Fermentation kinetics of Acidithiobacillus ferrooxidans for magnetosome synthesis improved by gluconic acid addition

Abstract:

[Objective] To clarify the promotion effects of different organic compounds on the formation of magnetosomes in Acidithiobacillus ferrooxidans BYM, so as to provide a new idea for safely and effectively improving the magnetosome yield. [Methods]Single-factor experiments were conducted to measure the effects of ten organic compounds on the ferrous oxidation of A. ferrooxidans BYM, and the organic compounds promoting the synthesis of magnetosomes were further screened by a 4 L fermentation system. The classical kinetic models (Logistic, Luedeking-Piret, and substrate consumption kinetic equations) were employed to build the kinetic models for the growth, magnetosome synthesis, and ferrous consumption of A. ferrooxidans BYM by batch fermentation experiments. [Results]The maximum magnetosome yield (2.00×10⁻³ g/L) was achieved with the addition of 10 mmol/L gluconic acid, in the presence of which the bacterial cells were oval and had a smooth surface. With the addition of gluconic acid, the fermentation kinetics of A. ferrooxidans BYM was in accordance with Logistic, Luedeking-Piret, and substrate consumption kinetic equations.[Conclusion] The addition of 10 mmol/L gluconic acid increases the magnetosome yield of A. ferrooxidans BYM by eight times. Gluconic acid changes the cell morphology and surface of A. ferrooxidans BYM. The kinetics models of cell growth, product formation, and substrate consumption can illustrate the batch fermentation of A. ferrooxidans BYM in the presence of gluconic acid.

Key words:Acidithiobacillus ferrooxidans;magnetosome;gluconic acid;fermentation kinetics;ferrous oxidation