**4. Algae**

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properties of these peptides.

**3.2 Chitin**

investigated.

gastrointestinal tract.

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

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

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

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

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*tract.*

**Figure 3.**

#### **4.1 Sulfated polysaccharides**

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 determined to possess significant various biological activities [79].

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* and *Gelidium* species [81].

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 subcritical water [91] extraction.

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

cell wall of *M. nitidum* and structurally consists of rhamnose with a sulfate-group substituent that forms main chains with branched side chains [98, 99].

This polysaccharide is extracted by hot water, though is poorly water soluble [100]. Several studies exhibit its biological activities such as antiviral, anticoagulant, antitumor, anti-inflammatory, anti-hypercholesterolemic, anti-obesity and anti-hypertensive properties. Further, *M. nitidum*-derived rhamnan sulfate is considered to promote the human health [100].

Calcium spirulan (Ca-SP) is another novel sulfated polysaccharide isolated from blue-green alga Spirulina platensis. Ca-SP is an attractive candidate therapeutic agent for viral infectious diseases because of its antivirus and antitumor activities [101, 102].

#### **4.2 Pigments**

#### *4.2.1 Carotenoids*

Carotenoids and chlorophylls are generally wasted together with the residual biomass during the extraction of phycocyanin or sulfated polysaccharide, while can isolate as valuable product from algae [103].

Carotenoids are the most widespread class of pigments that are characterized as natural colorant and antioxidants with healthy effects including anti-cancer, anti-diabetic anti-obesity and eye diseases. The bio-functional properties of algal carotenoids make them potentially to use in nutraceuticals, cosmeceuticals and feed supplements in aquaculture sectors. Carotenoids divided into primary and secondary based on their metabolism and function. Primary carotenoids are structural and functional components in the photosynthetic apparatus, which take direct part in photosynthesis. Secondary carotenoids refer to extra-plastidic pigments produced in large quantities, through carotenogenesis, after exposure to specific environmental stimuli [104].

Microalgae are a potential renewable resource of primary and secondary carotenoids. α-carotene, β-carotene, lutein, fucoxanthin, violaxanthin, zeaxanthin, and neoxanthin, are characterized as primary carotenoids while astaxanthin, canthaxanthin, and echinenone are secondary carotenoids. Astaxanthin, zeaxanthin, fucoxanthin and lutein receive much attention as commercial carotenoids [104].

Seaweeds are the important sources of bioactive compounds which have several human health benefits. The most predominant seaweed carotenoids, such as fucoxanthin, lutein, β-carotene and siphonaxanthin have remarkable biological functions and applications [105]. Pigments are waste during the polysaccharide extraction process. Thus, carotenoids are recovered from microalgae and seaweeds by different approaches including conventional solvent extraction, non-conventional methods including pulsed electric field [106, 107], moderate electric field [108], supercritical fluid extraction [109], pressurized liquid extraction [110], microwave ssisted extraction [111, 112], ultrasound assisted extraction [113], high pressure homogenization [114].

Fucoxanthin (C42H58O6) is the predominant carotenoid in brown algae (*Sargassum angustifolium*, *Laminaria japonica* and *Undaria pinnatifida*) and some microalgae (*Phaeodactylum tricornutum*, *Isochrysis galbana*, *Odontella aurita*) that accounting for more than 10% of the estimated total natural production of carotenoids. This yellowish-brown pigment exhibit remarkable biological properties, including anticancer, anti-inflammatory, antiobesity and neuroprotective activity [115–117]. Moreover, fucoxanthin extraction can be by-product of fucoidan extraction process as Yip et al., [118] obtained the fucoxanthin-rich extract from *S. binderi* with yield of 7.4 ± 0.4 mg/g.

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microwave [131].

(R-phycoerythrin) [123].

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Astaxanthin as king of antioxidant is found in microalgae such as *Haematococcus*.

Phycobiliproteins are natural fluorescent dyes which participate in photosynthesis. These pigments are assembled large, distinct granules as phycobilisomes, which are attached to the thylakoid membrane of chloroplast. These pigment-protein complex plays an important role in light-harvesting in cyanobacteria, red algae cryptomonads, glaucophytes and some pyrrophyceae [121, 122]. Phycobiliproteins are divided into two main groups; phycoerythrin (PE –bright pink red), phycocyanin (PC –deep blue). The main components of phycocyanins are C-phycocyanin (C-PC), R-phycocyanin (R-PC), and allophycocyanin (AP – bluish green) [121, 122]. Moreover, there are differences between in their structural position. PE is at the tip of the rod-like phycobilisomes, PC is in the middle, while AP forms a core attached to the reaction and energy transfer proceeds successively from PE to PC to AP and to chlorophyll [123]. The other classification of phycobiliproteins is based on their spectral attributes which including phycoerythrobilin (PEB, A max 560 nm), phycocyanobilin (PCB, A max 620–650 nm), phycobiliviolin (PXB, A max 575 nm) and phycourobilin (PUB, A max 498 nm) [123]. These biopigments have attracted much attention in medicines, foods, cosmetics and fluorescent materials. The recent research has brought attention to the use of phycobiliproteins as food colorant, health drink and coloring agent in confectionary and cosmetics because they are hydrophilic and stable at low temperature with some preservative like citric acid, in acidic and basic solutions [121, 123]. Moreover, phycobiliproteins are used in diagnostic kits in immunology as fluorescent tracer of antibodies [123] and gel electrophoresis and gel exclusion chromatography as marker because of their high

Phycocyanins have an apparent molecular mass of 140–210 kD and two subunits, α and β [124]. C-Phycocyanin is found in cyanobacteria strains such as *Spirulina* sp. (freshwater), *Phormidium* sp. (marine water) and *Lyngbya* sp. (marine water) [125]. However, the commercial source of this pigment is *Spirulina* which consists of about 20% of the dry weight of this algae [126]. Further, the other new

Recent studies have demonstrated the role of C-PC as antioxidant, anti-inflammatory, hepatoprotective, and as well as free radical scavenger [128, 129]. Various techniques are used to extract phycocyanin from *Arthrospira platensis* (*Spirulina*) biomass including in various approaches such as physical (freeze–thaw) or an enzymatic (lysozyme) [124], supercritical fluid extraction [130] andsonication and

Phycoerythrin also have numerous health benefits, however, the absorption spectrum of cyanobacteria phycoerythrin is deferent from red algae. The cyanobacteria phycoerythrin exhibits a single peak at 565 nm in the visible wavelength region, while the absorption spectrum of red algae phycoerythrin includes three peaks in the visible wavelength region at 500, 550 and 565 nm

Allophycocyanin is a light-harvesting pigment protein complex found mainly in *A. platensis*. This water-soluble pigment is broadly used in biochemical techniques such as a fluorescent probe, especially for flow cytometry. Further, allophycocyanin

*H. pluvialis* is rich in astaxanthin and provide a natural and inexpensive source of astaxanthin [119]. The antioxidant activity of astaxanthin is 100 and 10 times greater than those of vitamin E and β-carotene. Moreover, astaxanthin has a superior preventive effect toward photo-oxidative compared with canthaxanthin,

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

molecular absorptivity at visible wavelengths [122].

source of phycocyanin is *Anabaena oryzae* SOS13 [124, 127].

and β-carotene [120].

*4.2.2 Phycobiliproteins*

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

Astaxanthin as king of antioxidant is found in microalgae such as *Haematococcus*. *H. pluvialis* is rich in astaxanthin and provide a natural and inexpensive source of astaxanthin [119]. The antioxidant activity of astaxanthin is 100 and 10 times greater than those of vitamin E and β-carotene. Moreover, astaxanthin has a superior preventive effect toward photo-oxidative compared with canthaxanthin, and β-carotene [120].
