Prebiotic potential of the Saccharina latissima polysaccharides alginate, laminaran, and fucoidan
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With an increasing world population coupled with a higher standard of living follows an increased demand for food and feed. The utilization of the worlds land areas used for food and feed production is close to a maximum. As a result of this, it is expected that further development in food and feed production must take place in the world oceans. A resource with great potential found in the ocean are macroalgae. The nutritional content is high and varied, and cultivation of macroalgae does not require freshwater, fertilizer, or land area. In a world where antibiotic resistance is increasing, the need for probiotics and prebiotics is also increasing as these can stabilize the intestinal flora and reduce the antibiotic need in the livestock industry. The aim of this thesis has been to explore the use of polysaccharide from the brown algae Saccharina latissima as prebiotics. This has been investigated by several methods. Two cultures were cultured with laminaran, fucoidan, alginate, extract from Saccharina and pellet from the preparation of extract, as a source of carbon. These two cultures were; a culture consisting of the intestinal contents of mink fed on two different diets, both containing Saccharina latissima, and a collection of marine bacteria selected from previous research at SINTEF. To investigate development over time, 10% of the cultures were transferred to fresh medium after 2 days of incubation for mink cultures, and after 2 and 4 days, respectively, for two different runs of the marine culture. These transfers were repeated six times. For each transfer, the pH was measured. Based on these pH measurements, samples were selected for HPLC analysis to find acid and sugar content. For the mink culture all end cultures, in addition to the cultures after the fourth transfer, were sequenced using 16s rRNA sequencing, to investigate which, if any, bacterial genera that were able to utilize the polysaccharides from brown algae as substrates. For the marine cultures, only the final sample for the extract culture from run 2 was sequenced due to cultivation problems that led to too low DNA concentration for performing PCR amplification. In addition to these cultures, the three known probiotic bacterial strains Lactobacillus acidophilus, Bifidobacterum longum and Bifidobacterum bifidum were grown on fucoidan, laminaran, glucose, and fucose, to investigate their ability to utilize fucoidan and laminaran. There were indications that Lactobacillus and Bifidobacterium are able to use laminaran and fucoidan as carbon source. In addition, bacteria in culture were found to be able to ferment laminaran, fucoidan and alginate. However, sequencing results indicated that Lactobacillus and Bifidobacterium are outperformed by potentially harmful bacteria during growth. Thus, neither laminaran, fucoidan, nor alginate can be considered prebiotic.