Totally Atom-Economical Synthesis of Lactic Acid from Formaldehyde: Combined Bio-Carboligation and Chemo-Rearrangement Without the Isolation of Intermediates

Non-fermentative chemoenzymatic transformations have attracted great interest from both academia and industry. Here, we report a green chemoenzymatic cascade reaction that converts the C1 compound formaldehyde into lactic acid using a newly identified formolase variant and NaOH as catalysts with 100% atom economy and 82.9% overall yield under near-ambient conditions. The engineered formolase variant in this study exhibits a 19-fold substantially improved activity and improved formaldehyde resistance (up to 500 mM) and alters the main product from two-carbon glycolaldehyde (GA) to three-carbon dihydroxyacetone (DHA). The crystal structures of the parent formolase and identified variants were resolved to elucidate the molecular reason for the obtained improvement. Molecular dynamics simulation and molecular mechanics/generalized born surface area (MM/GBSA) analysis suggested that the identified amino acid substitutions allow more stable TPP-GA complexes in the active center of the dimeric formolase which is beneficial for the subsequent DHA generation.