|Proteins in seaweed : Ulva lactuca & Saccharina latissima|
Versleijen, M. (2018). Proteins in seaweed : Ulva lactuca & Saccharina latissima. Thesis. NIOZ Royal Institute for Sea Research: Yerseke. 35 pp.
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In a search for food source alternatives, seaweed seem a good option because it contains a high amount of proteins. The exact amount of proteins can be measured, which is mostly done by measuring the total amount of nitrogen by Kjeldahl and multiply the result with a factor of 6.25. This nitrogen to protein conversion factor is used for a lot of different protein containing matrixes, but seems not to apply to seaweed matrixes. So the aim of this project is to find a reliable method to determine protein and amino acid concentration and the amino acid composition in different species of seaweed biomass. Two species will be used, Ulva lactuca and Saccharina latissima. The total percentage of nitrogen was determined by the Dumas (U: 2.70% ± 0.01%, S: 3.48% ± 0.02%) and Kjeldahl method (U: 2.64% ± 0.18%, S: 3.01% ± 0.03%). The inorganic nitrogen originating of the nutrients was measured by the AutoAnalyzer (U: 0.11% ± 0.001%, S: 0.74% ± 0.02%), because this fraction of the nitrogen isn’t a part of the proteins. Also the in water soluble proteins were measured, by the normal Lowry method (U: 6.85% ± 0.43%, S: 3.21% ± 0.80%) and by a Lowry standard addition method (U: 9.74% ± 0.29%, S: 6.38% ± 0.54%). Proteins are build up out of amino acids, so the amount of all loose amino acids should be the same as the amount of the proteins. Unfortunately it is not possible to measure 100% of the amino acids. So with a HPLC-FD method are the amino acids measured, but they don’t give an overall overview. It still gives an image of the main amino acids. For both species are this L-Alanine, L-Glutamic acid L-Aspartic acid and L-Leucine. Despite the lack of an exact total amount of proteins, it was possible to calculate the nitrogen to protein conversion factor via the in water soluble measurements. This gave a value of 6.69 for U. lactuca and 4.23 for S. latissima. Which gives a percentage of 18.07% protein for U. lactuca and 14.71% protein for S. latissima.