This project was primarily concerned with clarifying the extent to which fungal delignification in solid substrate fermentations could be optimised and applied to enhancing the nutritional value of high-fibre lignocellulosic ruminant feeds. Ten fungi were assessed for their ability to grow on media containing cell-wall related phenolic compounds and polysaccharides. Five strains were selected as being particularly active in secreting enzymes depolymerising native insoluble crystalline celluloses and lignins. The key cell wall phenolic ferulic acid was shown to exhibit differential patterns of inhibition of saccharification of cell wall carbohydrates with differential effects on cellulose depolymerisation, endoglucanase and B-glucosidase production. Two strains were shown to secrete phenol oxidases, which were presumed to be laccases, and three produced lignin oxidases, assayed as ability to decolourise polymeric dyes in surface agar culture. Solid substrate fermentation of hay and b arley straw with lignocellulose-degrading fungi (Pleurotus sajo-caju, Chaetomium cellulolyticum and Trichoderma harzianum) gave increases in acid detergent lignin except with Coriolus versicolor or Phanerochaete chrysosporium. P. sajo-caju,C. versicolor and P. chrysosporium reduced the lignin content of spruce and birch sawdust but had no marked effect on that of rice bran. All the five fungi reduced polysaccharide contents of lignocelluloses, but depletion was not at a rate directly related to period of fermentation. Fermentations with mixed cultures of three lignolytic fungi (C. versicolor, P. sajo-caju and P. chrysosporium) led to greater reduction in lignin content than did with monocultures. Although synergistic attack was observed on total insoluble polysaccharides and hemicelluloses, this was not found with depolymerisation of celluloses. Accumulation of total solubles, both carbohydrates and phenolics, was also markedly higher with mixed than with monocultures. Five lignocelluloses were evaluated as feeds in a simulated rumen model system (RUSITEC). The lignocelluloses were supplied prior to and following fungal delignifications. Fungal pretreatment of spruce sawdust enhanced feed digestibility and daily carbon dioxide production; with untreated sawdust production of total gas and volatile acids, and bacterial population decreased with incubation in the rumen. Addition of chitin and D(+) glucosamine, major components of fungal cell walls, had no adverse effect on digestibility, production of acetate or fermentation gases except when concentrations reached >30% chitin and >1% glucosamine. The influence of cell-wall related phenolic compounds and a toxic fungal metabolite, aflatoxin, on fibre digestion and the output of rumen fermentation end products was studied. Addition of the phenolics or fungal metabolite led to varied effects on bacterial populations, volatile acid and gas (CH₄ & CO₂) evolution.

No description available.

No description available.

No description available.

No description available.

The pancreas is a gland composed essentially of digestive enzymes-producing acinar cells and hormone-producing endocrine cells. In particular, insulin is one of the best-known pancreatic hormones and it is a member of the large insulin superfamily, a group of evolutionary related proteins that includes also many insulin-like peptides (ILPs) in invertebrates. Although the pancreas has been extensively studied in vertebrates, little information is reported on ILPs and homologues of pancreatic endocrine and exocrine cell types in non-chordate deuterostomes. In order to fill this critical gap in pancreas evolution this thesis concerns the analysis of the orthologues of vertebrate pancreatic genes, both transcriptional factors and terminal differentiation genes, during embryo and larva development in the sea urchin Strongylocentrotus purpuratus, which among the chordate sister group ambulacraria, has proven to be a powerful instrument for evolutionary studies. To this end, the spatial expression of insulin-like molecules found in the sea urchin genome (Splgfl and SpIlgf2) and their predicted receptor (SpInsr) have been extensively studied. The outcomes of this thesis work suggest to rename Splgfl and SpIlgf2 as SpILPI and SpILP2, respectively. Remarkably, SpILPI has been found to be localized in a group of cells of the larval gut in a feeding-dependent fashion. Moreover, after cloning and characterizing the spatial expression of the orthologues of pancreatic transcriptional factors (SpNgn, SpNeuroD, Splsl, SpHnfl, SpPtfla) and exocrine pancreas terminal differentiation genes (SpCpa2L and SpPnlp), I proceeded in investigating the role of some of these genes by functional analysis experiments. During this characterization, several homologues of pancreatic and neuronal cell types have been identified. Notably, putative homologues of acinar cell types, that are clustered in the sea urchin larva stomach, and a peculiar neuronal cell type that secretes a novel neuropeptide were characterized. Finally, the outcome of this study is discussed in a comparative perspective with available data in other animal models in order to make hypotheses on the evolution of insulin-like molecules and pancreatic cell types across metazoan .

The sea urchin larval gut is a tripartite structure consisting of an esophagus, a stomach and an intestine. The morphological changes driving the formation of the functional larval gut are well described; however, very little is known about the molecular toolkit responsible for the differentiation of the gut and the final gain of digestive functions. In this study I focused on the transcription factors that determine the differentiation of two of the gut compartments, the stomach and the intestine. Two TFs play a key role: SpLox, whose vertebrate homologue is known for its essential role in the development and functioning of the pancreas, appears as a main regulator of stomach differentiation in the sea urchin and it is necessary for the acquirement of its digestive functions; SpCdx acts as a strong repressor of the stomach fate in the hindgut cells and it is responsible of proper intestine differentiation. I investigated the role of these two genes by functional analysis with a dual approach, studying the effect of perturbation of their upstream regulators and investigating their role in controlling gut specific terminal differentiation genes: the obtained net of gene regulatory inputs has been schematized in a Biotapestry diagram allowing a simple and immediate representation of some of the crucial gene interactions happening during sea urchin endoderm specification and differentiation processes. In this contest I analyzed retinoic acid putative role in the sea urchin embryonic development, discovering that exogenous treatments with this molecule determine a change in transcripts distribution along the antero-posterior axis of the gut: this represents the first example outside chordates of RA machinery function in development. Moreover, I extended the analysis of the GRN to another class of Echinoderrns, the Asteroidea Patiria miniata, aiming to assess the level of conservation of gene expression and function of the orthologue genes investigated in the sea urchin. With the same gene perturbation approach I found a total absence of conservation at the GRN level despite the very impressive conservation observed in the expression domains. The obtained two networks have been finally examined in a comparative perspective with the available data in vertebrates, analyzing the level of conservation and divergence between echinoderm and vertebrate gut patterning processes and providing a very powerful tool to decipher the changes in gene activities that over evolutionary time have shaped structures like the embryonic gut.

Studies were conducted to evaluate the effects of tannins on <i>in sacco</i> disappearance in the rumen and post-ruminal digestion using the mobile bag and pepsin-pancreatin (<i>in vitro</i>) methods, and the tube-feeding technique in poultry.  The treatment of <i>Lotus pedunculatus</i> with PEG increased <i>in sacco</i> disappearance compared with untreated lotus.  Quebracho tannin (QT) reduced the disappearance of lupin seeds and soyabean meal.   No effect of QT was found on the disappearance of chickpea, and an increase was observed for the disappearance of pea. <p class=MsoNormal>Tannins increased the excretion of nitrogenous compounds and sialic acid, and reduced nutrient digestibility of most feeds tested, as measured by the4 poultry model.  Tannins reduced the proportion of uric acid nitrogen in the excreta.  Tannins in lotus reduced intestinal digestion of N as measured by mobile bag and <i>in vitro</i> methods.  Nitrogen digestibility of soyabean meal and chickpea as measured by the mobile bag and <i>in vitro</i> methods was not affected by QT. Mimosa tannin (MT) inhibited the attachment of microbes to cellulose and decreased gas production.  Polyethylene glycol completely restored the gas production from cellulose treated with MT.   Pectin improved microbial attachment in the presence of MT, and the inhibition of the gas production from cellulose was partially restored.  The gas production from maize shoots decreased with MT, and it was restored with the addition of PEG.  Pectin did not improve the gas production from MT-treated maize shoots.  The presence of both MT and pectin improved EMPS, but reduced the incorporation of ¹⁵N into microbial protein.

No description available.

No description available.