Parmi les maladies affectant les pommes, la moisissure bleue causée par Penicillium expansum est une préoccupation majeure. Elle cause des pertes de rendement et de qualité dues également à la production de mycotoxines telles que la patuline (PAT) et la citrinine (CIT). La PAT est la plus alarmante en raison de ses propriétés cytotoxiques, génotoxiques et immunosuppressives.L'Union européenne (UE) a établi des réglementations spécifiques pour protéger la santé des consommateurs et des niveaux maximaux de 50 g / kg sont fixés pour les jus de fruits et les produits dérivés, 25 g / kg pour les purées de pommes et les compotes et 10 g / kg pour les aliments destinés aux bébés et aux jeunes enfants. En dépit de ces mesures, la PAT continue à être présente dans les aliments et / ou les boissons commerciaux, dépassant parfois les limites maximales. Des recherches supplémentaires sont par conséquent nécessaires pour minimiser la contamination des produits alimentaires par cette mycotoxine et son champignon producteur. Bien que la plupart des études sur P. expansum soient essentiellement centrées sur la PAT, le génomede ce champignon présente d'autres clusters de métabolites secondaires (SM) prédits dont certains peuvent être associés à des métabolites potentiellement toxiques. Afin de contrôler la synthèse de SM, l'étude des facteurs de transcription globaux régulant leur production est essentielle. Dans une première partie, le gène veA, appartenant à la famille des protéines du complexe velvet, a été caractérisé et son impact sur le développement du champignon, sa virulence et son métabolisme secondaire a été élucidé. La délétion de ce gène a conduit à une réduction de la production de PAT et de CIT et à une diminution de l'expression de leurs clusters de gènes. VeA a également un impact global sur le métabolisme secondaire, puisque 15 des 35gènes de structure présentent une régulation différentielle sur les milieux testés. Dans une deuxième partie, l’influence de l’acide ascorbique (AA) sur la concentration de PAT dans le jus de pomme trouble a été étudiée à la fois en laboratoire et en milieu semi-industriel. Une méthodologie analytique séparant la PAT et d'autres composés générés au cours de la réaction aété optimisée. Les conditions optimales d'action de l’AA sur la PAT ont été analysées. De plus,nous avons identifié des produits de dégradation moins toxiques que la PAT et résultant du traitement par l’AA. Pour conclure, cette thèse se rattache à la gestion des risques de la PAT dans le secteur des fruits ; elle apporte des connaissances et des améliorations significatives tant sur le plan fondamental que sur le plan pratique. Ces avancées résident principalement dans la description d'une souche mutée de P. expansum moins toxique que celle naturellement retrouvée dans la nature, et décrivant un additif alimentaire améliorant les qualités de nombreux produits transformés et diminuant la concentration de PAT en générant des composés moins toxiques. / Among diseases affecting apples, blue mould caused by Penicillium expansum is a major concern. It causes yield and quality losses, as well as food safety issues due to the production of mycotoxins such as patulin (PAT) and citrinin (CIT). PAT is the most worrying one and has cytotoxic, genotoxic and immunosuppressive properties. The European Union (EU) has established specific regulations to protect the consumer’s health and maximum levels of PAT of 5 g/kg is set for fruit juices and derived products, 25 g/kg for apple purees and compotes and 10g/kg for food intended for babies and young children. However, PAT is still found in commercial food and/or beverage products, sometimes exceeding the maximum limits and more research is needed to minimize contamination of food products by this mycotoxin and its fungus. Even though most studies on P. expansum have focused on PAT itself, the genome of this fungus exhibits other predicted secondary metabolite (SM) clusters, some of which may be associated with potentially toxic metabolites. In order to control the synthesis of SMs, the study of global transcription factors regulating their production is essential. In a first part, the veA gene, belonging to the velvet family, was characterised and its impact on the development of the fungus, its virulence and its secondary metabolism was elucidated. The disruption of this gene led to the failure in PAT and CIT production and a decrease in the expression of their gene cluster. It also revealed a global impact on the secondary metabolism, as 15 of 35 backbone genes showed differential regulation on the media tested. In a second part, the influence of ascorbic acid (AA) on the concentration of PAT in cloudy apple juice was studied on both lab and semi-industrial scale. An analytical methodology separating PAT and other compounds generated during the reaction was optimized. Optimal conditions of action of AA on PAT were studied. In addition, degradation products less toxic than PAT and resulting from AA treatment were identified. To conclude, this thesis is part of the risk management of PAT in the fruit sector; it provides significant improvements at both fundamental and practical levels. These advances are mainly characterized by the description of a mutated strain of P. expansum that is less toxic than that naturally occurring in nature, and the description of a food additive that improves numerous products qualities and affects PAT concentration, thusgenerating less toxic compounds

The subject of this thesis is the study of the degradation of polyurethanes in the weather conditions on the waste dumps and observation of the penetration of the potential degradation products into the environment.

The diploma thesis is focused on the identification of degradation products of organic dye Saturn Red L4B resulting by degradation in diaphragm discharge, using separation techniques with mass spectrometric detection.

Synthetic polymer materials have been a part of human life since the 20th century. A variety of their use had resulted in a growing demand for their mass production, which then led to their increasing accumulation at waste dumps. After their deposition, these materials are exposed to many environmental factors causing their decomposition and subsequent release of the degradation products into the environment. This thesis is focused on the analysis of the photodegradation products from synthetic polymer materials and particularly polyurethane foams modified with the biodegradable fillers. One dimensional GC/MS and two dimensional comprehensive gas chromatography with time-of-flight mass spectrometry (GCxGC/TOF-MS ) were used for the measurements. The most of photodegradation products of polyurethane foams are injurious to health and environment.

No description available.

A solid phase extraction (SPE) method was developed for simultaneous extraction of dicarboxylic acids and diols formed during hydrolysis of poly(butylene succinate), PBS, and poly(butylene adipate), PBA. The developed SPE method and subsequent GC-MS analysis were used to extract, identify and quantify low molecular weight products migrating from linear and branched poly(butylene adipate) (PBA) and poly(butylene succinate) (PBS) during aging in aqueous media. The combination of SPE and GC-MS proved to be a sensitive tool, able to detect small differences in the degradation rate during early stages of hydrolysis before any significant differences were observed by weight loss and molecular weight measurements. The detected low molecular weight products included monomers i.e. adipic acid and 1,4-butanediol for the PBA polymers and succinic acid and 1,4-butanediol for PBS. Several dimers and trimers i.e. hydroxybutyl adipate, hydroxybutyl succinate, di(hydroxybutyl) adipate, di(hydroxybutyl) succinate and hydroxybutyl disuccinate were also detected. Best extraction efficiency for 1,4-butanediol and succinic acid was achieved with a hydroxylated polystyrene-divinylbenzene resin as solid phase. Linear range for the extracted analytes was 1-500 ng/ml for adipic acid and 2-500 ng/ml for 1,4-butanediol and succinic acid. Detection and quantification limits for all analytes were between 1-2 ng/ml (S/N=3) and 2-7 ng/ml (S/N=10) respectively. Relative standard deviations were between 3 % and 7 %. Comparison of measured weight loss and the amount of monomeric products showed that weight loss during early stages of hydrolysis was mainly caused by the release of water-soluble oligomers that on prolonged ageing were further hydrolyzed to monomeric species. Significant differences in degradation rate could be assigned to degree of branching, molecular weight, aging temperature and degradation medium. Linear and branched PBA was mixed with PVC in solution cast films to study the effects of molecular weight and branching on plasticizer efficiency. Used as polymeric plasticizer, PBA formed a semi-miscible two-phase system with PVC where the amorphous part exhibited one single glass transition temperature and the degree of polyester crystallinity was dependent on molecular weight, degree of branching and blend composition. Plasticizing efficiency was favored by higher degree of branching and a 40 weight-percent polyester composition. / QC 20101209

The use of degradable biomedical materials has during the past decades indeed modernized medical science, finding applications in e.g. tissue engineering and drug delivery. The key question is to adapt the material with respect to mechanical properties, surface characteristics and degradation profile to suit the specific application. Degradation products are generally considered non-toxic and they are excreted from the human body. However, large amounts of hydroxy acids may induce a pH decrease and a subsequent inflammatory response at the implantation site. In this study, macromolecular design and a combination of cross-linking and adjusted hydrophilicity are utilized as tools to control and tailor degradation rate and subsequent release of degradation products from biomedical polyester-ethers. A series of different homo- and copolymers of -caprolactone (CL) and 1,5-dioxepan-2-one (DXO) were synthesized and their hydrolytic degradation was monitored in phosphate buffer solution at pH 7.4 and 37 °C for up to 546 days. The various materials comprised linear DXO/CL triblock and multiblock copolymers, PCL linear homopolymer and porous structure, and random cross-linked homo- and copolymers of CL/DXO using 2,2’-bis-(ε-caprolactone-4-yl) propane (BCP) as a cross-linking agent. The results showed that macromolecular engineering and controlled hydrophilicity of cross-linked networks were useful implements for customizing the release rate of acidic degradation products in order to prevent the formation of local acidic environments and thereby reduce the risk of inflammatory responses in the body. / QC 20101109

No description available.

No description available.

Konventionelle hitzesterilisierte, glukosehaltige Peritonealdialyselösungen (PDL) sind aufgrund ihres niedrigen pH-Wertes, ihrer hohen Glukosekonzentration und Osmolalität und ihres Gehaltes an Glukosedegradationsprodukten (GDP) bioinkompatibel. Alternativen zu glukosehaltigen PDL stellen aminosäuren- oder icodextrinhaltige PDL dar. Daneben enthalten auch neuere Glukose-PDL in Doppelkammersystemen aufgrund der Sterilisation von Glukose bei sehr niedrigem pH nur noch sehr geringe GDP-Konzentrationen. In dieser Arbeit wurden die akuten und chronischen Wirkungen verschiedener PDL auf humane peritoneale Mesothelzellen (HPMC) untersucht. Konfluente HPMC wurden mit den zu testenden PDL (glukosehaltige hitze- versus filtersterilisierte und konventionelle versus Doppelkammer-Glukose-PDL, 1% Aminosäuren-PDL und Icodextrin - alle bei neutralem pH-Wert) akut (1-4 Stunden Präinkubation) bzw. chronisch (bis zu 10 Tage) inkubiert. Die Zellvitalität (MTT-Assay) und IL-1beta-stimulierte Sekretion von IL-6 (Zellfunktion) wurden untersucht. Die akute und chronische Exposition von HPMC gegenüber hitzesteriliserten Peritonealdialyselösungen führte zu einer signifkanten Reduktion von Vitalität und Funktion der Zellen. Demgegenüber führte die Inkubation mit filtersteriliserten PDL und GDP-armen PDL zu einer weniger starken Beeinflussung von Vitalität und Funktion. Die aminosäurenhaltige PDL beeinflusste weder akut noch chronisch die Vitalität bzw. Funktion der Zellen negativ. Hingegen unterschied sich die icodextrinhaltige Lösung nicht wesentlich von der hitzesteriliserten PDL mit hohem Glukoseanteil. Die Verringerung des Gehaltes an GDP in PDL mittels Filtersterilisation bzw. alternativer Sterilisation in Zweikammerbeuteln hat einen positiven Einfluss auf Vitalität und Funktion von HPMC in vitro. Der Ersatz des osmotischen Agenz hingegen bedeutet nicht zwansgläufig eine bessere Biokompatibilität. / Conventional heat-sterilized glucose-containing peritoneal dialysis fluids (PDF) are bioincompatible due to their acidic pH, high glucose concentration and resulting hyperosmolality, and the presence of glucose degradation products (GDP). Alternatives to these solutions are PDL containing amino acids or icodextrin as the osmotic agent. Furthermore, novel glucose-based PDF contain only trace amounts of GDPs due to the sterilisation of glucose at very low pH in a dual-chamber container system. The present study examines the acute and chronic effects of different PDL on human peritoneal mesothelial cells (HPMC). Confluent HPMC were exposed to the different test PDF (glucose containing heat- versus filter-sterilised PDF and conventional versus dual-chambered glucose PDF, 1% amino-acid PDF and icodextrin – all at neutral pH) in an acute (1-4 hours preincubation) and chronic (up to 10 days) cell culture model. Cell viability (MTT assay) and IL-1beta stimulated IL-6 (cell function) release were assessed. Acute and chronic exposure of HPMC to heat-sterilised PDF resulted in a significant reduction of viability and cell function. In contrast, the incubation of filter-sterilised PDF and dual chambered low GDP solution had only minor effects on cell viability and function. Neither viability nor cell function were negatively affected by the amino-acid PDF following acute and chronic exposure. However, incubation with icodextrin resulted in a similar degree of inhibition as compared to incubation with conventional heat-sterilised glucose PDF. In conclusion, removal of GDP from PDF either via filter-sterilisation or manufacture in dual chambered containers helps to conserve viability and function of HPMC in vitro. However, the replacement of the osmotic agent per se does not necessarily result in improved biocompatibility.