FIG. 1.

Alternative process for conversion of glucose to ascorbic acid. An alternative process for conversion of glucose to ascorbic acid effected by whole cells, a recombinant enzyme, and a chemical catalyst. Membrane-bound oxidases convert glucose to 2,5-diketo-d-gluconic acid (2,5-DKG), with oxygen as the electron acceptor. A heterologous 2,5-diketo-d-gluconic acid reductase, in practice obtained from another organism, reduces 2,5-diketo-d-gluconic acid to 2-keto-l-gulonic acid (2-KLG). Known reductases are NADPH dependent. Finally, chemically catalyzed lactonization of 2-keto-l-gulonic acid generates ascorbic acid.