carbohydrates (43%) [4]. Lipid class composition reveals abundance
of neutral lipids, i.e., triacylglycerols (TAG, 27%) and free fatty acids
(FFA, 31%) followed by polar lipids (1%). The proportion of phytol
is 13%, chlorophyllides (non-phytol moiety of chlorophylls) 15%,
and other constituents 14% [4]. The low total lipid content (2.6%) in
the macroalgae Ulva armoricana consists of neutral lipids (56%),
glycolipids (29%), and phospholipids (15%) [5]. The sterol composition of the unsaponifiable fraction (21% of total lipids) is characterized by high contents of cholesterol and iso-fucosterol (35 and 25%,
respectively). Among chloroplast lipids, galacto- and sulfolipids
(mono- and digalactosyl- and sulfoquinovosyldiacylglycerols) and
phosphatidyl glycerol have been considered as distinctive lipids
between plant and animal or yeast cells [6]. Euglena gracilis is
considered a potentially useful cultivated organism and source of
biofuels [7]. It can grow by photosynthesis but can also metabolize
sugars. Under anaerobic conditions, when the culture medium
contains organic carbon source, wax esters are synthesized [8].
Various mechanical, chemical, and enzymatic methods are used
to extract lipids from algae biomass [9]. Solvent extraction procedures have been recently optimized in detail with the microalgae
Trachydiscus minutus biomass. The subsequent extraction approach
starting from water followed by 80% methanol and then by hexane/
isopropanol (50:50, v/v) proved to be the preferred method to
obtain the water-soluble metabolites, polar lipids, and nonpolar
TAG in the separate fractions [10]. After mechanical disruption of
the cells by lyophilization and grinding, e.g., solvent extraction can
be intensified by using Soxhlet extraction or accelerated solvent
extraction (ASE), which has been applied when studying TAG and
FFA in algae [11]. Compared to the chloroform/methanol 2:1
mixture, 2-ethoxyethanol provides superior lipid and hydrocarbon
recovery [12]. It is especially efficient in extracting wet biomass
rather than dried algal pellets.
High-performance liquid chromatography (HPLC) with evaporative light-scattering detection (ELSD) provides a rapid and relatively
simple method for monitoring the broad range of lipid classes of algae
strains [13]. In this technique, a comprehensive separation of both
nonpolar and polar lipids can be achieved on conventional silica
[14, 15] or monolithic silica columns [16]. With careful optimization,
diacylglycerol ethers (DAGE) can be separated from TAGs which have
very similar structure and polarity [17]. It is known that responses in
mass detection by light scattering are nonlinear and are better fitted to
polynomial curves. However, to obtain comprehensive intact lipid
profiles at subspecies level from microalgae extracts, ultrahigh performance liquid chromatography combined with high-resolution mass
spectrometry (UHPLC-MS) is the method of choice [18].
Characterization of algal fatty acid compositions involves hydrolysis of triacylglycerols and other intact lipids, followed by derivatization of the fatty acids to methyl esters (FAME) prior to analysis by
224
Tuulikki Sepp€ anen-Laakso et al.
of neutral lipids, i.e., triacylglycerols (TAG, 27%) and free fatty acids
(FFA, 31%) followed by polar lipids (1%). The proportion of phytol
is 13%, chlorophyllides (non-phytol moiety of chlorophylls) 15%,
and other constituents 14% [4]. The low total lipid content (2.6%) in
the macroalgae Ulva armoricana consists of neutral lipids (56%),
glycolipids (29%), and phospholipids (15%) [5]. The sterol composition of the unsaponifiable fraction (21% of total lipids) is characterized by high contents of cholesterol and iso-fucosterol (35 and 25%,
respectively). Among chloroplast lipids, galacto- and sulfolipids
(mono- and digalactosyl- and sulfoquinovosyldiacylglycerols) and
phosphatidyl glycerol have been considered as distinctive lipids
between plant and animal or yeast cells [6]. Euglena gracilis is
considered a potentially useful cultivated organism and source of
biofuels [7]. It can grow by photosynthesis but can also metabolize
sugars. Under anaerobic conditions, when the culture medium
contains organic carbon source, wax esters are synthesized [8].
Various mechanical, chemical, and enzymatic methods are used
to extract lipids from algae biomass [9]. Solvent extraction procedures have been recently optimized in detail with the microalgae
Trachydiscus minutus biomass. The subsequent extraction approach
starting from water followed by 80% methanol and then by hexane/
isopropanol (50:50, v/v) proved to be the preferred method to
obtain the water-soluble metabolites, polar lipids, and nonpolar
TAG in the separate fractions [10]. After mechanical disruption of
the cells by lyophilization and grinding, e.g., solvent extraction can
be intensified by using Soxhlet extraction or accelerated solvent
extraction (ASE), which has been applied when studying TAG and
FFA in algae [11]. Compared to the chloroform/methanol 2:1
mixture, 2-ethoxyethanol provides superior lipid and hydrocarbon
recovery [12]. It is especially efficient in extracting wet biomass
rather than dried algal pellets.
High-performance liquid chromatography (HPLC) with evaporative light-scattering detection (ELSD) provides a rapid and relatively
simple method for monitoring the broad range of lipid classes of algae
strains [13]. In this technique, a comprehensive separation of both
nonpolar and polar lipids can be achieved on conventional silica
[14, 15] or monolithic silica columns [16]. With careful optimization,
diacylglycerol ethers (DAGE) can be separated from TAGs which have
very similar structure and polarity [17]. It is known that responses in
mass detection by light scattering are nonlinear and are better fitted to
polynomial curves. However, to obtain comprehensive intact lipid
profiles at subspecies level from microalgae extracts, ultrahigh performance liquid chromatography combined with high-resolution mass
spectrometry (UHPLC-MS) is the method of choice [18].
Characterization of algal fatty acid compositions involves hydrolysis of triacylglycerols and other intact lipids, followed by derivatization of the fatty acids to methyl esters (FAME) prior to analysis by
224
Tuulikki Sepp€ anen-Laakso et al.