480
F. Md. Yusoff et al.
essential for vision and embryological development in human and animals. Thus
carotenoids, which are best known for their yellow, orange and red pigments, are
important micronutrients, used as functional bioactives, feed additives, natural food
ingredients and health supplements (Bonilla-Ahumada et al. 2018; Yusoff et al. 2019).
Carotenoid global market was approximately USD1.24 billion in 2016 and projected
to reach USD1.53 billion by 2021 (Heo et al. 2018).
Carotenoids can be synthesized by most photosynthetic organisms (for light
harvesting and photoprotection) and some non-photosynthetic organisms such as
bacteria and fungi. Rodriguez-Concepcion et al. (2018) summarized that carotenoids
can be found in 691 organisms and categorized them as carotenes (formed exclusively by carbon and hydrogen atoms) and xanthophylls (contain oxygenated radicals) based on their chemical composition. Xanthophylls are further classified into
those with hydroxyl (lutein and zeaxanthin), epoxide (violaxanthin, neoxanthin) or
carbonyl (canthaxanthin, capsaxanthin) groups. Other oxygenated groups in natural
carotenoids include carboxylic, acetate, lactone and sulphate groups.
Like the culture of microalgae biomass which is controlled by the physicochemical factors of the culture media, the molecular contents of microalgae cells
are also related to the surrounding environmental factors. Thus, microalgae and their
biomolecule productivity can be enhanced by manipulating the growth factors such
as light, temperature, pH, nutrients, aeration and mixing (Sun et al. 2015; Yusoff et al.
2019). Benavente-Valdés et al. (2016) manipulated different factors such as nutrient
sources (nitrogen, phosphorus, carbon) and physical factors (light intensity, salinity
and electromagnetic fields) to optimize the biomass and pigment yields in microalgae
culture. Similarly, Hagen et al. (2001) studied the effects of light, nitrate, acetate and
phosphate on the growth of H. pluvialis and concluded that more detail studies should
be carried out to determine the pathways of the pigment biosynthesis. Rearte et al.
(2018) demonstrated that lipids and carotenoid contents of a microalga, Golenkinia
sp. could be induced by increased salinity. Other carotenoids, such as lutein productivity also could be optimized by regulating light intensity and carbon source (Ho
et al. 2014; Heo et al. 2018). Thus, biotic stresses are important tools for metabolites in microalgae. Temperature, nutrient starvation, salinity and light affect PUFAs,
nitrogen and light stress stimulate phycobiliproteins, while salinity, light and nutrients influence carotenoids (Sun et al. 2015; Adenan et al. 2016; Benavente-Valdés
et al. 2016; Imaizumi et al. 2016; Rearte et al. 2018).
19.4.1 Astaxanthin
Astaxanthin (3, 30-dihydroxy-b,b-carotene-4,40 dione) is a red ketocarotenoid from
the xanthophyll group with high antioxidant property and thus demand a high
commercial market. Some plants, microalgae, bacteria and fungi are known to synthesize astaxanthin. Astaxanthin has superior health-related properties compared to
other carotenoids such as β-carotene, lutein, lycopene, canthaxanthin and vitamin
E, and thus a sought-after pigment globally as it is becoming a popular dietary
F. Md. Yusoff et al.
essential for vision and embryological development in human and animals. Thus
carotenoids, which are best known for their yellow, orange and red pigments, are
important micronutrients, used as functional bioactives, feed additives, natural food
ingredients and health supplements (Bonilla-Ahumada et al. 2018; Yusoff et al. 2019).
Carotenoid global market was approximately USD1.24 billion in 2016 and projected
to reach USD1.53 billion by 2021 (Heo et al. 2018).
Carotenoids can be synthesized by most photosynthetic organisms (for light
harvesting and photoprotection) and some non-photosynthetic organisms such as
bacteria and fungi. Rodriguez-Concepcion et al. (2018) summarized that carotenoids
can be found in 691 organisms and categorized them as carotenes (formed exclusively by carbon and hydrogen atoms) and xanthophylls (contain oxygenated radicals) based on their chemical composition. Xanthophylls are further classified into
those with hydroxyl (lutein and zeaxanthin), epoxide (violaxanthin, neoxanthin) or
carbonyl (canthaxanthin, capsaxanthin) groups. Other oxygenated groups in natural
carotenoids include carboxylic, acetate, lactone and sulphate groups.
Like the culture of microalgae biomass which is controlled by the physicochemical factors of the culture media, the molecular contents of microalgae cells
are also related to the surrounding environmental factors. Thus, microalgae and their
biomolecule productivity can be enhanced by manipulating the growth factors such
as light, temperature, pH, nutrients, aeration and mixing (Sun et al. 2015; Yusoff et al.
2019). Benavente-Valdés et al. (2016) manipulated different factors such as nutrient
sources (nitrogen, phosphorus, carbon) and physical factors (light intensity, salinity
and electromagnetic fields) to optimize the biomass and pigment yields in microalgae
culture. Similarly, Hagen et al. (2001) studied the effects of light, nitrate, acetate and
phosphate on the growth of H. pluvialis and concluded that more detail studies should
be carried out to determine the pathways of the pigment biosynthesis. Rearte et al.
(2018) demonstrated that lipids and carotenoid contents of a microalga, Golenkinia
sp. could be induced by increased salinity. Other carotenoids, such as lutein productivity also could be optimized by regulating light intensity and carbon source (Ho
et al. 2014; Heo et al. 2018). Thus, biotic stresses are important tools for metabolites in microalgae. Temperature, nutrient starvation, salinity and light affect PUFAs,
nitrogen and light stress stimulate phycobiliproteins, while salinity, light and nutrients influence carotenoids (Sun et al. 2015; Adenan et al. 2016; Benavente-Valdés
et al. 2016; Imaizumi et al. 2016; Rearte et al. 2018).
19.4.1 Astaxanthin
Astaxanthin (3, 30-dihydroxy-b,b-carotene-4,40 dione) is a red ketocarotenoid from
the xanthophyll group with high antioxidant property and thus demand a high
commercial market. Some plants, microalgae, bacteria and fungi are known to synthesize astaxanthin. Astaxanthin has superior health-related properties compared to
other carotenoids such as β-carotene, lutein, lycopene, canthaxanthin and vitamin
E, and thus a sought-after pigment globally as it is becoming a popular dietary