Enzyme-Assisted Fucoidan Extraction from Brown Macroalgae Fucus distichus subsp. evanescens and Saccharina latissima.

Thuan Thi Nguyen,Hang Thi Thuy Cao,Nanna Rhein-Knudsen,Tran Thi Thanh Van,Vy Ha Nguyen Tran,Vo Thi Dieu Trang,Jesper Holck,Maria Dalgaard Mikkelsen,Anne S Meyer,Anton B Rasin

doi:10.3390/md18060296

Abstract

Fucoidans from brown macroalgae (brown seaweeds) have different structures and many interesting bioactivities. Fucoidans are classically extracted from brown seaweeds by hot acidic extraction. Here, we report a new targeted enzyme-assisted methodology for fucoidan extraction from brown seaweeds. This enzyme-assisted extraction protocol involves a one-step combined use of a commercial cellulase preparation (Cellic®CTec2) and an alginate lyase from Sphingomonas sp. (SALy), reaction at pH 6.0, 40 °C, removal of non-fucoidan polysaccharides by Ca2+ precipitation, and ethanol-precipitation of crude fucoidan. The workability of this method is demonstrated for fucoidan extraction from Fucus distichus subsp. evanescens (basionym Fucus evanescens) and Saccharina latissima as compared with mild acidic extraction. The crude fucoidans resulting directly from the enzyme-assisted method contained considerable amounts of low molecular weight alginate, but this residual alginate was effectively removed by an additional ion-exchange chromatographic step to yield pure fucoidans (as confirmed by 1H NMR). The fucoidan yields that were obtained by the enzymatic method were comparable to the chemically extracted yields for both F. evanescens and S. latissima, but the molecular sizes of the fucoidans were significantly larger with enzyme-assisted extraction. The molecular weight distribution of the fucoidan fractions was 400 to 800 kDa for F. evanescens and 300 to 800 kDa for S. latissima, whereas the molecular weights of the corresponding chemically extracted fucoidans from these seaweeds were 10–100 kDa and 50–100 kDa, respectively. Enzyme-assisted extraction represents a new gentle strategy for fucoidan extraction and it provides new opportunities for obtaining high yields of native fucoidan structures from brown macroalgae.

Highlights

Fucoidans are a group of sulfated polysaccharides mainly found in the cell walls of brown seaweeds.Polysaccharides are intensively studied due to their useful bioactivities, such as antioxidant [1], Mar
We report the comparative isolation of fucoidans from two different brown seaweeds, F. evanescens and S. latissima, by acid extraction and enzymatic extraction while using Cellic® CTec2 from Novozymes and the alginate lyase SALy from Sphingomonas sp. [28]
The monosaccharide composition of F. evanescens and S. latissima was analyzed in order to evaluate the effect of using enzymes to extract fucoidans from brown seaweeds (Table 1)

Summary

Introduction

Fucoidans are a group of sulfated polysaccharides mainly found in the cell walls of brown seaweeds.Polysaccharides are intensively studied due to their useful bioactivities, such as antioxidant [1], Mar. Fucoidans are a group of sulfated polysaccharides mainly found in the cell walls of brown seaweeds. Based on the sugar composition, fucoidans from brown seaweeds were previously reported as sulfated fucans, mainly containing fucose and sulfate groups, galactofucans mainly consisting of sulfated fucose and galactose in different ratios, and urono-fucoidans with different monosaccharide units, less sulfate, and a large amount of uronic acid [8]. Fucoidans differ in their backbone structure and branching patterns and in presence and numbers of functional groups, such as sulfates and acetylations.

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