**Abstract**

Aquatic, marine and algae, is reservoir of bioactive compounds, which have considerable potential to supply novel ingredients toward the development of commercial functional food products. Meanwhile, several valuable by-products generate during the manufacturing process. Seafood is still an intact reservoir of valuable compounds with significant potential to provide unique compounds applicable in functional food development. Seafood, as an important part of the diet all around the world, can be used as a source of functional components that are positively affecting the human health. Annually, 50–80 percent of the seafood processing is discarded as waste every year. Algae are also the novel natural resources for their biological and pharmacological properties. This chapter will be discussing the innovations in seafood and algae sector through the valorization of their by-products. Firstly, protein production, its characterization and the protein hydrolysates derived from seafood will be reviewed. Subsequently, bioactivity of the peptides obtained from these protein hydrolysates and other bioactive compounds such as carotenoid compounds derived from seafood including fish, shrimp, alga, and so on will be included. Finally, the main components of algae including sulfated polysaccharides, pigments and proteins will be surveyed.

**Keywords:** seafood by-products, algae by-products, bioactive compounds, protein, pigments, carotenoids, sulfated polysaccharides

## **1. Introduction**

It is well-known that the seafood has been one of the most important parts of the human nutrition for a long time. According to reports obtained from FAO, the annual discard from global marine capture between 2010 and 2014 was 9.1 million tons. This huge amount of by-products represents 10.8% (10.1% –11.5%) of the annual average catch of 2010 to 2014 [1]. Utilizing this discarded part of the fishery industries could be environmentally and economically profitable.

Several value added products can be generated from seafood processing byproducts depending on which kind of seafood is processed. Based on this, this chapter is divided into 3 major parts; (I) fish by-products, (II) crustaceans, and (III) seaweeds. This study has provided a review of use of fish by-products to produce some value added products including proteins, peptides, and oil. These products are the most

important major products that have a promising future in global market. During last decades, different efforts have been done to utilize the seafood by-products to generate these value added products [2]. Obtaining proteins and peptides as functional and nutritional compounds from seafood by-products have been the objective of many researches [3–9].

Algae are an important renewable source of food, medicines and fertilizers and their utilization have increased in all around the world. They are considered to possess a high nutritional value and their metabolites, and associated biological activities, have particular significance for multiple nutraceutical, cosmetic and pharmaceutical applications [10, 11]. Seaweed consumption has a long tradition in Asian countries and has increased in European countries in over recent decades, due to increased awareness of their beneficial effects [12]. Thus, development of way for the utilization of marine algae for food, feed, and bioenergy is essential. One of the best way is conversion of biomass into a variety of valuable products which is known as biorefinery [13].

In recent years, numerous compounds with biological activities or pharmacological properties such as antibacterial, anti-inflammatory, anticancer, antiviral and anticoagulant are discovered in algae. Algae by-products can be used for human and animal as food, animal feed and ingredients of dietary supplements. Sulfated polysaccharides, pigments, proteins and lipid are the main by-products of algae [12].

This chapter focuses on important value added bioactive chemicals identified in seafood by products over the last years and describes the range of biological activities as well as industrial applications for which they are responsible.

### **2. Fish by-products**

#### **2.1 Proteins**

Fish by-products obtained from seafood processing industries contain huge amounts of head, skin, scales, bones, fins, viscera, and dark muscle. The protein content of these by-products is approximately 15%, which is similar to that of fish fillets. The muscle which is attached to this by-product contains two distinct type of proteins including structural (myofibrillar) (approximately 70–80%) and sarcoplasmic proteins (approximately 20–30%). These high nutritional value proteins (even more than red meat and milk casein) indicate remarkable functional and technological properties like water holding capacity, emulsifying activity, film forming ability, foam forming capacity, and gel forming ability [14–17]. Commercial gelatins are mostly obtained from mammalian (porcine and bovine) skins and bones. As the researches confirm, the substitution of mammalian gelatin with fish gelatin is an appropriate and appealing due to increasing concerns of researchers and consumers about the risks of transmission of the pathogenic vectors such as prions. Albeit, number of committees like the Scientific Steering Committee of the European Union, have stated that consumption of bovine bone gelatin is safe [18], researchers are still debating on this.

Nowadays, researches have become to notice on a unique protein which can be easily extracted from fish by-products especially skin, scales, bones, and fins. This valuable protein is collagen/gelatin. Collagen is the most abundant protein in tissues including skin and bones (approximately 30% of the total protein). The structural investigates show that collagen is a triple helix with three identical polypeptide chains. The primary structure of this protein is continuous repeating of the Gly-X-Y-sequence. The positions of X and Y are mostly proline and hydroxyproline, respectively. Different types of collagen (29 distinct types) have been discovered

**119**

**Figure 2**.

**Figure 1.**

**2.2 Peptides**

*Innovation in the Seafood Sector through the Valorization of By-Products*

so far, which have right-handed triple helical conformation. The difference among these types is due to the variety in their amino acid sequences as a result of genetic variants [19–21]. Fish gelatin could be extracted from its by-products by a partially denaturation of collagen usually performed by hot water. Before extraction of fish by-products, some pretreatments are needed to ready them for being used as a gelatin source. The pretreatment step is ordinarily an alkaline and/or and acidic swelling process. The alkaline and/or acidic pretreatment is used to partial cleavage of rigid cross-links in the collagen and remove non-collagenous materials. The enzymatic aided chemical pretreatments are those which can be supplemented or replaced by enzymatic reaction. The "conditioning process" is the known name of this step by manufacturers of gelatin. Afterward, the gelatin (warm water soluble) will be extracted from collagen (not soluble) by hot water at a specific temperature and time. There are lots of studies performed in this research area. In a paper authored by Mirzapour-Kouhdasht, Moosavi-Nasab [22], gelatin was optimized at different levels of time and temperature using the response surface methodology (RSM). The responses including yield, protein content, gel strength, and viscosity indicated that the optimum conditions were 70.71°C and 5.85 h. Rheological, structural, and functional experiments showed that the gelatin characteristics were acceptable compared to the commercial bovine gelatin. The pretreatment in these experiments was performed by alkaline solution. In another study [23], gelatin was produced from Common carp wastes using alkaline protease from *Bacillus licheniformis* PTCC 1595. The enzymatic reaction was performed in 5, 10, 15, 20, and 25 units per gram of wastes. The molecular weight distribution of the gelatin (**Figure 1**) showed that

*Molecular weight distribution analysis by SDS-PAGE for gelatins. CG (commercial gelatin) and FG (fish* 

this gelatin could be successively replace the commercial gelatin.

In some researches also fish gelatin is modified by some functional groups or chemical agents to improve the functional characteristics. In a study performed by [24], rheological, emulsifying, and structural properties of phosphorylated fish gelatin was investigated. The results of this study revealed that phosphorylation in a short time, enhances gel and rheological behavior of fish gelatin. Phosphorylation could improve the emulsions stability of fish gelatin as well. Authors stated that the structural properties of fish gelatin were significantly affected by this modification

Peptides obtained from seafood processing by-products have been reported to have potent biological activities including antioxidant activity [25–31], antihypertensive, anticancer, anti-inflammatory, and anticoagulant properties [22, 32–37]. Among all these researches, the use of gelatin derived from fish by-products has

*DOI: http://dx.doi.org/10.5772/intechopen.95008*

*wastes gelatin) (a) and for protease (b). Adapted from [23].*

*Innovation in the Seafood Sector through the Valorization of By-Products DOI: http://dx.doi.org/10.5772/intechopen.95008*

#### **Figure 1.**

*Innovation in the Food Sector Through the Valorization of Food and Agro-Food By-Products*

researches [3–9].

known as biorefinery [13].

**2. Fish by-products**

[18], researchers are still debating on this.

**2.1 Proteins**

important major products that have a promising future in global market. During last decades, different efforts have been done to utilize the seafood by-products to generate these value added products [2]. Obtaining proteins and peptides as functional and nutritional compounds from seafood by-products have been the objective of many

Algae are an important renewable source of food, medicines and fertilizers and their utilization have increased in all around the world. They are considered to possess a high nutritional value and their metabolites, and associated biological activities, have particular significance for multiple nutraceutical, cosmetic and pharmaceutical applications [10, 11]. Seaweed consumption has a long tradition in Asian countries and has increased in European countries in over recent decades, due to increased awareness of their beneficial effects [12]. Thus, development of way for the utilization of marine algae for food, feed, and bioenergy is essential. One of the best way is conversion of biomass into a variety of valuable products which is

In recent years, numerous compounds with biological activities or pharmacological properties such as antibacterial, anti-inflammatory, anticancer, antiviral and anticoagulant are discovered in algae. Algae by-products can be used for human and animal as food, animal feed and ingredients of dietary supplements. Sulfated polysaccharides, pigments, proteins and lipid are the main by-products of algae [12]. This chapter focuses on important value added bioactive chemicals identified in seafood by products over the last years and describes the range of biological activi-

Fish by-products obtained from seafood processing industries contain huge amounts of head, skin, scales, bones, fins, viscera, and dark muscle. The protein content of these by-products is approximately 15%, which is similar to that of fish fillets. The muscle which is attached to this by-product contains two distinct type of proteins including structural (myofibrillar) (approximately 70–80%) and sarcoplasmic proteins (approximately 20–30%). These high nutritional value proteins (even more than red meat and milk casein) indicate remarkable functional and technological properties like water holding capacity, emulsifying activity, film forming ability, foam forming capacity, and gel forming ability [14–17]. Commercial gelatins are mostly obtained from mammalian (porcine and bovine) skins and bones. As the researches confirm, the substitution of mammalian gelatin with fish gelatin is an appropriate and appealing due to increasing concerns of researchers and consumers about the risks of transmission of the pathogenic vectors such as prions. Albeit, number of committees like the Scientific Steering Committee of the European Union, have stated that consumption of bovine bone gelatin is safe

Nowadays, researches have become to notice on a unique protein which can be easily extracted from fish by-products especially skin, scales, bones, and fins. This valuable protein is collagen/gelatin. Collagen is the most abundant protein in tissues including skin and bones (approximately 30% of the total protein). The structural investigates show that collagen is a triple helix with three identical polypeptide chains. The primary structure of this protein is continuous repeating of the Gly-X-Y-sequence. The positions of X and Y are mostly proline and hydroxyproline, respectively. Different types of collagen (29 distinct types) have been discovered

ties as well as industrial applications for which they are responsible.

**118**

*Molecular weight distribution analysis by SDS-PAGE for gelatins. CG (commercial gelatin) and FG (fish wastes gelatin) (a) and for protease (b). Adapted from [23].*

so far, which have right-handed triple helical conformation. The difference among these types is due to the variety in their amino acid sequences as a result of genetic variants [19–21]. Fish gelatin could be extracted from its by-products by a partially denaturation of collagen usually performed by hot water. Before extraction of fish by-products, some pretreatments are needed to ready them for being used as a gelatin source. The pretreatment step is ordinarily an alkaline and/or and acidic swelling process. The alkaline and/or acidic pretreatment is used to partial cleavage of rigid cross-links in the collagen and remove non-collagenous materials. The enzymatic aided chemical pretreatments are those which can be supplemented or replaced by enzymatic reaction. The "conditioning process" is the known name of this step by manufacturers of gelatin. Afterward, the gelatin (warm water soluble) will be extracted from collagen (not soluble) by hot water at a specific temperature and time. There are lots of studies performed in this research area. In a paper authored by Mirzapour-Kouhdasht, Moosavi-Nasab [22], gelatin was optimized at different levels of time and temperature using the response surface methodology (RSM). The responses including yield, protein content, gel strength, and viscosity indicated that the optimum conditions were 70.71°C and 5.85 h. Rheological, structural, and functional experiments showed that the gelatin characteristics were acceptable compared to the commercial bovine gelatin. The pretreatment in these experiments was performed by alkaline solution. In another study [23], gelatin was produced from Common carp wastes using alkaline protease from *Bacillus licheniformis* PTCC 1595. The enzymatic reaction was performed in 5, 10, 15, 20, and 25 units per gram of wastes. The molecular weight distribution of the gelatin (**Figure 1**) showed that this gelatin could be successively replace the commercial gelatin.

In some researches also fish gelatin is modified by some functional groups or chemical agents to improve the functional characteristics. In a study performed by [24], rheological, emulsifying, and structural properties of phosphorylated fish gelatin was investigated. The results of this study revealed that phosphorylation in a short time, enhances gel and rheological behavior of fish gelatin. Phosphorylation could improve the emulsions stability of fish gelatin as well. Authors stated that the structural properties of fish gelatin were significantly affected by this modification **Figure 2**.

#### **2.2 Peptides**

Peptides obtained from seafood processing by-products have been reported to have potent biological activities including antioxidant activity [25–31], antihypertensive, anticancer, anti-inflammatory, and anticoagulant properties [22, 32–37]. Among all these researches, the use of gelatin derived from fish by-products has

**Figure 2.**

*Micrographs of control and phosphorylated fish gelatin. SEM (A) and AFM (B). Adapted from [24].*

been well investigated as a source of bioactive peptides with various biological activities. In a study performed by Jin, Teng [38], salmon skin collagen was hydrolyzed by different proteolytic enzymes including pepsin, trypsin, papain, and Alcalase 2.4 L. Hydrolysates obtained from trypsin hydrolysis reaction indicated the highest dipeptidyl peptidase IV (DPP-IV) inhibitory activity (66.12%). After fractionation and identification processes, a bioactive peptide with sequence of LDKVFR for DPP-IV inhibitory activity was detected to be responsible for this activity (IC50 value of 0.1 ± 0.03 mg/mL). In another research conducted by Mirzapour-Kouhdasht and Moosavi-Nasab [39], gelatin extracted from *Scomberomorus commerson* skin in combination with its hydrolysates obtained by Actinidin from kiwifruit was used to extent the shelf-life of whole shrimp (*Penaeus merguiensis*). The results revealed that the gelatin hydrolysates can be applied as a preservative coating agent for whole shrimp.

## **2.3 Oil**

Nowadays, of the most important nutritional substances which have gained much attention are Omega-3 long-chain polyunsaturated fatty acids (LCPUFA). These LCPUFA are necessary for human and animal physiology due to their

**121**

*Innovation in the Seafood Sector through the Valorization of By-Products*

structural and regulatory functions [40]. Fish by-products are a good natural source of LCPUFA, especially EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Fish oil is rich in vitamins (E, D, A). Due to these valuable components, fish oil consumption could be a promising way to impede some health risks such as inflammation, coronary heart diseases, obesity, arthritis, autoimmune disorders,

Generally, the extraction of oils from fish by-products can be divided in two categories including conventional and modern methods. Generally, in conventional methods the raw material (fish by-products obtained from fish processing industries) are first cooked. After the cooking, the by-products are sieved followed by pressing for oil extraction. Subsequently the extracted slurry is decanted and the oil

In comparison with conventional extraction method, the modern extraction methods such as supercritical fluid extraction (SFE) could be useful for reducing the oxidation of LCPUFA. In a research performed by Rubio-Rodríguez and coworkers [46], SFE method with carbon dioxide under moderate conditions (25 MPa and 313 K) was used to extract oil from different fish by-products. They resulted that SFE is an advantageous method for oil extraction from fish by-products. The authors stated that the SFE can impede lipid oxidation and reduce extraction of impurities. In another study conducted by Sabzipour and others [47], quality of rainbow trout (*Oncorhynchus mykiss*) by-products oil was investigated. However, the aim of this study was to determine the effect of different postmortem processing times and blanching methods. The authors presented that the degradation of fish by-products oil occurs faster than the fish tissue oil. So they surveyed the effect of different treatments on the quality of the fish by-products oil. According to their report, salt blanching could decrease the effects of delayed processing and led to a

However, the limitation of fish oil for utilization in food and pharmaceutical industries is related to the low stability and strong fishy flavor. The solution for this problem is to encapsulate the fish oil using different strategies to cover the off-flavor and also increase the stability. In a research performed by Drusch et al. [48], fish oil with was microencapsulated by spray-drying in a matrix of n-octenylsuccinatederivatized starch and sugars. The results of this study indicated that this protocol can increase the oxidative stability of fish oil without any significant changes in physicochemical properties of the oil such as particle size, oil droplet size, and true density. Another study conducted by Chen et al. [49], the fish oil co-encapsulated with phytosterol ester and limonene, prepared by spray-drying and freeze-drying methods. The wall material used for encapsulation were whey protein isolate and soluble corn fiber. Sensory analysis of the encapsulated fish oil showed that the addition of limonene could cover the fishy flavor. The authors also reported that this procedure could significantly enhance the oxidative stability of the fish oil during

Tremendous amounts of shrimp processing by-products (head and body carapace) are discarded annually, which could be an important source of bioactive molecules. The amount of by-products generated during processing is about 48–56% of the whole shrimp depending on the species. The major composition of these byproducts are protein (35–50%), polysaccharide (predominantly chitin) (15–25%),

*DOI: http://dx.doi.org/10.5772/intechopen.95008*

and cancer [41–44].

higher quality.

168 h of storage.

**3. Crustaceans**

**3.1 Proteins and peptides**

is stored in oil storing tanks [45].

#### *Innovation in the Seafood Sector through the Valorization of By-Products DOI: http://dx.doi.org/10.5772/intechopen.95008*

*Innovation in the Food Sector Through the Valorization of Food and Agro-Food By-Products*

been well investigated as a source of bioactive peptides with various biological activities. In a study performed by Jin, Teng [38], salmon skin collagen was hydrolyzed by different proteolytic enzymes including pepsin, trypsin, papain, and Alcalase 2.4 L. Hydrolysates obtained from trypsin hydrolysis reaction indicated the highest dipeptidyl peptidase IV (DPP-IV) inhibitory activity (66.12%). After fractionation and identification processes, a bioactive peptide with sequence of LDKVFR for DPP-IV inhibitory activity was detected to be responsible for this activity (IC50 value of 0.1 ± 0.03 mg/mL). In another research conducted by Mirzapour-Kouhdasht and Moosavi-Nasab [39], gelatin extracted from *Scomberomorus commerson* skin in combination with its hydrolysates obtained by Actinidin from kiwifruit was used to extent the shelf-life of whole shrimp (*Penaeus merguiensis*). The results revealed that the gelatin hydrolysates can be applied as a

*Micrographs of control and phosphorylated fish gelatin. SEM (A) and AFM (B). Adapted from [24].*

Nowadays, of the most important nutritional substances which have gained much attention are Omega-3 long-chain polyunsaturated fatty acids (LCPUFA). These LCPUFA are necessary for human and animal physiology due to their

preservative coating agent for whole shrimp.

**120**

**2.3 Oil**

**Figure 2.**

structural and regulatory functions [40]. Fish by-products are a good natural source of LCPUFA, especially EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Fish oil is rich in vitamins (E, D, A). Due to these valuable components, fish oil consumption could be a promising way to impede some health risks such as inflammation, coronary heart diseases, obesity, arthritis, autoimmune disorders, and cancer [41–44].

Generally, the extraction of oils from fish by-products can be divided in two categories including conventional and modern methods. Generally, in conventional methods the raw material (fish by-products obtained from fish processing industries) are first cooked. After the cooking, the by-products are sieved followed by pressing for oil extraction. Subsequently the extracted slurry is decanted and the oil is stored in oil storing tanks [45].

In comparison with conventional extraction method, the modern extraction methods such as supercritical fluid extraction (SFE) could be useful for reducing the oxidation of LCPUFA. In a research performed by Rubio-Rodríguez and coworkers [46], SFE method with carbon dioxide under moderate conditions (25 MPa and 313 K) was used to extract oil from different fish by-products. They resulted that SFE is an advantageous method for oil extraction from fish by-products. The authors stated that the SFE can impede lipid oxidation and reduce extraction of impurities. In another study conducted by Sabzipour and others [47], quality of rainbow trout (*Oncorhynchus mykiss*) by-products oil was investigated. However, the aim of this study was to determine the effect of different postmortem processing times and blanching methods. The authors presented that the degradation of fish by-products oil occurs faster than the fish tissue oil. So they surveyed the effect of different treatments on the quality of the fish by-products oil. According to their report, salt blanching could decrease the effects of delayed processing and led to a higher quality.

However, the limitation of fish oil for utilization in food and pharmaceutical industries is related to the low stability and strong fishy flavor. The solution for this problem is to encapsulate the fish oil using different strategies to cover the off-flavor and also increase the stability. In a research performed by Drusch et al. [48], fish oil with was microencapsulated by spray-drying in a matrix of n-octenylsuccinatederivatized starch and sugars. The results of this study indicated that this protocol can increase the oxidative stability of fish oil without any significant changes in physicochemical properties of the oil such as particle size, oil droplet size, and true density. Another study conducted by Chen et al. [49], the fish oil co-encapsulated with phytosterol ester and limonene, prepared by spray-drying and freeze-drying methods. The wall material used for encapsulation were whey protein isolate and soluble corn fiber. Sensory analysis of the encapsulated fish oil showed that the addition of limonene could cover the fishy flavor. The authors also reported that this procedure could significantly enhance the oxidative stability of the fish oil during 168 h of storage.

## **3. Crustaceans**

#### **3.1 Proteins and peptides**

Tremendous amounts of shrimp processing by-products (head and body carapace) are discarded annually, which could be an important source of bioactive molecules. The amount of by-products generated during processing is about 48–56% of the whole shrimp depending on the species. The major composition of these byproducts are protein (35–50%), polysaccharide (predominantly chitin) (15–25%),

minerals (10–15%), and a few percent carotenoids [50]. Recently production of bioactive peptides from shrimp by-products has gained attentions. Several researchers found that this source of by-products could be a good one to generate bioactive peptides with especial activities such as angiotensin converting enzyme inhibitory (ACE inhibitory) [51, 52], antimicrobial activity [53], antioxidant activity [52, 54], etc. More investigations are required to characterize the biological and functional properties of these peptides.

#### **3.2 Chitin**

The major value added product obtained from crustaceans is chitin which has the second position among frequent and used biopolymers in the world after cellulose [55, 56]. In fact, chitin is a polymer of β-(1 → 4)- *N* -acetyl- D–glucosamine units which is extracted mainly from shrimp and crabs. This polysaccharide could be found in arthropods exoskeleton or in the cell walls of fungi and yeast as the major prominent structural component [57–65]. Chitosan is a linear polysaccharide derived from chitin deacetylation [66]. Chitin and chitosan have attained lots of attentions due to their non-toxicity, biocompatibility, biodegradability, and low cost [56, 67]. Chitosan is known as a biologically active component in many fields such as food and pharmaceutical applications. A number of activities of this polysaccharide such as making delivery systems [68], tissue engineering [69], food packaging and film forming [70, 71], and antimicrobial and wound healing [72] are investigated.

One of the most important characteristics of chitosan which can affect its pharmaceutical and functional properties is the degree of acetylation. In case of designing delivery systems, the molecular weight of this bioactive molecule becomes more important due to changing the encapsulation efficiency [73]. It is very important to know that chitosan has a higher solubility in lower pH values due to protonation of the amino groups of the molecule [74]. Permeation enhancers substances can increase the absorption of encapsulated biological active compounds in the gastrointestinal tract. One of the mechanisms of this action is opening the tight junctions of the epithelium cells [75, 76]. Chitosan has a mucoadhesive nature and capable to open epithelial connections (tight junctions) of the epithelium cells [77, 78]. **Figure 3** shows a schematically the action place of permeation enhancers to increase the absorbance of bioactive components in gastrointestinal tract.

#### **Figure 3.**

*The action place of permeation enhancers to increase the absorbance of bioactive components in gastrointestinal tract.*

**123**

**Figure 4.**

*Innovation in the Seafood Sector through the Valorization of By-Products*

determined to possess significant various biological activities [79].

Phycocolloids or hydrocolloids are polysaccharides have been one of the most accessible and widely used in food industry as thickening and gel forming agent. Indeed, numerous sulfated polysaccharides from algae including agars, carrageenans and fucoidan (**Figure 4**) are the main bioactive components that have been

Agar is polysaccharide comprised of two major components, agarose and agaropectin and has been extracted from seaweeds for industrial purposes in pharmaceutical, cosmetics and food industry as gelling and thickening agent [80]. The commercially used seaweeds for the extraction of agar are mainly *Gracilaria*

In addition, carrageenan is another linear sulfated polysaccharides that extracted from red seaweed and exhibits several applications in food industries as gelling, thickening, and emulsifying attributes, clarification of beer and wines. Carrageenan mainly obtain from two algae *Kappaphycus* and *Eucheuma* [82]. Fucoidans, a complex sulfated groups with fucose which found mainly in cell-wall matrix of brown macroalgae [83]. In addition to fucose, fucoidan contain other monosaccharides such as glucose, galactose, rhamnose, xylose, mannose and uronic acids [84]. Numerous brown seaweeds have been used for fucoidan extraction including *Sargassum* [85, 86], *Undaria* [87], *Laminaria* [88], *Cladosiphon* [89], *Fucus* [90], *Saccharina* [91] and *Ascophyllum* [92]. Several investigations have been confirmed the biological activities of fucoidan including antitumor, anticoagulant, antioxidant, immunomodulatory, anti-inflammatory, antiviral, antithrombotic, and hepatoprotective effects [93, 94]. This bioactivity of fucoidan is depend on its molecular weight, the monosaccharide composition, the sulfate content, the position of the sulfate ester group, the extraction technique, and fucoidan structure [94]. Thus, several extraction techniques are used such as conventional methods (hot water) [95] and non-conventional methods such as pressurized liquid extraction [84], ultrasound [96], enzyme assisted [90], microwave assisted [97] and

Subsequently, the green algae *Monostroma nitidum* is the commercial source of a sulfated polysaccharide named rhamnan sulfate [98]. Rhamnan sulfate found in

*The chemical structure of (a) agar; (b) carrageenan, (c) fucoidan and (d) Rhamnan sulfate.*

*DOI: http://dx.doi.org/10.5772/intechopen.95008*

**4.1 Sulfated polysaccharides**

and *Gelidium* species [81].

subcritical water [91] extraction.

**4. Algae**

*Innovation in the Seafood Sector through the Valorization of By-Products DOI: http://dx.doi.org/10.5772/intechopen.95008*
