Chemoenzymatic oxidation of diols catalyzed by coimmobilized flavins and dehydrogenases

Enzyme driven oxidations catalyzed by alcohol dehydrogenases rely on the in situ NAD(P)+ regeneration. A wide variety of chemoenzymatic and fully enzymatic methods have been reported over the last 30 years to integrate the cofactor regeneration in biocatalytic oxidations. However, the most examples are limited to homogeneous systems where the reuse of both enzymes and chemical catalysts are challenging. In this work, we co-immobilize an alcohol dehydrogenase from Bacillus stearothermophilus with a flavin derivative (FMN), which performs as an organocatalyst that oxidizes NADH back to NAD+. This latter oxidized cofactor is sequentially utilized by the dehydrogenase to oxidize 1,w-diols. Remarkably, the immobilization chemistry of the FMN determines its efficiency to recycle the nicotinamide cofactor and, unlike in its free state, the immobilized FMN can oxidize NADH in dark. This is possible because the support where both enzyme and FMN are immobilized also captures NADH, and makes the electron transfer from the substrates to the cofactors more efficient. This work illustrates how the co-immobilization and confinement of bio and chemical catalysts on solid materials (heterogeneous system) enable chemoenzymatic cascades that are precluded in solution (homogeneous system).