336
J. Jeevanandam et al.
based on their structural cyclization, hydrogenation, and chemical groups that are
responsible for the bioactivity (Dutta et al. 2005).
Further, these colored pigments are categorized as major and minor carotenoid
groups. Carotenoids that constitute the physical characteristics of xanthophylls are
called major carotenoids, whereas the minor carotenoids are formed in large quantities by the microalgae due to firm external environmental stimulus (Eonseon
et al. 2003). Most carotenoids contain C40 hydrocarbon backbone, having basic
eight isoprenoid units with double bonds that are conjugated in the series. These
carotenoids could be cyclic or linear molecules with or without oxygen. Further,
carotene and xanthophylls are considered as two major carotenoids groups. Hydrocarbon carotenoids are called carotenes as they do not contain any oxygen compound
or its subordinates in their structures, whereas oxygenated derivatives of carotene are
xanthophylls with oxygen being in the group of hydroxyl form (e.g., Zeaxanthin),
oxi-groups (e.g., echinenone) or in combinations (e.g., astaxanthin) (Del Campo et al.
2000). Other substituent groups such as epoxy is present in violaxanthin and diadinoxanthin; acetyl group is present in dinoxanthin and fucoxanthin in the structures.
Additionally, xanthophylls being hydrophobic molecules are either membrane-linked
or have exclusive protein interactions via non-covalent bonds and are commonly
present in the membrane of thylakoids. Minor carotenoids are present in vesicles
formed by lipids and possess extraplastidic property (Grossman et al. 1995).
For most carotenoids, three major absorption maxima have been recorded. The
absorption maximum is affected by cyclization and oxygenation. The common
cyanobacterial carotenoids are β-carotene (only cyclic compounds), zeaxanthin,
ketocarotenoid, echinenone, and carotenoid glycoside myxoxanthophyll. Primary
carotenoids of green algae include β-carotene, lutein, and violaxanthnin that are
present within the chloroplasts along with chlorophyll. Till date, more than 600
xanthophylls have been reported with different oxygen containing groups and their
combinations (Lemoine and Schoefs 2010). Certain green algae, including Chlorella
sp. accumulates biomass of carotenoids and are considered as good sources of
carotenoids (Bhosale and Bernstein 2005).
Dunaliella salina is the preferred microalgae for β-carotene production due to
its highest carotenoid content (10% dry weight) (Prieto et al. 2011a). Under critical conditions such as nutrient limitation, high salt and light, these microalgae can
produce 14% of β-carotene in its dry weight. Growth rate and yield of β-carotene
by Dunaliella is increased, when seaweeds are cultivated at higher concentrations
(Raja et al. 2004). Dunaliella cultures are used to extract β-carotene using biphasic
aqueous or organic systems (Hejazi et al. 2003, 2004). Cyanobacterial species Synechocystis sp. PCC6803 and Synechococcus sp. PCC702 are good candidates that
accumulates β-carotene after genetic modification (Macias-Sanchez et al. 2009).
Moreover, the different strains of Synechococcus are reported to contain β-carotene,
equinone and other phycopigments at varying extents (Kaur et al. 2009). Extraction of carotenoids is performed using organic solvents including acetone, methanol,
or dimethyl sulfoxide (DMSO). Commercially, Dunaliella is cultivated throughout
J. Jeevanandam et al.
based on their structural cyclization, hydrogenation, and chemical groups that are
responsible for the bioactivity (Dutta et al. 2005).
Further, these colored pigments are categorized as major and minor carotenoid
groups. Carotenoids that constitute the physical characteristics of xanthophylls are
called major carotenoids, whereas the minor carotenoids are formed in large quantities by the microalgae due to firm external environmental stimulus (Eonseon
et al. 2003). Most carotenoids contain C40 hydrocarbon backbone, having basic
eight isoprenoid units with double bonds that are conjugated in the series. These
carotenoids could be cyclic or linear molecules with or without oxygen. Further,
carotene and xanthophylls are considered as two major carotenoids groups. Hydrocarbon carotenoids are called carotenes as they do not contain any oxygen compound
or its subordinates in their structures, whereas oxygenated derivatives of carotene are
xanthophylls with oxygen being in the group of hydroxyl form (e.g., Zeaxanthin),
oxi-groups (e.g., echinenone) or in combinations (e.g., astaxanthin) (Del Campo et al.
2000). Other substituent groups such as epoxy is present in violaxanthin and diadinoxanthin; acetyl group is present in dinoxanthin and fucoxanthin in the structures.
Additionally, xanthophylls being hydrophobic molecules are either membrane-linked
or have exclusive protein interactions via non-covalent bonds and are commonly
present in the membrane of thylakoids. Minor carotenoids are present in vesicles
formed by lipids and possess extraplastidic property (Grossman et al. 1995).
For most carotenoids, three major absorption maxima have been recorded. The
absorption maximum is affected by cyclization and oxygenation. The common
cyanobacterial carotenoids are β-carotene (only cyclic compounds), zeaxanthin,
ketocarotenoid, echinenone, and carotenoid glycoside myxoxanthophyll. Primary
carotenoids of green algae include β-carotene, lutein, and violaxanthnin that are
present within the chloroplasts along with chlorophyll. Till date, more than 600
xanthophylls have been reported with different oxygen containing groups and their
combinations (Lemoine and Schoefs 2010). Certain green algae, including Chlorella
sp. accumulates biomass of carotenoids and are considered as good sources of
carotenoids (Bhosale and Bernstein 2005).
Dunaliella salina is the preferred microalgae for β-carotene production due to
its highest carotenoid content (10% dry weight) (Prieto et al. 2011a). Under critical conditions such as nutrient limitation, high salt and light, these microalgae can
produce 14% of β-carotene in its dry weight. Growth rate and yield of β-carotene
by Dunaliella is increased, when seaweeds are cultivated at higher concentrations
(Raja et al. 2004). Dunaliella cultures are used to extract β-carotene using biphasic
aqueous or organic systems (Hejazi et al. 2003, 2004). Cyanobacterial species Synechocystis sp. PCC6803 and Synechococcus sp. PCC702 are good candidates that
accumulates β-carotene after genetic modification (Macias-Sanchez et al. 2009).
Moreover, the different strains of Synechococcus are reported to contain β-carotene,
equinone and other phycopigments at varying extents (Kaur et al. 2009). Extraction of carotenoids is performed using organic solvents including acetone, methanol,
or dimethyl sulfoxide (DMSO). Commercially, Dunaliella is cultivated throughout