Synthesis of 4-Pyridoxolactone from Pyridoxine Using a Combination of Transformed Escherichia coli Cells

We developed a simple and efficient synthesis for 4-pyridoxolactone starting with pyridoxine and using a whole-cell biotransformation by two transformed Escherichia coli cell types. One set of transformed cells expressed pyridoxine 4-oxidase, catalase, and chaperonin, while the second set expressed pyridoxal 4-dehydrogenase. With this combination of cells, pyridoxine was first oxidized to pyridoxal, which was then dehydrogenated to 4-pyridoxolactone by pyridoxine 4-oxidase and pyridoxal 4-dehydrogenase, respectively. In a reaction mixture containing the two transformed cell types, 10 mM of pyridoxine was completely converted into 4-pyridoxolactone at 30°C in 24 h. When starting with 80 mM of pyridoxine, it was necessary to add 0.5 mM or more of NAD+ to complete the reaction.