Investigation of the control of metabolic pathways in Clostridium acetobutylicum by the studies of glucose and non-glucose limitation, in vitro enzyme inhibition, and intermediary compound challenges in batch and continuous cultures
Roos, Joseph William
Papoutsakis, E. Terry
Master of Science
The fermentation of carbohydrates by Clostridium aoetobutylicum leads to the formation of acetate, acetoin, acetone, butanol, butyrate, ethanol, hydrogen, and carbon dioxide. The availability of ATP and NADH£ appears to be significant in determining the amount of products formed. Non-glucose limited, uncontrolled pH, batch cultures are capable of producing solvents. Increasing the ammonium to glucose ratio of these cultures resulted in an increase in acid formation and growth and a decrease in solvent yields. Maintaining a constant pH at 4.5 in batch cultures encouraged growth and glucose utilization resulting in glucose limited cultures. These ATP limited cultures gave high acid yields and small solvent yields. Butyraldehyde and acetoacetate influenced the metabolism of uncontrolled pH batch cultures. Their presence resulted in increased biomass formation but had mixed effects on acid and solvent production. A non-glucose limited continuous culture has been observed to produce butanol, acetone, butyrate and acetate, while under glucose limited conditions, continuous cultures produced primarily butyrate and acetate. In a glucose limited culture carbon monoxide was used to inhibit the hydrogenase activity. This inhibition resulted in an uptake of butyrate, a decrease in the rate of acetate production and a large increase in the specific rates of production of butanol, ethanol, and acetoin. Acetone was not affected.