Simplification of the Acidithiobacillus ferrooxidans Culture Process for Expanding the Field of Biomachining

Biomachining is an eco-friendly metal processing method with broad application potential. Nevertheless, the bacterial culture methods that are currently involved in biomachining require the intensive use of chemical reagents, especially FeSO₄, specialized equipment, and professional-level skills in the field of biology. Herein, the differences between two cultures with and without sterilization were evaluated. Acidithiobacillus ferrooxidans was cultured with iron instead of FeSO₄ in the culture medium. The chemical and biochemical parameters of the culture were analyzed by studying the area of exposed iron and continuously regulating the pH. Eliminating the sterilization and sterile inoculation of the medium is feasible for culturing A. ferrooxidans. The key to achieving a high bacterial density in culture with iron was to maintain the solution pH. The possibility of mass culturing A. ferrooxidans with steel cuttings was evaluated in a custom bioreactor, and the bacterial concentration reached 9 × 10⁷ cells/mL.