**6.1 Food applications**

Natural biopolymers as nanocarriers, such as cereals, alginate, starch, casein, whey protein, gelatin, zein, gluten, chitosan, and so on, have revolutionized the food industry as they have been successfully incorporated for encapsulating daily food by using nano- or microtechnology to ensure healthy, safe, sustainable, secure, and good-quality food [38].

Sodium alginate is a water-soluble polymer that creates highly viscous solutions and can be used as a stabilizer, stabilizer and thickener in various industries, especially food industries [39].

Alginate is commonly used in the food industry to modify some food characteristics such as rheology (thickening), water binding capacity, stabilizing emulsion, and film formation [40]. Combined active compound and alginate coating or thin-layered structures are used to increase the storage period of tomato (*Solanum lycopersicum* L.) [41], mushrooms (*Agaricus bisporus*) [42], shrimp [43], turkey filet [44], chicken thigh meat [45], low fat cut cheese [46], and meat [47]. Because of thickening and gelling properties, it can be used in sauces, jam, marmalade, syrups, ice cream toppings, and in fruit pies, and animal food. In the production process of ice cream, the use of propylene glycol alginate in low concentrations results in a soft tissue, low ice crystals and gives desirable feeling to customers during production to consumption. Another alginate application is stabilizing fruit drinks and beer. Alginate is useful in mayonnaise and salad dressing which we know of as water-in-oil emulsions [48]. Calcium alginate structures are considered by the meat industry as an alternative to natural casings from animals. In a 2015 study on the replacement of alginate structures with natural coatings in fermented sausages, at 12 \_C, it was found that alginate coatings could be a suitable alternative to natural coatings [49]. The physiological and rheological properties of alginates, as well as their applications as stabilizers, thickeners, gels, or pharmaceutical additives, are strongly influenced by the composition of uronic acids (M/G ratio) and the distribution of monomers along the chains [50]. Alginate is used due to its low-water solubility and high viscosity, especially in food products. This polysaccharide has antioxidant properties and prevents the unpleasant role of free radicals and oxidative damage in foods and improves the quality of nutrition. Its structural properties such as molecular weight, monosaccharide composition, and glycosidic branching affect its antioxidant activity. The molecular weight and M/G ratio of alginates play an important role in their ability to inhibit free radicals. Low-molecular weight polysaccharides were hypothesized to have more reducing hydroxyl groups (by mass) to accept and scavenge free radicals. On the other hand, the higher proportion of G monomers increases the antioxidant activity because the diaxial bonding in these blocks may cause a hindered rotation around the glycosidic bond. As a result, the flexibility of G-blocks increases, thereby affecting the availability of hydroxyl groups in sodium alginate and the ability to donate H-atoms. Alginates also have the ability to inhibit lipid peroxidation of phosphatidylcholine and linoleate liposomes, protect NT2 neurons from H2O2-induced neurotoxicity, and inhibit free radical chain reactions [51]. A study on sodium alginate from the Tunisian seaweed Gongolaria barbata (formly *Cystoseira barbata*) in 2015 found that it was composed of 37% manuronic and 63% guluronic acids. It is less sensitive to temperature changes and is more stable at an acidic pH. The compound has also been studied for its antioxidant properties and has moderate antioxidant activity and strong protective activity against DNA breakage. Therefore, this alginate could be used as a natural substance in the food or pharmaceutical industries [52]. Alginate is very useful to encapsulate

some strains of live cell of probiotics in both intestinal tract and food products [53]. The microencapsulation technique protects live bacteria during storage time [54]. Generally, alginate can be used as an additive (thickener, emulsifier, stabilizer, etc.) at very low concentrations in milk chocolate and as an ingredient in functional foods (probiotics and prebiotics) [53].

#### **6.2 Non-food applications**

Alginate is another biopolymer that has been used for wastewater treatment [55]. Calcium alginate was modified using graphene oxide and reduced with PEI to improve its adsorption performance for Pb (II), Hg (II), and Cd (II) from aqueous solutions. The study showed that functionalized graphene oxide calcium alginate had a better adsorption capacity as compared to the non-functionalized adsorbent beads. Maximum adsorption capacities of 602, 374, and 181 mg/g were observed for Pb (II), Hg (II), and Cd (II), respectively [56].

#### **6.3 Pharmaceutical applications**

Alginates are made up of two uronic acids: D-mannuronic acid (M) and L-guluronic acid (G) extracted from brown seaweeds Phaeophyceae and kelp [12, 13]. The alginic acid form of alginate is extracted from the seaweed in alkaline conditions, then precipitated and ion exchanged (e.g., with potassium). Alginates have a wide application in the cosmeceutical industry because of their use as high-stability thickening and gelling agents. The first alginate application in the cosmeceutical field started in 1927. Alginate is applicable in grafting the skin in plastic surgery. In wound dressings, hydrogels from gelatin, chitosan, pectin, and alginate are used in the creation of a moist environment in wounds. Calcium alginate, chitosan, collagen, and gelatin are a few examples of biopolymers used in the pharmaceutical industry for purposes such as controlled drug release, artificial skin, dental materials, and cosmetics, among others [55]. Alginate is a widely explored seaweed anionic polysaccharide offering numerous benefits such as non-toxicity, biocompatibility, biodegradability, non-antigenicity, and ease of gelation. It is employed in 3D bioprinting for a variety of biomedical and pharmaceutical applications, such as wound healing, cartilage repair, bone regeneration, and drug delivery [55].

The quality of the alginate mostly depends on the species and the climatic changes. The anionic biopolymer has the key property to form gels in the presence of cations. Sodium alginate is the most commonly used form of alginate used in biomedical and industrial applications [57]. Alginates can be molded to scaffolds, hydrogels, and composites for use in pharmaceutical applications. Some of the pharmaceutical applications of the alginates include drug delivery, protein delivery, wound dressings, and cell culture [58, 59]. Different forms of alginates are also used in blood vessel tissue regeneration, bone tissue engineering, cartilage tissue engineering, muscle, nerve, pancreas, and liver tissue engineering applications [60, 61].

In wound dressings, hydrogels from gelatin, chitosan, pectin, and alginate are used in the creation of a moist environment in wounds. Calcium alginate, chitosan, collagen, and gelatin are a few examples of biopolymers used in the pharmaceutical industry for purposes such as controlled drug release, artificial skin, dental materials, and cosmetics, among others. On the basis of the aforementioned pharmaceutical products, the global biopolymers market is expected to dominate the synthetic polymers market. Promisingly, according to Energias Market Research, the worldwide medical bio-based polymers market is predicted to witness a compound annual growth rate (CAGR) of 15.2% during 2018e24 [62].
