HEAD OF THE GROUP

Prof. Dr.-Ing. Kai Sundmacher
Prof. Dr.-Ing. Kai Sundmacher
Phone: +49 391 6110 351
Fax: +49 391 6110 353
Links: Publications

Team leaders

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Dr.-Ing. Tanja Vidaković-Koch
Phone:+49 391 6754630

Researchers

M. Sc. Thi Quynh Nga Do
M. Sc. Thi Quynh Nga Do
Phone: +49 391 6110 252
Dipl.-Ing. Miroslava Varničić
Phone:+49 391 6110 330

Biological Production Systems

Enzymatic Electrochemical Production Systems

Electroenzymatic processes combine the high selectivity of enzymatic catalysts with the electrochemical regeneration of their co-factors. This is a promising conceptual approach for the development of new biotechnological processes. In this context, the PSE group has investigated the synthesis of gluconic acid in a novel electroenzymatic reactor (Figure EnzElectro). Gluconic acid is an organic acid with applications in different industrial branches. It belongs to the commodities with an annual production of 60 kt. Gluconic acid can be obtained from the partial oxidation of glucose which is a renewable platform chemical. The current research in the PSE group is focused on the reactor level, where some important challenges in the field of electroenzymatic processes, like electrode performance and integration of enzymatic electrodes into the overall system have been tackled. Typically enzymatic electrodes feature very low current densities in the μA cm-2 range. By closely combining experiments with mathematical modeling PSE group has been able to increase the electrode performance significantly (to mA cm-2 range).

To achieve this, at first kinetics of enzymatic reactions were studied in detail by applying electrochemical impedance spectroscopy [1]. Furthermore enzyme distribution at the model surfaces was investigated by atomic force and fluorescence microscopies [2]. This knowledge was then cast into mathematical models of porous enzymatic electrodes, where kinetics has been combined with mass and charge balances [3-4]. This added further understanding into performance limited processes and gave important insights into enzyme and mediator utilizations giving hints for further performance improvements. The optimized enzymatic electrodes have been integrated into a membraneless electroenzymatic reactor [5]. Glucose conversion and selectivity have been investigated using nuclear magnetic resonance spectroscopy (NMR) under different structural and operational conditions. Glucose conversions ranging from 56% up to 81% at related selectivity from 97% to 76% have been achieved for different operational conditions. A space-time-yield of 18.2 mg h-1 cm -2 at 47% conversion was achieved, which is a significant improvement compared to the best published data [5 and references therein]. 

To the best of our knowledge this is the first study where gluconic acid has been produced in a purely enzymatic membraneless electrochemical reactor. The long-term stability of the enzymatic electrodes was excellent [5].These results appear very promising, the future focus of the project moves to the plant level where the here developed reactor concept will be combined with separation units in order to come closer to a dream process for conversion of renewables to platform chemicals.

<p><strong>Figure EnzElectro: <br /></strong>a) Scheme of electroenzymatic reactor with reactions mechanisms at anode (A1-A3) and cathode (C1-C4).<br /> b) Yield of gluconic acid over time during batch operation at stepwise voltastatic operation [5]. <br />c) Typical NMR spectrum of the product mixture.</p> Zoom Image

Figure EnzElectro:
a) Scheme of electroenzymatic reactor with reactions mechanisms at anode (A1-A3) and cathode (C1-C4).
b) Yield of gluconic acid over time during batch operation at stepwise voltastatic operation [5].
c) Typical NMR spectrum of the product mixture.

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Recent Publications

[1] Vidaković-Koch, T., Mittal, V. K., Varničić, M., Do Thi, Q. N. and Sundmacher, K. (2013). Application of electrochemical impedance spectroscopy for studying of enzyme kinetics. Electrochimica Acta, 110, 94-104.

[2] Varničić, M., Bettenbrock, K., Hermsdorf, D., Vidaković-Koch, T. and Sundmacher, K. (2014). Combined electrochemical and microscopic study of porous enzymatic electrodes with direct electron transfer mechanism. RSC Advances, 4(69), 36471-36479.

[3] Do Thi, Q. N., Varničić, M., Hanke-Rauschenbach, R., Vidaković-Koch, T. and Sundmacher, K. (2014). Mathematical modeling of a porous enzymatic electrode with direct electron transfer mechanism. Electrochimica Acta, 137, 616-626.

[4] Do Thi, Q. N., Varničić, M., Flassig, R., Vidaković-Koch, T. and Sundmacher, K. (2015). Dynamic and steady state 1-D model of mediated electron transfer in a porous enzymatic electrode. Bioelectrochemistry, 106, 3–13.

[5] Varničić, M., Vidaković-Koch, T. and Sundmacher, K. (2015) Gluconic acid synthesis in an electroenzymatic reactor. Electrochimica Acta, 174, 480-487.

 
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