74 DECEMBER 2023 • WORLD AQUACULTURE • WWW.WAS.ORG oil, and oil with an algal origin are all taken into consideration for the manufacturing of biodiesel since they are less expensive than edible oils from sunflower, palm, soybean, rapeseed, canola, jatropha, and cottonseed. Algal biodiesel production comprises harvesting biomass, drying, oil extraction, and further oil transesterification (Behera et al. 2014). Bio-oil, gas and biochar production. It may be possible to increase the production of heat, power, and transportation fuels from renewable resources by thermally converting seaweeds (Saqib et al. 2013). The primary sources for the production of bio-oil, gases, and biochar are primarily algal blooms, which are abundant in a number of eutrophic water bodies, and post-extraction residues (such as those from the lipid extraction for the production of biodiesel). Syngas mostly made of CO, H2, and CH4 is produced as a result of the gasification and pyrolysis of algal biomass, and it can then be transformed into ethanol, methanol, and methane (Suutari et al. 2015). As building elements for biorefineries, the gas and tar produced by these processes can also be used to produce high-value products (Bruhn et al. 2011). Sodium Alginate from waste seaweed. The massive influx of Sargassum causes a number of problems for coastal people since it disrupts fishers’ livelihoods, makes it difficult to launch boats, limits access to fishing resources, hinders tourism, and produces an extremely unpleasant odour during decomposition. The alginate industry processes algae and discarding around 80 percent of the algae biomass as different solid/liquid residual streams (Bojorges et al. 2022). Depending on the seaweeds growth conditions, various procedures are used to extract sodium alginate from different kinds of brown seaweed. Commercial sodium alginate is commonly produced from brown seaweed such Laminaria hyperborea, Laminaria digitata, Ascophyllum nodosum, and Macrocystis pyrifera, as well as to a lesser amount from Laminaria japonica, Eclonia maxima, and Sargassum sp. The seaweed is typically treated with an acid prior to extraction, and then it is treated with an alkaline solution in water. Fucoidan from Dealginated Kelp Waste Dealginated kelp waste is the solid industrial residues at the end of alginate production (Wang et al. 2020). Nowadays, large amount of kelp waste is frequently discarded directly or sold for very low price as biological fertilizer. This has led to problems including environmental contamination and has severely hampered the healthy development of the kelp industry (Gebreluel et al. 2020). Dealginated kelp waste still contains a certain amount of fucoidan. As a result, there are substanial economic and societal benefits to utilizing dealginated kelp waste to fucoidan production (Wang et al. 2020). Seaweed fertilizer. Seaweeds have been used as biofertilizer for centuries and considered as be a source of antioxidants, plant growth hormones, mineral nutrients, and many other organic compounds in addition to compensating for the deficiency of N, P, and K (Nabti et al. 2017). The use of seaweed extracts as fertilizer acts as stimulants for plants and supports its growth parameters, including seed germination rates that are faster, the development of the root system, as well as an increase in the quantity and size of leaves and fruits, the plant’s weight, and the strength of the plant (Di Filippo-Herrera et al. 2019). As the demand for inorganic fertilisers declines because of the scarcity of natural resources, seaweed’s potential as a commercial product stands out as an environmentally friendly (Gao et al. 2020). Seaweed fertilizer influences bacterial community succession through its effects on N concentrations during the composting process (Zhou et al. 2019) Valorization of Alginate industrial waste streams. Generally, the alginate extraction process at industrial level involves collection, transport and storage of the algae, with eventual addition of formaldehyde to prevent chemical or enzymatic reactions. An acid pre-treatment and alkaline extraction process generates large amounts of liquid and solid waste streams (Fawzy et al. 2017). Bio-plastic from seaweeds. Because of human demand and their versatility, petroleum-based plastics are becoming more and more prevalent on land, in rivers, and in the oceans. These plastics degrade into nanoparticles, which are then ingested by fish, birds, and the human placenta (Antoni et al. 2021). Seaweeds can be used as an alternative source for plastic, because of its biodegradability, ecofriendly and edibility (Helmes et al. 2018). Seaweed is a renewable source of biomass, and because it is formed of polymers made from sugars that contain carbon, it might be utilised to make biodegradable, high-quality bioplastics. Role in aquaculture. Brown seaweed polysaccharides including Fucoidan, Alginate, and Laminarin are used as immunostimulants in aquaculture. Fucoidan significantly increased total haemocyte count (THC) and differential haemocyte count in crustaceans fed a diet containing alginate. Fucoidan can improve lipid metabolism, which catabolizes body fat as a primary source of energy and results in effective protein synthesis in tissues and improved growth performance in aquatic animals (Niu et al. 2015). L. vannamei and M. rosenbergii were protected from WSSV infection by a fucoidan-rich diet (Sinurat et al. 2016). According to Ying (2008), O. niloticus fed with alginate fucoidan showed significantly increased levels of PHA and respiratory burst activity (RBA). Conclusion The potential for sustainable use of seaweeds waste as ingredients in food, feed, cosmetics, and medicinal products, as well as a source of raw materials for chemicals, biomaterials, and energetic products, is drawing more interest worldwide. Depending from seaweed types and species it is possible to extract different fatty acids, oils, natural pigments, antioxidants, high value biological components and other substances which can be used in production. Notes C. Sathishkumar, G. Sanjay and Amit Ranjan* TNJFU-Institute of Fisheries Post Graduate Studies, Vaniyanchavadi, Chennai-603 103 * Corresponding Author: amitranjanfcri@gmail.com References Ahmed, A. B. A., M. Adel, P. Karimi and M. Peidayesh. 2014. Pharmaceutical, cosmeceutical, and traditional applications of marine carbohydrates. Advances in Food and Nutrition Research 73: 197-220. An, C., Kuda, T., Yazaki, T., Takahashi, H and B. Kimura. 2013. FLX pyrosequencing analysis of the effects of the brown-algal fermentable polysaccharides alginate and laminaran on rat cecal microbiotas. Applied and Environmental Microbiology 79(3):860-866. Behera, S., R,Singh, R. Arora, N.K. Sharma, M. Shukla and S. Kumar. 2015. Scope of algae as third generation biofuels. Frontiers in Bioengineering and Biotechnology 2: 90-113. Bojorges, H., M. J. Fabra, A. López-Rubio and A. Martínez-Abad. 2022. Alginate industrial waste streams as a promising source of value-added
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