Orthogonal Valorization of 5-Hydroxymethylfurfural Using Self-Sufficient Heterogeneous Biocatalysts Composed of Two Co-Immobilized Dehydrogenases

Abstract

5-Hydroxymethyl furfural (HMF) is a key molecule in biorefineries, but its conversion into valuable products faces technological challenges. Biocatalysis offers a sustainable solution, yet high cofactor costs and poor enzyme recyclability hinder industrial implementation. In this work, we develop a self-sufficient heterogeneous biocatalyst (ssHB) composed of two NADH-dependent dehydrogenases co-immobilized with NADH on porous supports. This system enables redox disproportionation of HMF, yielding both 2,5-bis(hydroxymethyl)furan (BHMF) and 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). The reaction relies on NADH/NAD⁺ hydride transport, transferring hydrogen between HMF molecules. Volumetric productivities of 0.75–1.5 g L⁻¹ h⁻¹ and an 80% overall yield (40% per product) were achieved using boronic acid–functionalized supports. The system maintained the same yield over two cycles without additional cofactor, demonstrating efficient cofactor recycling with total turnover numbers (TTN_NADH) of 100–160, around 5 times higher than using exogenous cofactor. This work highlights the potential of self-sufficient heterogeneous biocatalysts to enhance cofactor efficiency and reduce process costs, paving the way for more sustainable biocatalytic valorization of HMF.