Review on Seaweed based valuable products and their applications

Abstract

Seaweeds are vital resources with economic, societal, and environmental values. These are inhabited in different climatic zones of the oceans. The major factors affecting seaweed distribution are temperature, tidal height, salinity, sea level rise, carbon dioxide (CO2) concentration, and ultraviolet (UV) radiation. Typically, seaweeds are considered a critical source of [bioactive compounds](http://Seaweeds are vital resources with economic, societal, and environmental values. These are inhabited in different climatic zones of the oceans. The major factors affecting seaweed distribution are temperature, tidal height, salinity, sea level rise, carbon dioxide (CO2) concentration, and ultraviolet (UV) radiation. Typically, seaweeds are considered a critical source of bioactive compounds that have broad applications in food, cosmetic, medical, and agricultural fields. Presently, nanomaterials are gaining more attraction in medicine, environment, and food and cosmetic industry. Several metallic nanoparticles (silver and gold) are synthesized from seaweeds. The yield of the bioactive compounds mainly depends on the seaweed species and the extraction method employed. Hence, updated knowledge on these aspects is required for further research. Based on the research outcomes published in journals indexed in Scopus, Web of Science, and regional journals, this review addresses (a) the extraction of bioactive compounds present in seaweeds, (b) the applications of the bioactive compounds obtained from seaweeds, (c) synthesis and applications of biochar and nanomaterials, and (d) application of seaweed extract for crop growth.) that have broad applications in food, cosmetic, medical, and agricultural fields. Presently, nanomaterials are gaining more attraction in medicine, environment, and food and cosmetic industry. Several metallic nanoparticles (silver and gold) are synthesized from seaweeds. The yield of the bioactive compounds mainly depends on the seaweed species and the extraction method employed. Hence, updated knowledge on these aspects is required for further research. Based on the research outcomes published in journals indexed in Scopus, Web of Science, and regional journals, this review addresses (a) the extraction of bioactive compounds present in seaweeds, (b) the applications of the bioactive compounds obtained from seaweeds, © synthesis and applications of biochar and nanomaterials, and (d) application of seaweed extract for crop growth.

Introduction

Seaweeds /marine algae are primitive non-flowering photosynthetic macrophytes present in tidal regions of the oceans; approximately 25,000 to 30,000 species have been identified yet (Santos et al., 2015) and are considered as natural renewable resources. Seaweeds are commercially exploited as they are fast growers, without the need for fertilizers in comparison to terrestrial plants (Lorbeer et al., 2013). Due to the growing demand for marine-based commodities, seaweed cultivation has become one of the leading occupations (Eggertsen and Halling, 2020). It is estimated that about 23.78 million tons (fresh weight) of seaweed was produced during 2012 by aquaculture (Rao et al., 2018). Presently, seaweed cultivation is being practiced in >50 countries, and 28.5 million tons of seaweed and other algae were harvested in 2014. The harvested seaweeds are directly consumed or used as a starting material to produce commercially important products such as hydrocolloids and fertilizers (FAO, 2016). The major hydrocolloids extracted from seaweeds such as alginate, carrageenan, and agar have wide applications in food, pharmaceutical, and biotechnological industries with a market value just above USD 1.1billion (Rhein-Knudsen et al., 2015). Thus, the research on seaweeds and their application have come a long way rapidly (Critchley et al., 2020). Although the distribution and commercial applications of seaweeds have been explored globally, several constraints are faced while gathering the data. Hence, this review highlights the current status of research in seaweed, and the applications.

Critical compounds extracted from seaweeds Seaweeds are rich in protein, amino acids, inorganic salts, vitamins, alginate, enzymes, plant hormones, polyphenols, and polysaccharides (Manimuthu et al., 2015). However, the bioavailability of the organic matter in seaweed biomass is limited by its structural intricacy and the inflexibility of its particles resulting in inefficient degradation (Jung et al., 2015). The seaweed species, Chaetomorpha antennina,contains an organic content of proteins, carbohydrates, and lipids (Premalatha et al., 2011). E. intestinalis contains natural astaxanthin, used as a dietary supplement for improving the quality of tiger shrimp (Penaeus monodon) (Mondal et al., 2015). Moreover, critical products, such as proteins, fatty acids, steroids, carotenoids, phycocolloids, microspotinelike aminoacids, halogenated compounds, and polyketides, are derived from marine-based microalgal species (Rengasamy etal.,2020). The bioactive compounds are present as storage polysaccharides in the cell wall of seaweeds. However, the types of compounds produced are speciesdependent (Holdt and Kraan, 2011), and those in the different groups of seaweeds are listed in Table 1.

Source : [Review on Seaweed based valuable products and their applications](http://Review on Seaweed based valuable products and their applications)