Butanol production from alkali-pretreated rice straw by co-culture of Clostridium thermocellum and Clostridium saccharoperbutylacetonicum.

•Alkali pretreatment significantly reduced lignin content of rice straw up to 76%.•Co-culture of cellulolytic and butanol producing Clostridium species was applied.•The co-culture system produced 5.5g/L of butanol from delignified rice straw.•Addition of cellulase enhanced butanol titer (6.9g/L) from delignified rice straw.•Enhancement of exoglucanase is important for butanol production from rice straw.