Nanofiltration for the Separation of Nonvolatile Products from Solutions Containing Ionic Liquids

Nanofiltration (NF) can be used to isolate nonvolatile compounds from solutions containing ionic liquids (IL). This was shown for the mixtures bromophenol blue/IL and lactose/IL. In both cases the product was rejected while the ionic liquid permeated. Alternatively, the rejection of the ionic liquid is possible as well. Such separations are possible because nanofiltration membranes are selective towards size and charge of the components.     

Kontinuierliche Reaktionsführung mit löslichen Enzymen

Continuous processes with soluble enzymes. This paper surveys the use of continuously operating enzyme-membrane reactors with enforced flow where the retention of soluble enzymes in the reaction vessel is achieved by means of an ultrafiltration membrane. This technique has been commercialized in the acylase process for the synthesis of L -amino acids on a 200 ton/year level. It is especially useful for the application of multi-enzyme systems with cofactor regeneration. The synthesis of L -tert-leucine from the corresponding α-keto acid has been achieved on a kilogram scale. Coenzymes coupled to water soluble polymers are retained in the membrane-reactor together with the enzymes. Use of suitable conditions prevents loss of enzyme and coenzyme by passage through the membrane or by deactivation. Therefore the costs of enzymes and coenzymes are no longer limitations for economic processes. In the continuously operating enzyme-membrane reactor regeneration of the coenzyme up to 600 000 times was achieved. In continuous peptide synthesis space-time yields of 25 kg/(l d) were obtained. To suppress side reactions very high catalyst concentrations are possible, yielding residence times below 4 min.     

Polymerized ionic liquids-based hydrogels with intrinsic antibacterial activity: Modern weapons against antibiotic-resistant infections

In this study, the inherent antibacterial activity of 11 different polymerized ionic liquids (PILs)-based hydrogels as well as their corresponding monomers was examined in an extensive screening. The methicillin-resistant Staphylococcus aureus Xen 30 (MRSA Xen 30) and Pseudomonas aeruginosa Xen 5 (P. aeruginosa Xen 5) were chosen as test microorganisms. Both are typical representatives of gram-positive and gram-negative bacteria, respectively. Six of the 11 tested monomers were able to eradicate more than 80% of P. aeruginosa Xen 5 cells in suspension. Unfortunately, the anionic, neutral and zwitterionic representatives lost their function after polymerization. However, the cationic gels retained their antibacterial activity with nearly 100% eradication of selected microorganisms - even at the smallest amount tested. Bactericidal activity against gram-positive MRSA Xen 30 was high when the bacteria were treated with the imidazolium-based monomers. Five of the tested compounds showed rather limited bactericidal activity <50% killed bacteria. The weak antibacterial activities could be significantly increased by crosslinking them to three-dimensional networks. As a result, all the hydrogels possessed strong killing efficiencies of at least 68% and were able to maintain this activity even at low hydrogel volume fractions. These findings are very promising for the development of new antibacterial materials for medical applications, for example, stent coatings.     

Einfluss der Reaktorkonfiguration auf die Enantioselektivität einer kinetischen Racematspaltung

The optical purity of a product at the reactor outlet depends not only on the enantioselectivity of the catalyst, but also on the reactor configuration. Different reactor configurations are compared with respect to the enantiomeric excess (ee) at a respective conversion that can be achieved in a kinetic resolution of a racemate. For batch, fed‐batch and plug flow reactors enantioselectivities (E value) of 35 are sufficient to achieve high enantiomeric excess. For a continuously operated stirred tank reactor high ee values are only obtained for E values higher than 190.     

Fuzzy filtering for robust bioconcentration factor modelling

This study introduces a fuzzy filtering based technique for rendering robustness to the modelling methods. We consider a case study dealing with the development of a model for predicting the bioconcentration factor (BCF) of chemicals. The conventional neural/fuzzy BCF models, due to the involved uncertainties, may have a poor generalization performance (i.e. poor prediction performance for new chemicals). Our approach to improve the generalization performance of neural/fuzzy BCF models consists of (1) exploiting a fuzzy filter to filter out the uncertainties from the modelling problem, (2) utilizing the information about uncertainties, being provided by the fuzzy filter, for the identification of robust BCF models with an increased generalization performance. The approach has been illustrated with a data set of 511 chemicals (Dimitrov, S., Dimitrova, N., Parkerton, T., Comber, M., Bonnell, M., Mekenyan, O., 2005. Base-line model for identifying the bioaccumulation potential of chemicals. SAR and QSAR in Environmental Research 16 (6), 531–554) taking different types of neural/fuzzy modelling techniques.     

In situ generated O-glycan core 1 structure as substrate for Gal(beta 1-3)GalNAc beta-1,6-GlcNAc transferase

beta-Galactosidase from bovine testes was used in a one pot reaction together with a recombinant beta-1,6-GlcNAc transferase for the synthesis of GlcNAc(beta 1-6)GalNAc(alpha 1-OBn) (core 6-Bn). The galactosidase, which reversibly links galactose via a (beta 1-3) linkage to N-acetylgalactosamine, provides the substrate for the GlcNAc transferase in situ. The synthesis was carried out with a yield > 90%.     

Integrated optic polymeric components fabricated withmicrostructured strip-off covers

Fabrication of integrated optic polymeric components by moulding waveguide and fibre alignment grooves to a substrate in a one-step process, and subsequently filling the waveguide grooves by means of a microstructured strip-off cover which is later removed, is presented. The latest measurement results on waveguide attenuation, coupling losses owing to passive fibre-waveguide coupling and excess loss values are given     

Novel paclitaxel-coated angioplasty balloon catheter based on cetylpyridinium salicylate: Preparation,characterization and simulated use in an in vitro vessel model

Drug-coated balloons (DCB), which have emerged as therapeutic alternative to drug-eluting stents in percutaneous cardiovascular intervention, are well described with regard to clinical efficiency and safety within a number of clinical studies. In vitro studies elucidating the correlation of coating method and composition with DCB performance are however rare but considered important for the understanding of DCB requirements and the improvement of established DCB. In this context, we evaluated the applicability of a pipetting, dip-coating, and spray-coating process for the establishment of DCB based on paclitaxel (PTX) and the ionic liquid cetylpyridinium salicylate (Cetpyrsal) as novel innovative additive in three different compositions. Among tested methods and compositions, the pipetting process with 50 wt.% PTX resulted in most promising coatings as drug load was less controllable by the other processes and higher PTX contents led to considerable drug crystallization, as visualized by electron microscopy, accelerating PTX loss during short-term elution. Applying these conditions, homogeneous coatings could be applied on balloon catheter, whose simulated use in an in vitro vessel model revealed percental drug losses of 36 and 28% during transit and percental drug transfers of 12 and 40% under expansion for coatings applied in expanded and folded balloon condition, respectively. In comparison to literature values, these results support the high potential of Cetpyrsal as novel DCB matrix regarding low drug loss and efficient drug transfer.