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RWTH Aachen University, Diss., 2017; 166 pp., (2017)., In the last two decades, the exponential increase of pharmaceuticals and personal care products (PPCPs) in the aquatic environment has received growing concern due to their potential risks to the environment and human health. PPCPs can undergo a series of physical, chemical and/or microbial transformation processes in natural water and engineered systems, to form a wide range of transformation products (TPs). Some TPs may be more persistent and toxic than their parent compounds. However, identification of TPs is a major challenge due to the great diversity of chemicals, the unknown or incomplete understanding of transformation processes, the complexity of the matrices under which the chemicals may be present, and their low concentrations in the environment. More importantly, there is a lack of knowledge regarding toxicity, biological endpoints, and other bio-tools available for the toxicological assessment of both known and unknown TPs.This PhD dissertation aims to study transformation processes of PPCPs in natural water and wastewater treatment plants (WWTPs), and further to evaluate the toxicological effects of the parent compounds and their TPs. For this purpose, we developed an efficient laboratory workflow, which combined electrochemistry-mass spectrometry (EC-MS) and toxicological bioassays together. EC online coupling with MS can simulate transformation reactions in EC cell and detect transformation products in the following mass spectrometers, which was applied in the present study to study transformation mechanisms of PPCPs. The electrochemical reactions were scaled up in a batch EC reactor to receive larger amounts of a reaction mixture, which was subsequently purified and concentrated by solid phase extraction (SPE). Toxicological tests were conducted for the parent compound and its reaction mixture. The workflow can provide a simple and rapid laboratory method for transformation study and risk assessment of PPCPs in water. Carmazepine (CBZ) was chosen as a model compound to verify the workflow. It was proven that the workflow can efficiently screen transformation products and possible toxicological effects of TPs.Electrochemical advanced oxidation processes (EAOPs) are developed for the prevention and remediation of persistent organic pollutants in water treatment. Persistent fluoroquinolones antibiotics (FQs) can be effectively treated by EAOPs. While the removal of FQs during EAOPs, a series of hydroxylation and piperazinyl ring cleavage TPs were formed with the fluoroquinolone core unchanged. Oxidation mixtures of ciprofloxacin (CIP) and Norfloxacin (NOR) retained the antibacterial properties with lower activity compared to their parent compounds, while the antibacterial activity of OFL was almost eliminated after oxidation. In the algal growth inhibition test, the toxicity of CIP and NOR to the green algae (Desmodesmus subspicatus) after electrochemical oxidation, remained unchanged, while that of OFL significantly increased. Although electrochemical oxidation efficiently removed the FQs in water, the potential environmental risks of the FQs after EAOPs should be highlighted due to the residual antibacterial activity and increase toxicity of their TPs.With regard to bioactive PPCPs, biotransformation is one of the most important transformation processes in natural water and WWTPs. Triclosan (TCS), a widely used antimicrobial agent, is toxic to aquatic organisms and may have endocrine disrupting effects. Biodegradation is an efficient way to remove TCS. EC-MS is recognized as a suitable tool to mimic phase I metabolism reactions catalyzed by cytochrome P450, which was used for simulation of biotransformation processes in the present study. Hydroxylation, methoxylation, ether cleavage and cyclization of TCS during simulated biotransformation formed eight TPs. Two dioxin derivatives (OH-DCDD and MeO-DCDD) and three chlorinated phenols (2,4-DCP, 3,5-dichlorocatechol and chlorohydroquinone) were detected, which may be persistent and toxic compounds. Hydroxyl- and methyl- TCS were also found. TCS and six TPs were estimated to have toxic potential by QSAR modeling and can mainly cause AhR-mediated dioxin like effects. The toxicity of TCS on zebrafish embryos was found to slightly increase after simulated biotransformation, indicating the formation of toxic products.Finally, a literature review demonstrated various exposure and effected-analysis tools, which can be used for toxicological evaluation of known and unknown TPs. The review discussed the usages and limitations of chemical analysis of TPs and hence suggests the potential suitability of these bioassays to be used as additionally regulatory tool.In conclusion, the present dissertation contributes to a laboratory workflow as an alternative of traditional methods to study transformation processes of PPCPs in natural water and WWTPs. This workflow can be applied to investigate more organic pollutants in future study, in particular, to provide early-stage assessment of new chemicals introduced to the environment. The workflow is also recommended to support regulation decisions in the utility of organic chemicals., Published by Aachen

Considerable effort has been dedicated to the chemical depolymerization of lignin, a biopolymer constituting a possible renewable source for aromatic value-added chemicals. However, these efforts yielded limited success up until now. Efficient lignin conversion might necessitate novel catalysts enabling new types of reactions. The use of multiple catalysts, including a combination of biocatalysts, might be necessary. New perspectives for the combination of bio- and inorganic catalysts in one-pot reactions are emerging, thanks to green chemistry-driven advances in enzyme engineering and immobilization and new chemical catalyst design. Such combinations could offer several advantages, especially by reducing time and yield losses associated with the isolation and purification of the reaction products, but also represent a big challenge since the optimal reaction conditions of bio- and chemical catalysis reactions are often different. This mini-review gives an overview of bio- and inorganic catalysts having the potential to be used in combination for lignin depolymerization. We also discuss key aspects to consider when combining these catalysts in one-pot reactions

Characterization of carbon nanotube dispersions requires measurement of both, concentration and surface area.

RWTH Aachen University, Diss., 2017; 230 Seiten(2017). = RWTH Aachen University, Diss., 2017, Lignocellulosic biomass constitutes a promising renewable feedstock for replacement of crude oil for the production of fuels and chemicals. Next to cellulose, lignin is the second most abundant biomass component making up around 25 % of the world’s biomass. Lignin is predominantly used for the production of heat and power. However, due to the aromatic structure lignin could serve as a renewable feedstock for valuable functionalized aromatic chemicals if it can be depolymerized effectively. Basidiomyceteous white-rot fungi effectively degrade lignin in nature using a mixture of extracellular enzymes. Consequently, applying these enzymes for lignin depolymerization might present an interesting alternative to the chemical options usually considered. The present thesis explores the potential valorization of lignin through oxidative depolymerization by applying lignin modifying enzymes (LMEs). Moreover, a new high-throughput microplate respiratory assay for efficient characterization of oxygen consuming LMEs like laccases and glucose oxidases was developed. Furthermore, an enzyme immobilization method initially developed for the immobilization of laccases on fumed silica nanoparticles (fsNP) was optimized and adapted for the immobilization of several LMEs on fsNP and superparamagnetic nanoparticles (MPs) to allow enzyme reuse and enhance enzymatic stability.The high-throughput microplate respiratory assay allows multi-parallel measurement of O2-consumption by enzymatic reactions in 24 or 96 well plate formats. The newly developed and validated method enables the comparative quantitation of LME characteristics. Moreover, in comparison to assays based on substrate transformation measurements, it allows direct assessment of the enzymatic activity, provides information about reaction stoichiometry, and is unaffected by possible radical chain reactions or competition between different substrates. Therefore, it allows obtaining ample data on enzymes using oxygen as a substrate and has the potential to illuminate aspects of enzymatic reactions that cannot be assessed using common enzymatic assays focusing on product formation. Enzyme immobilization on nano-composites, i.e., fsNP was performed following a previously developed immobilization method. This method was adapted and optimized for enzyme immobilization on fsNP using laccase as model enzyme regarding the consumables required. Next it was amended in order to allow immobilization of specific enzyme combinations enabling the production of defined multi-enzyme fsNP. Finally, it was further optimized in order to allow for a more efficient production of enzyme-fsNP on the kilogram-scale. Subsequently, the method was adapted for enzyme immobilization on MP and optimized regarding specific activity and stability of the biocatalysts using response surface methodology (RSM). The biocatalysts showed considerably higher stability compared with the dissolved enzymes over a pH range from 3 to 9 and in the presence of several chemical denaturants. Different LME and LME combinations were screened regarding their ability to degrade lignin in the presence and absence of organic co-solvents. Organic solvents were used to increase the accessibility of the hydrophobic biopolymer to the enzymes. Considerable oxidation of lignin could be achieved using oxidative LME in combination with organic solvents. Especially in mixtures containing dimethyl sulfoxide (DMSO) or methanol (MeOH) the formation of stable monomeric substances was observed. The main monomeric reaction product was identified as 2,6-dimethoxy benzoquinone (DMBQ) and was produced at a yield of up to 2.20±0.05 wt%. However, higher molecular weight reaction products were produced as well indicating the occurrence of lignin condensation and polymerization reactions.Several redox-mediators were tested in combination with laccases to extend the reactivity of the enzymes beyond phenolic groups on lignin. Five different technical lignins were used as feedstock. Furthermore, after biocatalytic treatment the water insoluble lignin was treated in an additional step leading to formic acid induced lignin depolymerization. The sequential treatment allowed the production of considerable amounts of lignin oligomers as well as some phenolic monomeric compounds. Yields depended on the exact treatment as well as the lignin material used. One lignin, i.e., soda lignin from wheat straw was selected for further process optimization using RSM. At optimized conditions up to 45 wt% of lignin could be solubilized either in aqueous solution after the first treatment or in ethyl acetate (EtAc) after the second (chemical) treatment. The solubilized products were mainly low molecular weight aromatic mono- and oligomers. The developed process constitutes a promising first step towards a possible lignin valorization strategy. However, further improvements of the process as well as more detailed study of downstream processing and possible applications of reaction products are necessary before realization can be considered., Published by Aachen

Additional file 1. The German version of original article.

Additional file 1. The 20th Annual Meeting of SETAC GLB took place September 7–10, 2015 in Zurich, Switzerland. The complete program and abstracts are available as Additional file 1.