Author: Andrew Lorbeer
Lorbeer, Andrew, 2016 Advanced and integrated technologies for the valorization of South Australia's unique seaweed resources, Flinders University, School of Medicine
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Australia’s southern coastline is a biodiversity hotspot for seaweed, with up to 1,500 described species, of which approximately 62 % are endemic to the region. South Australia also has close trading ties with Asia, and strong technological capabilities, and is therefore well-placed for the advanced manufacturing of seaweed-derived products. However, the seaweed industry in South Australia is currently limited to the small-scale manufacture of agricultural commodities from beach-cast and imported algae. We set out to assess the potential of South Australia’s seaweed resources as feedstocks for higher-value products, and to develop advanced and integrated processing technologies for their valorization. Ecklonia radiata was selected as the model feedstock due to its abundance, potential for aquaculture, and possession of compounds of commercial interest. The primary aim was the extraction of fucoidans due to their high commercial value. When the kinetics of a classical extraction process were studied, it was found that only 22% of the total available fucoidan was extracted from E. radiata, accompanied by a gradual reduction in purity, cleavage of sulfate groups, and rapid depolymerization The pre-treatment of algae was trialed using enzymes and ionic liquids, with the aim of disassociating the fucoidans from other components that may hinder their extraction. However, no significant improvements in yield were observed. It was thus hypothesized that a biorefinery approach may be necessary for the comprehensive valorization of seaweed biomass. A sequential extraction process was devised, based around the acidic extraction of fucoidans and the sodium carbonate extraction of alginates. The acidic treatment was considered to be a critical step, as it served as both an extractant for fucoidan and an important pre-treatment for alginate extraction. Therefore, response surface methodology and desirability functions were used to predict the best overall process for improved fucoidan yield and the high-yielding sequential extraction of high molecular weight alginates. The optimized process was applied to three other brown algae: Durvillaea potatorum, Seirococcus axillaris, and Macrocystis pyrifera, and the products were assessed for key indicators of value. The fucoidans from E. radiata demonstrated the ability to stimulate the proliferation of human skin fibroblasts; the alginates from S. axillaris had strong gel-forming capacity; and the alginate extract of M. pyrifera was lightly colored and highly viscous. Finally, a techno-economic analysis was performed to assess the potential industrial production of fertilizers, fucoidans and alginates in South Australia. The integrated production of fucoidans and fertilizers from M. pyrifera was predicted to be the most profitable option. In a scenario of limited biomass availability, the project could break even if a minimum of 140 dry tonnes of feedstock could be accessed annually. The studies outlined in this thesis are expected to guide decision making, and facilitate the development of sustainable, yet profitable marine-based industries in South Australia and elsewhere. Hopefully, this will stimulate investment in regional communities, and allow them to participate internationally in the emerging “blue economy”.
Keywords: Seaweed, macroalgae, fucoidan, alginate, biorefinery, brown algae
Subject: Medical Biotechnology thesis, Biotechnology thesis
Thesis type: Doctor of Philosophy
School: School of Medicine
Supervisor: Professor Wei Zhang