Novel process for producing 6-deoxy monosaccharides from l-fucose by coupling and sequential enzymatic method

We biosynthesized 6-deoxy-l-talose, 6-deoxy-l-sorbose, 6-deoxy-l-gulose, and 6-deoxy-l-idose, which rarely exist in nature, from l-fucose by coupling and sequential enzymatic reactions. The first product, 6-deoxy-l-talose, was directly produced from l-fucose by the coupling reactions of immobilized d-arabinose isomerase and immobilized l-rhamnose isomerase. In one-pot reactions, the equilibrium ratio of l-fucose, l-fuculose, and 6-deoxy-l-talose was 80:9:11. In contrast, 6-deoxy-l-sorbose, 6-deoxy-l-gulose, and 6-deoxy-l-idose were produced from l-fucose by sequential enzymatic reactions. d-Arabinose isomerase converted l-fucose into l-fuculose with a ratio of 88:12. Purified l-fuculose was further epimerized into 6-deoxy-l-sorbose by d-allulose 3-epimerase with a ratio of 40:60. Finally, purified 6-deoxy-l-sorbose was isomerized into both 6-deoxy-l-gulose with an equilibrium ratio of 40:60 by l-ribose isomerase, and 6-deoxy-l-idose with an equilibrium ratio of 73:27 by d-glucose isomerase. Based on the amount of l-fucose used, the production yields of 6-deoxy-l-talose, 6-deoxy-l-sorbose, 6-deoxy-l-gulose, and 6-deoxy-l-idose were 7.1%, 14%, 2%, and 2.4%, respectively.