A Cell-Free Multi-enzyme Cascade Reaction for the Synthesis of CDP-Glycerol

CDP-glycerol is a nucleotide-diphosphate-activated version of glycerol. In nature, it is required for the biosynthesis of teichoic acid in Gram-positive bacteria, which is an appealing target epitope for the development of new vaccines. Here, a cell-free multi-enzyme cascade was developed to synthetize nucleotide-activated glycerol from the inexpensive and readily available substrates cytidine and glycerol. The cascade comprises five recombinant enzymes expressed in Escherichia coli that were purified by immobilized metal affinity chromatography. As part of the cascade, ATP is regenerated in situ from polyphosphate to reduce synthesis costs. The enzymatic cascade was characterized at the laboratory scale, and the products were analyzed by high-performance anion-exchange chromatography (HPAEC)-UV and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). After the successful synthesis had been confirmed, a design-of-experiments approach was used to screen for optimal operation conditions (temperature, pH value and MgCl₂ concentration). Overall, a substrate conversion of 89 % was achieved with respect to the substrate cytidine.     

Inhibitor and Activator: Dual Role of Subsurface Sulfide Enables Selective and Efficient Electro-Oxidation of Methanol to Formate on CuS@CuO Core-Shell Nanosheet Arrays

Selective electro-oxidation of aliphatic alcohols into value-added carboxylates at lower potentials than that of the oxygen evolution reaction (OER) is an environmentally and economically desirable anode reaction for clean energy storage and conversion technologies. However, it is challenging to achieve both high selectivity and high activity of the catalysts for the electro-oxidation of alcohols, such as the methanol oxidation reaction (MOR). Herein, a monolithic CuS@CuO/copper-foam electrode for the MOR with superior catalytic activity and almost 100% selectivity for formate is reported. In the core-shell CuS@CuO nanosheet arrays, the surface CuO directly catalyzes MOR, while the subsurface sulfide not only serves as an inhibitor to attenuate the oxidative power of the surface CuO to achieve selective oxidation of methanol to formate and prevent over-oxidation of formate to CO₂ but also serves as an activator to form more surface O defects as active sites and enhances the methanol adsorption and charge transfer to achieve superior catalytic activity. CuS@CuO/copper-foam electrodes can be prepared on a large scale by electro-oxidation of copper-foam at ambient conditions and can be readily utilized in clean energy technologies.     

Zur Notwendigkeit von Gefällen bei Parkdecks

Sowohl bei der Planung und dem Bau neuer als auch bei der Begutachtung bestehender Parkbauten wird immer wieder die Frage diskutiert, ob die Ausbildung eines Gefälles prinzipiell notwendig ist. Dabei werden verschiedene Argumente zusammengebracht, die zum einen aus der Betrachtung der Nutzung und Gebrauchstauglichkeit des Gebäudes als Parkbau und zum anderen aus der Frage der Dauerhaftigkeit der Tragkonstruktion aus Stahlbeton oder Spannbeton resultieren. Ziel dieses Beitrags ist, diese Argumente zusammenzustellen und zu ordnen. Anhand der verschiedenen Aspekte soll erläutert werden, warum im neuen DBV‐Merkblatt “Parkhäuser und Tiefgaragen” darauf verzichtet wurde, die Ausbildung eines Gefälles als Regelbauweise in jedem Fall zu fordern und – stattdessen – es dem Bauherrn zu überlassen, aufgrund einer Abwägung differenzierter Argumente für und gegen ein Gefälle eine sachgerechte Entscheidung zu treffen. On the Necessity of Gradients at Parking Decks When design and executing new car parks or when surveying existing ones, an often discussed question is whether a gradient of parking decks is always necessary. In this context different arguments are commonly used. These arguments have been collected and reviewed under the aspect of usability as a car park on the one hand and under the aspect of durability of the reinforced construction on the other hand. It has been shown why in the new DBV‐Code of Practice “Multi‐Storey and Underground Car Parks” an incline is not required as a standard construction method in every case. Instead of that it has been concluded that an appropriate owner's decision on pro or contra an incline would be reasonable and necessary based on the above consideration of differentiated arguments.     

Optimierung eines Raumes mithilfe von DIN 18599‐4 (Tageslicht), DIN 4108‐2 (sommerlicher Wärmeschutz) und weiterführenden Simulationen

Room optimisation based on DIN 18599‐4 (Daylight), DIN 4108‐2 (Thermal comfort during summer) and simulations. DIN 18599‐4 is successfully used as a tool for optimising daylight quality in office spaces with respect to dimensions and window size and positioning. Further room optimisation with respect to thermal comfort during summer based on DIN 4108‐2 can lead to uncomfortable conditions, as shown in comparative simulations. Comfortable conditions can be achieved with further optimisation measures based on simulation programs and thermal comfort evaluation based on DIN EN 15251. Recommendations for relevant room parameters including shading, natural ventilation and artificial light switching are provided.     

Temperature- and stress-dependent electromechanical properties of phase-boundary-engineered KNN-based piezoceramics

The influence of stress on the small-signal dielectric permittivity and piezoelectric coefficient of polycrystalline lead-free perovskite 0.92(Na_1/2K_1/2)NbO₃–(0.08 − x)Bi_1/2Li_1/2TiO₃–xBaZrO₃ (x = 0, 0.02, 0.04, 0.06, and 0.07) was characterized under different constant uniaxial stress up to −200 MPa within a temperature range of −150 to 450°C, revealing stress-induced suppression of the electromechanical response as well as shifts in the phase boundaries. For all compositions, the interferroelectric and ferroelectric–paraelectric phase transitions were shifted to higher temperatures under the uniaxial compressive stress. Interestingly, the sensitivity to the applied stress was found to increase with increasing BZ/BLT ratio in the system. The origin of a different extent of stress-sensitivity with BZ/BLT ratio is suggested to be related to the change in the crystal structure. Additionally, at temperatures below −50°C, the relative permittivity showed a significant increase under applied compressive stress.     

Cell-Free Multi-Enzyme Synthesis and Purification of Uridine Diphosphate Galactose

High costs and low availability of UDP-galactose hampers the enzymatic synthesis of valuable oligosaccharides such as human milk oligosaccharides. Here, we report the development of a platform for the scalable, biocatalytic synthesis and purification of UDP-galactose. UDP-galactose was produced with a titer of 48 mM (27.2 g/L) in a small-scale batch process (200 μL) within 24 h using 0.02 g_enzyme/g_product. Through in-situ ATP regeneration, the amount of ATP (0.6 mM) supplemented was around 240-fold lower than the stoichiometric equivalent required to achieve the final product yield. Chromatographic purification using porous graphic carbon adsorbent yielded UDP-galactose with a purity of 92 %. The synthesis was transferred to 1 L preparative scale production in a stirred tank bioreactor. To further reduce the synthesis costs here, the supernatant of cell lysates was used bypassing expensive purification of enzymes. Here, 23.4 g/L UDP-galactose were produced within 23 h with a synthesis yield of 71 % and a biocatalyst load of 0.05 g_{total_protein}/g_product. The costs for substrates per gram of UDP-galactose synthesized were around 0.26 €/g.     

Tool Chain to Extract and Contextualize Process Data for AI Applications

Summarizing a key use case of a research workstream of the German publicly funded KEEN project, methods and tool chains are demonstrated to extract and to contextualize process data in an automated way based on engineering information. The contextualized process data serves as a high-quality data source for machine learning methods. The article covers the applied basic methodical approaches, design decisions and the results of a successful pilot installation of the developed tool chain.