Bioconversion of Butyric Acid to Butanol by Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564) in a Limited Nutrient Medium

This study was designed to investigate the ability of Clostridium saccharoperbutylacetonicum N1-4 to produce butanol in a limited nutrient medium using mixtures of glucose and butyric acid as substrates. Specific combinations of glucose and butyric acid were found to influence the enhancement and retardation of butanol production as well as the reduction and modulation of the number of bacterial cells. Increasing the butyric acid concentration leads to the inhibition of bacterial growth, whereas the presence of (0-5 g/L) butyric acid and (0-10 g/L) glucose enhances the butanol production. The combination of 5 g/L butyric acid with 5 and 10 g/L of glucose was found to be the most suitable, but the use of glucose at concentrations greater than 10 g/L shifted the optimal butyric acid concentrations to 10 and 15 g/L for maximum butanol production signifying the requirement of a specific combination of glucose and butyric acid for enhanced butanol production in the fermentation process. C. saccharoperbutylacetonicum N1-4 demonstrated the ability to produce butanol in the absence of glucose, but no acetone or ethanol was produced under these conditions, reflecting the nature of the pathways involved in the production of butanol using only butyric acid. Ten grams per litre of butyric acid was found able to produce 13 g/L of butanol in the presence of 20 g/L of glucose, and 0.7 g/L butanol was produced in the absence of glucose. This study indicates the importance of the glucose to butyric acid ratio to the enhancement of butanol production.