Clarisa Naa Shormeh Darko 1, Rando Tuvikene 1, Neill Jurgens Goosen 2
1 School of Natural Sciences and Health, Tallinn University, Narva mnt 29, Tallinn, 10120, Estonia
2 Department of Process Engineering, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa
Alginates extracted from two brown seaweeds, Ecklonia maxima and Sargassum fluitans sourced from the Atlantic Ocean along the southern and western coasts of Africa, respectively, are assessed for variations in their physicochemical characteristics. Three different fractions of alginate from each substrate were extracted for this study via a sequential extraction procedure. The first fractions (F1) of both species were extracted at room temperature whereas the last two sets (F2 and F3) were at higher temperatures. Fraction three (F3) from E. maxima yielded the highest alginate, about ~59% more than Sargassum fluitans. The molecular weight of the first fractions (F1) in both substrates were the highest (MW > 400 kDa) with the least recorded as 44 kDa for F3 from E. maxima. Monosaccharide compositions of the fractions analyzed using HPLC-PAD were similar but of relatively different molar ratios. FTIR analyses on all six fractions from both species showed broad bands around ~1027 cm-1 and 1100 cm-1 which are indicative of the -OH bending of guluronic and mannuronic acid units, respectively. Fractions from Sargassum fluitans recorded least M/G values from the 1H NMR analysis conducted on fractions of both species. The present study shows that the Ghanaian Sargassum fluitans yields notably brittle gels compared to the highly elastic alginate extracted from the South African Ecklonia maxima. This reported varying physicochemical properties provides an evidence for the potential suitability of these phycocolloids for either high or low gel-strength applications.