The underlying physiology of algal antioxidant compounds is reviewed in the context of seaweed biology and utilization. The application of seaweed antioxidants in foods, food supplements, nutraceuticals and medicine is considered from the perspective of benefits to human health. We advocate that direct consumption of seaweed products for their antioxidant composition alone provides a useful alternative to non-natural substances, while simultaneously providing worthwhile nutritional benefits. Economic utilization of seaweeds for their antioxidant properties remains in its infancy. This review provides examples ranging from laboratory studies through to clinical trials where antioxidants derived from seaweeds may provide major health benefits that warrant subsequent investigative studies and possible utilization.
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Marine-derived sulfated polysaccharides possess various antiviral activities against a broad range of enveloped and non-enveloped viruses. It has become the potential source of antiviral drugs for pharmaceutical develop- ment. In this review, we will discuss the different types of sulfated polysaccharides and their structural classi- fication. Some of the major sulfated polysaccharides with potent antiviral activity, including carrageenan, agar, ulvan, fucoidan, and alginates, are considered in this review. The mechanism of these sulfated polysaccharides in inhibiting the different stages of the viral infection process inside the host cell is also demonstrated. It involves blocking the initial entry of the virus or inhibiting its transcription and translation by modulating the immune response of the host cell. In addition, we explore the potential of sulfated polysaccharides as antiviral agents in preventing recent Corona Virus Disease-2019 (COVID-19).
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Total lipids from the Brazilian brown seaweed Sargassum vulgare were extracted with chloroform/methanol 2:1 and 1:2 (v/v) at room temperature. After performing Folch partition of the crude lipid extract, the lipids recovered from the Folch lower layer were fractionated on a silica gel column eluted with chloroform, acetone and methanol. The fraction eluted with methanol, presented a strong orcinol-positive band characteristic of the presence of sulfatides when examined by TLC. This fraction was then purified by two successive silica gel column chromatography giving rise to fractions F4I86 and F4II90 that exhibited strong activity against herpes simplex virus type 1 and 2. The chemical structures present in both fractions were elucidated by ESI-MS and 1H/13C NMR analysis HSQC fingerprints based on their tandem-MS behavior as Sulfoquinovosyldiacylglycerols (SQDGs). The main SQDG present in both fractions and responsible for the anti-herpes activity observed was identified as 1,2-di-O-palmitoyl-3-O-(6-sulfo-α-d-quinovopyranosyl)-glycerol.
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Intensive fish aquaculture has raised serious environmental concerns, including eutrophication, harmful algal blooms, fish kills, etc. Integrated multi-trophic aquaculture (IMTA) may be the most suitable aquaculture technology to achieve environmental and economic sustainability. The objectives of present study are to review the status of aquaculture and IMTA in Korea; and to determine the challenges to apply the principles of IMTA to intensive monoculture in Korean coastal waters. Korea has been one of the leading countries in aquaculture. Like other advanced countries in aquaculture, such as China and Japan, most aquaculture practices in Korea are intensive monoculture and farms are highly concentrated in bays or estuaries with restricted circulation. In intensive open water aquaculture in these waters, nutrient producers (finfish) are cultured mostly in southeastern Korea whereas extractive organisms (seaweeds) are farmed in the southwestern Korea. There are relatively small areas of overlap between these monocultures, causing environmental issues and reduction in the quality of aquacultured products. Recent attempts of IMTA in Korean coastal waters suggest that IMTA can be a good management tool for improving Korean aquaculture although there are still challenges to overcome. These challenges include development of temperature tolerant species/strains of extractive organisms such as seaweeds and sea cucumbers. Most aquacultured seaweed and sea cucumber species in Korea do not grow well during the summer months, when the release of finfish effluent is at its peak. It is essential to the future success of aquaculture in Korea that a coastal zone management (CZM) be developed that reflects coordinating fed and extractive organisms in coastal bays and estuaries rather them keeping them isolated from one another. The importance of a new regulatory framework advocating IMTA solutions will be essential for environmental protection and continued success of aquaculture in Korea. Although this review is a case study in Korea for IMTA, it will also provide critical information for coastal managers, aquaculturists and regulators in other countries where there are intensive monocultures of fed and extractive organisms.
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Edible seaweeds are a good source of antioxidants, dietary fibers, essential amino acids, vitamins, phytochemi- cals, polyunsaturated fatty acids, and minerals. Many studies have evaluated the gelling, thickening and thera- peutic properties of seaweeds when they are used individually. This review gives an overview on the nutritional, textural, sensorial, and health-related properties of food products enriched with seaweeds and sea- weed extracts. The effect of seaweed incorporation on properties of meat, fish, bakery, and other food products were highlighted in depth. Moreover, the positive effects of foods enriched with seaweeds and seaweed extracts on different lifestyle diseases such as obesity, dyslipidemia, hypertension, and diabetes were also discussed. The results of the studies demonstrated that the addition of seaweeds, in powder or extract form, can improve the nutritional and textural properties of food products. Additionally, low-fat products with less calories and less sat- urated fatty acids can be prepared using seaweeds. Moreover, the addition of seaweeds also affected the health properties of food products. The results of these studies demonstrated that the health value, shelf-life and overall quality of foods can be improved through the addition of either seaweeds or seaweed extracts.
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Integrated multi-trophic aquaculture (IMTA) involves strategic co-culture of organisms so that wastes from one species are used to grow another. Seaweeds can be used in IMTA systems to remove and utilise dissolved inorganic nutrients from fish aquaculture, improving environmental performance and providing economic benefits through diversification and increased productivity. IMTA with seaweed could be applied to assist sustainable expansion of fish farming in South Australia (SA), where dissolved nitrogen (N) wastes limit environmental carrying capacity. Seaweed farming is also of interest in Australia to meet increasing demand for seaweed products, of which Australia is a net importer. Several native seaweeds have been identified as potential candidates for aquaculture in SA based on general knowledge of their biology and potential economic value, but specific knowledge of their suitability for cultivation was lacking. I investigated eight candidate seaweeds, comprising four red (Solieria robusta, Gelidium australe, Pterocladia lucida, Plocamium angustum) and four brown (Ecklonia radiata, Cystophora subfarcinata, Sargassum linearifolium, Scytothalia dorycarpa) species, to determine which species were most suitable for farming, with specific emphasis on application to IMTA in SA. I assessed feasibility of cultivation and potential for nutrient remediation of the eight species in two field trials and in laboratory experiments, and applied species distribution modelling (SDM) to identify the most suitable candidate species for aquaculture in the vicinity of current SA fish farms. My research identified the red seaweed Solieria robusta and the brown seaweed Ecklonia radiata as the most suitable species for aquaculture. The red Gelidium australe showed promising growth in a pilot field trial and removed the most N in a 4-week laboratory trial, but S. robusta grew best in laboratory trials and would remove more N over time due to its faster growth. Solieria robusta tolerated a wider temperature range and grew better at higher temperatures than G. australe. SDM results demonstrated that S. robusta has high environmental suitability in aquaculture zones throughout Spencer Gulf, where all SA finfish farming currently occurs, while G. australe was poorly suited to most existing aquaculture zones. Pterocladia lucida and Plocamium angustum had slower growth rates, and SDMs indicated low suitability in aquaculture zones. There was little difference in field performance of the brown seaweeds, apart from Scytothalia dorycarpa, which performed poorly, but Ecklonia radiata was most amenable to hatchery reproduction and cultivation. SDM showed that several aquaculture zones in southern Spencer Gulf had good suitability for E. radiata. Seedstock production methods used for commercially farmed relatives were successfully applied to S. robusta and E. radiata, and I developed protocols that can be employed to upscale production of these seaweeds. Solieria robusta and E. radiata demonstrated the ability to accumulate tissue N, and N uptake rates comparable to other IMTA seaweeds, supporting the suitability of these species for IMTA. Data from my experiments help to inform suitable depths, locations and seasons for cultivation of these seaweeds, and to incorporate N removal by seaweeds into biogeochemical models. These experiments provide the foundation for developing seaweed aquaculture in southern Australia, including IMTA.
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Integrated multi-trophic aquaculture (IMTA) involves strategic co-culture of organisms so that wastes from one species are used to grow another. Seaweeds can be used in IMTA systems to remove and utilise dissolved inorganic nutrients from fish aquaculture, improving environmental performance and providing economic benefits through diversification and increased productivity.
IMTA with seaweed could be applied to assist sustainable expansion of fish farming in South Australia (SA), where dissolved nitrogen (N) wastes limit environmental carrying capacity. Seaweed farming is also of interest in Australia to meet increasing demand for seaweed products, of which Australia is a net importer. Several native seaweeds have been identified as potential candidates for aquaculture in SA based on general knowledge of their biology and potential economic value, but specific knowledge of their suitability for cultivation was lacking. I investigated eight candidate seaweeds, comprising four red (Solieria robusta, Gelidium australe, Pterocladia lucida, Plocamium angustum) and four brown (Ecklonia radiata, Cystophora subfarcinata, Sargassum linearifolium, Scytothalia dorycarpa) species, to determine which species were most suitable for farming, with specific emphasis on application to IMTA in SA. I assessed feasibility of cultivation and potential for nutrient remediation of the eight species in two field trials and in laboratory experiments, and applied species distribution modelling (SDM) to identify the most suitable candidate species for aquaculture in the vicinity of current SA fish farms.
My research identified the red seaweed Solieria robusta and the brown seaweed Ecklonia radiata as the most suitable species for aquaculture. The red Gelidium australe showed promising growth in a pilot field trial and removed the most N in a 4-week laboratory trial, but S. robusta grew best in laboratory trials and would remove more N over time due to its faster growth. Solieria robusta tolerated a wider temperature range and grew better at higher temperatures than G. australe. SDM results demonstrated that S. robusta has high environmental suitability in aquaculture zones throughout Spencer Gulf, where all SA finfish farming currently occurs, while G. australe was poorly suited to most existing aquaculture zones. Pterocladia lucida and Plocamium angustum had slower growth rates, and SDMs indicated low suitability in aquaculture zones. There was little difference in field performance of the brown seaweeds, apart from Scytothalia dorycarpa, which performed poorly, but Ecklonia radiata was most amenable to hatchery reproduction and cultivation. SDM showed that several aquaculture zones in southern Spencer Gulf had good suitability for E. radiata.
Seedstock production methods used for commercially farmed relatives were successfully applied to S. robusta and E. radiata, and I developed protocols that can be employed to up- scale production of these seaweeds. Solieria robusta and E. radiata demonstrated the ability to accumulate tissue N, and N uptake rates comparable to other IMTA seaweeds, supporting the suitability of these species for IMTA. Data from my experiments help to inform suitable depths, locations and seasons for cultivation of these seaweeds, and to incorporate N removal by seaweeds into biogeochemical models. These experiments provide the foundation for developing seaweed aquaculture in southern Australia, including IMTA.
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A component of the recent Australian Centre for International and Agricultural Research-funded sandfish project in the Philippines, Vietnam and Australia has been to build and refine economic decision tools for both sea ranching and pond-based culture of sandfish. Presented here is the background to these models and some basic theory required to understand model outputs. Models take a discounted cash flow approach to predicting returns over a given life cycle. Output includes the expected annual returns when the farm is paid off, and the maximum interest rate at which funds can be borrowed to invest in the project. A risk module allows the user to incorporate anticipated risk to return from a range of sources. Access to these models is open, and a web address is provided.
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Underutilized marine resources (e.g., algae, fish, and shellfish processing by-products), as sustainable alternatives to livestock protein and interesting sources of bioactive com- pounds, have attracted the attention of the researchers. Aquatic products processing industries are growing globally and producing huge amounts of by-products that often discarded as waste. However, recent studies pointed out that marine waste contains several valuable components including high-quality proteins, lipids, minerals, vitamins, enzymes, and bioactive compounds that can be used against cancer and some cardiovascular disorders. Besides, previously conducted studies on algae have shown the presence of some unique biologically active compounds and valuable proteins. Hence, this chapter points out recent advances in this area of research and discusses the importance of aquaculture and fish processing by-products as alternative sources of proteins and bioactive compounds.
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Discussion of Tyler Cowen's book, ‘The Great Stagnation’.
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