Application of the all-in-one electrode for in situ H2O2 generation in hydroxylation catalyzed by unspecific peroxygenase from Agrocybe aegerita

Abstract

The versatile unspecific peroxygenase from the fungus Agrocybe aegerita (AaeUPO) is capable to perform hydroxylation of various substrates, even unactivated CH bonds. The technical application of AaeUPO is still limited due to an instability towards its co-substrate hydrogen peroxide (H2O2). Electrochemical synthesis of H2O2 is an attractive approach that provides controllable in situ generation of H2O2. The aims of this study are to promote catalyst efficiency and develop an individually tailored system for H2O2-dependent reactions. Herein, an All-in-One electrode (AiO) system with a carbon felt cathode is used to generate H2O2in situ and combined for the first time with an enzymatic hydroxylation. The AiO electrode combines the counter and working electrode in a single rod structure. This shape provides convenient integration into conventional bioreactors, thus, converting them into bioelectrochemical systems (BES). Hydroxylation of 4-ethylbenzoic acid (EBA) catalyzed by the recombinant AaeUPO (rAaeUPO) was chosen as the model reaction. Total turnover number (TTN) up to 450,000 mol mol−1 and turnover frequency (TOF) up to 7.7 s − 1 were achieved using the AiO electrode system. The H2O2 productivity was identified as the limiting factor in the hydroxylation of EBA. However, with numbering-up or surface enlargement, this process could have great potential as an optimizable platform for H2O2-dependent enzymatic reactions.