparticles of 21.73 g/L was achieved with 1.0 mM ZnSO4
under optimal conditions of peptone extract (20 g/L), yeast extract (10 g/L), meat extract (10 g/L),
K2HPO4 (0.25 g/L), FeSO4⋅7H2O (0.002 g/L), NaCl (2.5 g/L), pH 6, 32°C, and a 200-mL volume.
The ZnO nanoparticles’ production was confirmed by the formation of white aggregates. The UV
absorption spectrum showed one peak at 376 nm, which also confirmed the formation of nanoparticles.
Transmission electron microscopy revealed that the nanoparticles were large rods of 11.6-43.97
nm diameter, and 355.91 nm length. Importantly, the ZnO nanoparticles exhibited broad antimicrobial
activity against gram-positive and gram-negative bacteria and a unicellular fungus.
Conclusion: The concentrations of ZnSO4 ions, ferrous ions, and peptone and meat extracts, and the
interactions between them, were observed to be the main parameters influencing ZnO nanoparticles’