Organic Acid and Solvent Production: Butanol, Acetone, and Isopropanol; 1,3- and 1,2-Propanediol Production; and 2,3-Butanediol Production

Abstract

The versatility of bacteria in the production of commercially useful chemicals is well represented by the fermentations that produce butanol, acetone, isopropanol, 1,3- and 1,2-propanediol, and 2,3-butanediol. Most of these chemicals can be synthesized from petroleum-derived feedstock chemicals. The merit of industrial applications of these fermentations ultimately depends on the economics of the bioprocesses or the need for a chiral product, which is more easily achieved through a bioprocess. Butanol, acetone, and isopropanol were traditionally used as solvents, and the industrial fermentation producing these chemicals was thus known as the solvent fermentation. Solvent fermentation is performed by several species of Clostridia, and it was the first industrial fermentation utilizing pure cultures and aseptic techniques. Its large scale was also unprecedented. Butanol has desirable properties as an automobile fuel, and this potential use has received much attention. Current efforts in improving butanol fermentation for industrial uses focus on the development of less expensive raw materials, a higher final product concentration, and bacterial strains that are more amenable to genetic manipulations. Whereas 1,2-propanediol is produced in large quantities by a chemical process, 1,3-propanediol has been more difficult to produce via chemical synthesis. Because of the usefulness of 1,3-propanediol as a monomer for the production of polyester for fiber applications, industrial interest in bioproduction of this monomer remains high. 2,3-Butanediol is produced by a number of bacteria, and it is a commercial chemical intermediate. Perhaps the greatest potential for 2,3-butanediol lies in high-value, special-product uses, which may make a fermentation route competitive.

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