photobiocatalysis

Photobiocatalysis refers to the use of light to initiate, accelerate, or control enzymatic transformations. It sits at the intersection of photochemistry and biocatalysis, enabling reactions that can be difficult or inefficient under traditional thermal conditions. In many systems, visible light is applied either to directly photoactivate light-absorbing cofactors within enzymes or to drive reactions through external photocatalysts that shuttle energy or electrons to the biocatalyst.

The approaches in photobiocatalysis include direct photoactivation of flavin-, heme-, or other photosensitive cofactors within enzymes, and the use of photoredox catalysts to generate reactive intermediates that interact with enzymes or substrates. Another common strategy is photosensitive cofactor regeneration, where light-powered processes restore cofactors such as NAD(P)H used by many biocatalysts. In one-pot or tandem setups, the photocatalytic step and the enzymatic step operate sequentially or simultaneously to produce complex products with high stereochemical control.

Applications span the synthesis of enantioenriched pharmaceuticals and fine chemicals, asymmetric reductions and oxidations, and sustainable biomass upgrading. Photobiocatalysis has been explored with enzymes such as ene-reductases and other oxidoreductases, often in combination with visible-light photosensitizers or engineered photoresponsive enzymes.

Advantages of photobiocatalysis include milder reaction conditions, high chemo- and enantioselectivity, and potential use of renewable light sources. Limitations include possible photodamage to enzymes, oxygen sensitivity, photobleaching of catalysts, and challenges in scaling light-delivery and achieving broad substrate scope. Ongoing research aims to develop robust photoactive enzymes, compatible photocatalysts, and reactor designs that harness solar energy for sustainable synthesis.