Enhancement of butanol production in Clostridium acetobutylicum SE25 through accelerating phase shift by different phases pH regulation from cassava flour

•A severe delay of phase shift was observed in ABE fermentation from cassava flour.•Phase shift was smoothly triggered due to different pH regulation strategy performance.•Direct fermentation of cassava flour to produce butanol was successfully achieved by SE25.•The correlation between phase shift and produced butanol was investigated.•The higher and lower pH would respectively be beneficial to cell growth and solvent production.

A prominent delay with 12 h was encountered in the phase shift from acidogenesis to solventogenesis in butanol production when the substrate—glucose was replaced by cassava flour. To solve this problem, different phase of pH regulation strategies were performed to shorten this delay time. With this effort, the phase shift occurred smoothly and the fermentation time was shortened. Under the optimal conditions, 16.24 g/L butanol and 72 h fermentation time were achieved, which were 25.3% higher and 14.3% shorter than those in the case of without pH regulation. Additionally, the effect of CaCO3 on “acid crash” and butanol production was also investigated. It was found that organic acids reassimilation would be of benefit to enhance butanol production. These results indicated that the simple but effective approach for acceleration of phase shift is a promising technique for shortening the fermentation time and improvement of butanol production.

Graphical abstractDifferent phase of pH regulation strategies with CaCO3 addition were performed to deal with the problem of phase shift delay when cassava flour was used as the substrate for ABE fermentation. With this effort, the phase shift occurred smoothly and the fermentation time was shortened. Furthermore, the effect of CaCO3 on “acid crash” and butanol production was also investigated. It was found that organic acids reassimilation would be of beneficial to enhance the butanol yield.Figure optionsDownload full-size imageDownload as PowerPoint slide