Flavin-Decorated Proteins and Bacteria Enable Photoenzymatic Amine Valorisation

The search for more sustainable catalytic methods, such as biocatalysis and photocatalysis, has greatly contributed to a sustainable future of synthetic chemistry. Within photocatalysis, flavin-type heterocycles are powerful tools for oxidative transformations but often suffer from poor water solubility, photostability, and limited reusability. Here, we provide a proof-of-concept strategy to bridge the gap between photocatalysis and biocatalysis through the development of artificial flavin biomolecules. A 7-/8-carboxyflavin derivative was synthesized and covalently attached to protein surfaces via a biocompatible amide coupling reaction, creating an artificial flavin-decorated protein with oxidative properties. This biophotocatalyst operates efficiently in water under mild conditions, enabling the photooxidation of primary amines without external oxidants. It was also integrated into one-pot, sequential cascade reactions with whole-cell biocatalysts to achieve the enantioselective synthesis of (R)-benzoin and chiral secondary alcohols. Furthermore, the flavin photocatalyst was immobilized on the surface of Escherichia coli cells through a similar process, creating a recyclable, heterogeneous cellular photocatalyst. These modified bacteria exhibited high activity in amine oxidation, could be easily recycled, and maintained performance over multiple reaction cycles without evidence of catalyst leaching. Overall, this work establishes a versatile framework for constructing hybrid biophotocatalytic systems and showcases how they can contribute to environmentally sustainable synthesis through reactions in water and catalyst recycling.