Medium optimization to improve growth and iron uptake by Bacillus tequilensis ASFS1 using fractional factorial designs

Many notable applications have been described for magnetic nanoparticles in delivery of diverse drugs and bioactive compounds into cells, magnetofection for the treatment of cancer, photodynamic therapy, photothermal therapy, and magnetic particle imaging (MPI). In response to the growing demand for magnetic nanoparticles for drug delivery or biomedical imaging applications, more effective and eco-friendly methodologies are required for large-scale biosynthesis of this nanoparticles. The major challenge in the large-scale biomedical application of magnetic nanoparticles lies in its low efficiency and optimization of nanoparticle production can address this issue. In the current study, a prediction model is suggested by the fractional factorial designs. The present study aims to optimize culture media components for improved growth and iron uptake of this strain. The result of optimization for iron uptake by the strain ASFS1 is to increase the production of magnetic nanoparticles by this strain for biomedical applications in the future. In the present study, design of experiment method was used to probe the effects of some key medium components (yeast extract, tryptone, FeSO₄, Na₂-EDTA, and FeCl₃) on Fe content in biomass and dried biomass of strain ASFS1. A 2^5-1 fractional factorial design showed that Na₂-EDTA, FeCl₃, yeast extract-tryptone interaction, and FeSO₄-Na₂-EDTA interaction were the most parameters on Fe content in biomass within the experimented levels (p < 0.05), while yeast extract, FeCl₃, and yeast extract-tryptone interaction were the most significant factors within the experimented levels (p < 0.05) to effect on dried biomass of strain ASFS1. The optimum culture media components for the magnetic nanoparticles production by strain ASFS1 was reported to be 7.95 g L^-1 of yeast extract, 5 g L^-1 of tryptone, 75 μg mL^-1 of FeSO₄, 192.3 μg mL^-1 of Na₂-EDTA and 150 μg mL^-1 of FeCl₃ which was theoretically able to produce Fe content in biomass (158 μg mL^-1) and dried biomass (2.59 mg mL^-1) based on the obtained for medium optimization. Using these culture media components an experimental maximum Fe content in biomass (139 ± 13 μg mL^-1) and dried biomass (2.2 ± 0.2 mg mL^-1) was obtained, confirming the efficiency of the used method.