Tuplakuori-rakenne eristettyihin muoviputkiin

Eristettyjen muoviputkien kuljetus- tai asennusvaiheessa on mahdollista, että putken suojakuori rikkoutuu mekaanisen iskun vaikutuksesta ja putken sisään pääsee vettä. Huonoimmassa tapauksessa vesi pääsee etenemään suojakuoren ja eristekerroksen välissä talon sisälle ja aiheuttaa mittavat kosteusvahingot. Tämän diplomityön tarkoituksena oli selvittää, onko eristetylle muoviputkelle mahdollista toteuttaa tuotantotaloudellisesti tuplakuori-rakenne. Tuplakuoren tarkoituksena oli tässä työssä estää putken sisärakenteisiin päässeen veden eteneminen putken pitkittäissuunnassa. Diplomityössä käsiteltiin muutamia vaihtoehtoisia ratkaisuja toteuttaa tuplakuori-rakenne joista lopulta päädyttiin keskittymään muovikalvon käyttöön. Muovikalvon käytöllä oli lähinnä kaksi tarkoitusta. Tärkeimpänä oli saada muovikalvo sulamaan eristekerroksen ja suojakuoren väliin. Tällöin sulanut muovikalvo toimisi liiman tavoin ja hitsaisi eristekerroksen ja suojakuoren toisiinsa kiinni. Näin veden eteneminen eristekerroksen ja suojakuoren välissä saataisiin estetyksi. Muovikalvo oli myös tarkoitus kiristää eristepaketin päälle niin kireälle, että eristepaketin halkaisijaa saataisiin pienennettyä. Muovikalvon käyttöön perehdyttiin suorittamalla tuotantolinjalla koeajoja. Koeajoissa kokeiltiin erilaisia ja erikokoisia putkituotteita erilaisilla tuotantoparametreilla. Näin pyrittiin löytämään parhaat parametrit ja arvot, joilla muovikalvoa pystyttäisiin tulevaisuudessa käyttämään jatkuvassa tuotannossa. Koeajojen tuloksista voitiin havaita, että kalvoitetut putkituotteet käyttäytyivät tuotannossa hyvin eri tavoin.

PLANT GROWTH-PROMOTING MICROBIAL INOCULANT FOR Schizolobium parahyba pv. parahyba

ABSTRACTSchizolobium parahyba pv. amazonicum (Huber ex Ducke) Barneby (paricá) occurs naturally in the Amazon and is significant commercial importance due to its rapid growth and excellent performance on cropping systems. The aim of this paper was to evaluate a microbial inoculants such as arbuscular mycorrhiza fungi (AMF) and Rhizobium sp. that promote plant growth. The inocula was 10 g of root colonized and spores of Glomus clarum and/or 1 mL of cell suspension (107 CFU/mL) of Rhizobium sp. and/or 100 g of chemical fertilizer NPK 20-05-20 per planting hole. The experimental design was complete randomized blocks with five replications and eight treatments (n = 800). Plant height, stem diameter and plant survival were measured. The results were tested for normality and homogeneity of variances and analyzed by ANOVA and Tukey test (p < 0.05). Rhizobium sp and AM fungi showed no effect on plant growth. Environmental factors probably influenced the effectiveness of symbiosis of both microorganisms and plant growth. The chemical fertilizer increased S. parahyba growth. During the first 120 days plants suffered with drought and frost, and at 180 days plants inoculated with microorganism plus chemical fertilizer showed higher survival when compared with control. The results showed that the microbial inoculants used showed an important role on plant survival after high stress conditions, but not in plant growth. Also was concluded that the planting time should be between November to December to avoid the presence of young plants during winter time that is dry and cold.

Initial development of two eucalyptus hybrid submitted to irrigation

The eucalyptus offers several advantages compared to other forestry species and, by using the irrigation can increase productivity and decrease production time. The objective of the present study was to evaluate two hybrid eucalyptus (Grancam and Urograndis), no irrigation, dripping and micro sprinkler irrigated at 90, 120, 150 and 180 days after transplanting (DAT). The experiment was conducted at the experimental irrigation area in the State University of Mato Grosso do Sul, in the municipality of Aquidauna - State of MS, Brazil. The experimental design was randomized blocks, split plot with four blocks and two replications within each block, and the plots were composed by irrigation treatments (dripping, micro sprinkler irrigate and dry) and the subplots the hybrids (Grancam and Urograndis).The total area of the experiment had 3 hectares, where each plot consisted of 1 ha. It was evaluated plant height, stem diameter and canopy, stem basal area, the relationship between height and stem diameter, the relationship between height and canopy diameter and stem volume. Data were subjected to analysis of variance and compared by Tukey test at 5% probability. Irrigation systems and dripping sprinkle provide greater plant height, stem diameter, canopy diameter, stem basal area and stem volume.

Spontaneous poisoning by larvae of Perreyia flavipes (Pergidae) in sheep

From a flock of 175 Texel sheep 25 animals died after consumption of a sawfly larvae subsequently identified as Perreyia flavipes. The disease occurred in June-July 2006 on a farm located in the county of Encruzilhada do Sul, Rio Grande do Sul, Brazil. Although there were 11 cattle in the same paddock, none of them was affected. High numbers of compact masses containing up to 150 larvae were scattered in the paddock where the animals were grazing. Most affected sheep showed severe apathy during 24-36 h before death, but weakness, muscular tremors and depression were also observed. Necropsy was performed on six sheep and the main macroscopic lesions were hemorrhages in the subcutaneous tissues, endocardium, gallbladder wall, and abomasal mucosa. In all animals was found hydrothorax, hydropericardium, ascites, and mild jaundice. Edema in the abomasal folds, mesentery, perirenal tissues, and gallbladder wall were also seen. The livers were yellowish with disseminated pinpoint hemorrhages in the parenchyma and had an enhanced lobular pattern. Perreyia flavipes larval body fragments and heads were found in the forestomach contents of the six sheep. Feces were scant, dry and formed balls coated by mucus and streaks of blood. Similar contents were also present at the end of the cecum. Prominent microscopic lesions included severe and diffuse periacinar or massive necrosis of hepatocytes associated with multifocal random hemorrhages. Diffuse necrosis of lymphoid follicles in lymph nodes and Peyer's patches, lymphoid depletion and necrosis in germinative centers of the spleen, and diffuse vacuolization in the renal tubular epithelia were also seen.

Streamside management zone (SMZ) efficiency in herbicide retention from simulated surface flow

Plot-scale overland flow experiments were conducted to evaluate the efficiency of streamside management zones (SMZs) in retaining herbicides in runoff generated from silvicultural activities. Herbicide retention was evaluated for five different slopes (2, 5, 10, 15, and 20%), two cover conditions (undisturbed O horizon and raked surface), and two periods under contrasting soil moisture conditions (summer dry and winter wet season) and correlated to O horizon and site conditions. Picloram (highly soluble in water) and atrazine (moderately sorbed into soil particles) at concentrations in the range of 55 and 35 µg L-1 and kaolin clay (approximately 5 g L-1) were mixed with 13.000 liters of water and dispersed over the top of 5 x 10 m forested plots. Surface flow was collected 2, 4, 6, and 10 m below the disperser to evaluate the changes in concentration as it moved through the O horizon and surface soil horizon-mixing zone. Results showed that, on average, a 10 m long forested SMZ removed around 25% of the initial concentration of atrazine and was generally ineffective in reducing the more soluble picloram. Retention of picloram was only 6% of the applied quantity. Percentages of mass reduction by infiltration were 36% for atrazine and 20% for picloram. Stronger relationships existed between O horizon depth and atrazine retention than in any other measured variable, suggesting that better solid-solution contact associated with flow through deeper O horizons is more important than either velocity or soil moisture as a determinant of sorption.

Naudanlanta biokaasulaitosraaka-aineena, käsittely ja logistiikka

Maatalouden lietelannasta saatavien ravinteiden talteenotto ja kierrätys ovat viime aikoina nousseet yhä tärkeämmäksi tavoitteeksi. Ravinteiden tehokas kierrätystapa saadaan ai-kaiseksi käsittelemällä lietelantaa. Lannan käsittelyketjuja on monenlaisia; tässä työssä naudan lannan käsittelyketju muodostuu separoinnista ja mädätyksestä. Tämän diplomityön tarkoituksena oli selvittää naudan lannan mekaanisen separoinnin ja logistiikan kannattavuus märkämädätys- ja kuivamädätyskäsittelyketjussa. Käsittelyketju-jen kannattavuus tai kannattamattomuus on esitetty eri skenaarioissa muodostettujen kus-tannuslaskentojen perusteella. Skenaarioiden kustannuslaskelmat ovat toisiinsa verratta-vissa, jolloin ne voidaan asettaa niin ikään paremmuusjärjestykseen. Viides skenaario ei ole suoraan verrattavissa muihin skenaarioihin, koska siinä lannankäsittelyketjua on tar-kasteltu eri näkökulmasta, keskittämällä suurimmalle maatilalle. Mekaanisista separaattoreista tarkasteltiin työssä ruuvipuristinta, dekantterilinkoa ja ul-koistettua separointipalvelua. Lannan logistiikkakustannuksissa huomioitiin lannan kulje-tusta traktori- ja säiliöautolla tai traktorilla. Separoinnin kustannus liitettiin osaksi logis-tiikkakustannusta. Työn tuloksien perusteella voidaan todeta dekantterilingon separointi-kustannuksen olevan taloudellisesti kannattamattomin johtuen pienestä lantakapasiteetista ja separaattorin korkeasta investointihinnasta. Ravinteiden osalta linko osoittautui tehok-kaimmaksi menetelmäksi erottamaan ravinteet eri jakeisiin. Lannan käsittely separointipalvelulla oli edullisin skenaario, jonka vuosittaiseksi kustan-nukseksi saatiin säiliö- ja kuorma-autolla lantaa kuljetettaessa 58 700 € ja traktorilla kul-jetettaessa 60 400 €. Kallein lannan käsittely oli dekantterilingolla, jonka vuosittaiseksi kustannukseksi saatiin lantaa säiliö- ja kuorma-autolla kuljetettaessa 121 000 € ja trakto-rilla kuljetettaessa 123 300 €. Lannan separointi maatilalla osoittautui kannattavammaksi kuin käsittelemättömän lietteen kuljetus biokaasulaitokselle.

Liver oxidative stress of the grey mullet Mugil cephalus presents seasonal variations in Ennore estuary

The objective of this study was to determine the liver oxidative stress status of grey mullets living in heavy-metal-rich polluted Ennore estuary compared with unpolluted Kovalam estuary. Fish were collected from both estuaries during the monsoon and summer seasons from October 2004 to September 2006. Fish liver homogenate (N = 20 per group) was prepared for evaluating oxidative stress parameters. Fish living in the polluted estuary had significantly higher lipid oxidation products, conjugated dienes (0.346 ± 0.017 vs 0.141 ± 0.012 DA233/mg protein), lipid hydroperoxides (0.752 ± 0.032 vs 0.443 ± 0.03 nmol/mg protein), and lipid peroxides (3.447 ± 0.14vs 1.456 ± 0.096 nmol MDA/mg protein) than those of the unpolluted estuary during the summer. In contrast, significantly lower levels of superoxide dismutase (20.39 ± 1.14 vs 53.63 ± 1.48 units/mg protein) and catalase (116 ± 6.87vs 153 ± 8.92 units/mg protein) were detected in the liver of fish from the polluted estuary (Ennore) compared to fish from the unpolluted estuary (Kovalam) during the summer. Variations in most of the oxidative stress parameters were observed between the summer and monsoon seasons, indicating the importance of seasonal variation for estuaries and their inhabitants.

A Bayesian Approach for Forecasting Heat Load in a District Heating System

The growing population in cities increases the energy demand and affects the environment by increasing carbon emissions. Information and communications technology solutions which enable energy optimization are needed to address this growing energy demand in cities and to reduce carbon emissions. District heating systems optimize the energy production by reusing waste energy with combined heat and power plants. Forecasting the heat load demand in residential buildings assists in optimizing energy production and consumption in a district heating system. However, the presence of a large number of factors such as weather forecast, district heating operational parameters and user behavioural parameters, make heat load forecasting a challenging task. This thesis proposes a probabilistic machine learning model using a Naive Bayes classifier, to forecast the hourly heat load demand for three residential buildings in the city of Skellefteå, Sweden over a period of winter and spring seasons. The district heating data collected from the sensors equipped at the residential buildings in Skellefteå, is utilized to build the Bayesian network to forecast the heat load demand for horizons of 1, 2, 3, 6 and 24 hours. The proposed model is validated by using four cases to study the influence of various parameters on the heat load forecast by carrying out trace driven analysis in Weka and GeNIe. Results show that current heat load consumption and outdoor temperature forecast are the two parameters with most influence on the heat load forecast. The proposed model achieves average accuracies of 81.23 % and 76.74 % for a forecast horizon of 1 hour in the three buildings for winter and spring seasons respectively. The model also achieves an average accuracy of 77.97 % for three buildings across both seasons for the forecast horizon of 1 hour by utilizing only 10 % of the training data. The results indicate that even a simple model like Naive Bayes classifier can forecast the heat load demand by utilizing less training data.

Feasibility of industrial implementation of laser cutting into paper making machine

Laser cutting implementation possibilities into paper making machine was studied as the main objective of the work. Laser cutting technology application was considered as a replacement tool for conventional cutting methods used in paper making machines for longitudinal cutting such as edge trimming at different paper making process and tambour roll slitting. Laser cutting of paper was tested in 70’s for the first time. Since then, laser cutting and processing has been applied for paper materials with different level of success in industry. Laser cutting can be employed for longitudinal cutting of paper web in machine direction. The most common conventional cutting methods include water jet cutting and rotating slitting blades applied in paper making machines. Cutting with CO2 laser fulfils basic requirements for cutting quality, applicability to material and cutting speeds in all locations where longitudinal cutting is needed. Literature review provided description of advantages, disadvantages and challenges of laser technology when it was applied for cutting of paper material with particular attention to cutting of moving paper web. Based on studied laser cutting capabilities and problem definition of conventional cutting technologies, preliminary selection of the most promising application area was carried out. Laser cutting (trimming) of paper web edges in wet end was estimated to be the most promising area where it can be implemented. This assumption was made on the basis of rate of web breaks occurrence. It was found that up to 64 % of total number of web breaks occurred in wet end, particularly in location of so called open draws where paper web was transferred unsupported by wire or felt. Distribution of web breaks in machine cross direction revealed that defects of paper web edge was the main reason of tearing initiation and consequent web break. The assumption was made that laser cutting was capable of improvement of laser cut edge tensile strength due to high cutting quality and sealing effect of the edge after laser cutting. Studies of laser ablation of cellulose supported this claim. Linear energy needed for cutting was calculated with regard to paper web properties in intended laser cutting location. Calculated linear cutting energy was verified with series of laser cutting. Practically obtained laser energy needed for cutting deviated from calculated values. This could be explained by difference in heat transfer via radiation in laser cutting and different absorption characteristics of dry and moist paper material. Laser cut samples (both dry and moist (dry matter content about 25-40%)) were tested for strength properties. It was shown that tensile strength and strain break of laser cut samples are similar to corresponding values of non-laser cut samples. Chosen method, however, did not address tensile strength of laser cut edge in particular. Thus, the assumption of improving strength properties with laser cutting was not fully proved. Laser cutting effect on possible pollution of mill broke (recycling of trimmed edge) was carried out. Laser cut samples (both dry and moist) were tested on the content of dirt particles. The tests revealed that accumulation of dust particles on the surface of moist samples can take place. This has to be taken into account to prevent contamination of pulp suspension when trim waste is recycled. Material loss due to evaporation during laser cutting and amount of solid residues after cutting were evaluated. Edge trimming with laser would result in 0.25 kg/h of solid residues and 2.5 kg/h of lost material due to evaporation. Schemes of laser cutting implementation and needed laser equipment were discussed. Generally, laser cutting system would require two laser sources (one laser source for each cutting zone), set of beam transfer and focusing optics and cutting heads. In order to increase reliability of system, it was suggested that each laser source would have double capacity. That would allow to perform cutting employing one laser source working at full capacity for both cutting zones. Laser technology is in required level at the moment and do not require additional development. Moreover, capacity of speed increase is high due to availability high power laser sources what can support the tendency of speed increase of paper making machines. Laser cutting system would require special roll to maintain cutting. The scheme of such roll was proposed as well as roll integration into paper making machine. Laser cutting can be done in location of central roll in press section, before so-called open draw where many web breaks occur, where it has potential to improve runability of a paper making machine. Economic performance of laser cutting was done as comparison of laser cutting system and water jet cutting working in the same conditions. It was revealed that laser cutting would still be about two times more expensive compared to water jet cutting. This is mainly due to high investment cost of laser equipment and poor energy efficiency of CO2 lasers. Another factor is that laser cutting causes material loss due to evaporation whereas water jet cutting almost does not cause material loss. Despite difficulties of laser cutting implementation in paper making machine, its implementation can be beneficial. The crucial role in that is possibility to improve cut edge strength properties and consequently reduce number of web breaks. Capacity of laser cutting to maintain cutting speeds which exceed current speeds of paper making machines what is another argument to consider laser cutting technology in design of new high speed paper making machines.

Automated static image analysis as a novel tool in describing the physical properties of dietary fiber

Abstract The growing interest in the usage of dietary fiber in food has caused the need to provide precise tools for describing its physical properties. This research examined two dietary fibers from oats and beets, respectively, in variable particle sizes. The application of automated static image analysis for describing the hydration properties and particle size distribution of dietary fiber was analyzed. Conventional tests for water holding capacity (WHC) were conducted. The particles were measured at two points: dry and after water soaking. The most significant water holding capacity (7.00 g water/g solid) was achieved by the smaller sized oat fiber. Conversely, the water holding capacity was highest (4.20 g water/g solid) in larger sized beet fiber. There was evidence for water absorption increasing with a decrease in particle size in regards to the same fiber source. Very strong correlations were drawn between particle shape parameters, such as fiber length, straightness, width and hydration properties measured conventionally. The regression analysis provided the opportunity to estimate whether the automated static image analysis method could be an efficient tool in describing the hydration properties of dietary fiber. The application of the method was validated using mathematical model which was verified in comparison to conventional WHC measurement results.

Characterization of amine-based CO2 adsorbent for Direct Air Capture

Direct air capture technologies extract CO2 from air at a concentration of as low as 400ppm. The captured CO2 can be used for the production of synthetic methane or liquid fuels. In the literature survey of this thesis, results related to direct air capture by using solid sorbents are presented and critically discussed. In the experimental part, a proprietary amine functionalized resin is characterized for direct air capture. Structural comparison is also made to a commercial resin of similar type. Based on the literature survey, the most important parameters in direct air capture process are low adsorption and desorption temperatures, good cyclic stability in dry and humid conditions, high CO2 outlet purity and a high working capacity. Primary amine functionalized solid sorbents are found to often have good qualities for direct air capture, but overall process performance is rarely studied exhaustively. Based on FTIR spectra, both resin adsorbents are found to be consisted of polystyrene functionalized with primary amine, and capture CO2 by forming carbamate. The commercial resin is more porous, has a slightly higher particle size and contains fewer impurities. Important physical parameters are gained of the proprietary resin, such as internal porosity and median particle size. The resin’s amine group is found to endure thermal treatment reasonably well. CO2 adsorption capacity gained by thermal gravimetry from 400ppm CO2 is highest at 25oC, and is found to be reasonable compared to values presented in literature. Thus, the resin is stated to exhibit promising qualities for direct air capture.

Synthèse de brosses de polyélectrolytes par polymérisation initiée depuis une surface de mica et étude de leur réponse en fonction du pH et de la force ionique

Cette thèse rapporte le greffage chimique de brosses de polymères neutres de poly(acrylate de tert-butyle) (PtBA) et de brosses chargées d’acide polyacrylique (PAA) sur des substrats de mica afin d’étudier leur conformation en fonction de la densité de greffage, du pH et de la force ionique. Le greffage est réalisé par polymérisation contrôlée par transfert d’atome (ATRP) initiée depuis la surface de mica afin de contrôler la croissance du polymère et sa densité de greffage. L’étude de la conformation des brosses de PtBA et de PAA a été menée avec la technique AFM en mesurant les épaisseurs des films à sec et gonflés sous différentes conditions de solvant, de pH et de force ionique. Une monocouche d’amorceurs est tout d’abord greffée sur du mica porteur de groupes hydroxyles créés par plasma (Ar/H2O). Cette couche a été caractérisée par des mesures d’angle de contact et par la technique TOF-SIMS. L’amorceur greffé a ensuite permis d’initier l’ATRP directement depuis la surface pour former des brosses neutres de PtBA liés de façon covalente au mica. La croissance linéaire de l’épaisseur du film avec la masse molaire du polymère en solution et le taux de conversion montre que la polymérisation est contrôlée. De plus, la ré-initiation des chaînes greffées atteste du caractère vivant de la polymérisation. L’hydrolyse des brosses de PtBA, confirmée par des mesures d’angle de contact, d’épaisseur et par FT-IR, conduit à des brosses de PAA. Les différentes couches greffées sont stables à l’air, en milieu organique et en milieu aqueux et leur gonflement est réversible. Le degreffage de la couche de PAA est observé suite à une longue exposition à pH basique. Cette étude représente le premier exemple de brosses greffées chimiquement sur du mica par polymérisation initiée depuis la surface. La variation des paramètres de la réaction de greffage de l’amorceur, tels que la concentration et la durée de réaction, a permis de contrôler le taux de recouvrement de l’amorceur et la densité de greffage du polymère. Une grande gamme de taux de recouvrement de l’amorceur est accessible et se traduit par un intervalle de densités de greffage allant de faibles à élevées (e.g. 0,04 chaîne/nm2 à 0,5 chaîne/nm2). L’étude de la conformation des chaînes de PtBA dans le DMF montre que cet intervalle de densités recouvre le régime crêpe au régime brosse. Le gonflement de brosses de PAA et la variation de la hauteur de la brosse L ont été étudiés en fonction de la densité de greffage, du pH et du sel ajouté cs (NaCl). Une transition brusque de collapsée à étirée est observée avec l’augmentation du pH, indépendamment de la densité de greffage. A pH neutre, les brosses sont collapsées et se comportent comme des brosses neutres en mauvais solvant. A pH basique, les brosses sont gonflées et chargées et se trouvent dans un régime de Pincus caractéristique des polyélectrolytes forts. En présence de sel, les charges sont partiellement écrantées et les répulsions électrostatiques dominent toujours dans la brosse. Cette étude contribue à une meilleure compréhension du comportement complexe des brosses de polyélectrolytes faibles et apporte un soutien expérimental à la théorie sur le comportement de ces brosses.

Étude des mécanismes d’inactivation des microorganismes suite à un traitement à l’ozone

Une partie du travail a mené a un dépôt de brevet.

Cru ; suivi de Cruauté nécessaire : le devoir d'une vérité autobiographique chez Guibert, Dustan et Rémès

Situé entre entre le roman et le récit personnel, Cru. prend la forme d'un aller-retour entre fiction et autobiographie. Le texte, construit à l'aide d'une écriture syncopée et brute, présente deux personnages homosexuels à l'ère « post-sida », alors que ceux-ci tentent de comprendre ce que veut dire « être un homme » dans un contexte social où le mépris (envers les autres et soi-même) est encore présent, mais peut-être encore plus pernicieux qu'auparavant, parce que camouflé sous l'idée d'une acceptation globale. Au final, Cru. soulève la délicate question du droit à la vérité dans une démarche autobiographique et celle de l'implication de la cruauté dans un récit qui ne concerne pas que l'auteur, mais son entourage aussi. Cruauté nécessaire : le devoir d'une vérité autobiographique chez Guibert, Dustan et Rémès est un essai qui vise l'analyse de différents procédés se rattachant à l'écriture autobiographique homosexuelle des années 1990, particulièrement aux textes appartenant à la littérature du sida. Si l'autobiographie vise, dans une certaine mesure, le dévoilement de la vérité, comment ne pas parler de cruauté alors que les auteurs qui la pratiquent y vont de révélations qui ne concernent pas qu'eux? Si le processus d'écriture autobiographique se veut bénéfique, le résultat est-il purement diabolique? Il faudra d'abord, évidemment, définir ce que l'on entend par « vérité » et « cruauté » (lire « bénéfique » et « maléfique »). En ce qui concerne le Bien et le Mal, les textes de Bataille et Nietzsche contribueront à définir deux concepts qui peuvent, souvent, être relatifs. En confrontant les textes des trois auteurs français – tous séropositifs au moment de l'écriture – à différentes théories autobiographiques (Doubrovsky, Lejeune, Miraux) et identitaires (Foucault, Schecter, Butler), et à certains écrits sur le devoir et la responsabilité (Donner, Brooks), l'on tentera de démontrer que la cruauté dont Guibert, Dustan et Rémès font preuve est essentielle à l'écriture autobiographique.

Perspectives de l'usage de poudre de jaunes d’oeuf comme additif alimentaire contre Campylobacter jejuni chez le poulet : mode d'immunisation et effet de l’encapsulation

La campylobactériose est une zoonose causée par Campylobacter jejuni, une bactérie commensale du poulet, considérée comme la principale source de contamination humaine. C. jejuni est rarement retrouvé dans le tube digestif des poulets avant deux ou trois semaines d'âge. Ce qui pourrait s'expliquer par la transmission d'une immunité maternelle (anticorps IgY) transmise aux poussins via le jaune d'œuf. À la Chaire de recherche en Salubrité des Viandes (CRSV), la caractérisation d'anticorps IgY extraits de jaunes d'œufs frais a montré des niveaux de production d’anticorps différents selon le mode d’immunisation et suggère, in vitro, des effets sur ce pathogène. Ce qui laisse penser qu'en tant qu'additif alimentaire, une poudre de jaunes d'œuf potentialisée permettrait de lutter contre C. jejuni chez le poulet à griller. Dans ce travail, le processus de fabrication de l'additif (déshydratation par « Spray dry » puis encapsulation) a été évalué et les différents modes d'immunisation des poules pondeuses ont également été comparés. Les anticorps ont été extraits des différentes poudres de jaunes d'œuf ou du produit final encapsulé, et caractérisés in vitro (dosage / ELISA, test de mobilité, bactéricidie, western blot). Puis, une évaluation in vivo de la capacité de ces poudres encapsulées, incorporée à 5 % dans la moulée, afin de réduire ou de bloquer la colonisation intestinale des oiseaux par C. jejuni a été testée. In vitro, les résultats ont montré des concentrations d'anticorps et d'efficacité variables selon le type de vaccination. Dans cette étude, on a observé que le « Spray dry » a concentré les anticorps dans les poudres et que ces anticorps sont restés fonctionnels contre C. jejuni. On a également observé que l'encapsulation n’entraîne pas une perte quantitative des anticorps contenus dans les poudres. Malgré les résultats in vitro encourageants, les résultats in vivo ne révèlent aucune inhibition ou réduction de la colonisation des oiseaux par C. jejuni. L’absence d’efficacité la poudre de jaunes d’œuf encapsulée dans notre étude n’est pas due à une perte quantitative et/ou qualitative des anticorps comme soutenu dans les expériences in vitro. Ce qui démontre que les recherches doivent être poursuivies afin de déterminer les conditions optimales de l'utilisation de la poudre de jaune d'œuf in vivo, en tant qu'additif alimentaire chez les poulets