Factorial Experimental Design for Optimization of Zinc Oxide Nanoparticles Production

Abstract

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. Method: 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’ yield.