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Showing papers by "DECHEMA published in 2017"


Journal ArticleDOI
TL;DR: It is demonstrated that inorganic photocatalysts such as gold–titanium dioxide efficiently provide H2O2 through the methanol‐driven reductive activation of ambient oxygen in amounts that ensure that the enzyme remains highly active and stable.
Abstract: Selective oxyfunctionalisation of inert C-H bonds under mild conditions can be achieved using peroxygenases. This approach, however, is impaired by the poor robustness of these enzymes in the presence of hydrogen peroxide as the stoichiometric oxidant. Here, we demonstrate that inorganic photocatalysts such as gold-titanium dioxide efficiently provide H2O2 from methanol-driven reductive activation of ambient oxygen in suitable amounts to ensure high reactivity and robustness of the enzyme. Using this approach stereoselective hydroxylation of ethyl benzene to (R)-1-phenyl ethanol in high enantioselectivity (>98% ee) and excellent turnover numbers of the biocatalyst (>71.000) was achieved.

95 citations


Journal ArticleDOI
TL;DR: The integration of new testing methods and strategies in product development, testing and regulation stages are presented with examples of the application of in silico, omics and in vitro methods.
Abstract: Green Toxicology refers to the application of predictive toxicology in the sustainable development and production of new less harmful materials and chemicals, subsequently reducing waste and exposure. Built upon the foundation of “Green Chemistry” and “Green Engineering”, “Green Toxicology” aims to shape future manufacturing processes and safe synthesis of chemicals in terms of environmental and human health impacts. Being an integral part of Green Chemistry, the principles of Green Toxicology amplify the role of health-related aspects for the benefit of consumers and the environment, in addition to being economical for manufacturing companies. Due to the costly development and preparation of new materials and chemicals for market entry, it is no longer practical to ignore the safety and environmental status of new products during product development stages. However, this is only possible if toxicologists and chemists work together early on in the development of materials and chemicals to utilize safe design strategies and innovative in vitro and in silico tools. This paper discusses some of the most relevant aspects, advances and limitations of the emergence of Green Toxicology from the perspective of different industry and research groups. The integration of new testing methods and strategies in product development, testing and regulation stages are presented with examples of the application of in silico, omics and in vitro methods. Other tools for Green Toxicology, including the reduction of animal testing, alternative test methods, and read-across approaches are also discussed.

68 citations


Journal ArticleDOI
TL;DR: In this article, the joining of aluminum to steel was conducted by ultrasound enhanced friction stir welding (USE-FSW), which was introduced into one of the metal sheets by an ultrasonic roll seam module synchronously to the FSW-process.

52 citations


Journal ArticleDOI
TL;DR: In this article, a microreview summarizes recent developments in heterogeneous photoredox catalysis, with a special focus on materials, reactors, and reaction design to optimize yields, including the integration of enzymatic processes.

47 citations


Journal ArticleDOI
01 Jun 2017
TL;DR: In this article, the authors describe various technologies for energy storage and their potential applications in the context of Germany's Energiewende, i.e. the transition towards a more sustainable energy system.
Abstract: The current energy system is subject to a fundamental transformation: A system that is oriented towards a constant energy supply by means of fossil fuels is now expected to integrate increasing amounts of renewable energy to achieve overall a more sustainable energy supply. The challenges arising from this paradigm shift are currently most obvious in the area of electric power supply. However, it affects all areas of the energy system, albeit with different results. Within the energy system, various independent grids fulfill the function of transporting and spatially distributing energy or energy carriers, and the demand-oriented supply ensures that energy demands are met at all times. However, renewable energy sources generally supply their energy independently from any specific energy demand. Their contribution to the overall energy system is expected to increase significantly. Energy storage technologies are one option for temporal matching of energy supply and demand. Energy storage systems have the ability to take up a certain amount of energy, store it in a storage medium for a suitable period of time, and release it in a controlled manner after a certain time delay. Energy storage systems can also be constructed as process chains by combining unit operations, each of which cover different aspects of these functions. Large-scale mechanical storage of electric power is currently almost exclusively achieved by pumped-storage hydroelectric power stations. These systems may be supplemented in the future by compressed-air energy storage and possibly air separation plants. In the area of electrochemical storage, various technologies are currently in various stages of research, development, and demonstration of their suitability for large-scale electrical energy storage. Thermal energy storage technologies are based on the storage of sensible heat, exploitation of phase transitions, adsorption/desorption processes, and chemical reactions. The latter offer the possibility of permanent and loss-free storage of heat. The storage of energy in chemical bonds involves compounds that can act as energy carriers or as chemical feedstocks. Thus, they are in direct economic competition with established (fossil fuel) supply routes. The key technology here – now and for the foreseeable future – is the electrolysis of water to produce hydrogen and oxygen. Hydrogen can be transformed by various processes into other energy carriers, which can be exploited in different sectors of the energy system and/or as raw materials for energy-intensive industrial processes. Some functions of energy storage systems can be taken over by industrial processes. Within the overall energy system, chemical energy storage technologies open up opportunities to link and interweave the various energy streams and sectors. Chemical energy storage not only offers means for greater integration of renewable energy outside the electric power sector, it also creates new opportunities for increased flexibility, novel synergies, and additional optimization. Several examples of specific energy utilization are discussed and evaluated with respect to energy storage applications. The article describes various technologies for energy storage and their potential applications in the context of Germany’s Energiewende, i.e. the transition towards a more sustainable energy system. Therefore, the existing legal framework defines some of the discussions and findings within the article, specifically the compensation for renewable electricity providers defined by the German Renewable Energy Sources Act, which is under constant reformation. While the article is written from a German perspective, the authors hope this article will be of general interest for anyone working in the areas of energy systems or energy technology.

37 citations


Journal ArticleDOI
TL;DR: The role of chloride impurities in molten NaNO3-KNO3 (solar salt) mixture on corrosion behavior of low-chromium ferritic-martensitic X20CrMoV11-1 steel (X20) and stainless steel 316 (SS316) was studied at 600
Abstract: The role of chloride impurities in molten NaNO3-KNO3 (solar salt) mixture on corrosion behavior of low-chromium ferritic-martensitic X20CrMoV11-1 steel (X20) and stainless steel 316 (SS316) was studied at 600 °C. Gravimetric and metallographic methods were employed to characterize the kinetics of oxidation and the resulting corrosion products. Steel X20 showed non-protective character in both low- (up to 0.02 wt% Cl−) and high- (up to 0.25 wt% Cl−) chloride salts by forming a thick and non-compact oxide scale. A significant increase in weight gain was observed when X20 steel was immersed in the high-chloride-containing salt. Furthermore, the scale underwent severe deformation. SS316 showed superior corrosion resistance in both low- and high-chloride salts. Oxide scales formed on both steels included two zones: an outer Na-rich oxide and an inner mixed oxide based on Fe2O3 and Fe3O4 structures. The morphology and composition of these zones were significantly different on X20 and SS316 steels. A passive Cr-rich oxide layer at the metal/oxide interface was characterized as a protective layer. In the case of stainless steel 316 this layer showed even higher continuity when tested in the high-chloride salt resulting in better protection during the isothermal test.

32 citations


Journal ArticleDOI
TL;DR: In the bioelectrochemical system, no lag phase occurred and specific growth rate of C. necator was 0.09 h⁻¹, and electrochemical robustness of the reaction media was proven.
Abstract: Microbial electrosynthesis is a relatively new research field where microbial carbon dioxide fixation based on the energy supplied by a cathode is investigated. Reaction media used in such bioelectrochemical systems have to fulfill requirements of classical biotechnology as well as electrochemistry. The design and characterization of a medium that enables fast electroautotrophic growth of Cupriavidus necator in microbial electrosynthesis was investigated in detail. The identified chloride-free medium mainly consists of low buffer concentration and is supplied with trace elements. Biotechnologically relevant parameters, such as high-specific growth rates and short lag phases, were determined for growth characterization. Fast growth under all conditions tested, i.e. heterotrophic, autotrophic and electroautotrophic was achieved. The lag phase was shortened by increasing the FeSO₄ concentration. Additionally, electrochemical robustness of the reaction media was proven. Under reductive conditions, no deposits on electrodes or precipitations in the media were observed and no detectable hydrogen peroxide evolved. In the bioelectrochemical system, no lag phase occurred and specific growth rate of C. necator was 0.09 h⁻¹. Using this medium shortens seed train drastically and enables fast electrobiotechnological production processes based on C. necator.

31 citations


Journal ArticleDOI
TL;DR: In this paper, anorganische Photokatalysatoren wie goldbeladenes Titandioxid zur effizienten Bereitstellung geeigneter Mengen an H2O2 durch reduktive Aktivierung von Umgebungssauerstoff and simultaner Oxidation von Methanol eignen und gleichzeitig eine hohe Reaktivitat and Stabilitat des Enzyms gewahrleisten.
Abstract: Selektive Oxyfunktionalisierungen von inerten C-H-Bindungen konnen unter milden Bedingungen durch den Einsatz von Peroxygenasen erreicht werden. Dieser Ansatz wird jedoch durch die schlechte Stabilitat der Enzyme in Anwesenheit stochiometrischer Mengen des Oxidationsmittels Wasserstoffperoxid erschwert. Hier zeigen wir, dass sich anorganische Photokatalysatoren wie goldbeladenes Titandioxid zur effizienten Bereitstellung geeigneter Mengen an H2O2 durch reduktive Aktivierung von Umgebungssauerstoff und simultaner Oxidation von Methanol eignen und gleichzeitig eine hohe Reaktivitat und Stabilitat des Enzyms gewahrleisten. Mithilfe dieses Ansatzes konnte die stereoselektive Hydroxylierung von Ethylbenzol zu (R)-1-Phenylethanol in hoher Enantioselektivitat (>98 % ee) und sehr hoher katalytischer Produktivitat (TON>71.000) erreicht werden.

29 citations


Journal ArticleDOI
TL;DR: In this article, a completely integrated photocatalyst-light emitter units which are wirelessly powered from outside the reaction vessel using resonant inductive coupling were investigated. And they demonstrated the universal applicability of the concept, three representative photocatalytic reactions, H2O2 production, methylene blue degradation and nitrobenzene reduction to aniline.

27 citations


Journal ArticleDOI
TL;DR: In this article, the authors present an overview of the current state of the art in high-temperature corrosion research, and sketch an outlook on expected future developments in this area.
Abstract: High-temperature corrosion research will face a significant change in the near future. Up until now, this research area was dominated by materials issues related to the use of fossil fuels in energy conversion and transportation. Recent political decisions in many of the industrialized countries resulted in a paradigm shift towards the preference of non-fossil renewable energy and CO2 neutral or CO2-free technologies. These political constraints driving the development of new energy conversion technologies in combination with new materials and new manufacturing methods lead to new challenges in high-temperature corrosion research. The availability of advanced investigation techniques as well as increased IT power provides significant potential for the improved in-depth understanding of corrosion mechanisms and the development of comprehensive and reliable lifetime models. The present overview addresses all these aspects and attempts to sketch an outlook, although incomplete, on expected future developments in high-temperature corrosion research.

27 citations


Journal ArticleDOI
Thomas Krieg1, Franziska Enzmann1, Dieter Sell, Jens Schrader1, Dirk Holtmann1 
TL;DR: In this article, the correlation between the parameters XBH and XBA of the activated sludge model number 1 (ASM1) and the measured current flow in MFCs was investigated for the first time.

Journal ArticleDOI
Michael Schütze1
19 Sep 2017-JOM
TL;DR: In this paper, the role of the operation environment in high-temperature abrasion resistance is discussed. And the authors address the recent developments in these areas and the requirements for future work, including thermal barrier coatings on TiAl and surface quality in additive manufacturing.
Abstract: In the temperature range where TiAl alloys are currently being used in jet engine and automotive industries, surface reaction with the operating environment is not yet a critical issue. Surface treatment may, however, be needed in order to provide improved abrasion resistance. Development routes currently aim at a further increase in operation temperatures in gas turbines up to 800°C and higher, and in automotive applications for turbocharger rotors, even up to 1050°C. In this case, oxidation rates may reach levels where significant metal consumption of the load-bearing cross-section can occur. Another possibly even more critical issue can be high-temperature-induced oxygen and nitrogen up-take into the metal subsurface zone with subsequent massive ambient temperature embrittlement. Solutions for these problems are based on a deliberate phase change of the metal subsurface zone by diffusion treatments and by using effects such as the halogen effect to change the oxidation mechanism at high temperatures. Other topics of relevance for the use of TiAl alloys in high-temperature applications can be high-temperature abrasion resistance, thermal barrier coatings on TiAl and surface quality in additive manufacturing, in all these cases-focusing on the role of the operation environment. This paper addresses the recent developments in these areas and the requirements for future work.

Journal ArticleDOI
TL;DR: In this article, hollow graphitized carbon spheres (HGS) with mesoporous structure were tested as catalyst support in middle temperature (90-110°C) direct methanol fuel cell (DMFC) cathode.
Abstract: In conventional low temperature PEM fuel cells, catalyst activity and stability rely on adequate structure and morphology of carbon support material, especially at the cathode that is exposed to high potential values. Degree of graphitization as well as pore distribution are decisive parameters for corrosion resistivity, catalyst utilization and mass transport. In this work, hollow graphitized carbon spheres (HGS) with mesoporous structure were tested as catalyst support in middle temperature (90–110 °C) direct methanol fuel cell (DMFC) cathode. Influence of catalyst loading and concentration as well as working temperature on power density was studied in a 5 cm 2 laboratory cell. Best results in terms of MEA performance were achieved with a catalyst loading of 2 mg Pt cm −2 at both electrodes and an extremely dense Pt concentration on carbon support of 50 and 40 wt% at the anode and cathode, respectively at 110 °C. Additionally, thermal pretreatment of carbon-supported catalyst up to 850 °C led to increase in particle size up to 7 nm and as a consequence to substantial higher ECSA retention during accelerated degradation test (ADT) under half-cell conditions.

Journal ArticleDOI
TL;DR: The relationship between morphology and productivity and the positive effects of micro- and macroparticle enhanced cultivation on rebeccamycin production with this strain in the pellet-like morphology was investigated and an adjusted mechanical stress, through the addition of macro-shaped glass bead particles, led to the desired increase in productivity.

Journal ArticleDOI
TL;DR: It is demonstrated that it is in principle possible to further exploit the EMCP by establishing an alternative central carbon metabolic pathway in M. extorquens AM1, opening many possibilities for the biotechnological production of EMCP-derived compounds in future.
Abstract: The ethylmalonyl-CoA pathway (EMCP) is an anaplerotic reaction sequence in the central carbon metabolism of numerous Proteo- and Actinobacteria. The pathway features several CoA-bound mono- and dicarboxylic acids that are of interest as platform chemicals for the chemical industry. The EMCP, however, is essential for growth on C1 and C2 carbon substrates and therefore cannot be simply interrupted to drain these intermediates. In this study, we aimed at reengineering central carbon metabolism of the Alphaproteobacterium Methylobacterium extorquens AM1 for the specific production of EMCP derivatives in the supernatant. Establishing a heterologous glyoxylate shunt in M. extorquens AM1 restored wild type-like growth in several EMCP knockout strains on defined minimal medium with acetate as carbon source. We further engineered one of these strains that carried a deletion of the gene encoding crotonyl-CoA carboxylase/reductase to demonstrate in a proof-of-concept the specific production of crotonic acid in the ...


Journal ArticleDOI
TL;DR: In this paper, the compositional and microstructural changes, which occur during the thermocyclic exposure, are correlated with the mechanical properties of NiAl diffusion coatings Prior to and after thermoclic exposure at 900, 1050 and 1100 °C for durations up to 1000h four-point bending flexural tests with in-situ acoustic emission measurement are used to determine the fracture strain of the coating.

Journal ArticleDOI
Hendrik Schewe1, Andrea Kreutzer2, Isabell Schmidt1, Christian Schubert2, Jens Schrader1 
TL;DR: Lowering the pH during the bioprocess and increasing trace element and vitamin concentrations prevented loss of cell dry weight concentration in the maturation phase and proved to be critical for astaxanthin concentration and purity.
Abstract: Astaxanthin additions to animal diets predominantly serve as colorization aid to satisfy consumer expectations and desire for a consistent product with familiar coloration, e.g. the characteristic pink colorization of the flesh of species being produced by aquaculture. The heterobasidiomycetous yeast Phaffia rhodozyma (Xanthophyllomyces dendrorhous) can be used as natural feed source of astaxanthin. However, currently, the majority of astaxanthin used for the feed market is produced by chemical synthesis. We present a further step in direction of a competitive production of natural astaxanthin in an optimized bioprocess with non-genetically modified Phaffia rhodozyma. After medium optimization AXJ-20, a mutant strain of P. rhodozyma wild-type strain ATCC 96594, was able to grow to a cell dry weight concentration of over 114 g per kg of culture broth in a fed-batch process. In this bioprocess, where pH was lowered from 5.5 to 3.5 during the maturation phase, AXJ-20 produced the highest value reported for astaxanthin production with P. rhodozyma up to now: 0.7 g astaxanthin per kg of culture broth with a space-time-yield of 3.3 mg astaxanthin per kg of culture broth per hour. Lowering the pH during the bioprocess and increasing trace element and vitamin concentrations prevented loss of cell dry weight concentration in the maturation phase and proved to be critical for astaxanthin concentration and purity.

Journal ArticleDOI
TL;DR: There is strong evidence for the slow oxygen reduction being one the causes, as the competing back-reduction of nitrate leads to the release of nitrogen dioxide, and engineering the photocatalyst for a better oxygen reduction efficiency should also increase the nitrate selectivity.
Abstract: Semiconductor photocatalysis could be an effective means to combat air pollution, especially nitrogen oxides, which can be mineralized to nitrate. However, the reaction typically shows poor selectivity, releasing a number of unwanted and possibly toxic intermediates such as nitrogen dioxide. Up to now, the underlying principles that lead to this poor selectivity were not understood so a knowledge-based catalyst design for more selective materials was impossible. Herein, we present strong evidence for the slow oxygen reduction being one the causes, as the competing back-reduction of nitrate leads to the release of nitrogen dioxide. Consequently, engineering the photocatalyst for a better oxygen reduction efficiency should also increase the nitrate selectivity.

Journal ArticleDOI
TL;DR: A tunable L-rhamnose inducible system was established and characterized using enhanced green fluorescent protein (eGFP) and the novel plasmid expands the tool box for engineering the highly flexible production host C. necator.

Journal ArticleDOI
TL;DR: A new strategy for the synthesis of peracids was investigated, based on a continuous stirred tank reactor and the avoidance of liquid/liquid interfaces by performing the reaction in a single-phase organic solution, which enables high peracid space-time yields with a reduced demand of enzymes.

Journal ArticleDOI
TL;DR: In this paper, the microstructure evolution of (Si,Pt)-modified aluminide coatings has been investigated by means of SEM, EDX, XRD and EPMA.
Abstract: The microstructure evolution of (Si,Pt)-modified aluminide coatings has been investigated. Coatings were prepared by slurry silico-aluminizing of different thicknesses of platinum-electroplated GTD-111 Ni-based superalloy. Microstructure and phase characterizations were conducted by means of SEM, EDX, XRD and EPMA. The composition of the coating's outer layer altered from single β-(Ni,Pt)Al phase to two phase β-NiAl + PtAl 2 by increasing the initial Pt thickness. Silicon diffusion into the coating is shown to be less in the presence of the PtAl 2 phase. Furthermore, refractory metal-containing precipitates in the outer two phase layer of the platinum modified coating were replaced by silicides in the corresponding (Si,Pt)-modified aluminide coating.

Journal ArticleDOI
TL;DR: In this article, chromium and aluminum diffusion coatings were developed and applied on P91 steel for an application in modern fossil power plants with biomass combustion, and the improvement of the corrosion resistance was illustrated using metallographic methods such as electron probe micro-analysis.
Abstract: In modern fossil power plants, biomass is used more and more as secondary fuel in addition to coal. This leads to a significant decrease of the carbon footprint of such power plants. However, the demands on the corrosion resistance of the materials in the boilers increase because of chlorine in the atmosphere and salt-containing sulfides and chlorides. Heat-resistant ferritic–martensitic steels such as P91 are of great interest as superheater material. However, their corrosion resistance has to be improved for an application in modern fossil power plants with biomass combustion. For this purpose, chromium and aluminum diffusion coatings were developed and applied on P91 steel. The uncoated and coated material was investigated in a simulated biomass–brown coal ash with CaSO4, Na2SO4, K2SO4, KCl, and Al2O3 deposits and an atmosphere containing nitrogen with H2O, CO2, O2, SO2, and HCl. The improvement of the corrosion resistance is illustrated using metallographic methods such as electron probe micro-analysis.

Journal ArticleDOI
TL;DR: The current work shows prospects of using directed evolution to generate P450 enzymes suitable for use with alternative electron delivery systems, including zinc/cobalt(III)sepulchrate as electron delivery system for an increased hydroxylation activity of 1,8-cineole.
Abstract: Directed evolution is a powerful method to optimize enzyme properties for application demands. Interesting targets are P450 monooxygenases which catalyze the stereo- and regiospecific hydroxylation of chemically inert C-H bonds. Synthesis employing P450s under cell-free reaction conditions is limited by low total turnover numbers, enzyme instability, low product yields and the requirement of the expensive co-factor NADPH. Bioelectrocatalysis is an alternative to replace NADPH in cell-free P450-catalyzed reactions. However, natural enzymes are often not suitable for using non-natural electron delivery systems. Here we report the directed evolution of a previously engineered P450 CinA-10aa-CinC fusion protein (named P450cin-ADD-CinC) to use zinc/cobalt(III)sepulchrate as electron delivery system for an increased hydroxylation activity of 1,8-cineole. Two rounds of Sequence Saturation Mutagenesis (SeSaM) each followed by one round of multiple site-saturation mutagenesis of the P450 CinA-10aa-CinC fusion protein generated a variant (Gln385His, Val386Ser, Thr77Asn, Leu88Arg; named KB8) with a 3.8-fold increase in catalytic efficiency (28 µM-1 min-1) compared to P450cin-ADD-CinC (7 µM-1 min-1). Furthermore, variant KB8 exhibited a 1.5-fold higher product formation (500 µM µM-1 P450) compared to the equimolar mixture of CinA, CinC and Fpr using NADPH as co-factor (315 µM µM-1 P450). In addition, electrochemical experiments with the electron delivery system platinum/cobalt(III)sepulchrate showed that the KB8 variant had a 4-fold higher product formation rate (0.16 nmol (nmol) P450-1 min-1 cm-2) than the P450cin-ADD-CinC (0.04 nmol (nmol) P450-1 min-1 cm-2). In summary, the current work shows prospects of using directed evolution to generate P450 enzymes suitable for use with alternative electron delivery systems.

Journal ArticleDOI
TL;DR: With the ospCSTR augmented by enzyme dosing, this work reports an economical process for a chemo-enzymatic epoxidation of sensitive terpenes like e.g., α-pinene.

Journal ArticleDOI
TL;DR: In this paper, a mathematical model is developed in which the different steps which are required for the formation of metal chlorides and their removal from the surface are described, and it is assumed that the slowest of such formation or transport steps determines the kinetics of high temperature corrosion.
Abstract: Operating atmospheres of many industrial high temperature processes contain a certain amount of halogens, in most cases chlorine. Halogens have the tendency of forming volatile metal chlorides of the general formula MxCly, which are well known to play a critical role in high temperature corrosion processes, when present at a significant amount. Thermodynamic calculations give a valuable hint, whether a reaction product can occur and how volatile such products can potentially be, when the partial pressures are calculated. However, such calculations reflect thermodynamically stable conditions, while in open systems the local kinetics control the process of surface reactions. For each specific condition, the reaction rates and thus the corrosion rates have to be determined. In previous work, we have shown that corrosion kinetics which lead to the formation of volatile products follows different steps. In this work, a mathematical model is developed in which the different steps, which are required for the formation of metal chlorides and their removal from the surface are described. It is assumed that the slowest of such formation or transport steps determines the kinetics of high temperature corrosion. The application of this model on the literature data shows that by this model it becomes possible to identify the slowest and therefore rate determining step.

Journal ArticleDOI
TL;DR: DaNa2.0 serves as a platform to implement trusted knowledge on nanomaterials for an objective discussion, hindering both risk assessment for nanommaterials, as well as the knowledge communication to all involved stakeholders.
Abstract: The use of nanotechnology and advanced materials promises to revolutionise many areas of technology and improve our daily life. In that respect, many positive effects on the environment are expected, either directly, by developing new technologies for remediation, filtering techniques or energy generation, or indirectly, by e.g. saving resources due to lower consumption of raw materials, or lower energy and fuel consumption due to reduced weight of vehicles. However, such beneficial effects of new technologies are often confronted by concerns regarding the safety of novel substances or materials. During the past 10 years, great effort has been put into research on potential hazards of nanomaterials towards environmental organisms. As the methodology for reliable assessment of nanomaterials was immature, many studies reporting contradictory results have been published, hindering both risk assessment for nanomaterials, as well as the knowledge communication to all involved stakeholders. Thus, DaNa2.0 serves as a platform to implement trusted knowledge on nanomaterials for an objective discussion.

Journal ArticleDOI
TL;DR: The impact of the particle addition to the Streptomyces cultures on the sustainability of the bioprocess was proven by using the E-factor, which denotes the amount of waste generated per product equivalent.

Journal ArticleDOI
TL;DR: The design of an optimal process is particularly crucial when the reactants deactivate the biocatalyst and the reaction cascades of the chemo‐enzymatic epoxidation where the intermediate peroxy acid is produced by an enzyme are still limited by enzyme inhibition and deactivation by hydrogen peroxide.
Abstract: The design of an optimal process is particularly crucial when the reactants deactivate the biocatalyst. The reaction cascades of the chemo-enzymatic epoxidation where the intermediate peroxy acid is produced by an enzyme are still limited by enzyme inhibition and deactivation by hydrogen peroxide. To avoid additional effects caused by interfaces (aq/org) and to reduce the process limiting deactivation by the substrate hydrogen peroxide, a single-phase concept was applied in a fed-batch and a continuous process (stirred tank), without the commonly applied addition of a carrier solvent. The synthesis of peroxyoctanoic acid catalyzed by Candida antarctica lipase B was chosen as the model reaction. Here, the feasibility of this biocatalytic reaction in a single-phase system was shown for the first time. The work shows the economic superiority of the continuous process compared to the fed-batch process. Employing the fed-batch process reaction rates up to 36 mmol h−1 per gramcat, and a maximum yield of 96 % was achieved, but activity dropped quickly. In contrast, continuous operation can maintain long-term enzyme activity. For the first time, the continuous enzymatic reaction could be performed for 55 h without any loss of activity and with a space-time yield of 154 mmol L−1 h−1, which is three times higher than in the fed-batch process. The higher catalytic productivity compared to the fed-batch process (34 vs. 18 gProd g−1cat) shows the increased enzyme stability in the continuous process.

Journal ArticleDOI
TL;DR: A mediated electroenzymatic process to regenerate the NADPH in combination with an old yellow enzyme was investigated and process conditions with high productivities and 90% electron transfer efficiency were identified.
Abstract: Old yellow enzymes are able to catalyze asymmetric C=C reductions. A mediated electroenzymatic process to regenerate the NADPH in combination with an old yellow enzyme was investigated. Due to the fact that the overall process was affected by a broad set of parameters, a design of experiments (DoE) approach was chosen to identify suitable process conditions. Process conditions with high productivities of up to 2.27 mM/h in combination with approximately 90% electron transfer efficiency were identified.