Optimisation of Zinc Oxide Nanoparticle Biosynthesis Using Saccharomyces Cerevisiae with Box-Behnken Design

Zinc oxide nanoparticles have wide applications as catalysts, antimicrobial agents, drug delivery agents, etc. because of their intrinsic properties. Various methods can be applied to synthesise nanoparticles, one of which is the biosynthesis process. Biosynthesis is more eco-friendly than chemical and physical methods. In the present study, the optimisation of zinc oxide nanoparticle biosynthesis using the yeast Saccharomyces cerevisiae was performed by applying a response surface method called the Box–Behnken design (BBD). Three factors were optimised in the present study, namely the concentration of zinc acetate as the precursor (X1), concentration of the S. cerevisiae fermentation broth (X2), and the incubation time (X3). The mass of zinc oxide nanoparticles (Y) was recorded as the response of the experiment. The product was then characterised by fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and particle size analyser (PSA). The optimum conditions for the preparation of zinc oxide nanoparticles were found to be 0.3 M, 100% (v/v), and 24 h as the zinc acetate concentration, medium concentration, and incubation time, respectively. The FTIR analysis showed peaks at ~600 cm, which is characteristic for ZnO stretching. From the XRD result, the ZnO nanoparticles with hexagonal structure was confirm. The SEM/EDS analysis confirmed that the morphology was spherical and showed the major energy emission for zinc and oxygen. Moreover, the PSA analysis revealed that the smallest size was 218.6 nm (12%) when the synthesis was performed at the optimum conditions, while when the incubation time was prolonged for 120 h, the size decreased to 134.2 nm.