Biocatalytic Synthesis of Nitriles through Dehydration of Aldoximes: The Substrate Scope of Aldoxime Dehydratases

Nitriles, which are mostly needed and produced by the chemical industry, play a major role in various industry segments, ranging from high‐volume, low‐price sectors, such as polymers, to low‐volume, high‐price sectors, such as chiral pharma drugs. A common industrial technology for nitrile production is ammoxidation as a gas‐phase reaction at high temperature. Further popular approaches are substitution or addition reactions with hydrogen cyanide or derivatives thereof. A major drawback, however, is the very high toxicity of cyanide. Recently, as a synthetic alternative, a novel enzymatic approach towards nitriles has been developed with aldoxime dehydratases, which are capable of converting an aldoxime in one step through dehydration into nitriles. Because the aldoxime substrates are easily accessible, this route is of high interest for synthetic purposes. However, whenever a novel method is developed for organic synthesis, it raises the question of substrate scope as one of the key criteria for application as a “synthetic platform technology”. Thus, the scope of this review is to give an overview of the current state of the substrate scope of this enzymatic method for synthesizing nitriles with aldoxime dehydratases. As a recently emerging enzyme class, a range of substrates has already been studied so far, comprising nonchiral and chiral aldoximes. This enzyme class of aldoxime dehydratases shows a broad substrate tolerance and accepts aliphatic and aromatic aldoximes, as well as arylaliphatic aldoximes. Furthermore, aldoximes with a stereogenic center are also recognized and high enantioselectivities are found for 2‐arylpropylaldoximes, in particular. It is further noteworthy that the enantiopreference depends on the E and Z isomers. Thus, opposite enantiomers are accessible from the same racemic aldehyde and the same enzyme.     

The Effect of Antibacterial Particle Incorporation on the Mechanical Properties,Biodegradability, and Biocompatibility of PLA and PHBV Composites

The composites based on polylactide (PLA) and poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) with the addition of antibacterial particles: silver (Ag) and copper oxide (CuO) are characterized. Basic mechanical properties and biodegradation processes, as well as biocompatibility of materials with human cells are determined. The addition of Ag or CuO to the polymers do not significantly affect their mechanical properties, flammability, or biodegradation rate. However, several differences between the base materials are observed. PLA‐based composites have higher tensile and impact strength values, while PHBV‐based ones have a higher modulus of elasticity, as well as better mechanical properties at elevated temperatures. Concerning biocompatibility, each of the tested materials support the growth of fibroblasts over time, although large differences are observed in the initial cell attachment. The analysis of hydrolytic degradation effects on the structure of materials shows that PHBV degrades much faster than PLA. The results of this study confirm the good potential of the investigated biodegradable polymer composites with antibacterial particles for future biomedical applications.     

Advanced Measures to Characterize Mechanical Properties of Refractories

The thermomechanical modelling method is becoming an important tool nowadays for the refractory researchers,suppliers and end-users. On one hand,applications focus on the post-mortem thermomechanical analysis to interpret the occurred failure phenomena of refractories in service. On the other hand,a priori investigation is very helpful for the design of refractory lining concepts before putting them into effect; as a result it will minimize the probability of refractory lining premature failure and save costs for the refractory suppliers as well as for the end-users. For both investigation routines,suitable material constitutive models and testing approaches are of relevance. Existing material constitutive models often used for refractories are the fictitious crack model acting for tensile failure,the Mohr-Coulomb or Drucker-Prager model describing shear failure,and the Norton-Bailey model representing creep. To characterize the tensile and shear failure of refractories at room temperature and elevated temperatures,a wedge splitting test and a modified shear test can be applied,respectively. The creep behavior and corresponding creep parameters of refractories can be determined with an appropriate creep testing device at elevated loads. The proper application of material constitutive models and testing approaches allows for improving the thermo-mechanical modelling and the optimization of the lining design.     

Structure‐Based Mechanism of Oleate Hydratase from Elizabethkingia meningoseptica

Hydratases provide access to secondary and tertiary alcohols by regio‐ and/or stereospecifically adding water to carbon‐carbon double bonds. Thereby, hydroxy groups are introduced without the need for costly cofactor recycling, and that makes this approach highly interesting on an industrial scale. Here we present the first crystal structure of a recombinant oleate hydratase originating from Elizabethkingia meningoseptica in the presence of flavin adenine dinucleotide (FAD). A structure‐based mutagenesis study targeting active site residues identified E122 and Y241 as crucial for the activation of a water molecule and for protonation of the double bond, respectively. Moreover, we also observed that two‐electron reduction of FAD results in a sevenfold increase in the substrate hydration rate. We propose the first reaction mechanism for this enzyme class that explains the requirement for the flavin cofactor and the involvement of conserved amino acid residues in this regio‐ and stereoselective hydration.     

Funktionspolymere-ein interdisziplinäres forschungsgebiet-

Functional polymers differ from structural polymers in various aspects. The most evident difference is their lack of visibility as they are mostly empolyed in surface applications, e.g. as crystal growth modifiers to inhibit encrustation in detergents, as hair setting agents, or as electro-conductive films. Additional important differences concerning the motivation for new developments, market aspects, and customer relationships are the subject of this paper. The development of technology and market competence in the field of functional polymers and the special problems of low-volume, high-performance chemicals are discussed in detail. The paper deals with examples of recent developments: Polyaramides for membranes, 3,4-polyethylenedioxythiophene as an electroconductive polymer, polyaspartic acid as a biodegradable polycarboxylate in detergents, highly crosslinked, insoluble vinylpyrrolidone/vinylimidazole copolymers for the removal of heavy metals from wine, and finally an insoluble, crosslinked polyvinylpyrrolidone-iodine complex for the sterile filtration of liquids. The outlook discusses the research challenges which remain before a full understanding of the structure/property relationships can be attained.     

Solution Structure and Dynamics of the Small Protein HVO_2922 from Haloferax volcanii

Past sequencing campaigns overlooked small proteins as they seemed to be irrelevant due to their small size. However, their occurrence is widespread, and there is growing evidence that these small proteins are in fact functionally very important in organisms found in all kingdoms of life. Within a global proteome analysis for small proteins of the archaeal model organism Haloferax volcanii, the HVO_2922 protein has been identified. It is differentially expressed in response to changes in iron and salt concentrations, thus suggesting that its expression is stress-regulated. The protein is conserved among Haloarchaea and contains an uncharacterized domain of unknown function (DUF1508, UPF0339 family protein). We elucidated the NMR solution structure, which shows that the isolated protein forms a symmetrical dimer. The dimerization is found to be concentration-dependent and essential for protein stability and most likely for its functionality, as mutagenesis at the dimer interface leads to a decrease in stability and protein aggregation.     

Development of enhanced three-dimensional printed packings for scale-up of distillation columns: A successful case study

This publication presents a general approach for the enhancement of packings regarding scalability, separation efficiency, and fluid dynamic properties using three-dimensional (3D) printing. The methodology is used to develop miniaturized, scalable packings for process development, and scale-up applications. For this purpose, a 3D printable computer-aided design version of the Rombopak 9M industrial packing (RP9M-3D), which is known for its positive scalability properties, was created. An initial characterization by means of computational fluid dynamics simulations and mass transfer measurements reveals positive but also negative design properties. These findings are used to create a more advanced, miniaturized packing structure, the XW-Pak. The evolved structure is compared to the RP9M-3D. The simulation and experimental results show that the enhanced packing, which is still in the early stages of development, exhibits higher separation efficiencies with improved scalability properties at the same void fraction and surface area than the RP9M-3D.     

Modulation of Aβ42 Aggregation Kinetics and Pathway by Low-Molecular-Weight Inhibitors

The aggregation of amyloid-β 42 (Aβ42) is directly related to the pathogenesis of Alzheimer's disease. Here, we have investigated the early stages of the aggregation process, during which most of the cytotoxic species are formed. Aβ42 aggregation kinetics, characterized by the quantification of Aβ42 monomer consumption, were tracked by real-time solution NMR spectroscopy (RT-NMR) allowing the impact that low-molecular-weight (LMW) inhibitors and modulators exert on the aggregation process to be analysed. Distinct differences in the Aβ42 kinetic profiles were apparent and were further investigated kinetically and structurally by using thioflavin T (ThT) and transmission electron microscopy (TEM), respectively. LMW inhibitors were shown to have a differential impact on early-state aggregation. Insight provided here could direct future therapeutic design based on kinetic profiling of the process of fibril formation.     

Schadstoffe in Altholz

Occasionally, it is assumed that wood can be fed into an endless usage cascade. This assumption is investigated based on data from new and used chipboards, as well as waste wood of category AI–AIII. The results show, based on 468 data sets, that pollutant concentrations in waste wood vary over a wide range. Depending on the sample group, 46 % to 69 % of the samples examined would not be suitable for material use according to the applicable Waste Wood Ordinance. It must be assumed that waste wood already contains pollutants in relevant concentrations after a single use and can therefore only be fed into the material cycle a second time after the results of an analytical examination are available. An organoleptic examination is not sufficient for this purpose.     

Analytical Methods for the Rapid Determination of Solid Biofuel Quality

Fuel properties of solid biofuels are essential aspects for the energy-efficient and low-emission operation of biomass heat and power plants. Hence, fuel quality parameters are often defined and used for pricing in supply contracts. To simplify and accelerate analytical approaches, rapid analysis devices are required to determine fuel properties such as water- and ash content, calorific value, and chemical composition on-site. This article gives an overview about available technologies and, if applicable, their current state of use as rapid analysis devices for solid biofuels.