Enhanced Cell Density Culture of Thiobacillus ferrooxidans in Membrane-Type Bioreactor with Electrolytic Reduction Unit for Ferric Ion

Abstract

Enhanced cell density culture of Thiobacillus ferrooxidans was achieved by using a membrane-type bioreactor with cell filtration and iron recycling units. Using an electrolytic bath with an anion exchange membrane, microbially produced Fe³⁺ could be reduced to Fe²⁺ without loss of main nutrients in the medium. It was confirmed that T. ferrooxidans exhibited active growth in the electrochemically regenerated medium. In the repeated-batch culture with cell filtration and feeding of the regenerated medium, the cell concentration obtained was at least 4–11 times higher than that in a conventional batch culture. In this culture system, the measurement of medium redox potential made it possible to estimate the concentrations of cells and iron, and to determine the time for culture filtration and medium-feeding operations.