Title Promoter Affiliations Abstract "Collisional excitation of nitrile molecules in the interstellar medium" "Jérôme Loreau" "Quantum Chemistry and Physical Chemistry" "Molecules are ubiquitous in the universe and can be used to gain insights into the composition and evolution of stars and galaxies. Among these, about one third are composed of six atoms or more and are termed “organic” as they contain at least one carbon atom. The presence of these molecules in space demonstrates that a complex chemistry occurs even at low temperatures and densities, and their study can inform us about the conditions that prevailed when the solar system formed. Nitriles in particular have been detected in a wide variety of astrophysical environments. A major bottleneck of models developed to determine the abundance of these molecules arises from the lack of information on the collisional excitation of molecules, in particular for molecules that consist of more than five atoms. The main objective of this project is to develop and use methods to compute rate coefficients for the rotational excitation of nitrile organic molecules by collisions with helium atoms or hydrogen molecules in the interstellar medium based on ab initio potential energy surfaces. This will lead to an improved knowledge of the abundance of nitriles molecules in space as well as to a better understanding of gas-phase processes." "Zinc protoporphyrin IX formation in relation to the colouring of nitrite-free dry fermented sausages." "Ilse Fraeye, Chris Michiels" "Bioengineering Technology, Ghent and Aalst Technology Campuses, Centre for Food and Microbial Technology" "The colour of fresh meat is mainly determined by myoglobin, which is found in large quantities in mammalian muscles (≈ 30% of the total muscle proteins). Myoglobin has a globular structure and consists of one chain of 153 amino acids enclosing a non-protein heme group. This heme group, an iron-containing protoporphyrin IX, is the active center of myoglobin and directly responsible for the colour of meat.Traditionally, sodium nitrite and/ or potassium nitrate are used for the colouring of meat products. Nitric oxide (NO), formed after the reduction of the added nitrite and/ or nitrate, is bound to heme. This resulting nitrosyl myoglobin gives raw meat products their characteristic red colour.Consumers are increasingly aware of the impact and the importance of a healthy lifestyle and therefore have a growing interest in healthy food. Because of this increasing awareness, the use of ""chemical"" additives is becoming less obvious. Especially sodium nitrite (E250) and potassium nitrate (E252) are controversial. Although nitrite also increases the microbial shelf-life and safety, this additive is nevertheless considered to be undesirable as it is involved in the formation of carcinogenic N-nitrosamines. Therefore, strict regulations were formulated to limit the use of nitrite and nitrate. Under current European legislation, the maximum allowed amount of sodium nitrite for all meat products is only 150 mg / kg [Directive 2006/52 / EC].For a long time nitrosyl myoglobin was regarded as the only molecule that could give meat products their attractive red colour. In contrast to this generally accepted idea, however, it was established in 2004 that the red colour of Parma ham, a traditional Italian dried ham, was not due to the formation of nitrosyl myoglobin but zinc protoporphyrin IX was identified as the colour-forming pigment. Similar to heme, zinkprotopofyrine IX has a protoporphyrin IX structure, but instead of iron zinc is complexed in the pyrrole ring.Until now, the formation mechanism of zinc protoporphyrin IX has not yet been clarified sufficiently. More knowledge about this red pigment, however, would be interesting to replace sodium nitrite or potassium nitrate in other meat products with regard to the colour formation, such as, for example, in dry fermented sausages. The purpose of this doctoral study is to assess whether zinc protoporphyrin IX can be formed during the production of nitrite-free dry fermented sausage and what effect it has on colour formation. Additionally, investigation will be done on the influence of product and process factors on formation of this natural pigment, in order to obtain an attractive colour in meat products without any addition of additives." "Climate-smart soil management strategies for sorghum production at the Lake Victoria Basin of Kenya" "Jan Diels" "Forest, Nature and Landscape, Soil and Water Management" "Study Title: Impact of organic amendments on Soil Properties and GHG Emissions, and Performance of Grain Sorghum Background of the study The atmospheric concentration of carbon dioxide (CO2) has risen by over 40 % since 1750 and continues to rise at the rate of 2.0 ± 1.0 ppm Y-1 (IPCC, 2014). The rising concentration of CO2 and other greenhouse gases (GHGs) has caused a significant increase in global mean air temperatures (Allen et al., 2004). The rising air temperatures have led to increased heat waves, high evapotranspiration rates and subsequently, high decomposition rates in most tropical soils (Tebaldi et al., 2006). From the modeling perspective, Martin et al. (2021) estimated that a 30 to 40% increase of carbon (C) input will be necessary to obtain a 40/00 annual increase of soil organic carbon (SOC) stocks over 30 years. But there is a biophysical limitation to the 40/00 that is linked to soil nutrients, particularly to Nitrogen (N). C and N cycles are tightly coupled and increase of C input also increases the demand for N. This may impact the N cycle and associated N2O emissions. Secondly, organic amendments such as manures contain readily decomposable N-rich compounds; there is a significant risk that they may enhance N2O emissions (Cayuela et al., 2010). This study will explore a number of knowledge gaps. Firstly, little is known about the actual interactions between the SOC dynamics and the N-cycle over the entire growing season under field conditions. Secondly, little understanding exists on whether the process controlling production of N2O in presence of poultry manure is a consequence of change in N and/or P-availability. Lastly, biochar enhances organo-mineral interactions and increases water holding capacity (WHC), soil pH, Ca2+ and Mg2+ availability in soil (Glaser et al., 2002; Chan et al., 2007). Can this translate to enhanced nutrient use efficiency under different soil types? Statement of the problem In most tropical environments, sustainable agriculture faces significant constraints due to low nutrient status and rapid mineralization of SOM as a result of increasing temperatures (Zech et al., 1997). This has led to negative nutrient balances across the whole of Sub-Saharan Africa, by 26 kg N, 3kg P and 19 kg K ha-1 yr-1 (Drechsel et al., 2001). Under such circumstances, the efficiency of applied fertilizers is low. The long term benefit of assigning more land to agriculture will not offset the negative environmental impacts of land degradation in the future (Tilman et al., 2002). Instead, a more holistic approach which includes improved soil fertility management, attention to crop varieties, in aggregate leading to reduced negative impacts and improved sustainability is vital (Barrow, 2012). Application of biochar to soils is now considered as a potential valuable input and remedy to restore soil fertility. This consequently, raises agricultural productivity while restoring carbon for long-term, which helps to mitigate climate change. This study will assess how N2O emissions may be affected by increased SOC pools in presence or absence of biochar on different soil types. Study goal To investigate biochar, poultry manure and their mixture as tools to enhance and sustain agricultural productivity, as well as reduce greenhouse gas emissions through improved soil quality. Specific objectives include: i. To determine the effect of poultry manure, biochar and their mixture on soil physico-chemical properties. ii. To evaluate the effect of poultry manure, biochar and their mixture on nutrient uptake and nutrient use efficiency of sorghum. iii. To investigate the impact of poultry manure, biochar and their mixture on carbon sequestration and GHG emissions on different soil types. iv. To determine the effect of poultry manure, biochar and their mixture on growth and grain yield of sorghum. Hypotheses i. The application of biochar, poultry manure and their mixture would improve soil properties such as water holding capacity, soil pH and nutrient availability. ii. The application of biochar, poultry manure and their mixture would improve nutrient uptake and nutrient use efficiency of sorghum. iii. The addition of biochar and biochar-poultry manure mixture would enhance carbon sequestration and reduce GHG emissions. iv. The application of biochar, poultry manure and their mixture would improve growth and grain yield of sorghum. Justification of the study The production of N2O is increasingly being linked to an increase in denitrification which may be driven by a provision of C to denitrifiers during methane (CH4) oxidation. A better understanding of such interactions is necessary to evaluate the benefits of different management practices aimed at increasing SOC storage and to predict the full GHG balance of each practice. The effects of multiple types of organic amendments on SOC storage and N2O emissions have been evaluated in short-term experiments for various soil types, climates, soil incorporation practices and amendments types including crop residues, manure, composts of various origin and maturation stages and sewage sludge. A meta-analysis (Charles et al., 2017) concluded that the N2O emission factors (EFs) related to N inputs were mainly controlled by the C:N ratios of the added material, but that many other factors influenced emission, such as soil properties (texture, drainage, SOC and N content), and climatic factors. However, studies focusing on the effects of organic soil amendments at field scale are limited; there is therefore an urgent need to study N2O emissions at field scale level in order to improve assessments of the effect of climate change. Biochar use is one of the methods with highest potential to sequester carbon in soils compared to natural C-cycle. It is a carbon rich by-product of lignocellulosic biomass pyrolysis. Its usage has been identified as an essential strategy for reducing greenhouse gas emissions by enhancing carbon sequestration (Cayuela et al., 2014). Its efficiency is twofold; It has high proportion of the feedstock C bound in persistent molecular structures obtained from slow pyrolysis of OM, it has longer mean residence time in soils than SOM; that is >100 years verses about 50 years. In combining the above effects; biochar appears at least eight times more efficient at storing SOC than the return of non-pyrolysed residues (Abel et al., 2013). Materials and methods The trials will be conducted in two different sites at the Lake Victoria Basin; the soil types are chromic acrisols and nito-rhodic ferralsols (FAO, 2014). Soil physiochemical properties including soil water content (SWC), soil pH, electrical conductivity (EC), total soil organic carbon (SOC), total nitrogen (N), available phosphorous (P), nitrate-nitrogen (NO3-N), ammonium-nitrogen (NH4-N), exchangeable cations, cation exchange capacity (CEC) and emission of carbon dioxide (CO2) and nitrous oxide (N2O). Plant parameters including leaf chlorophyll content, specific leaf weight, Leaf C, N, P, K concentrations, plant height, biomass and grain yield and nutrient use efficiency (NUE). Soil analysis Soil pH will be measured in H2O and in 0.01 M CaCl2 using pH meter and a 1:2.5 soil weight to extractant-volume ratio. Soil water content (SWC) at 0-12 cm depth will be taken using a HydroSense II soil moisture probe (Campbell Scientific, Inc.). CO2 and N2O fluxes will be quantified using static chambers. Gas samples will be analyzed by gas chromatograph equipped with Flame Ionization Detector (FID) for CO2 and Electronic Capture Detector (ECD) for N2O. The EC will be determined by a conductivity meter on a 1:2.5 soil: water suspension (Rayment and Higginson, 1992). Exchangeable K, Na, Ca and Mg will be determined using 1M ammonium acetate extraction buffered at pH 7, at a soil: solution ratio of 1: 20 (Rayment and Higginson, 1992) and atomic absorption analysis. CEC will be calculated as the sum of exchangeable K, Na, Ca and Mg. Soil NO3-N and NH4-N will be determined calorimetrically by an automated photometer using 1M KCL extraction method (Rayment and Lyons, 2011). Total N and C concentrations will be determined using an elemental analyzer fitted with a Zero Blank Auto-sampler (Costech Analytical Technologies, INC). Olsen P will be extracted using sodium bicarbonate at a pH of 8.5 and determined using the UV-VIS spectrophotometry (Okalebo et al., 2002). The chemical components of manure and biochar will be determined in the laboratory following similar methods for soil analysis. Plant tissue analysis Relative leaf chlorophyll content will be measured using a SPAD-502 (Konica Minolta, Tokyo) based on transmittance at wavelength regions 650nm (for chlorophyll) and 940 nm (as a control). Total plant N and C concentrations will be determined using an elemental analyzer fitted with a Zero Blank Auto-sampler (Costech Analytical Technologies, INC). Plant P concentration will be determined photometrically using the molybdate blue method (Mills and Jones, 1996). Plant K concentration will be determined after wet digestion with sulfuric acid, by atomic absorption spectrometry (Watson et al., 1990). References Abel, S., Peters, A., Trinks, S., Schonsky, H., Facklam, M., and Wessolek, G. (2013). Impact of biochar and hydrochar addititon on water retention and water repellency of sandy soil. Geoderma 202-203, 183-191. Barrow, C.J. (2012). Biochar: Potential for countering land degradation and for improving agriculture. Applied Geography 34, 21-28. Cayuela, M., Oenema, O., Kuikman, P., Bakker, R., and Van Groenigen, J. (2010). Bioenergy by-products as soil amendments? Implications for carbon sequestration and greenhouse gas emissions: GCB Bioenergy 2, 201-213. Cayuela, M., Van Zwieten, L., Singh, B., Jeffery, S., Roig, A., AND Sanchez-Monedero, M. (2014). Bichar’s role in mitigating soil nitrous oxide emissions: A review and meta-analysis. Agriculture, Ecosystems and Environment 191, 5-16. Chan, K., and Xu, Z. (2009). Biochar: Nutrient properties and their enhancement. In “Biochar for environmental management” (J. Lehmann and S. Joseph, eds.), pp. 67-84. Earthscan London, UK." "Carbonation, decalcification and recalcification of Calcium-Silicate-Hydrate" "Özlem Cizer" "Materials and Constructions" "Background The hydration of cement is a process involving multiple compounds and steps. From the moment water is added to the cement mix, cement grains start dissolving to form an ionic solution. Oversaturation of ions leads to the precipitation of hydration products, in which Calcium-Silicate-Hydrate (C-S-H) is the main constituent phase, bearing most of the calcium in hydrated cement. The physical and chemical properties of C-S-H is of great interest when it comes to designing cementitious materials. Characterization of C-S-H in cement paste is, however, complicated due to its complex structure, lack of long-range order, variation in Ca/Si ratio across the parent specimen, and potential admixtures of Ca(OH)2 (portlandite), CaCO3 (calcite, vaterite or aragonite) or unreacted C3S. Preparation of C-S-H In an effort to understand C-S-H structure, physical and chemical properties, studies have extensively used homogeneous, synthetic single-phase C-S-H prepared from the direct reaction of CaO and SiO2, or the double decomposition of sodium silicate and calcium nitrate. The main advantage of synthetic route is the possibility to easily modify Ca/Si ratio of C-S-H, since Ca/Si is arguable the major factor influencing C-S-H structure. On the opposite, C-S-H obtained from hydrated C3S or OPC paste ensures simlarities to the natural process of hydration. Degradation of C-S-H One of the major concerns when it comes to testing on synthetic C-S-H stems from the popular employment of its powder form. Processes such as carbonation and decalcification are heavily governed by mode of transport within the samples of interest. Likewise, decalcification is a combination of dissolution and diffusion, with the diffusion usually being the rate-limiting process. Therefore, the mode of transport in the specimens will be the governing factor to decalcification. The transfer of carbonation and decalcification knowledge from C-S-H powder to C-S-H embedded in cement matrices requires synthetic C-S-H to be prepared in a 3D shape. In this project, C-S-H from synthetic route will be studied in parallel with C-S-H from natural hydration. Both powder and bulk forms of C-S-H are subjected to similar environmental conditions such as CO2 concentration, relative humidity, NH4NO3 concentration. Such comparison provides an insight into how degradation behaviours differ between different types of C-S-H. Recalcification The process of recalcification was reported twice in the literature. Recalcification promises a reparation to degraded structures, restoring Ca/Si ratio and homogeneity across the samples. Effects of recalcification on different types of C-S-H will be investigated in this project. Research questions: 1) What are the differences in the crystal structure of synthetic C-S-H compared to C-S-H at the same Ca/Si but prepared from hydrated C3S paste, and from hydrated Portland cement? 2) How do different types of C-S-H respond to chemical degradation (carbonation and decalcification), and to recalcification? 3) Are decalcification and recalcification reversible processes? Can recalcification be used to repair Ca/Si of degraded structures? If yes, will C-S-H crystalline structure be the same as the intact reference?" "Textural and (bio) chemical changes during conventional ageing and chemical pre-treatments of common beans: towards understanding the development of the hard-to-cook defect" "Marc Hendrickx" "Food and Microbial Technology (CLMT)" "Soaking followed by cooking is a common method to process raw common bean seeds towards consumption. The hard-to-cook (HTC) defect, that can develop in beans during post-harvest storage at adverse conditions (conventionally aged beans) is an important factor decreasing the cookability of beans, therefore hampering their utilisation. In addition, the texture evolution of beans during cooking could be affected by soaking/cooking media. The studies carried out so far on the HTC defect suggest the pectin-cation-phytate hypothesis facilitated by membrane damages to be the most plausible. This hypothesis states that pectin in the cell wall/middle lamella crosslinks with minerals released from phytate hydrolysis resulting in insoluble pectates, prolonging cooking times required for bean softening. As for texture changes induced by soaking/cooking media (e.g. CaCl2 solutions, sodium acetate buffer and sodium citrate buffer), limited researches explored the mechanisms in detail. Today, the mechanisms of HTC defect/texture changes in beans after storage or treated by specific chemicals have not been fully elucidated. Therefore, the aim of this research work is to investigate the cooking behaviour in relation to compositional changes in conventionally aged beans and beans treated by chemicals to further understand the (bio) chemical reactions involved in texture changes of beans during cooking.In the first study, starting from the pectin-cation-phytate theory, the texture evolution during cooking and associated composition changes in red kidney beans treated by (0.01 M, 0.05 M and 0.1 M) CaCl2 solutions or sodium acetate buffer (0.1 M, pH 4.4, 41 °C with soaking times: 2, 4, 8 and 12 h) were investigated to understand the relation between (bio) chemical reactions and the cooking behaviour. For beans soaked and cooked in CaCl2 solutions, higher Ca2+ concentrations resulted in longer cooking times and higher final bean hardness values. The phytate content in these beans remained constant during cooking while exogenous Ca2+ migrated into the cotyledons and seed coats during soaking and cooking. For beans soaked in sodium acetate buffer for different times, delayed softening associated with increased phytate hydrolysis was observed in beans with longer soaking times in the buffer. This suggests that endogenous Ca2+ released from phytate hydrolysis contributed to the delayed cooking of these beans. It indicates that both exogenous Ca2+ from soaking/cooking media and endogenous Ca2+ from phytate hydrolysis contributed to the texture changes of beans during cooking. These results show that divalent cations (e.g. Ca2+ and Mg2+) are important factors influencing the cookability of beans.To further explore the role of Ca2+ migration in texture changes in detail, in situ cation analysis of beans with different pre-treatments (fresh beans, conventionally aged beans, beans treated in CaCl2 solutions or sodium acetate buffer) was carried out using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). In addition, their degree of pectin methyl esterification (DM) was determined. Texture-based bean classification was exploited in selecting samples to relate the (bio) chemical changes to texture at single bean level. In conventionally aged beans, a negative correlation was shown between pectin DM of beans after soaking and cooked bean texture as well as a positive correlation of the cell wall-bound Ca2+ and texture of cooked beans. This indicates that the pectin DM after storage and pectin Ca2+ crosslinking in the cell wall/middle lamella (promoted by heating) largely contributed to the texture changes observed. In beans treated by CaCl2, crosslinking of pectin with exogenous Ca2+ occurred during soaking but even more so during cooking, delaying bean softening. For beans treated by acetate buffer, the pectin crosslinking with endogenous Ca2+ released from phytate hydrolysis at the cell wall/middle lamella can be the crucial factor delaying bean softening during cooking.Next, the cooking behaviour and phytate changes in ten bean accessions with different pre-treatments (fresh beans soaked in deionised water, conventionally aged beans, beans treated in CaCl2 solution and beans soaked a sodium acetate buffer) were investigated and compared. The potential of using such chemical pre-treatments as a tool to predict the sensitivity of different accessions to HTC development during conventional ageing was explored. Based on the results, it can be concluded that soaking and cooking beans in 0.01 M CaCl2 cannot be used to predict the susceptibility of these bean accessions to develop the HTC. Beans soaked in acetate buffer showed a similar or higher extent of IP6 hydrolysis compared to conventionally aged beans. The significantly positive correlations of IP6 changes in beans undergoing these treatments suggest that soaking in acetate buffer (pH 4.4, 41 °C, soaking time: 12 h) is a good tool to predict IP6 hydrolysis in conventionally aged beans (35 °C, 83% relative humidity, 3 months). In addition, soaking beans in acetate buffer can also be exploited to predicted the cooking time changes in different bean accessions (except for yellow bean-KATB1) after conventional ageing. However, although the HTC to some extents can be predicted in this way, the mechanism of HTC development during conventional ageing might not be identical to the mechanisms involved in the accelerated tests proposed.In the last chapter the potential of soaking in a sodium citrate buffer (0.1 M, pH 4.4, 41 °C, different soaking times) to increase the cookability of beans was explored. The cooking kinetics of beans soaked in citrate buffer for different times suggest that longer soaking times in the buffer promote bean softening during cooking. An evaluation of (bio) chemical changes indicates that the citrate buffer complexes the minerals released from phytate hydrolysis and also limits phytate hydrolysis, therefore inhibiting the cation mediated cross-linking of pectin at the cell wall/middle lamella. On the other hand, the citrate in the soaking medium might also binds inherently bound Ca2+ e.g. initially bound by pectin. Consequently, pectin solubilisation during cooking in beans treated in a citrate buffer was faster compared to fresh beans. Starch gelatinisation and protein denaturation were not responsible for changes in bean softening.This PhD work explored the mechanisms of HTC development reflected in the texture changes of beans during cooking after conventional ageing or chemical pre-treatments (with CaCl2, sodium acetate buffer or sodium citrate buffer). It reveals that pectin-Ca2+ crosslinking (Ca2+ from soaking/cooking media or released from phytate hydrolysis) is the main factor influencing the texture evolution of beans (with different pre-treatments) during cooking. In addition, the utility of chemical pre-treatments as an accelerated test to evaluate the sensitivity towards HTC development was evaluated. Soaking beans in sodium acetate buffer is suggested to predict HTC development in conventionally aged beans. Within addition, soaking in a sodium citrate buffer represents a convenient method to accelerate bean softening during cooking." "Tuning oxidation states of terbium and europium towards high purity terbium-161 and samarium-153 for medical applications" "Koen Binnemans" "Sustainable Chemistry for Metals and Molecules" "Radionuclides have a variety of medical applications as radiopharmaceuticals. The most significant and frequent use is in diagnostic imaging to visualize infected, cancerous or damaged areas (e.g. after a heart attack) in the body. More recently, therapeutic radiopharmaceuticals have gained more interest, particularly in cancer treatment, as the ionizing radiation can target and destroy harmful tumor cells in a precise and selective manner. In recent years, various radionuclides from the lanthanide series have been utilized and are investigated in nuclear medicine. Radiolanthanides are highly promising for use in nuclear medicine due to their chemical similarities, allowing for coordination compounds of the same type to be used in a range of diagnostic and therapeutic applications. Terbium, for instance, has four radioisotopes with distinct decay properties, energies, and half-lives that can be utilized in non-invasive theranostic applications. To produce carrier-free terbium-161, highly enriched gadolinium-160 targets are neutron-irradiated in the Belgian Reactor 2 (BR2). Terbium-161 emits low-energy beta particles along with gamma photons, and possesses properties similar to lutetium-177. Moreover, the co-emission of Auger electrons makes terbium-161 even more attractive for beta and Auger electron therapy.Another example, samarium-153, is a radiolanthanide that can be effectively used in medicine due to its favorable half-life and stable daughter isotope europium-153, which ensures no significant additional side effects in the human body. It is often coordinated by EDTMP, sold commercially as Quadramet® and Lexidronam®, used for treatment of painful bone metastases caused by various cancers. The beta emission of samarium-153 is utilized to destroy harmful cancer cells, and its gamma emission is also used in imaging to visualize infected areas in the human skeleton. Like many other medical radioisotopes, samarium-153 can be most efficiently produced in a nuclear research reactor by irradiating a highly enriched target with neutrons in a high thermal neutron flux, resulting in a product with high yield, purity, and specific activity.In addition to their dominant trivalent oxidation state, some lanthanides can also exist in the divalent or tetravalent oxidation states. This change in valence state alters their chemical properties and make intragroup lanthanide separations easier. Although hydrated terbium(III) ions typically have a highly positive reduction potential, they can be electrochemically oxidized to their tetravalent state and stabilized in highly concentrated carbonate solutions. Terbium(III) can be oxidized to terbium(IV) in aqueous carbonate, nitrate, and periodate media. To examine the stability of terbium(III) complexes in aqueous electrolytes, spectroscopic and elemental analyses were conducted, with a parametric study focusing on pH, terbium concentration, salt concentration, and applied electrical potentials. The lowest applied potential value to oxidize terbium(III) was +0.9 V vs. Ag/AgCl in periodate medium, while nitrate and periodate media offered poor terbium(IV) stabilization compared to a carbonate medium. Therefore, an aqueous carbonate medium appears to be the most promising medium for developing a separation process based on terbium oxidation state change. Successful separation of terbium(IV) from trivalent lanthanides was achieved, performing ion exchange chromatography with the carbonate form of the Dowex-IX8 resin. Sufficient characterization and remarkable reproducibility of the methodology demonstrates the potential of this methodology as a new separation process for the purification of terbium(IV).Finally, the divalent oxidation state of europium was investigated based on the electrochemical reduction of europium(III) to europium(II) in aqueous nitrate, chloride and perchlorate media. The kinetic parameters were studied using a rotating disk electrode. As a next step, separation of samarium from europium was achieved using a TEVA column in nitrate form. The feasibility of this separation method was tested using the samarium-153 and europium-152 radioisotopes in the same concentration ratio as the concentration ratio of these elements present in a dissolved irradiated enriched samarium-152 target." "Assessing genetic and phenotypic diversity of Brettanomyces yeast" "Bart Lievens, Kathleen Marchal" "Bioengineering Technology, Group T Leuven Campus, Computer Science Technology, De Nayer (Sint-Katelijne-Waver) Campus, Centre of Microbial and Plant Genetics" "Brettanomyces yeast species, with Brettanomyces (Dekkera) bruxellensis being the most important, are generally reported to be spoilage yeasts in the beer and wine industry due to the production of phenolic off-flavors. The aromas imparted, which can be described as ‘medicinal and ‘barnyard’, are colloquially known as “Brett” character and are generally considered negative for beer and wine quality. However, the same compounds are regarded positively when produced during certain fermentation processes, such as the production of some styles of beer (e.g. lambic and gueuze). Despite its economic importance, surprisingly little is known about the biology, physiology and ecology of Brettanomyces yeasts. Herein, several aspects of Brettanomyces yeast biology and ecology were studied,  with particular emphasis on B. Bruxellensis, thus contributing to a better understanding of the biology and ecology of these important influencers of flavor profile.In the first chapter (Chapter I), we give a comprehensive literature overview of the state-of-the-art of Brettanomyces research, emphasizing areas that were particularly well explored at the start of this PhD study, including aroma-associated aspects and methods for detection and identification. We also focused on recent genetic and genomic studies providing novel insights into the biology and evolution of B. bruxellensis. In Chapter II, we assessed the genetic relationships between 50 Brettanomyces strains belonging to all species presently identified within the genus and isolated from different food products and beverages using established DNA fingerprinting methods. These methods included ribosomal RNA (rRNA) gene sequencing, random amplified polymorphic DNA (RAPD) PCR, arbitrarily primed (AP) PCR and repetitive element PCR fingerprinting (rep-PCR). Our results support earlier findings that Brettanomyces yeasts form a genetically diverse clade, even within a species, and are represented by several subgroupings. Further our results revealed an intriguing correlation between B. bruxellensis genotype groups and the respective source of isolation, suggesting niche adaptation. To further explore this relationship, we first sequenced a (beneficial) beer isolate of B. bruxellensis (VIB X9085; ST05.12/22) and compared its genome sequence with the genome sequences of two wine spoilage strains (AWRI 1499 and CBS 2499) (Chapter III). In addition to strain-specific single nucleotide polymorphisms (SNPs) and insertions/deletions (InDels), structural genome variation was found between our strain and both wine strains, with some genomic regions specifically deleted in the beer strain. These included, but were not limited to, a region harboring the B. bruxellensis nitrate assimilation cluster and a region representing a cluster of genes mainly involved in carbon metabolism. Next, in Chapter IV, metabolic differences in carbon and nitrogen assimilation between different B. bruxellensis strains from different beverages (beer, wine and soft drink) were thoroughly assessed using Biolog Phenotype Microarrays. While some similarities of physiology were noted, many traits were variable among strains. Interestingly, some phenotypes were found that could be linked to strain origin, especially for the assimilation of particular α- and β-glycosides as well as α- and β-substituted monosaccharides. Based upon gene presence or absence, an α-glucosidase and β-glucosidase were found explaining the observed phenotypes. Further, using a PCR screen on a large number of B. bruxellensis isolates we have been able to specifically link a genomic deletion (e.g. harboring a β-glucosidase gene) to the beer strains, suggesting that this region may have a fitness cost for B. bruxellensis in certain fermentation systems such as brewing. Additionally, our work indicates that most beer strains are diploid, whereas the vast majority of wine strains are known to be triploid, suggesting that the additional set of chromosomes may confer a selective advantage in environments such as wineries. Finally, in Chapter V a series of fermentation tests were performed, in which different B. bruxellensis strains were inoculated in different media representative of different ecological niches of the yeast (i.e. beer, wine and soft drink). Utilisation of different sugars was quantified and production of (off-) flavors was monitored after one month of fermentation. Our results revealed that not only the medium (which may contain different (off-) flavor precursors), but also the yeast strain mediates the formation of the typical Brettanomyces (off-) flavors. Moreover, a (moderate) correlation was found between the origin of the strains and their impact on the volatile composition of the media. Only strains originally isolated from wine produced typical Brettanomyces off-flavors when inoculated in wine, whereas strains originally isolated from beer or soft drink did not, for example. Vice versa, in strong golden pale ale (Duvel), beer strains behaved differently from the other strains. Altogether, these results suggest that the interaction between medium and strain affects the outcome of potential (off-) flavor production.Together, the components of this PhD study provide tools to discriminate Brettanomyces strains and reveal a first glimpse into the genetic diversity and genomic and phenotypic plasticity of B. bruxellensis. Our findings are relevant for the wine industry as well as for the beer industry. After all, deeper understanding of the ecology of B. bruxellensis not only provides novel insights into the evolution of this intriguing yeast species, it will also facilitate avoidance of wine spoilage and improvement of B. bruxellensis strains for brewing." "Roasting and Selective Leaching of NdFeB Magnets" "Bart Blanpain" "Sustainable Chemistry for Metals and Molecules, Sustainable Metals Processing and Recycling, Process Engineering for Sustainable Systems Section" "NdFeB magnets currently dominate the magnet market due to their superior magnetic properties with maximum volume minimization. NdFeB magnets are composed of 25-35 wt. % rare earth elements (REE) along with ca. 1 wt. % B and the rest being transition metals (mainly Fe). REE, other than Nd, such as Dy, Pr, Tb and Gd or exogen elements, other than Fe, such as Al, Co, Ga, Nb, Si, Cu and Zr can also be present as minor admixtures. Depending on the operation medium, these magnets are usually also coated with Ni, Zn, etc. or can be embedded in epoxy. The on-going monopoly of China on REE oxide production in the last two decades along with continuously increasing demand for REE impose serious supply risks for certain REE (e.g. Nd and Dy). Due to their high REE content along with their increasing production rate, efficient recycling options for pre-consumer and end-of-life (EOL) NdFeB magnets are needed to combat that supply problem.To achieve these goals, 3 different hydrometallurgical or combined hydro- and pyrometallurgical flow sheets have been developed and completed within this thesis. These are namely, (1) Sulfation, Selective Roasting and Water Leaching, (2) Nitration, Calcination and Water Leaching, and (3) Complete Leaching, Iron Removal and Electrolysis. Both of the first two flow sheets were a combination of pyro- and hydrometallurgical methods and enabled >95 % REE and 90 wt. %).In the third flow sheet, a different and only-hydrometallurgical approach was taken. Here, in addition to previous targets, it was aimed to recover minor but valuable base metals (e.g. Co, Ni and Cu) along with complete recycling of consumed acid and chemicals after electrolysis stage. However, this stage was found to be problematic and not a good candidate for purification of the leachate for REE. Additional steps were studied to overcome these problems and were found to be quite successful. However, the overall flow sheet extended significantly thereby requiring a justification through economic analysis. In the last phase of the doctorate, a separate work flow was studied, namely, (4) Comparative Oxidation Behaviors of Hydrogenated NdFeB Magnets. Here, it was aimed to investigate the thermal oxidation behaviours of differently hydrogenated magnets. Hydrogenation treatments are the most promising methods to physically remove waste NdFeB magnets from their surroundings. The oxidation tendency of the product after such treatments can be of importance for both direct and indirect recycling routes. While the initial composition of the magnet was found to have little or no effect on the oxidation behaviour of both hydrogenated and non-hydrogenated magnets, the hydrogenation treatment type had direct impact via both particle size distribution and oxidation mechanism. Among all 5 hydrogenation treatments, the hydrogenation decrepitation (HD) method was found to be the most effective treatment for subsequent conventional oxidative roasting-acid leaching flow sheet while disproportionated magnets were found to be the most stable powders." "Green fertilizer upcycling from manure: Technological, economic and environmental sustainability demonstration" "Siegfried Vlaeminck" "Department of Biochemical and microbial technology, Department of Agricultural economics, Department of Plant production, Forschungszentrum Jülich, University of Natural Resources and Life Sciences, University of Santiago de Compostela, University of Girona" "European pigs and cows jointly produce about 1.27 billion tennes of manure per year. a largely unexploited resource of organic carbon and nutrients, and therefore an exquisite 'mining' opportunity. ManureEcoMine proposes an integrated approach to the treatment and reuse of animal husbandry wast in nitrate vulnerable and sensitive areas and beyond. by applying the eco-innovative principles of sustainability. resource recovery and energy efficiency. Technologies of proven efficacy in the wastewater treatment field will be combined in several process configurations to demonstrate their technological and environmental potential at pilot scale for cow and pig manure. Anaerobic digestion (mesophilic/thermophilic), ammonia stripping, struvite precipitation and partial nitritation/anammox will be key technolohies. To render the cradle-to-cradle approach complete. The fertilizer and potential trace contaminants effects of recovered nutrients on plant growth and soil health and emissions will established, and safety will be managed. Life cycle analyses will determine the sustainability of the concept as such. and identify the most environmentally friendly technology and most effective and safe reuse strategy. Finally, the boundaries of economic viability will be determined."