The small intestine generally transports dietary fats to circulation in triglyceride (TG)-rich lipoproteins. The two main intestinal lipoproteins are chylomicron (CM) and very low-density lipoprotein (VLDL). Unfortunately, studies on the CM biogenesis and intestinal transport of dietary fats have been hampered by the lack of an adequate in vitro model. In this study, we investigated the possible factors that might increase the efficiency of CM production by Caco-2 cells. We utilized sequential NaCl gradient ultracentrifugation to isolate the CMs that were secreted by the Caco-2 cells. To confirm the successful isolation of the CMs, we performed Fat Red 7B staining, TG reading, apolipoprotein B (ApoB) measurement, and transmission electron microcopy (TEM) analysis. We then tested the effects of cell differentiation, oleic acid, mono-olein, egg lecithin, incubation time, and collagen matrix on CM secretion. We found that cell differentiation, oleic acid, and lecithin were critical for CM secretion. Using the Transwell system, we further confirmed that the CMs produced by our Caco-2 cells contained significant amount of TGs and ApoB-48 such that they could be detected without the use of isotope labeling. In conclusion, when fully differentiated Caco-2 were challenged with oleic acid, lecithin, and sodium taurocholate, 21% of their total number of lipoproteins were CMs with the diameter of 80-200 nm.

This work investigates ways to prevent and manage hyperglycemia using preventive nutrition. Uncontrolled and chronic hyperglycemia is a global health issue leading to many health problems including diabetes. This thesis details the manipulation of highly retrograded starch particles in order to produce particles that are digested slowly to release glucose at a prolonged and moderate rate to prevent this. The first section of this study utilized acid hydrolysis to alter starch structure and change digestibility. The hydrolysis treatment showed that hydrolysis of native starch prior to particle formation changed the structure in a way that increased digestibility. The second section of this work introduced polyphenols into the particles which only a marginal effect on digestion. Overall the actual process of retrograding and making the particles themselves appeared to create particles that were more resistant to digestion. These could be used in a product to deliver a moderate glycemic response.

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<p> The blood and sugars, on which adult black-flies fed, stimulated the buccal sensilla so that blood. went directly to the midgut and sugars to the crop. Agglutinin and anticoagulant were found in the salivary glands of female simuliids. </p> <p> The sequence of peritropbic membrane formation and disappearance are discussed in relation to blood digestion. </p> <p> Digestive enzymes, such as that of trypsin and invertase activity occurred in the midgut of both sexes of several black-fly species unfed or fed on sucrose, but an increase in enzyme Activity was stimulated in females by a blood meal. A weak amylase-like activity was found in the midgut, but the activity was not stimulated by blood- feeding. A greater amylase activity was found in the residual fluid (haemolymph). Trypsin activity in females, but not in males, increased also after feeding blood-sucrose mixtures. Blackfly invertase promoted oligosaccharide synthesis. Trypsin, amylase and invertase showed pH optima of 8.4, 6.5 and 6.2 respectively. </p> / Thesis / Doctor of Philosophy (PhD)

Les bactéries probiotiques doivent être en mesure de survivre pendant la digestion gastrique afin d'atteindre le côlon et ainsi conférer des bienfaits sur la santé humaine. Le potentiel des matrices d'origine laitière pour soutenir les probiotiques a souvent été décrit, mais celui des produits végétaux tels que la sève d'érable pour cette application reste peu connue, alors que l'engouement pour ces produits est en croissance. L'objectif de ce mémoire était d'évaluer la viabilité cellulaire par l'utilisation du propidium monoazide (PMA) couplé à la qPCR, ainsi que d'évaluer l'expression de cinq gènes reliés au stress atpA, dnaK, galK, groEL et hrcA par RT-qPCR lors de la digestion gastrique in vitro (TIM-1) de trois souches commerciales (Bifidobacterium animalis ssp. lactis A026, Lacticaseibacillus paracasei A234, Lacticaseibacillus rhamnosus A119) ainsi que de la souche de référence Lacticaseibacillus rhamnosus GG (ATCC 53103) contenues dans de la sève d'érable. Les résultats ont indiqué que toutes les souches ont maintenu un taux de survie élevé suite à la digestion gastrique; B. animalis ssp. lactis A026 (7.14 log de cellules viables/mL), L. paracasei A234 (8.12 log de cellules viables/mL), L. rhamnosus A 119 (8.48 log de cellules viables/mL) et L. rhamnosus GG (8.36 log de cellules viables/mL) et que l'expression de certains gènes de stress ciblés avait été modulée pendant la digestion gastrique. Seule la souche L. rhamnosus GG a montré une modulation au niveau de l'expression de tous les gènes ciblés. Dans l'ensemble, l'expression d'au moins un gène associé à la réponse au stress a été modulée pour toutes les souches probiotiques pendant la digestion gastrique dans la matrice de sève d'érable. Face aux stress de la digestion gastrique, les différentes réponses du métabolisme des bactéries probiotiques permettent une meilleure survie cellulaire. En définitive, ces quatre souches ont le potentiel d'être utilisées comme probiotiques dans une matrice de sève d'érable, ce qui pourrait mener au développement d'une boisson fonctionnelle. / The probiotic bacteria must be able to survive during gastric digestion in order to reach the colon and thus provide human health benefits. The potential of dairy matrices to support probiotics has often been described, but plant products such as maple sap for this application remains little known, while the interest for these products is growing. The objective of this thesis was to evaluate cell viability by the use of propidium monoazide (PMA) coupled to qPCR, as well as to evaluate the expression of five genes linked to stress atpA, dnaK, galK, groEL and hrcA by RT-qPCR during in vitro gastric digestion (TIM-1) of three commercial strains (Bifidobacterium animalis ssp. lactis A026, Lacticaseibacillus paracasei A234, Lacticaseibacillus rhamnosus A119) as well as the reference strain Lacticaseibacillus rhamnosus GG (ATCC 53103) delivered in maple sap. The results indicated that all strains maintained a high survival rate after gastric digestion; B. animalis subsp. lactis A026 (7.14 log of viable cells/mL), L. paracasei A234 (8.12 log of viable cells/mL), L. rhamnosus A119 (8.48 log of viable cells/mL), and L. rhamnosus GG (8.36 log of viable cells/mL) and that the expression of certain target stress genes was modulated during gastric digestion. Only L. rhamnosus GG strain showed modulation in the expression of all target genes. Overall, the expression of at least one gene associated with the stress response was modulated for all probiotic strains during gastric digestion in the maple sap matrix. Faced with the stress of gastric digestion, the different responses of the metabolism of probiotic bacteria allow better cell survival. Ultimately, these four strains have the potential to be used as probiotics in a maple sap matrix, which could lead to the development of a functional drink.

The application of anaerobic digestion (AD) as a sustainable waste management technology is growing worldwide, due to high energy prices as well as increasingly strict environmental regulations. The growth of the AD industry necessitates exploring new substrates for their utilisation in AD processes. The present work investigates the AD of two recalcitrant biomass: lignocelluloses and keratin-rich residues. The complex nature of these waste streams limits their biological degradation; therefore, suitable pre-processing is required prior to the AD process.In the first part of the study, the effects of organic solvent pre-treatments on bioconversion of lignocelluloses (straw and forest residues) to biogas were evaluated. Pre-treatment with N-methylmorpholine-N-oxide (NMMO) resulted in minor changes in the composition of the substrates, while their digestibility significantly increased. Furthermore, due to the high cost of the NNMO, the effect of pre-treatment with the recycled solvent was also explored. Since it was found that the presence of small traces of NMMO in the system after the treatment has inhibitory effects on AD, pre-treatments of forest residues using other organic solvents, i.e. acetic acid, ethanol, and methanol, were investigated too. Although pre-treatments with acetic acid and ethanol led to the highest methane yields, the techno-economical evaluation of the process showed that pre-treatment with methanol was the most viable economically, primarily due to the lower cost of methanol, compared to that of the other solvents.In the second part of the work, wool textile wastes were subjected to biogas production. Wool is mainly composed of keratin, an extremely strong and resistible structural protein. Thermal, enzymatic and combined treatments were, therefore, performed to enhance the methane yield. The soluble protein content of the pre-treated samples showed that combined thermal and enzymatic treatments had significantly positive effects on wool degradation, resulting in the highest methane yields, i.e. 10–20-fold higher methane production, compared to that obtained from the untreated samples.In the last part of this thesis work, dry digestion of wheat straw and wool textile waste, as well as their co-digestion were studied. The total solid (TS) contents applied in the digesters were between 6–30% during the investigations. The volumetric methane productivity was significantly enhanced when the TS was increased from 6 to 13–21%. This can be a beneficial factor when considering the economic feasibility of large-scale dry AD processes.

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