Date of Award


Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy


Biological Sciences

First Advisor

Dr.Aidan Coffey


Prebiotics are selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microbiota that confers benefits upon host well-being and health’ It is not the prebiotic by itself but rather the changes induced in microflora composition that is responsible for its effects. Several sources of prebiotic were used in this study, namely extracellular polysaccharides (EPS) originating from Lactic Acid Bacteria (LAB), barley, oat. Laminaria digitata. Laminaria hyperborea and Saccharomyces cerevisiae. EPS-producing LAB were isolated from a wide variety of environmental and gastrointestinal niches. The strains were typed and classified according to their EPS-producing ability and selected strains were identified for possible commercial potential. Nevertheless, because of the constraints in terms of prebiotic yield from LAB, the cereal, seaweed and yeast were chosen better as sources of polysaccharide for large animal studies where their influence on gut microflora could be studied in a more meaningful way. In these cases, the polysaccharides were glucans - a heterogeneous group of (3-linked polyglucoses and which have attracted the attention of the pharmaceutical and functional food industry because of their positive effects on animal and human health. The prebiotic properties of cereal, algal and yeast P-glucans were thus investigated at the microbiological and molecular level on the Lactobacillus, Bifidobacterium (potential probiotics populations) and enterobacterium group in the mammalian gastrointestinal tract. Throughout the thesis, the effects of supplementing porcine diets with various forms of these polysaccharides were evaluated using conventional plating and denaturing gradient gel electrophoresis (DGGE). These results clearly showed the interspecies fluctuations of the lactobacilli, bifidobacteria in some cases in response to the diets, and it also documented the effects on members of the enterobacteria. Research and development of these biotic products have helped pave the way towards finding a successful replacement for antibiotic growth promoters (AGP) during the weaning phase of pig production.

Access Level


Included in

Bacteriology Commons