An assessment of physical and chemical conditions in alginate extraction from two cultivated brown algal species in Norway: Alaria esculenta and Saccharina latissima

Abstract

Alginates are linear anionic polysaccharides originating from brown algae. Their properties target several application areas in in food-, technical- and pharmaceutical industries, and thus they are highly valued. Norway is currently the largest producer of cultivated seaweed in Europe, where the predominant species are Alaria esculenta and Saccharina latissima. So far, the utilisation of these two species have mainly been targeting food and feed applications. However, utilisation of these species for much broader application areas, including biopolymer and biomaterial markets, is of great interest. Both species are interesting candidates for future alginate production, but protocols for efficient extraction of high-quality alginate are lacking. In the present study, protocols for alginate extraction from fresh A. esculenta and S. latissima have been established. This has been accomplished by the identification and variation of key parameters in the extraction protocol, including pH, temperature and incubation times, and study of their effects on alginate quality and purity. Optimal conditions in the present study were found to be pH 9 in the alkaline extraction, and short extraction time (1–5 hours). The alginates extracted at pH 9 had a yield of 185 ± 7 and 229 ± 12 mg/g dry weight seaweed, and a weight average molecular weight (Mw) of 537 ± 12 and 503 ± 24 kDa in A. esculenta and S. latissima, respectively. The purity of the extracted alginates was evaluated based on the content of coextracted impurities and was found to be comparable with high-quality commercial alginates.