continuous butanol fermentation from xylose with high cell density by cell recycling system

a continuous butanol production system with high-density clostridium saccharoperbutylacetonicum n1-4 generated by cell recycling was established to examine the characteristics of butanol fermentation from xylose. in continuous culture without cell recycling, cell washout was avoided by maintaining ph > 5.6 at a dilution rate of 0.26 h⁻¹, indicating ph control was critical to this experiment. subsequently, continuous culture with cell recycling increased cell concentration to 17.4 g l⁻¹, which increased butanol productivity to 1.20 g l⁻¹ h⁻¹ at a dilution rate of 0.26 h⁻¹ from 0.529 g l⁻¹ h⁻¹ without cell recycling. the effect of dilution rates on butanol production was also investigated in continuous culture with cell recycling. maximum butanol productivity (3.32 g l⁻¹ h⁻¹) was observed at a dilution rate of 0.78 h⁻¹, approximately 6-fold higher than observed in continuous culture without cell recycling (0.529 g l⁻¹ h⁻¹).