Chemoenzymatic methods for inorganic and organic chemistry, employing flavins and flavoenzymes

PhD Program

Speaker

Sergio Fernando Castillo Pacheco

When

2026/11/06
11:00

Place

Seminario Bergara - Faculty of Chemistry (EHU), Donostia / San Sebastián

Add to calendar

iCal

PhD Thesis defense by Sergio Fernando Castillo Pacheco

Supervisor: Luca Salassa (Ikerbasque Research Professor) and Fernando López-Gallego 

Biocatalysis

This thesis investigates chemoenzymatic strategies integrating oxidoreductases, flavin-based organocatalysts, and metals to enable alcohol oxidation, cofactor regeneration, and cellular redox modulation.

First, alcohol dehydrogenase was co-immobilized with flavin derivatives to couple diol oxidation with NADH oxidation and NAD+ regeneration. Although this heterogeneous system supported chemoenzymatic catalysis, its operational reusability was limited. Subsequent experimental and computational investigations identified nonspecific flavin-protein interactions as a cause of premature enzyme inactivation. These findings guided the development of immobilization strategies to mitigate catalyst incompatibility. Next, metals were investigated as alternatives to oxygen in flavin-mediated catalytic cycles. Flavins and flavoenzymes were shown to use metal substrates as terminal electron acceptors under anaerobic conditions. Building on this finding, NADH oxidase was coupled with iron oxalate to establish an anaerobic cofactor-regeneration system. Integration with alcohol dehydrogenase in a flow reactor enabled benzyl alcohol oxidation, demonstrating the feasibility of coupled enzymatic transformations without oxygen. Finally, riboflavin-ruthenium(II) complexes were investigated as catalysts to promote NADH consumption and modulate cellular redox balance. In parallel, NADH oxidase was engineered to accommodate these flavin-metal complexes within its catalytic site, laying the groundwork for artificial metalloenzymes with potential applications in intracellular redox regulation.

Collectively, this work identifies strategies for integrating biological and synthetic catalysts, advancing approaches to anaerobic biotransformation and cellular redox control.