Effects of rifampicin and chloramphenicol on product and enzyme levels of the acid- and solvent-producing pathways of Clostridium acetobutylicum (ATCC 824)

As part of an ongoing study of regulation of acid and solvent production in Clostridium acetobutylicum, the effects of rifampicin and chloramphenicol were determined on product formation, enzyme activity, and enzyme stability in vivo of enzymes and metabolites associated with those pathways. The in vitro activities of phosphotransbutyrylase, butyrate kinase, CoA transferase, butyraldehyde dehydrogenase, and butanol dehydrogenase were assayed over the entire fermentation. The enzymes in the solvent-producing pathways were more affected by the addition of rifampicin and chloramphenicol than those in the acid-producing pathways. All of the enzymes measured appeared to be stable in vivo, with the important exception of butyraldehyde dehydrogenase. The position of butyraldehyde dehydrogenase as a branchpoint enzyme in the use of butyryl-CoA, coupled with the short half-life for butyraldehyde dehydrogenase in vivo, indicates that butyraldehyde dehydrogenase may be a key enzyme in controlling the switch from the production of butyrate to the production of butanol.