Our research primarily involves Clostridium which is a species containing strains with the rare ability To produce the useful chemical isopropanol, in addition to acetone, butanol and ethanol. In related studies, we also included another solvent-producing organism, and Bacillus macerans, which is a facultative anaerobe and produces a high level of acetone and ethanol under anaerobic conditions. Because B. macerans does not produce butyric ac id or butanol, it provides a simpler system for the study of the acetoacetyl-CoA-reacting enzymes and also an organism outside the clostridial group for a mechanistic study of the solventogenic switch. The objectives for this report period were to purify and characterize distinct forms of alcohol dehydrogenases; to purify and characterize acetoacetyl-CoA-reacting enzymes; and to study the organization of solvent-production genes.

The long-term goal of the project is to understand the fundamental properties of biological solvent production. Our approach is to elucidate first the molecular properties of solvent-producing enzymes and then to apply to information gained from the enzymological study to investigate control mechanisms for the solvent-producing pathways and the expression of solvent-production genes. Our research primarily involves two strains of Clostridium beijerinckii: C. Beijerinckii NRRL B593 which produces isopropanol in addition to acetone, butanol, and ethanol, and C. beijerinckii NRRL B592 which produces acetone, butanol and ethanol, but not isopropanol. In more recent studies, we also included another solvent-producing organism, Bacillus macerans. Objectives for the reporting period were: to characterize the distinct types of alcohol dehydrogenase; to purify and characterize acetoacetyl-CoA-reacting enzymes; and to clone and sequence the gene encoding the primary/secondary alcohol dehydrogenase of C beijerinckii NRRL B593 and to search for the promoter region for solvent-production genes.