One-pot enzymatic synthesis of L-threitol from C1 formaldehyde

Abstract

Here, we report an enzymatic cascade reaction converting 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 attempts of NADH regeneration systems were investigated to facilitate the recycling of NADH in the reaction system. 405.7 mM (49.6 g/L) L-threitol was achieved from the conversion of formaldehyde in a one-pot reaction system with 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 were achieved in the one-pot two-step reaction system that NADH was efficiently recycled by using methanol dehydrogenase and isopropanol.