UPTAKE OF ORGANIC-ACIDS BY CLOSTRIDIUM-ACETOBUTYLICUM B18 UNDER CONTROLLED PH AND REDUCED BUTANOL INHIBITION

Uptake of organic acids by Clostridium acetobutylicum B18 was studied at controlled pH. and under reduced butanol inhibition conditions. A p ervaporative membrane module was placed in the fermenter to remove but anol from the fermentation broth. Uptake of added butyric acid followe d zero order kinetics at pH 4.75 and first order kinetics at pH 5.75. At pH 5.25 the kinetic order shifted from zero to first order as the b utyric acid was taken up. At the point of order shift undissociated bu tyric acid (UBA) concentration was approximately 0.5 g/L. Unlike butyr ic acid, uptake of acetic acid followed first order kinetics regardles s of pH. The difference in acid uptake kinetics could be explained by the combined effect of acid diffusion across the cell membrane and int racellular enzymatic reaction The acid concentration for kinetic order shift seemed to be dependent upon pH and the kind of the acid used. G lucose was consumed simultaneously with added acids. Both butyric and acetic acids were taken up simultaneously but the rate was faster for butyric acid, Added butyric acid was completely assimilated whereas ac etic acid uptake was incomplete.