STIMULATORY EFFECTS OF CALCIUM CARBONATE ON BUTANOL PRODUCTION BY SOLVENTOGENIC Clostridium species

Solventogenic Clostridium species are motile Gram positive anaerobic bacteria used for the fermentative production of acetone-butanol-ethanol (ABE). The addition of CaCO3 to semi-defined P2 medium was investigated to evaluate its impact on growth, amelioration of butanol toxicity, glucose utilization, and ABE production by solventogenic Clostridium species. Two Clostridium species commonly used in industrial production of fermentative-derived ABE were used in the study. Under culture conditions of the present study, CaCO3 enhanced growth of and total ABE production by solventogenic Clostridium species (C. acetobutylicum ATCC 824 and C. beijerinckii 260 produced more than 24 and 22 g/L ABE, respectively) by 31% to 46%. Dramatically increased growth of solventogenic Clostridium species and fermentation rate resulted in greater ABE concentration and productivity for treatments containing CaCO3 relative to the control with no CaCO3 addition. The addition of CaCO3 into P2 medium, in addition, increased butanol tolerance by more than 40% indicating that elevated levels of ABE produced by solventogenic Clostridium species may have occurred due to enhanced tolerance of butanol in the presence of CaCO3.