Biancacci C1, Chen J2, Qi H3, Allardyce B4, Nishiwaki H5, Ii H5, Turchini G6, Bellgrove A1
1Deakin University, School of Life and Environmental Sciences, Centre for Integrative Ecology, Warrnambool campus, P.O. Box 423, Warrnambool, Victoria 3280, Australia.
2Southwest Petroleum University, Chengdu, Sichuan Province, China.
3School of Science, STEM College, RMIT University, 124 La Trobe Street, Melbourne, VIC 3000, Australia.
4Institute for Frontier Materials, Deakin University, Geelong Waurn Ponds campus, 75 Pigdons Rd, Waurn Ponds, Victoria, Australia.
5Faculty of Systems Engineering, Wakayama University, 930 Sakaedani, Wakayama 640-8510, Japan
6 University of Melbourne, School of Agriculture and Food, Grattan Street, Parkville, VIC 3010, Australia
Alginates are used widely in foods, textiles and pharmaceuticals for their gelling properties but are currently available from Australian seaweeds for Durvillaea potatorum only. Variability in the alginate yield and composition is common, with implications for commercial applications. We assessed temporal and spatial variation in the characterisation of alginates from three Australian brown seaweeds, D. potatorum, Ecklonia radiata and Phyllospora comosa. Samples were collected from three regions in Victoria, Australia over autumn, winter, and spring; alginates were extracted from dried biomass and the yield, viscosity, residual cellulose and M:G ratio (β-D-mannuronic acid relative to α-L-guluronic acid residues) characterised. Because metals can bind to alginates and affect toxicity, we also analysed the concentration of copper (Cu), manganese (Mn), iron (Fe), lead (Pb), zinc (Zn) and arsenic (As). Average alginate yields varied significantly among species (47% for D. potatorum, 37% for P. comosa and 28% for E. radiata), and spatially and temporally. Highest yields for all species were in spring, when maximum average yields for P. comosa (59%) exceeded those of D. potatorum (37 – 55%) at all sites. Viscosity varied temporally, highest in spring. M:G ratio differed amongst species (average 1.4 for D. potatorum and ~1 for the other species), but also varied temporally and spatially. Residual cellulose ranged 12 – 27% and was highest in P. comosa. Concentrations of all metals were below the maximum tolerable level for human consumption. Results suggest P. comosa should be considered for alginate production with an optimal spring harvest, but site selection may be important.