Chemical and Enzyme-Assisted Extraction of Fucoidan from two Species of Brown Macroalgae (Ascophyllum nodosum and Saccharina latissima)

Abstract

Marine environments contain half of the global biodiversity and are a major source of bioactive compounds. Macroalgae are vital species in marine ecosystems and are known to produce several bioactive compounds and polysaccharides that possesses several bioactivities. These molecules are traditionally extracted using methods that heavily rely on hazardous solvents and heat, that more importantly generates waste and emissions. Sustainability has gained worldwide attention and has led scientists to explore more environmentally friendly extraction methods that have a lower environmental impact. The main goal of this thesis was to compare the fucoidan yield of a conventional method against a new, greener extraction method (enzyme-assisted extraction, EAE) from two species of brown macroalgae commonly found in Norway: Ascophyllum nodosum and Saccharina latissima. In addition, the polyphenol/phlorotannin, alginate and monomeric sugars content was analyzed. The chemical extraction (CE) method was conducted at 80 Degree Celsius for 4 hours with 0.1 M HCl. It was tested three different enzymes (Depol692, Depol 793 and Cellulase 13), in addition to a control sample were tested and compared in EAE. The EAE method was conducted at 50 Degree Celsius for 3 hours with pH 5. The polyphenol/phlorotannin content was analyzed after lyophilization, while the carbohydrate-, L-fucose- and alginate content in the macroalgae were analyzed using two different methods of acid hydrolysis. The CE method resulted in a general higher fucose and carbohydrate yield from A. nodosum, indicating higher release of fucoidan and other polysaccharides compared to EAE. However, limited amounts of polyphenols/phlorotannins were detected in the samples after CE, indicating that the process may be harmful for the compounds. In contrast, the extraction yield of polyphenols/phlorotannins after EAE was good. In general, CE resulted in the higher extraction yield of fucoidan, compared to EAE. None of the enzymes used in this study showed a high efficiency compared to the control or CE. However, all enzymes showed potential in degrading the algal cell wall, but further studies are needed to make thorough conclusions on this potential.