Isolation, Characterisation, Modification and Application of Fucoidan from Fucus vesiculosus
Fucoidan is a natural occurring, heterogeneous sulphated marine polysaccharide from brown algae. Due to its special structure it is said to possess interesting biological activities. During the implementation of this project, methods were developed to extract fucoidan from Fucus vesiculosus (bladder wrack), analyse it, modify it and test it concerning the different biologic activities. The main focus point was to find hydrolytic enzymes as the special sulphatation pattern of the fucoidan may be destroyed by unspecific (e.g. chemical) hydrolysis. In the beginning, the algae were collected and the extraction procedure as well as the purification steps were optimised with regard to the yield of these polysaccharides. As the proportion of fucoidan in the algae is subject to seasonal variations, a yield of 1% could be obtained. Two big fractions of fucoidan were produced. Due to the special heterogeneous structure of the polysaccharides, it was very difficult to characterise them. During the project, several methods for detection were established and developed. The combination of these methods allowed a clearer picture of the produced fucoidans to be drawn. By means of a special carbohydrate gel electrophoresis, size exclusion chromatography, colorimetric tests, elemental analysis as well as a combination of gas chromatography and mass spectrometry, the high molecular fucoidan fraction (FVEhigh), could be elucidated to be 1,300 kDa. The sulphatation degree of this fraction was estimated to be 8.45%. The other fraction (FVElow) was 30-50 kDa in size and had a sulphatation grade of 2.62%. For comparison, commercial fucoidan (Fucoidan Sigma) was estimated to 300 kDa in size and a sulphatation grade of 7.9%. Determination of the monosaccharide composition revealed, that FVEhigh was composed of 78% of fucose and only minor parts of xylose, mannose and galactose. FVElow, however, consisted of only 59% fucose, 4% xylose, 9% mannose and 4% galactose.