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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.
The Kremer-Grest (KG) bead-spring model is a near standard in Molecular Dynamic simulations of generic polymer properties. It owes its popularity to its computational efficiency, rather than its ability to represent specific polymer species and conditions. Here we investigate how to adapt the model to match the universal properties of a wide range of chemical polymers species. For this purpose we vary a single parameter originally introduced by Faller and Müller-Plathe, the chain stiffness. Examples include polystyrene, polyethylene, polypropylene, cis-polyisoprene, polydimethylsiloxane, polyethyleneoxide and styrene-butadiene rubber. We do this by matching the number of Kuhn segments per chain and the number of Kuhn segments per cubic Kuhn volume for the polymer species and for the Kremer-Grest model. We also derive mapping relations for converting KG model units back to physical units, in particular we obtain the entanglement time for the KG model as function of stiffness allowing for a time mapping. To test these relations, we generate large equilibrated well entangled polymer melts, and measure the entanglement moduli using a static primitive-path analysis of the entangled melt structure as well as by simulations of step-strain deformation of the model melts. The obtained moduli for our model polymer melts are in good agreement with the experimentally expected moduli.
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.
Mechanical forces/tensile stresses are critical determinants of cellular growth, differentiation and migration patterns in health and disease. The innovative “CellDrum technology” was designed for measuring mechanical tensile stress of cultured cell monolayers/thin tissue constructs routinely. These are cultivated on very thin silicone membranes in the so-called CellDrum. The cell layers adhere firmly to the membrane and thus transmit the cell forces generated. A CellDrum consists of a cylinder which is sealed from below with a 4 μm thick, biocompatible, functionalized silicone membrane. The weight of cell culture medium bulbs the membrane out downwards. Membrane indentation is measured. When cells contract due to drug action, membrane, cells and medium are lifted upwards. The induced indentation changes allow for lateral drug induced mechanical tension quantification of the micro-tissues. With hiPS-induced (human) Cardiomyocytes (CM) the CellDrum opens new perspectives of individualized cardiac drug testing. Here, monolayers of self-beating hiPS-CMs were grown in CellDrums. Rhythmic contractions of the hiPS-cells induce membrane up-and-down deflections. The recorded cycles allow for single beat amplitude, single beat duration, integration of the single beat amplitude over the beat time and frequency analysis. Dose effects of agonists and antagonists acting on Ca2+ channels were sensitively and highly reproducibly observed. Data were consistent with published reference data as far as they were available. The combination of the CellDrum technology with hiPS-Cardiomyocytes offers a fast, facile and precise system for pharmacological and toxicological studies. It allows new preclinical basic as well as applied research in pharmacolgy and toxicology.
Reconstructive surgery and tissue replacements like ureters or bladders reconstruction have been recently studied, taking into account growth and remodelling of cells since living cells are capable of growing, adapting, remodelling or degrading and restoring in order to deform and respond to stimuli. Hence, shapes of ureters or bladders and their microstructure change during growth and these changes strongly depend on external stimuli such as training. We present the mechanical stimulation of smooth muscle cells in a tubular fibrin-PVDFA scaffold and the modelling of the growth of tissue by stimuli. To this end, mechanotransduction was performed with a kyphoplasty balloon catheter that was guided through the lumen of the tubular structure. The bursting pressure was examined to compare the stability of the incubated tissue constructs. The results showed the significant changes on tissues with training by increasing the burst pressure as a characteristic mechanical property and the smooth muscle cells were more oriented with uniformly higher density. Besides, the computational growth models also exhibited the accurate tendencies of growth of the cells under different external stimuli. Such models may lead to design standards for the better layered tissue structure in reconstructing of tubular organs characterized as composite materials such as intestines, ureters and arteries.
In most beers, producers strive to minimize haze to maximize visual appeal. To detect the formation of particulates, a measurement system for sub-micron particles is required. Beer haze is naturally occurring, composed of protein or polyphenol particles; in their early stage of growth their size is smaller than 2 µm. Microscopy analysis is time and resource intensive; alternatively, backscattering is an inexpensive option for detecting particle sizes of interest.
In the present work an optical sensor in combination with a spectrally resolved detection device for in-line particle-size-monitoring for quality control in beer production is presented. The principle relies on the size and wavelength dependent backscatter of growing particles in fluids. Measured interference structures of backscattered light are compared with calculated theoretical values, based on Mie-Theory, and fitted with a linear least square method to obtain particle size distributions. For this purpose, a broadband light source in combination with a process-CCD-spectrometer (charge ? coupled device spectrometer) and process adapted fiber optics are used. The goal is the development of an easy and flexible measurement device for in-line-monitoring of particle size. The presented device can be directly installed in product fill tubes or vessels, follows CIP- (cleaning in place) and removes the need of sample taking. A proof of concept and preliminary results, measuring protein precipitation, are presented.
The terms bioeconomy and biorefineries are used for a variety of processes and developments. This short introduction is intended to provide a delimitation and clarification of the terminology as well as a classification of current biorefinery concepts. The basic process diagrams of the most important biorefinery types are shown.
Cupriavidus necator H16 gains increasing attention in microbial research and biotechnological application due to its diverse metabolic features. Here we present a tightly controlled gene expression system for C. necator including the pBBR1-vector that contains hybrid promoters originating from C. necator native tolC-promoter in combination with a synthetic tetO-operator. The expression of the reporter gene from these plasmids relies on the addition of the exogenous inducer doxycycline (dc). The novel expression system offers a combination of advantageous features as; (i) high and dose-dependent recombinant protein production, (ii) tight control with a high dynamic range (On/Off ratio), which makes it applicable for harmful pathways or for toxic protein production, (iii) comparable cheap inducer (doxycycline, dc), (iv) effective at low inducer concentration, that makes it useful for large scale application, (v) rapid, diffusion controlled induction, and (vi) the inducer does not interfere within the cell metabolism. As applications of the expression system in C. necator H16, the growth ability on glycerol was enhanced by constitutively expressing the E. coli glpk gene-encoding for glycerol kinase. Likewise, we used the system to overcome the expression toxicity of mevalonate pathway in C. necator H16. With this system, the mevalonate-genes were successfully introduced in the host and the recombinant strains could produce about 200 mg/l mevalonate.
Genetically humanized mice for proteins involved in drug metabolism and toxicity and mice engrafted with human hepatocytes are emerging as promising in vivo models for improved prediction of the pharmacokinetic, drug–drug interaction, and safety characteristics of compounds in humans. This is an overview on the genetically humanized and chimeric liver-humanized mouse models, which are illustrated with examples of their utility in drug metabolism and toxicity studies. The models are compared to give guidance for selection of the most appropriate model by highlighting advantages and disadvantages to be carefully considered when used for studies in drug discovery and development.