TY - JOUR A1 - Müller, Tim M. A1 - Leise, Philipp A1 - Lorenz, Imke-Sophie A1 - Altherr, Lena A1 - Pelz, Peter F. T1 - Optimization and validation of pumping system design and operation for water supply in high-rise buildings JF - Optimization and Engineering N2 - The application of mathematical optimization methods for water supply system design and operation provides the capacity to increase the energy efficiency and to lower the investment costs considerably. We present a system approach for the optimal design and operation of pumping systems in real-world high-rise buildings that is based on the usage of mixed-integer nonlinear and mixed-integer linear modeling approaches. In addition, we consider different booster station topologies, i.e. parallel and series-parallel central booster stations as well as decentral booster stations. To confirm the validity of the underlying optimization models with real-world system behavior, we additionally present validation results based on experiments conducted on a modularly constructed pumping test rig. Within the models we consider layout and control decisions for different load scenarios, leading to a Deterministic Equivalent of a two-stage stochastic optimization program. We use a piecewise linearization as well as a piecewise relaxation of the pumps’ characteristics to derive mixed-integer linear models. Besides the solution with off-the-shelf solvers, we present a problem specific exact solving algorithm to improve the computation time. Focusing on the efficient exploration of the solution space, we divide the problem into smaller subproblems, which partly can be cut off in the solution process. Furthermore, we discuss the performance and applicability of the solution approaches for real buildings and analyze the technical aspects of the solutions from an engineer’s point of view, keeping in mind the economically important trade-off between investment and operation costs. KW - Technical Operations Research KW - MINLP KW - MILP KW - Experimental validation KW - Pumping systems Y1 - 2020 U6 - https://doi.org/10.1007/s11081-020-09553-4 SN - 1573-2924 VL - 2021 IS - 22 SP - 643 EP - 686 PB - Springer ER - TY - CHAP A1 - Müller, Tim M. A1 - Altherr, Lena A1 - Leise, Philipp A1 - Pelz, Peter F. T1 - Optimization of pumping systems for buildings: Experimental validation of different degrees of model detail on a modular test rig T2 - Operations Research Proceedings 2019 N2 - Successful optimization requires an appropriate model of the system under consideration. When selecting a suitable level of detail, one has to consider solution quality as well as the computational and implementation effort. In this paper, we present a MINLP for a pumping system for the drinking water supply of high-rise buildings. We investigate the influence of the granularity of the underlying physical models on the solution quality. Therefore, we model the system with a varying level of detail regarding the friction losses, and conduct an experimental validation of our model on a modular test rig. Furthermore, we investigate the computational effort and show that it can be reduced by the integration of domain-specific knowledge. KW - Experimental validation KW - MINLP KW - Engineering optimization KW - Water supply system KW - Network design Y1 - 2020 SN - 978-3-030-48438-5 U6 - https://doi.org/10.1007/978-3-030-48439-2_58 N1 - Annual International Conference of the German Operations Research Society (GOR), Dresden, Germany, September 4-6, 2019 SP - 481 EP - 488 PB - Springer CY - Cham ER - TY - CHAP A1 - Müller, Tim M. A1 - Altherr, Lena A1 - Ahola, Marja A1 - Schabel, Samuel A1 - Pelz, Peter F. T1 - Optimizing pressure screen systems in paper recycling: optimal system layout, component selection and operation N2 - Around 60% of the paper worldwide is made from recovered paper. Especially adhesive contaminants, so called stickies, reduce paper quality. To remove stickies but at the same time keep as many valuable fibers as possible, multi-stage screening systems with several interconnected pressure screens are used. When planning such systems, suitable screens have to be selected and their interconnection as well as operational parameters have to be defined considering multiple conflicting objectives. In this contribution, we present a Mixed-Integer Nonlinear Program to optimize system layout, component selection and operation to find a suitable trade-off between output quality and yield. KW - Mixed-integer nonlinear problem KW - MINLP KW - Process engineering KW - Paper recycling KW - Multi-criteria optimization Y1 - 2018 SN - 978-3-030-18499-5 U6 - https://doi.org/10.1007/978-3-030-18500-8_44 SP - 355 EP - 361 PB - Springer CY - Cham ER - TY - CHAP A1 - Müller, Tim M. A1 - Altherr, Lena A1 - Ahola, Marja A1 - Schabel, Samuel A1 - Pelz, Peter F. ED - Rodrigues, H. C. T1 - Multi-Criteria optimization of pressure screen systems in paper recycling – balancing quality, yield, energy consumption and system complexity T2 - EngOpt 2018 Proceedings of the 6th International Conference on Engineering Optimization N2 - The paper industry is the industry with the third highest energy consumption in the European Union. Using recycled paper instead of fresh fibers for papermaking is less energy consuming and saves resources. However, adhesive contaminants in recycled paper are particularly problematic since they reduce the quality of the resulting paper-product. To remove as many contaminants and at the same time obtain as many valuable fibres as possible, fine screening systems, consisting of multiple interconnected pressure screens, are used. Choosing the best configuration is a non-trivial task: The screens can be interconnected in several ways, and suitable screen designs as well as operational parameters have to be selected. Additionally, one has to face conflicting objectives. In this paper, we present an approach for the multi-criteria optimization of pressure screen systems based on Mixed-Integer Nonlinear Programming. We specifically focus on a clear representation of the trade-off between different objectives. Y1 - 2019 SN - 978-3-319-97773-7 U6 - https://doi.org/10.1007/978-3-319-97773-7_105 N1 - EngOpt 2018 Proceedings of the 6th International Conference on Engineering Optimization. 17-19 September 2018. Lisboa, Portugal PB - Springer International Publishing CY - Basel ER - TY - JOUR A1 - Müller, Martin A1 - Hirschfeld, Julian A1 - Lambertz, Rita A1 - Schulze Lohoff, Andreas A1 - Lustfeld, Hans A1 - Pfeifer, Heinz A1 - Reißel, Martin T1 - Validation of a novel method for detecting and stabilizing malfunctioning areas in fuel cell stacks JF - Journal of power sources N2 - In this paper a setup for detecting malfunctioning areas of MEAs in fuel cell stacks is described. Malfunctioning areas generate electric cross currents inside bipolar plates. To exploit this we suggest bipolar plates consisting not of two but of three layers. The third one is a highly conducting layer and segmented such that the cross currents move along the segments to the surface of the stack where they can be measured by an inductive sensor. With this information a realistic model can be used to detect the malfunctioning area. Furthermore the third layer will prevent any current inhomogeneity of a malfunctioning cell to spread to neighbouring cells in the stack. In this work the results of measurements in a realistic cell setup will be compared with the results obtained in simulation studies with the same configuration. The basis for the comparison is the reliable characterisation of the electrical properties of the cell components and the implication of these results into the simulation model. The experimental studies will also show the limits in the maximum number of segments, which can be used for a reliable detection of cross currents. Y1 - 2014 U6 - https://doi.org/10.1016/j.jpowsour.2014.08.045 SN - 1873-2755 (E-Journal); 0378-7753 (Print) VL - 272 SP - 225 EP - 232 PB - Elsevier CY - Amsterdam ER - TY - CHAP A1 - Müller, Karsten A1 - Hüben, Susanne T1 - From rehabilitation strategy up to formation of lots : implementation of a computer-aided decision support system T2 - 11th International Conference on Urban Drainage, Edinburgh, Scotland, UK, 31st August to 5th September 2008 Y1 - 2008 ER - TY - CHAP A1 - Müller, Karsten A1 - Fischer, B. T1 - Objective condition assessment of sewer systems T2 - Strategic asset management of water supply and wastewater infrastructures : invited papers from the 2nd IWA Leading Edge Conference on Strategic Asset Management (LESAM), Lisbon, October [17 - 19] 2007 / ed. by Helene Alegre and Maria do Céu Almeida Y1 - 2009 SN - 9781843391869 SP - 521 EP - 534 PB - IWA Publ. CY - London ER - TY - JOUR A1 - Müller, Janina A1 - Beckers, Mario A1 - Mußmann, Nina A1 - Bongaerts, Johannes A1 - Büchs, Jochen T1 - Elucidation of auxotrophic deficiencies of Bacillus pumilus DSM 18097 to develop a defined minimal medium JF - Microbial Cell Factories N2 - Background Culture media containing complex compounds like yeast extract or peptone show numerous disadvantages. The chemical composition of the complex compounds is prone to significant variations from batch to batch and quality control is difficult. Therefore, the use of chemically defined media receives more and more attention in commercial fermentations. This concept results in better reproducibility, it simplifies downstream processing of secreted products and enable rapid scale-up. Culturing bacteria with unknown auxotrophies in chemically defined media is challenging and often not possible without an extensive trial-and-error approach. In this study, a respiration activity monitoring system for shake flasks and its recent version for microtiter plates were used to clarify unknown auxotrophic deficiencies in the model organism Bacillus pumilus DSM 18097. Results Bacillus pumilus DSM 18097 was unable to grow in a mineral medium without the addition of complex compounds. Therefore, a rich chemically defined minimal medium was tested containing basically all vitamins, amino acids and nucleobases, which are essential ingredients of complex components. The strain was successfully cultivated in this medium. By monitoring of the respiration activity, nutrients were supplemented to and omitted from the rich chemically defined medium in a rational way, thus enabling a systematic and fast determination of the auxotrophic deficiencies. Experiments have shown that the investigated strain requires amino acids, especially cysteine or histidine and the vitamin biotin for growth. Conclusions The introduced method allows an efficient and rapid identification of unknown auxotrophic deficiencies and can be used to develop a simple chemically defined tailor-made medium. B. pumilus DSM 18097 was chosen as a model organism to demonstrate the method. However, the method is generally suitable for a wide range of microorganisms. By combining a systematic combinatorial approach based on monitoring the respiration activity with cultivation in microtiter plates, high throughput experiments with high information content can be conducted. This approach facilitates media development, strain characterization and cultivation of fastidious microorganisms in chemically defined minimal media while simultaneously reducing the experimental effort. Y1 - 2018 U6 - https://doi.org/10.1186/s12934-018-0956-1 SN - 1475-2859 VL - 17 IS - 1 SP - Article No. 106 PB - BioMed Central ER - TY - JOUR A1 - Mühl, Thomas A1 - Binnebösel, Marcel A1 - Klinge, Uwe A1 - Goedderz, Thomas T1 - New objective measurement to characterize the porosity of textile implants JF - Journal of Biomedical Materials Research Part B: Applied Biomaterials. 84B (2008), H. 1 Y1 - 2008 SN - 1552-4981 SP - 176 EP - 183 ER - TY - CHAP A1 - Möhring, S. A1 - Wulfhorst, H. A1 - Roth, J. A1 - Tippkötter, Nils T1 - Pretreatment strategies for lignocellulosic biomass T2 - New frontiers of biotech-processes (Himmelfahrtstagung) : 02-04 May 2016, Rhein-Mosel-Halle, Koblenz/Germany Y1 - 2016 SP - 131 PB - DECHEMA CY - Frankfurt am Main ER - TY - GEN A1 - Möhring, S. A1 - Wulfhorst, H. A1 - Capitain, C. A1 - Roth, J. A1 - Tippkötter, Nils T1 - Fractioning of lignocellulosic biomass: Scale-down and automation of thermal pretreatment for parameter optimization T2 - Chemie Ingenieur Technik N2 - In order to efficiently convert lignocellulose, it is often necessary to conduct a pretreatment. The biomass considered in this study typically comprises of agricultural and horticultural residues, as well as beechwood. A very environmentally friendly method, namely, fungal pretreatment using white-rot fungi, leads to an enhanced enzymatic hydrolysis. In contrast to other processes presented, the energy input is extremely low. However, the fungal growth on the lignocellulosic substrates takes several weeks at least in order to be effective. Thus, the reduction of chemicals and energy for thermal processing is a target of our current research. Liquid hot water (LHW) and solvent-based pretreatment (OrganoSolv) require more complex equipment, as they depend on high temperatures (160 – 180 °C) and enhanced pressure (up to 20 bar). However, they prove to be promising processes in regard to the fractioning of lignocellulose. For optimal lignin recovery the parameters differ from those established in cellulose extraction. A novel screening system scaled down to a reaction volume of 100 mL has been developed and successfully tested for this purpose. Y1 - 2016 U6 - https://doi.org/10.1002/cite.201650288 SN - 0009-286X SN - 1522-2640 (eISSN) N1 - ProcessNet-Jahrestagung und 32. DECHEMA-Jahrestagung der Biotechnologen 2016, 12. - 15. September 2016, Eurogress Aachen VL - 88 IS - 9 SP - 1229 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Möhren, Felix A1 - Bergmann, Ole A1 - Janser, Frank A1 - Braun, Carsten T1 - Assessment of structural mechanical effects related to torsional deformations of propellers JF - CEAS Aeronautical Journal N2 - Lifting propellers are of increasing interest for Advanced Air Mobility. All propellers and rotors are initially twisted beams, showing significant extension–twist coupling and centrifugal twisting. Torsional deformations severely impact aerodynamic performance. This paper presents a novel approach to assess different reasons for torsional deformations. A reduced-order model runs large parameter sweeps with algebraic formulations and numerical solution procedures. Generic beams represent three different propeller types for General Aviation, Commercial Aviation, and Advanced Air Mobility. Simulations include solid and hollow cross-sections made of aluminum, steel, and carbon fiber-reinforced polymer. The investigation shows that centrifugal twisting moments depend on both the elastic and initial twist. The determination of the centrifugal twisting moment solely based on the initial twist suffers from errors exceeding 5% in some cases. The nonlinear parts of the torsional rigidity do not significantly impact the overall torsional rigidity for the investigated propeller types. The extension–twist coupling related to the initial and elastic twist in combination with tension forces significantly impacts the net cross-sectional torsional loads. While the increase in torsional stiffness due to initial twist contributes to the overall stiffness for General and Commercial Aviation propellers, its contribution to the lift propeller’s stiffness is limited. The paper closes with the presentation of approximations for each effect identified as significant. Numerical evaluations are necessary to determine each effect for inhomogeneous cross-sections made of anisotropic material. KW - Lifting propeller KW - Extension–twist coupling KW - Trapeze effect KW - Centrifugal twisting moment Y1 - 2024 U6 - https://doi.org/10.1007/s13272-024-00737-7 SN - 1869-5590 (eISSN) SN - 1869-5582 N1 - Corresponding author: Felix Möhren PB - Springer CY - Wien ER - TY - JOUR A1 - Möhren, Felix A1 - Bergmann, Ole A1 - Janser, Frank A1 - Braun, Carsten T1 - On the influence of elasticity on propeller performance: a parametric study JF - CEAS Aeronautical Journal N2 - The aerodynamic performance of propellers strongly depends on their geometry and, consequently, on aeroelastic deformations. Knowledge of the extent of the impact is crucial for overall aircraft performance. An integrated simulation environment for steady aeroelastic propeller simulations is presented. The simulation environment is applied to determine the impact of elastic deformations on the aerodynamic propeller performance. The aerodynamic module includes a blade element momentum approach to calculate aerodynamic loads. The structural module is based on finite beam elements, according to Timoshenko theory, including moderate deflections. Several fixed-pitch propellers with thin-walled cross sections made of both isotropic and non-isotropic materials are investigated. The essential parameters are varied: diameter, disc loading, sweep, material, rotational, and flight velocity. The relative change of thrust between rigid and elastic blades quantifies the impact of propeller elasticity. Swept propellers of large diameters or low disc loadings can decrease the thrust significantly. High flight velocities and low material stiffness amplify this tendency. Performance calculations without consideration of propeller elasticity can lead to decreased efficiency. To avoid cost- and time-intense redesigns, propeller elasticity should be considered for swept planforms and low disc loadings. KW - Propeller KW - Finite element method KW - Blade element method KW - Propeller elasticity KW - Aeroelasticity Y1 - 2023 U6 - https://doi.org/10.1007/s13272-023-00649-y SN - 1869-5590 (Online) SN - 1869-5582 (Print) N1 - Corresponding author: Felix Möhren VL - 14 SP - 311 EP - 323 PB - Springer Nature CY - Berlin ER - TY - CHAP A1 - Möhren, Felix A1 - Bergmann, Ole A1 - Janser, Frank A1 - Braun, Carsten T1 - On the determination of harmonic propeller loads T2 - AIAA SCITECH 2023 Forum N2 - Dynamic loads significantly impact the structural design of propeller blades due to fatigue and static strength. Since propellers are elastic structures, deformations and aerodynamic loads are coupled. In the past, propeller manufacturers established procedures to determine unsteady aerodynamic loads and the structural response with analytical steady-state calculations. According to the approach, aeroelastic coupling primarily consists of torsional deformations. They neglect bending deformations, deformation velocities, and inertia terms. This paper validates the assumptions above for a General Aviation propeller and a lift propeller for urban air mobility or large cargo drones. Fully coupled reduced-order simulations determine the dynamic loads in the time domain. A quasi-steady blade element momentum approach transfers loads to one-dimensional finite beam elements. The simulation results are in relatively good agreement with the analytical method for the General Aviation propeller but show increasing errors for the slender lift propeller. The analytical approach is modified to consider the induced velocities. Still, inertia and velocity proportional terms play a significant role for the lift propeller due to increased elasticity. The assumption that only torsional deformations significantly impact the dynamic loads of propellers is not valid. Adequate determination of dynamic loads of such designs requires coupled aeroelastic simulations or advanced analytical procedures. Y1 - 2023 U6 - https://doi.org/10.2514/6.2023-2404 N1 - AIAA SCITECH 2023 Forum, 23-27 January 2023, National Harbor, Md & Online PB - AIAA ER - TY - JOUR A1 - Mykoniou, Konstantin A1 - Butenweg, Christoph A1 - Holtschoppen, Britta A1 - Klinkel, Sven T1 - Seismic response analysis of adjacent liquid-storage tanks JF - Earthquake engineering and structural dynamics N2 - A refined substructure technique in the frequency domain is developed, which permits consideration of the interaction effects among adjacent containers through the supporting deformable soil medium. The tank-liquid systems are represented by means of mechanical models, whereas discrete springs and dashpots stand for the soil beneath the foundations. The proposed model is employed to assess the responses of adjacent circular, cylindrical tanks for harmonic and seismic excitations over wide range of tank proportions and soil conditions. The influence of the number, spatial arrangement of the containers and their distance on the overall system's behavior is addressed. The results indicate that the cross-interaction effects can substantially alter the impulsive components of response of each individual element in a tank farm. The degree of this impact is primarily controlled by the tank proportions and the proximity of the predominant natural frequencies of the shell-liquid-soil systems and the input seismic motion. The group effects should be not a priori disregarded, unless the tanks are founded on shallow soil deposit overlying very stiff material or bedrock. KW - liquid-structure interaction KW - seismic response KW - impulsive effects KW - liquid-storage tank KW - structure-soil-structure interaction Y1 - 2016 U6 - https://doi.org/10.1002/eqe.2726 SN - 1096-9845 (E-Journal); 0098-8847 (Print) VL - 45 IS - 11 SP - 1779 EP - 1796 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Musholt, Petra B. A1 - Schöndorf, Thomas A1 - Pfützner, Andreas A1 - Hohberg, Cloth A1 - Kleine, Iris A1 - Fuchs, Winfried A1 - Hehenwarter, Silvia A1 - Dikta, Gerhard A1 - Kerschgens, Benedikt A1 - Forst, Thomas T1 - Combined Pioglitazone and Metformin Treatment Maintains the Beneficial Effect of Short-Term Insulin Infusion in Patients with Type 2 Diabetes: Results from a Pilot Study JF - Journal of Diabetes Science and Technology. 3 (2009), H. 6 Y1 - 2009 SN - 1932-2968 SP - 1442 EP - 1450 PB - Sage Publishing CY - London ER - TY - JOUR A1 - Muschallik, Lukas A1 - Molinnus, Denise A1 - Jablonski, Melanie A1 - Kipp, Carina Ronja A1 - Bongaerts, Johannes A1 - Pohl, Martina A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Selmer, Thorsten A1 - Siegert, Petra T1 - Synthesis of α-hydroxy ketones and vicinal (R, R)-diols by Bacillus clausii DSM 8716ᵀ butanediol dehydrogenase JF - RSC Advances N2 - α-hydroxy ketones (HK) and 1,2-diols are important building blocks for fine chemical synthesis. Here, we describe the R-selective 2,3-butanediol dehydrogenase from B. clausii DSM 8716ᵀ (BcBDH) that belongs to the metal-dependent medium chain dehydrogenases/reductases family (MDR) and catalyzes the selective asymmetric reduction of prochiral 1,2-diketones to the corresponding HK and, in some cases, the reduction of the same to the corresponding 1,2-diols. Aliphatic diketones, like 2,3-pentanedione, 2,3-hexanedione, 5-methyl-2,3-hexanedione, 3,4-hexanedione and 2,3-heptanedione are well transformed. In addition, surprisingly alkyl phenyl dicarbonyls, like 2-hydroxy-1-phenylpropan-1-one and phenylglyoxal are accepted, whereas their derivatives with two phenyl groups are not substrates. Supplementation of Mn²⁺ (1 mM) increases BcBDH's activity in biotransformations. Furthermore, the biocatalytic reduction of 5-methyl-2,3-hexanedione to mainly 5-methyl-3-hydroxy-2-hexanone with only small amounts of 5-methyl-2-hydroxy-3-hexanone within an enzyme membrane reactor is demonstrated. Y1 - 2020 U6 - https://doi.org/10.1039/D0RA02066D SN - 2046-2069 VL - 10 SP - 12206 EP - 12216 PB - Royal Society of Chemistry (RSC) CY - Cambridge ER - TY - JOUR A1 - Muschallik, Lukas A1 - Molinnus, Denise A1 - Bongaerts, Johannes A1 - Pohl, Martina A1 - Wagner, Torsten A1 - Schöning, Michael Josef A1 - Siegert, Petra A1 - Selmer, Thorsten T1 - (R,R)-Butane-2,3-diol Dehydrogenase from Bacillus clausii DSM 8716T: Cloning and Expression of the bdhA-Gene, and Initial Characterization of Enzyme JF - Journal of Biotechnology N2 - 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. Y1 - 2017 U6 - https://doi.org/10.1016/j.jbiotec.2017.07.020 SN - 0168-1656 VL - 258 SP - 41 EP - 50 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Muschallik, Lukas A1 - Kipp, Carina Ronja A1 - Recker, Inga A1 - Bongaerts, Johannes A1 - Pohl, Martina A1 - Gelissen, Melanie A1 - Schöning, Michael Josef A1 - Selmer, Thorsten A1 - Siegert, Petra T1 - Synthesis of α-hydroxy ketones and vicinal diols with the Bacillus licheniformis DSM 13T butane-2, 3-diol dehydrogenase JF - Journal of Biotechnology N2 - The enantioselective synthesis of α-hydroxy ketones and vicinal diols is an intriguing field because of the broad applicability of these molecules. Although, butandiol dehydrogenases are known to play a key role in the production of 2,3-butandiol, their potential as biocatalysts is still not well studied. Here, we investigate the biocatalytic properties of the meso-butanediol dehydrogenase from Bacillus licheniformis DSM 13T (BlBDH). The encoding gene was cloned with an N-terminal StrepII-tag and recombinantly overexpressed in E. coli. BlBDH is highly active towards several non-physiological diketones and α-hydroxyketones with varying aliphatic chain lengths or even containing phenyl moieties. By adjusting the reaction parameters in biotransformations the formation of either the α-hydroxyketone intermediate or the diol can be controlled. Y1 - 2020 SN - 2590-1559 U6 - https://doi.org/10.1016/j.jbiotec.2020.09.016 VL - 202 IS - Vol. 324 SP - 61 EP - 70 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Murib, Mohammed Sharif A1 - Yeap, Weng-Siang A1 - Martens, Daan A1 - Bienstman, Peter A1 - Ceuninck, Ward de A1 - Grinsven, Bart van A1 - Schöning, Michael Josef A1 - Michiels, Luc A1 - Haenen, Ken A1 - Ameloot, Marcel A1 - Serpengüzel, Ali A1 - Wagner, Patrick T1 - Photonic detection and characterization of DNA using sapphire microspheres JF - Journal of biomedical optics N2 - A microcavity-based deoxyribonucleic acid (DNA) optical biosensor is demonstrated for the first time using synthetic sapphire for the optical cavity. Transmitted and elastic scattering intensity at 1510 nm are analyzed from a sapphire microsphere (radius 500  μm, refractive index 1.77) on an optical fiber half coupler. The 0.43 nm angular mode spacing of the resonances correlates well with the optical size of the sapphire sphere. Probe DNA consisting of a 36-mer fragment was covalently immobilized on a sapphire microsphere and hybridized with a 29-mer target DNA. Whispering gallery modes (WGMs) were monitored before the sapphire was functionalized with DNA and after it was functionalized with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The shift in WGMs from the surface modification with DNA was measured and correlated well with the estimated thickness of the add-on DNA layer. It is shown that ssDNA is more uniformly oriented on the sapphire surface than dsDNA. In addition, it is shown that functionalization of the sapphire spherical surface with DNA does not affect the quality factor (Q≈104) of the sapphire microspheres. The use of sapphire is especially interesting because this material is chemically resilient, biocompatible, and widely used for medical implants. Y1 - 2014 U6 - https://doi.org/10.1117/1.JBO.19.9.097006 SN - 1560-2281 (E-Journal); 1083-3668 (Print) VL - 19 IS - 9 SP - 097006 PB - SPIE CY - Bellingham ER -