Joel T. Kidgell1,2, Susan M. Carnachan2, Marie Magnusson3, Rebecca J. Lawton3, Ian M. Sims2, Simon F. R. Hinkley2, Rocky de Nys1, Christopher R. K. Glasson3
1 MACRO – The Centre for Macroalgal Resources and Biotechnology, College of Science and Engineering, James Cook University, Townsville, Australia, 4811
2 The Ferrier Research Institute, Victoria University of Wellington, Wellington, New Zealand, 5010
3 Environmental Research Institute, School of Science, University of Waikato, Tauranga, New Zealand, 3110
Ulvan are sulfated polysaccharides from the green seaweed, Ulva. A host of bioactivities (e.g., anti-inflammatory, anti-viral, anti-hyperlipidemic) and a complex structure suggest potential applications for ulvan ranging from biomaterials to drug delivery molecules. However, much of the data underpinning these promising applications comes from polysaccharides extracted from Ulva with a blade morphology (e.g., the genus holotype, U. lactuca). In contrast, there is limited data on ulvans from filamentous morphologies of Ulva.
We used standardised procedures to characterise and compare ulvan from blade and filamentous species of Ulva collected from the Bay of Plenty, Aotearoa New Zealand. Distinct differences in the chemical composition, structure, and gelling properties of ulvans from blade (U. australis, U. rigida, U. sp. B, and Ulva sp.) and filamentous (U. flexuosa, U. compressa, U. prolifera, and U. ralfsii) species of Ulva were quantified. Ulvan isolated from blade species had higher yields (14.0-19.3%) and iduronic acid content (IdoA = 7-18 mol%), and lower molecular weight (Mw = 190-254 kDa) and storage moduli (G’ = 0.1-6.6 Pa) than filamentous species (yield = 7.2-14.6%; IdoA = 4-7 mol%; Mw = 260-406 kDa; G’ = 22.7-74.2 Pa).
The linkage composition and sulfation of four of these ulvans were then compared. The predominant residues present from all four ulvans where 1,4-rhamnose 3-sulfate and 1,4-glucuronic acid; 69-87 mol% combined. However, ulvans from filamentous species also contained high proportions of branching/sulfated residues not detected in ulvans from blade species, supporting the morphology-based division in these polysaccharides.