Klaus-Michael Mangold

Sequential reductive and oxidative biodegradation of chloroethenes stimulated in a coupled bioelectro-process.

This article for the first time demonstrates successful application of electrochemical processes to stimulate sequential reductive/oxidative microbial degradation of perchloroethene (PCE) in mineral medium and in contaminated groundwater. In a flow-through column system, hydrogen generation at the cathode supported reductive dechlorination of PCE to cis-dichloroethene (cDCE), vinyl chloride (VC), and ethene (ETH). Electrolytically generated oxygen at the anode allowed subsequent oxidative degradation of the lower chlorinated metabolites. Aerobic cometabolic degradation of cDCE proved to be the bottleneck for complete metabolite elimination. Total removal of chloroethenes was demonstrated for a PCE load of approximately 1.5 μmol/d. In mineral medium, long-term operation with stainless steel electrodes was demonstrated for more than 300 days. In contaminated groundwater, corrosion of the stainless steel anode occurred, whereas DSA (dimensionally stable anodes) proved to be stable. Precipitation of calcareous deposits was observed at the cathode, resulting in a higher voltage demand and reduced dechlorination activity. With DSA and groundwater from a contaminated site, complete degradation of chloroethenes in groundwater was obtained for two months thus demonstrating the feasibility of the sequential bioelectro-approach for field application.

Immobilization of histidine-tagged proteins on electrodes.

The development of new enzyme immobilization techniques that do not affect catalytic activity or conformation of a protein is an important research task in biotechnology including biosensor applications and heterogeneous reaction systems. One of the most promising approaches for controlled protein immobilization is based on the immobilized metal ion affinity chromatography (IMAC) principle originally developed for protein purification. Here we describe the current status and future perspectives of immobilization of His-tagged proteins on electrode surfaces. Recombinant proteins comprising histidine-tags or histidine rich native proteins have a strong affinity to transition metal ions. For metal ion immobilization at the electrode surface different matrices can be used such as self-assembled monolayers or conductive polymers. This specific technique allows a reversible immobilization of histidine-tagged proteins at electrodes in a defined orientation which is an important prerequisite for efficient electron transfer between the electrode and the biomolecule. Any application requiring immobilized biocatalysts on electrodes can make use of this immobilization approach, making future biosensors and biocatalytic technologies more sensitive, simpler, reusable and less expensive while only requiring mild enzyme modifications.

Gas diffusion electrode as novel reaction system for an electro-enzymatic process with chloroperoxidase

The versatile enzyme chloroperoxidase was used in a new reaction system, based on a gas diffusion electrode, for enzymatic chlorinations, sulfoxidations and oxidations. This is the first report on the combination of hydrogen peroxide production at a GDE with an enzymatic reaction.

Polypyrrole as the Active Material for Potentiometric Sensors

In this study two types of sensor applications using polypyrrole (PPy) as the active material will be considered. The fisrt part deals with the development of a new type of pH glass electrode, where PPy is used as a mixed electron/ion conductor, to replace the conventional liquid junction reference electrode in a buffer electrolyte solution by an all-solid-state contact interface. The second part deals with PPy as an ion-sensitive material for the development of a potentiometric sensor, e.g. for the measurement of the pH or the detection of iron in aqueous solutions.

Relaxation of polythiophenes bridged by alkyl chains

Abstract The electrochemical redox behaviour of alkyl bridged polythiophene derivatives poly(1,6-bis(3-thienyl-)hexane) and poly(1,12-bis(3-thienyl-)dodecane) are investigated by cyclic voltammetry and compared to poly((3-hexyl-)- thiophene) and poly((3-dodecyl-)thiophene). In addition the thermal characteristics of these polymers are determined by differential scanning calorimetry. The polythiophene derivatives exhibit a temperature and time dependent redox behaviour.

Application of gas diffusion electrodes in bioelectrochemical syntheses and energy conversion

Combining the advantages of biological components (e.g., reaction specificity, self‐replication) and electrochemical techniques in bioelectrochemical systems offers the opportunity to develop novel efficient and sustainable processes for the production of a number of valuable products. The choice of electrode material has a great impact on the performance of bioelectrochemical systems. In addition to the redox process at the electrodes, interactions of biocatalysts with electrodes (e.g., enzyme denaturation or biofouling) need to be considered. In recent years, gas diffusion electrodes (GDEs) have proved to be very attractive electrodes for bioelectrochemical purposes. GDEs are porous electrodes, that posses a large three‐phase boundary surface. At this interface, a solid catalyst supports the electrochemical reaction between gaseous and liquid phase. This mini‐review discusses the application of GDEs in microbial and enzymatic fuel cells, for microbial electrolysis, in biosensors and for electroenzymatic synthesis reactions. Biotechnol. Bioeng. 2016;113: 260–267.

Structural modified polythiophene by cross-linking alkyl chains

The electrochemical redox behaviour of alkyl bridged poly(α,ω-bis(3-thienyl-)alkane)s is investigated and compared to poly(3-alkylthiophene)s.

Characterization of a membrane-separated and a membrane-less electrobioreactor for bioelectrochemical syntheses

Bioelectrochemical systems (BESs) have the potential to contribute to the energy revolution driven by the new bio‐economy. Until recently, simple reactor designs with minimal process analytics have been used. In recent years, assemblies to host electrodes in bioreactors have been developed resulting in so‐called “electrobioreactors.” Bioreactors are scalable, well‐mixed, controlled, and therefore widely used in biotechnology and adding an electrode extends the possibilities to investigate bioelectrochemical production processes in a standard system. In this work, two assemblies enabling a separated and non‐separated electrochemical operation, respectively, are designed and extensively characterized. Electrochemical losses over the electrolyte and the membrane were comparable to H‐cells, the bioelectrochemical standard reaction system. An effect of the electrochemical measurements on pH measurements was observed if the potential is outside the range of −1,000 to +600 mV versus Ag/AgCl. Electrobiotechnological characterization of the two assemblies was done using Shewanella oneidensis as an electroactive model organism. Current production over time was improved by a separation of anodic and cathodic chamber by a Nafion® membrane. The developed electrobioreactor was used for a scale‐up of the anaerobic bioelectrochemical production of organic acids and lysine from glucose using an engineered Corynebacterium glutamicum. Comparison to a small‐scale custom‐made electrobioreactor indicates that anodic electro‐fermentation of lysine and organic acids might not be limited by the BES setup but by the biocatalysis of the cells.