*4.2.2 Phycobiliproteins*

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

substituent that forms main chains with branched side chains [98, 99].

considered to promote the human health [100].

isolate as valuable product from algae [103].

[101, 102].

**4.2 Pigments**

*4.2.1 Carotenoids*

tal stimuli [104].

pressure homogenization [114].

with yield of 7.4 ± 0.4 mg/g.

cell wall of *M. nitidum* and structurally consists of rhamnose with a sulfate-group

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

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

Carotenoids and chlorophylls are generally wasted together with the residual biomass during the extraction of phycocyanin or sulfated polysaccharide, while can

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 environmen-

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

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*

**124**

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 molecular absorptivity at visible wavelengths [122].

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

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 microwave [131].

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 (R-phycoerythrin) [123].

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 has promising applications as antioxidative, anti-inflammatory, antitumor, anti-enterovirus and hepatoprotective [132]. Despite its potential biochemical and therapeutic benefits, there are some challenges in its downstream processing including difficulty in primary extraction and purification, containing lower proportion of phycobiliprotein rather than phycocyanin and the resistance of cell membrane to disruption cause extraction of 50–60% of A-PC by conventional methods. Moreover, the main objective of pigment extraction form *spirulina* is C-PC, consequently, remaining high content of A-PC (about 40–50%) in biomass after C-PC extraction [133].

#### **4.3 Proteins**

Algae protein waste is a by-product derived from water-extraction process of microalgae, during algae essence manufacturing. The underutilized algae wastes, containing above 50% protein, have low economical value to be used as animal feed. The pepsin hydrolysate from algae protein waste exhibited antioxidative activity in preliminary experiments, indicating that algae waste might become a new protein source for selection of novel antioxidative peptides [134].

Furthermore, protein hydrolysates from marine sources such as algae by-products, have generally been used to produce seafood flavorings. A high flavor quality is difficult to ensure for seafood flavoring that is produced from marine animal sources because of their high susceptibility to lipid oxidation and the high cost of removing excess fat. Seaweed by-products after agar extraction are good sources of plant protein and contain taste-active amino acids, such as aspartic acid, glutamic acid, arginine, and lysine, in addition to a low fat content [135].

A seaweed protein hydrolysate using 10% bromelain for 3 h, resulted in high level of arginine, lysine, and leucine as free amino acids. These amino acids exhibited an umami taste and a seaweed odor [135].

Most microalgae contain high level of protein which discarded or damaged during biofuels production, while are good candidate for protein extraction and consequently, obtain lipid-rich product as by-product as feedstock for biofuels production. Even though proteins are major algae biomass component, usually they are undervalued compared to minor components such as omega fatty acids, pigments or other possible valuable buy-products [136].

For instance, Garcia-Moscoso et al. [136] extracted more than 60 wt% of nitrogen content of *Scenedesmus* sp. by subcritical water medium then the lipid-rich residue used as suitable feedstock for biofuel production.

There are numerous investigations about algae protein waste and extraction of peptides or amino acids with functional properties. For instance, the antioxidative peptide of VECYGPNRPQF was isolated by pepsin from *Chlorella vulgaris*. This peptide had some bioactivity such as DNA protective effect against hydroxyl radicals, gastrointestinal enzyme-resistance, and strong antioxidant properties. Fractionation of proteins exhibited the high level of aspartic acid, glutamic acid, leucine and lysine [134]. This amino acid sequence (VECYGPNRPQF) can act as cheap and natural anticancer peptide because had antiproliferation and induced a post-G1 cell cycle arrest in AGS cells with no cytotoxicity effect in WI-38 lung fibroblasts cells [137].

Moreover, protein isolation, as valuable by-product, from defatted *Nannochloropsis*, can be obtained after lipid extraction during biofuel production. Defatted and non-defatted *Nannochloropsis* contained 56.9% and 40.5% protein respectively. The protein yields by alkaline (pH 11 and 60 C) extraction method were 16% and 30% respectively. These isolated proteins had a high molecular weight approximately 250 kDa [138].

**127**

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

protein content reported 18.3, 4.6, 6.2 and 7.1% respectively [140].

Macroalgae are also a suitable protein source and rich in protein after extraction

Brown algae such as *Laurencia filiformis*, *L. intricata*, *Gracilaria domingensis* and *Gracilaria. birdiae* can supply dietary proteins for human and animals because their

Combination of acid-alkaline process is another protein isolation from algae. First acid and then alkaline extraction is an alternative extraction by 59% protein recovery from brown seaweed *Ascophyllum nodosum*. The obtained protein had

This chapter indicated that seafood by-products are one of the most important sources of value added products that can play an important role in the global market due to the increasing growth of demands for health beneficiary products. Through this opportunity and based on our research background for many years, we decided to provide important information about some value-added products obtained from seafood by-products. Proteins and peptides are a major part of the seafood by-products composition that can easily provide essential amino acids and bioactive peptides with health beneficent. Fish oil is another valuable product that could be extracted from seafood by-products. This source is rich in LCPUFA and decreases the risks of chronic diseases such as cardiovascular issues, thereby directly related to our health. Marine algae are a versatile, abundant, and valuable source of many compounds that have been widely used for many industries. The presence of bioactive compounds such as sulfated polysaccharide, carotenoid, and protein makes them a suitable candidate in biomedical applications. It seems, they will play an important role in human life because of their broad applications in food, pharma-

of their polysaccharide, lipid and polyphenols. Among three seaweed *Porphyra umbilicalis*, *Ulva lactuca*, and *Saccharina latissimi*, the highest protein isolated using pH- shift method (71%) was related to the *P. umbilicalis*. Furthermore, among different extraction methods including pH-shift method, accelerated solvent extraction and sonication in water and precipitation by ammonium sulfate, pH shift process is promising approach. However, the yield and extraction approach are

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

influence by type and species of seaweed [139].

about 2–4 kDa molecular weight [141].

ceutical, and cosmetic industries.

The authors declare no conflict of interest.

**Conflict of interest**

**5. Conclusions**

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

Macroalgae are also a suitable protein source and rich in protein after extraction of their polysaccharide, lipid and polyphenols. Among three seaweed *Porphyra umbilicalis*, *Ulva lactuca*, and *Saccharina latissimi*, the highest protein isolated using pH- shift method (71%) was related to the *P. umbilicalis*. Furthermore, among different extraction methods including pH-shift method, accelerated solvent extraction and sonication in water and precipitation by ammonium sulfate, pH shift process is promising approach. However, the yield and extraction approach are influence by type and species of seaweed [139].

Brown algae such as *Laurencia filiformis*, *L. intricata*, *Gracilaria domingensis* and *Gracilaria. birdiae* can supply dietary proteins for human and animals because their protein content reported 18.3, 4.6, 6.2 and 7.1% respectively [140].

Combination of acid-alkaline process is another protein isolation from algae. First acid and then alkaline extraction is an alternative extraction by 59% protein recovery from brown seaweed *Ascophyllum nodosum*. The obtained protein had about 2–4 kDa molecular weight [141].
