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. (C) 2015 Elsevier Ltd. All rights reserved.