Continuous biohydrogen production by a degenerated strain of Clostridium acetobutylicum ATCC 824

Degenerated strains of Clostridium acetobutylicum lack the ability to produce solvents and to sporulate, allowing the continuous production of hydrogen and organic acids. A degenerated strain of Clostridium acetobutylicum was obtained through successive batch cultures. Its kinetic characterization showed a similar specific growth rate than the wild type (0.25 h⁻¹), a higher butyric acid production of 6.8 g·L⁻¹ and no solvents production. A steady state was reached in a continuous culture at a dilution rate of 0.1 h⁻¹, with a constant hydrogen production of 507 mL·h⁻¹, corresponding to a volumetric rate of 6.10 L·L⁻¹ d⁻¹, and a yield of 2.39 mol of H₂ per mole of glucose which represents 60% of the theoretical maximum yield. These results suggest that the degeneration is an interesting alternative for hydrogen production with this strain, obtaining a high hydrogen production in a continuous culture with cells in a permanent acidogenic state.