@article{PilasYaziciSelmeretal.2018,
  author    = {Pilas, Johanna and Yazici, Y. and Selmer, Thorsten and Keusgen, M. and Sch{\"o}ning, Michael Josef},
  title     = {Application of a portable multi-analyte biosensor for organic acid determination in silage},
  series = {Sensors},
  volume    = {18},
  journal   = {Sensors},
  number    = {5},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {1424-8220},
  doi       = {10.3390/s18051470},
  pages     = {12 Seiten},
  year      = {2018},
  abstract  = {Multi-analyte biosensors may offer the opportunity to perform cost-effective and rapid analysis with reduced sample volume, as compared to electrochemical biosensing of each analyte individually. This work describes the development of an enzyme-based biosensor system for multi-parametric determination of four different organic acids. The biosensor array comprises five working electrodes for simultaneous sensing of ethanol, formate, d-lactate, and l-lactate, and an integrated counter electrode. Storage stability of the biosensor was evaluated under different conditions (stored at +4 °C in buffer solution and dry at -21 °C, +4 °C, and room temperature) over a period of 140 days. After repeated and regular application, the individual sensing electrodes exhibited the best stability when stored at -21 °C. Furthermore, measurements in silage samples (maize and sugarcane silage) were conducted with the portable biosensor system. Comparison with a conventional photometric technique demonstrated successful employment for rapid monitoring of complex media.},
  language  = {en}
}
@article{PilasSelmerKeusgenetal.2019,
  author    = {Pilas, Johanna and Selmer, Thorsten and Keusgen, Michael and Sch{\"o}ning, Michael Josef},
  title     = {Screen-printed carbon electrodes modified with graphene oxide for the design of a reagent-free NAD+-dependent biosensor array},
  series = {Analytical Chemistry},
  volume    = {91},
  journal   = {Analytical Chemistry},
  number    = {23},
  publisher = {ACS Publications},
  address   = {Washington},
  doi       = {10.1021/acs.analchem.9b04481},
  pages     = {15293 -- 15299},
  year      = {2019},
  language  = {en}
}
@article{RoehlenPilasSchoeningetal.2017,
  author    = {R{\"o}hlen, Desiree and Pilas, Johanna and Sch{\"o}ning, Michael Josef and Selmer, Thorsten},
  title     = {Development of an amperometric biosensor platform for the combined determination of l-Malic, Fumaric, and l-Aspartic acid},
  series = {Applied Biochemistry and Biotechnology},
  volume    = {183},
  journal   = {Applied Biochemistry and Biotechnology},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {1559-0291},
  doi       = {10.1007/s12010-017-2578-1},
  pages     = {566 -- 581},
  year      = {2017},
  abstract  = {Three amperometric biosensors have been developed for the detection of L-malic acid, fumaric acid, and L -aspartic acid, all based on the combination of a malate-specific dehydrogenase (MDH, EC 1.1.1.37) and diaphorase (DIA, EC 1.8.1.4). The stepwise expansion of the malate platform with the enzymes fumarate hydratase (FH, EC 4.2.1.2) and aspartate ammonia-lyase (ASPA, EC 4.3.1.1) resulted in multi-enzyme reaction cascades and, thus, augmentation of the substrate spectrum of the sensors. Electrochemical measurements were carried out in presence of the cofactor β-nicotinamide adenine dinucleotide (NAD+) and the redox mediator hexacyanoferrate (III) (HCFIII). The amperometric detection is mediated by oxidation of hexacyanoferrate (II) (HCFII) at an applied potential of + 0.3 V vs. Ag/AgCl. For each biosensor, optimum working conditions were defined by adjustment of cofactor concentrations, buffer pH, and immobilization procedure. Under these improved conditions, amperometric responses were linear up to 3.0 mM for L-malate and fumarate, respectively, with a corresponding sensitivity of 0.7 μA mM-1 (L-malate biosensor) and 0.4 μA mM-1 (fumarate biosensor). The L-aspartate detection system displayed a linear range of 1.0-10.0 mM with a sensitivity of 0.09 μA mM-1. The sensor characteristics suggest that the developed platform provides a promising method for the detection and differentiation of the three substrates.},
  language  = {en}
}
@article{PilasYaziciSelmeretal.2017,
  author    = {Pilas, Johanna and Yazici, Yasemen and Selmer, Thorsten and Keusgen, Michael and Sch{\"o}ning, Michael Josef},
  title     = {Optimization of an amperometric biosensor array for simultaneous measurement of ethanol, formate, d- and l-lactate},
  series = {Electrochimica Acta},
  volume    = {251},
  journal   = {Electrochimica Acta},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0013-4686},
  doi       = {10.1016/j.electacta.2017.07.119},
  pages     = {256 -- 262},
  year      = {2017},
  abstract  = {The immobilization of NAD+-dependent dehydrogenases, in combination with a diaphorase, enables the facile development of multiparametric sensing devices. In this work, an amperometric biosensor array for simultaneous determination of ethanol, formate, d- and l-lactate is presented. Enzyme immobilization on platinum thin-film electrodes was realized by chemical cross-linking with glutaraldehyde. The optimization of the sensor performance was investigated with regard to enzyme loading, glutaraldehyde concentration, pH, cofactor concentration and temperature. Under optimal working conditions (potassium phosphate buffer with pH 7.5, 2.5 mmol L-1 NAD+, 2.0 mmol L-1 ferricyanide, 25 °C and 0.4\% glutaraldehyde) the linear working range and sensitivity of the four sensor elements was improved. Simultaneous and cross-talk free measurements of four different metabolic parameters were performed successfully. The reliable analytical performance of the biosensor array was demonstrated by application in a clarified sample of inoculum sludge. Thereby, a promising approach for on-site monitoring of fermentation processes is provided.},
  language  = {en}
}
@article{DemmerChowdhurySelmeretal.2017,
  author    = {Demmer, Julius K. and Chowdhury, Nilanjan Pal and Selmer, Thorsten and Ermler, Ulrich and Buckel, Wolfgang},
  title     = {The semiquinone swing in the bifurcating electron transferring flavoprotein/butyryl-CoA dehydrogenase complex from Clostridium difficile},
  series = {Nature Communications},
  volume    = {8},
  journal   = {Nature Communications},
  number    = {1},
  issn      = {2041-1723},
  doi       = {10.1038/s41467-017-01746-3},
  pages     = {1 -- 10},
  year      = {2017},
  language  = {en}
}
@article{RoehlenPilasDahmenetal.2018,
  author    = {R{\"o}hlen, Desiree and Pilas, Johanna and Dahmen, Markus and Keusgen, Michael and Selmer, Thorsten and Sch{\"o}ning, Michael Josef},
  title     = {Toward a Hybrid Biosensor System for Analysis of Organic and Volatile Fatty Acids in Fermentation Processes},
  series = {Frontiers in Chemistry},
  journal   = {Frontiers in Chemistry},
  number    = {6},
  publisher = {Frontiers},
  address   = {Lausanne},
  doi       = {10.3389/fchem.2018.00284},
  pages     = {Artikel 284},
  year      = {2018},
  abstract  = {Monitoring of organic acids (OA) and volatile fatty acids (VFA) is crucial for the control of anaerobic digestion. In case of unstable process conditions, an accumulation of these intermediates occurs. In the present work, two different enzyme-based biosensor arrays are combined and presented for facile electrochemical determination of several process-relevant analytes. Each biosensor utilizes a platinum sensor chip (14 × 14 mm²) with five individual working electrodes. The OA biosensor enables simultaneous measurement of ethanol, formate, d- and l-lactate, based on a bi-enzymatic detection principle. The second VFA biosensor provides an amperometric platform for quantification of acetate and propionate, mediated by oxidation of hydrogen peroxide. The cross-sensitivity of both biosensors toward potential interferents, typically present in fermentation samples, was investigated. The potential for practical application in complex media was successfully demonstrated in spiked sludge samples collected from three different biogas plants. Thereby, the results obtained by both of the biosensors were in good agreement to the applied reference measurements by photometry and gas chromatography, respectively. The proposed hybrid biosensor system was also used for long-term monitoring of a lab-scale biogas reactor (0.01 m³) for a period of 2 months. In combination with typically monitored parameters, such as gas quality, pH and FOS/TAC (volatile organic acids/total anorganic carbonate), the amperometric measurements of OA and VFA concentration could enhance the understanding of ongoing fermentation processes.},
  language  = {en}
}
@article{SchiffelsSelmer2019,
  author    = {Schiffels, Johannes and Selmer, Thorsten},
  title     = {Combinatorial assembly of ferredoxin-linked modules in Escherichia coli yields a testing platform for Rnf-complexes},
  series = {Biotechnology and Bioengineering},
  journal   = {Biotechnology and Bioengineering},
  number    = {accepted article},
  publisher = {Wiley},
  address   = {Weinheim},
  doi       = {10.1002/bit.27079},
  pages     = {1 -- 36},
  year      = {2019},
  language  = {en}
}
@article{DantismRoehlenSelmeretal.2019,
  author    = {Dantism, Shahriar and R{\"o}hlen, Desiree and Selmer, Thorsten and Wagner, Torsten and Wagner, Patrick and Sch{\"o}ning, Michael Josef},
  title     = {Quantitative differential monitoring of the metabolic activity of Corynebacterium glutamicum cultures utilizing a light-addressable potentiometric sensor system},
  series = {Biosensors and Bioelectronics},
  volume    = {139},
  journal   = {Biosensors and Bioelectronics},
  publisher = {Elsevier},
  address   = {Amsterdam},
  doi       = {10.1016/j.bios.2019.111332},
  pages     = {Artikel 111332},
  year      = {2019},
  language  = {en}
}
@article{MuschallikMolinnusBongaertsetal.2017,
  author    = {Muschallik, Lukas and Molinnus, Denise and Bongaerts, Johannes and Pohl, Martina and Wagner, Torsten and Sch{\"o}ning, Michael Josef and Siegert, Petra and Selmer, Thorsten},
  title     = {(R,R)-Butane-2,3-diol Dehydrogenase from Bacillus clausii DSM 8716T: Cloning and Expression of the bdhA-Gene, and Initial Characterization of Enzyme},
  series = {Journal of Biotechnology},
  volume    = {258},
  journal   = {Journal of Biotechnology},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0168-1656},
  doi       = {10.1016/j.jbiotec.2017.07.020},
  pages     = {41 -- 50},
  year      = {2017},
  abstract  = {The gene encoding a putative (R,R)-butane-2,3-diol dehydrogenase (bdhA) from Bacillus clausii DSM 8716T was isolated, sequenced and expressed in Escherichia coli. The amino acid sequence of the encoded protein is only distantly related to previously studied enzymes (identity 33-43\%) and exhibited some uncharted peculiarities. An N-terminally StrepII-tagged enzyme variant was purified and initially characterized. The isolated enzyme catalyzed the (R)-specific oxidation of (R,R)- and meso-butane-2,3-diol to (R)- and (S)-acetoin with specific activities of 12 U/mg and 23 U/mg, respectively. Likewise, racemic acetoin was reduced with a specific activity of up to 115 U/mg yielding a mixture of (R,R)- and meso-butane-2,3-diol, while the enzyme reduced butane-2,3-dione (Vmax 74 U/mg) solely to (R,R)-butane-2,3-diol via (R)-acetoin. For these reactions only activity with the co-substrates NADH/NAD+ was observed. The enzyme accepted a selection of vicinal diketones, α-hydroxy ketones and vicinal diols as alternative substrates. Although the physiological function of the enzyme in B. clausii remains elusive, the data presented herein clearly demonstrates that the encoded enzyme is a genuine (R,R)-butane-2,3-diol dehydrogenase with potential for applications in biocatalysis and sensor development.},
  language  = {en}
}
@article{MolinnusMuschallikGonzalezetal.2018,
  author    = {Molinnus, Denise and Muschallik, Lukas and Gonzalez, Laura Osorio and Bongaerts, Johannes and Wagner, Torsten and Selmer, Thorsten and Siegert, Petra and Keusgen, Michael and Sch{\"o}ning, Michael Josef},
  title     = {Development and characterization of a field-effect biosensor for the detection of acetoin},
  series = {Biosensors and Bioelectronics},
  volume    = {115},
  journal   = {Biosensors and Bioelectronics},
  publisher = {Elsevier},
  address   = {Amsterdam},
  doi       = {10.1016/j.bios.2018.05.023},
  pages     = {1 -- 6},
  year      = {2018},
  abstract  = {A capacitive electrolyte-insulator-semiconductor (EIS) field-effect biosensor for acetoin detection has been presented for the first time. The EIS sensor consists of a layer structure of Al/p-Si/SiO₂/Ta₂O₅/enzyme acetoin reductase. The enzyme, also referred to as butane-2,3-diol dehydrogenase from B. clausii DSM 8716T, has been recently characterized. The enzyme catalyzes the (R)-specific reduction of racemic acetoin to (R,R)- and meso-butane-2,3-diol, respectively. Two different enzyme immobilization strategies (cross-linking by using glutaraldehyde and adsorption) have been studied. Typical biosensor parameters such as optimal pH working range, sensitivity, hysteresis, linear concentration range and long-term stability have been examined by means of constant-capacitance (ConCap) mode measurements. Furthermore, preliminary experiments have been successfully carried out for the detection of acetoin in diluted white wine samples.},
  language  = {en}
}