Manufacture of L-ascorbic acid and D-erythorbic acid

Abstract

A process for producing L-ascorbic acid (vitamin C) from 2-keto-L-gulonic acid or D-erythorbic acid from 2-keto-D-gluconic acid by contacting 2-keto-L-gulonic acid or 2-keto-D-gluconic acid, respectively, in solution with a lactonase, particularly one belonging to the enzyme class EC 3.1.1.x, according to the classification of Enzyme Nomenclature. The solvent for this reaction can be water, an aqueous alcohol, a non-alcoholic organic solvent or a mixture of an aqueous alcohol and a non-alcoholic organic solvent. The contacting is generally performed in a temperature range of 0.degree. C. to 120.degree. C. and a pH range of 1.5 to 12. In each case the starting material can be in the form of the free acid, the sodium salt, or the calcium salt. The so-produced vitamin C has very well known uses, and the alternatively produced D-erythorbic acid is useful as an antioxidant for food additives.

Dependencies are inferred from the claim text.