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Application of electrochemical approach for in situ H2O2 generation in enzyme catalysis
Citation Link: https://doi.org/10.15480/882.15986
Publikationstyp
Doctoral Thesis
Date Issued
2025
Sprache
English
Author(s)
Advisor
Referee
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2025-10-02
Institute
TORE-DOI
Citation
Technische Universtität Hamburg (2025)
Hydrogen peroxide (H2O2) is an environmentally safe chemical and widely employed as a co-substrate in biocatalytic processes. Among various enzymes that are capable of utilizing H2O2 as a co-substrate, the recombinant unspecific peroxygenase from the fungus Agrocybe aegerita (rAaeUPO) stands out as the favorite due to its stability and versatility. Nevertheless, the technical application and combination of rAaeUPO and H2O2 in the biotechnological field remains challenging. This is due to the toxicity of H2O2 towards biocatalysts and the inactivation of rAaeUPO at an elevated concentration of H2O2. The precise dosing of H2O2 is of great importance, yet very challenging. A number of strategies have been explored to mitigate the deactivation effect of H2O2. Thus far, they have been largely deemed unsatisfactory due to the dilution effect or formation of complex by-products. An electrochemical approach represents an attractive method that provides controllable in situ generation of H2O2. The objective of this dissertation is to develop a fully controllable system for the electrochemical in situ generation of H2O2, designed as an optimizable platform for H2O2-dependent enzymatic reactions and to promote catalyst efficiency. To address these challenges, the All-in-One (AiO) electrode system was employed for the in situ generation of H2O2. This concept was integrated with the enzymatic hydroxylation, catalyzed by rAaeUPO, to establish a bioelectrochemical system (BES). The maximum H2O2 productivity and Faradaic efficiency achieved in the AiO electrode system were 0.87 µM min-1 cm-2 and 60%, respectively. The application of the AiO electrode within the BES yielded promising results, achieving a total turnover number (TTN) of 450,000 mol mol-1 and a turnover frequency (TOF) of 7.7 s-1. By incorporating aeration and increasing the number of electrodes, the specific surface area was enhanced, resulting in an increase in both TTN and TOF up to 700,000 mol mol-1 and 20.1 s-1, respectively, with a productivity of 1.3 g L-1 d-1. Although H2O2 productivity was identified as the limiting factor, the system demonstrated considerable potential for optimization through surface modification of the electrode. Moreover, this dissertation compared two modes of in situ H2O2 electrogeneration: the conventional galvanostatic mode and the H2O2-stat mode. The two modes were tested within the gas diffusion electrode system, employing the identical enzymatic reaction. While the galvanostatic mode demonstrated a maximum H2O2 productivity of 5.5 µM min-1 cm-2 and a productivity of 10.5 g L-1 d-1 at 6.4 mA cm-2, the H2O2-stat mode, particularly at a H2O2 concentration limit of 0.2 mM, yielded favorable outcomes with a TTN of 655,000 mol mol-1, a TOF of 80.3 s-1, and a productivity of 6.1 g L-1 d-1. The successful application of the H2O2-stat mode highlights its potential as a more effective alternative to the galvanostatic approach, significantly enhancing the process performance of rAaeUPO and advancing the field of enzymatic electrosynthesis.
Subjects
Hydrogen peroxide
Unspecific peroxygenase
Enzyme catalysis
Bioelectrochemical system
Electrochemistry
DDC Class
541.37: Electrochemistry
572: Biochemistry
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Sayoga_Giovanni_Application of Electrochemical Approach for in situ H2O2 Generation in Enzyme Catalysis.pdf
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