Published October 2002
Ascorbic acid (vitamin C) is a water soluble vitamin found widely both in the plant and animal kingdoms. It is of major importance in human nutrition and maintenance of good health. Current world production is estimated at approximately 80,000 metric tons per year with a world wide market in excess of $600 million. It is synthesized both biologically and chemically from D-glucose.
The world's two largest producers of ascorbic acid are BASF and Roche. DSM will soon acquire Roche's vitamins business. Chinese producers are also a significant source of ascorbic acid in world markets. The synthesis of L-ascorbic acid developed in 1934 by Reichstein and Grussner has remained a cornerstone for the commercial production of vitamin C. Almost all industrial processes for ascorbic acid are derived from the Reichstein and Grussner process. The process is a complicated route that begins with D-glucose and has six major steps.
As an alternative to the Reichstein-Grussner process, the Advanced Technology Program of the National Institute of Standards and Technology has supported an effort by Genencor, Eastman Chemical, MicroGenomics Company, Argonne National Laboratory, and Electrosynthesis Company to develop continuous biocatalytic systems for making ascorbic acid. The focus of this review is a 2000 Genencor patent application for the preparation of 2-keto-L-gulonic acid, an important ascorbic acid intermediate, by biocatalytic conversion of glucose. We examine the economics and technical issues for a new grass-roots 20 million lb/yr (9,000 t/yr) ascorbic acid facility based on this biocatalysis technology.
Our economic evaluation, based on PEP's concept of the process, indicates that the process is viable and will be competitive with existing Reichstein-Grussner technologies.
The advantage of reduced capital investment that this technology offers provides a better potential for new ascorbic acid production investment. Process related issues that need improvement include enzyme stabilities and high cofactor cost. The ultimate vision of manufacturing ascorbic acid directly from glucose by fermentation remains elusive. Additional bioengineering is required to advance the direct fermentation of glucose route to commercialization. In the meanwhile, the biocatalysis route to 2-keto-L-gulonic acid is a good alternative to the conventional Reichstein-Grussner process for ascorbic acid manufacture.