Clostridium acetobutylicum produced more butanol in the medium containing corn steep liquor (CSL) than in a complex medium without CSL Addition of CSL to CAB medium increased sugar consumption by the bacterium. Similar results were obtained in the fermentation using CAB medium containing lactate. The ratio for the butanol produced to acetone of the control culture was 1.8, whilst that of the culture containing 44 mM lactate was 5.2. From these results it is hypothesized that lactate functions as an electron flow modulator in the fermentation. This finding has been utilized for the successful butanol fermentation of a non-corn based agricultural byproduct, palm oil waste.