72 DECEMBER 2023 • WORLD AQUACULTURE • WWW.WAS.ORG tween 10 and 30 percent of the biomass by dry weight (DW) and are now the only seaweeds that are exploited economically. Globally, around 236,000 tons (DW) of alginophytes were harvested in 2015 to generate 24,644 tons of alginate (Porse and Rudolph 2017). The remainder, almost 90 percent in residue, was disposed of as garbage along with the remaining 10 percent of the feedstock. For alginate businesses, the ongoing disposal of such residual biomass and effluents has become a problem. On the other hand, a number of studies have indicated that alginate and other products may be recovered. Alginophytic seaweed biomass can be used to extract other biochemical elements such as proteins, minerals, and cellulose in addition to alginate, effectively utilizing the entire biomass. The right use of feedstock for value goods could increase the income of seaweed farmers and reduce the amount of waste that is released by the seaweed processing industry. To address the rising demand for seaweed, there is an international effort to create a sustainable method for effectively using seaweed biomass. The production of residues is reduced by the seaweed biorefinery, leading to a system with almost no waste. This strategy encourages the use of recyclable and reusable wastes in a circular economy. Seaweed Composition and Properties Brown seaweeds (Figure 1) are known for their polysaccharides, or hydrocolloids, like alginates, fucoidan, and lamnarin, which are utilised extensively in the food industry and many other sectors. Proteins, lipids, carbohydrates, vitamins, and minerals are among the nutritional components found in seaweeds but the amount of each nutrient varies based on the season and the region of production (Connan et al. 2004). In general, seaweeds have high concentrations of macro elements, such as potassium, calcium, iron, and iodine, all vitamins except vitamin D, and a wide range of antioxidants in high concentrations (Holdt and Kraan 2011). Bioactive compounds. Seaweeds often have high concentrations of polysaccharides, minerals, polyunsaturated fatty acids, and vitamins, low concentrations of lipids, and high concentrations of bioactive compounds, making them a good source of nutritious food (Holdt and Kraan 2011). In addition, bioactive compounds are used in the cosmetic and pharmaceutical industries (Ahmed et al., 2014). Phlorotannins (seaweed phenols). Phlorotannins are synthesized by the polymerization of phloroglucinol produced through the acetate-malonate pathway, also known as the polyketide pathway. Seaweed is a great, sustainable resource because of the presence of specific distinct bioactive components that are not found in terrestrial biomass. Seaweeds are becoming more and more popular throughout the world as possible sustainable constituents in foods, feed, and cosmetics. Seaweeds have medicinal uses, as well as serving as starting points for the production of chemicals and biomaterials. Aquatic habitats colonized by seaweeds are mostly utilized by coastal communities. Unprocessed forms of many seaweed species are typically utilized for medical purposes, in human meals, as animal feed, and as fertilizers to improve agricultural soil. Seaweeds are a source of vital trace elements like iron, manganese, copper, zinc, cobalt, selenium, and iodine and are high in potassium, sodium, calcium, magnesium, and phosphorus. In terms of proteins, minerals, lipids and fiber, macroalgae may differ greatly from one another. Seaweeds typically have a high mineral content because they can take in inorganic materials from the environment. Despite having a high polysaccharide content, seaweeds only have a modest amount of lipids, primarily polyunsaturated fatty acids (PUFAs). Because of the abundance of bioactive chemicals, including polyphenols, peptides, and polysaccharides found in seaweeds they constitute a biotechnological resource with high diversity in composition and functional qualities. When seaweed aquaculture is taken into account, marine and coastal (ponds and lagoons) aquaculture (63.2 million tons) accounted for 55.2 percent of the overall world aquaculture production (114.5 million tons), whereas inland aquaculture accounted for 44.8 percent in 2018 (FAO 2020).Taking into account only marine and coastal aquaculture, seaweeds (32.4 million tons) contributed 51.3 percent of all aquaculture in 2018 (FAO 2020). Brown algae are one of the most exploited and promising families of macroalgae due to their high concentration of useful substances including functional polysaccharides (e.g., fucoidan, laminarin), polyphenols, phlorotannins, protein, vitamins, and minerals. Brown seaweed (15 million tons) has historically accounted for roughly 46.1 percent of total seaweed production (FAO 2020). In fact, it appears that the utilisation of marine biomass and the valorization of by-products of seafood, whether directly or through the extraction of biopolymers, represent promising alternatives that could result in more economically advantageous and environmentally responsible uses of marine resources. Depending on the species, alginophytic seaweeds make up beValorization of Seaweed Waste and its Potential Use C. Sathishkumar, G. Sanjay and Amit Ranjan Brown Seaweeds are known for their polysaccharide components.
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