14 The Bioeconomy of Production of Microalgal Pigments
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(Guedes et al. 2011). The major microalgal pigments, their source, biological effects
and applications are mentioned in Table 14.1.
14.3.2 Chlorophylls
Chlorophyll molecules are green fat-soluble pigment, universally present in all algal
groups and are classified into three major types, namely, a, b and c of chlorophyll. The
basic structural unit of these molecules is a ring of porphyrin that are coordinated to
a central magnesium atom. Each porphyrin ring consists of a tetrapyrrole ring having
four carbon and one nitrogen in each pyrrole ring (Humphrey 2004). The structural
differences in chlorophyll a (ring II has methyl group) and chl b (formyl group)
is responsible for different absorption maxima (Scheer et al. 2004). Chlorophyll
c is a reddish-brown pigment and similar to chlorophyll b. The pigment obtained
from Chlorophyll a is blue and green in color, having an extreme optical absorption at 660–665 nm, whereas pigment from chlorophyll b is yellow and green in
color with absorption maxima at 642–652 nm (Humphrey 1980; Begum et al. 2015).
Chlorophyll a photosynthetic pigment is highly present in cyanobacteria and red
algae. Chlorophyll b is present in chlorophyta, euglenophyta and marine microalgae,
whereas chlorophyll c is present in dinoflagellates. The green alga Chlorella sp. is
named as Emerald food as it has high (7%) chlorophyll content and is the main
source of chlorophyll production (Bewicke and Potter 2009a). Chlorophyll b is the
major pigment in alga Spirogyra, Chlorella, and Euglena gracilis, whereas Chlorophyll c is present in Fucus vesiculosus, Dunaliella salina, Amphidinium carterae,
and Cryptomonas sp.
The chlorophyll extraction method traditionally involves solvents of organic
origin, namely, acetone, ethanol, diethylformamide, and methanol that dissolve
lipoproteins and lipids into extract phase. Pretreatment methods before extraction, including homogenization and sonication disrupts the cells, so that chlorophyll extraction process is efficient. Homogenization followed by the use of
dimethyl formamide as solvent led to effectual chlorophyll a extraction from algae
Stichococcus sp. and Chlorella sp. (Schumann et al. 2005). Phycopigment extraction
via fluid at supercritical condition (SFE) is better than the solvent-based approaches,
as no carcinogenic solvent is involved, and the extract has better purity with less
processing steps. Being an inert, inflammable, cheap, and readily available, CO 2
are used as SFE in multiple studies, where chlorophyll is extracted from microalgae
Synechococcus sp. (Macias-Sanchez et al. 2009). Following extraction, polyethylene
powder in chromatography column is used in an economically patented method for
separation of chlorophyll a and b from other pigments. The final purification process
involves sucrose filled column that yields highly pure and crystalline chlorophyll
molecules.
333
(Guedes et al. 2011). The major microalgal pigments, their source, biological effects
and applications are mentioned in Table 14.1.
14.3.2 Chlorophylls
Chlorophyll molecules are green fat-soluble pigment, universally present in all algal
groups and are classified into three major types, namely, a, b and c of chlorophyll. The
basic structural unit of these molecules is a ring of porphyrin that are coordinated to
a central magnesium atom. Each porphyrin ring consists of a tetrapyrrole ring having
four carbon and one nitrogen in each pyrrole ring (Humphrey 2004). The structural
differences in chlorophyll a (ring II has methyl group) and chl b (formyl group)
is responsible for different absorption maxima (Scheer et al. 2004). Chlorophyll
c is a reddish-brown pigment and similar to chlorophyll b. The pigment obtained
from Chlorophyll a is blue and green in color, having an extreme optical absorption at 660–665 nm, whereas pigment from chlorophyll b is yellow and green in
color with absorption maxima at 642–652 nm (Humphrey 1980; Begum et al. 2015).
Chlorophyll a photosynthetic pigment is highly present in cyanobacteria and red
algae. Chlorophyll b is present in chlorophyta, euglenophyta and marine microalgae,
whereas chlorophyll c is present in dinoflagellates. The green alga Chlorella sp. is
named as Emerald food as it has high (7%) chlorophyll content and is the main
source of chlorophyll production (Bewicke and Potter 2009a). Chlorophyll b is the
major pigment in alga Spirogyra, Chlorella, and Euglena gracilis, whereas Chlorophyll c is present in Fucus vesiculosus, Dunaliella salina, Amphidinium carterae,
and Cryptomonas sp.
The chlorophyll extraction method traditionally involves solvents of organic
origin, namely, acetone, ethanol, diethylformamide, and methanol that dissolve
lipoproteins and lipids into extract phase. Pretreatment methods before extraction, including homogenization and sonication disrupts the cells, so that chlorophyll extraction process is efficient. Homogenization followed by the use of
dimethyl formamide as solvent led to effectual chlorophyll a extraction from algae
Stichococcus sp. and Chlorella sp. (Schumann et al. 2005). Phycopigment extraction
via fluid at supercritical condition (SFE) is better than the solvent-based approaches,
as no carcinogenic solvent is involved, and the extract has better purity with less
processing steps. Being an inert, inflammable, cheap, and readily available, CO 2
are used as SFE in multiple studies, where chlorophyll is extracted from microalgae
Synechococcus sp. (Macias-Sanchez et al. 2009). Following extraction, polyethylene
powder in chromatography column is used in an economically patented method for
separation of chlorophyll a and b from other pigments. The final purification process
involves sucrose filled column that yields highly pure and crystalline chlorophyll
molecules.