Effects of Microbial Growth Conditions on Synthesis of Magnetite Nanoparticles using Indigenous Fe(III)-Reducing Bacteria

Recent researches have shown that microbe–metal interactions play an important role in metal cycling and biomineralization in subsurface environments. The objective of this research was to study the effects of microbial growth conditions for size control on the synthesis of magnetite nanoparticles using Fe(III)-reducing bacteria enriched from intertidal flat sediments in Korea. The microbial formation of the magnetite nanoparticles was examined under various incubation temperatures (8–35 °C), concentrations (20–60 mM) of magnetite precursor, medium pHs (6.5–8.5), and incubation times (0–3 weeks). The Fe(III)-reducing bacteria formed 2~10 nm-sized magnetite (Fe3O4) by reduction of 40 mM akaganeite, especially under the conditions at 25 °C and medium pH = 8.5 within a 1-week incubation time. The magnetite nanoparticles formed by microbial processes exhibited superparamagnetic behavior.