One-pot enzymatic synthesis of l-threitol from C1 formaldehyde†

Here, we report an enzymatic cascade reaction converting a high concentration of formaldehyde into l-threitol. The cascade reaction starts with the carboligation of formaldehyde catalyzed by formolase and fructose-6-phosphate aldolase, generating l-erythrulose. Subsequently, a newly identified l-threitol dehydrogenase facilitates the conversion of l-erythrulose into l-threitol, utilizing NADH as a coenzyme. Three types of NADH regeneration systems were investigated to facilitate the recycling of NADH in the reaction system. 405.7 mM (49.6 g L⁻¹) l-threitol was achieved from the conversion of formaldehyde in a one-pot reaction system with a self-sufficient NADH recycling system, which is based on the oxidation of glycerol catalyzed by glycerol dehydrogenase. Furthermore, the highest yield (89.4%; 251.3 mM) of l-threitol from formaldehyde was achieved in the one-pot two-step reaction system in which NADH was efficiently recycled by using methanol dehydrogenase and isopropanol.