biomass extraction, the yield is higher, but the associated cost due to biomass
drying is considerable (Taher et al. 2014). On the other hand, if wet biomass is
used, the cell rupture is realized in the solution where the microalgae were cultivated (Ghasemi Naghdi et al. 2016) and better energy efficient is achieved, but lipid
extraction yield is low (Taher et al. 2014).
4.1 Organic Solvent Extraction
Lipid extraction with organic solvents is based on the interaction between long
hydrophobic chains of fatty acids and neutral lipids through van der Waals forces,
forming globules in the cytoplasm (Medina et al. 1998), which in presence of a
nonpolar solvent form a solvent–lipid complex, that leave the cell due to a concentration gradient (Halim et al. 2012). Similar mechanism is applied for the
extraction of polar lipids when polar solvents like alcohols are used, due to the
interruption of hydrogen bonds (Pragya et al. 2013). An ideal solvent must have
certain characteristics like non-toxic, cheap, volatile, and selective compound
(Rawat et al. 2011).
4.2 Soxhlet Extraction
This method has the advantage that the cells are in constant contact with fresh
organic solvent, avoiding the equilibrium limitation present in batch processes with
solvents (Mubarak et al. 2015). It has been demonstrated that using this method, it
is possible to recover almost all the microalgae lipids, been the reference method to
compare with another extraction methods (Prommuak et al. 2012).
4.3 Bligh and Dyer’s Method
The Bligh and Dyer’s method is one of the most common methods for lipid
extraction, using 1:2 chloroform/methanol (v/v); the lipids in the chloroform phase
are separated (Ranjith Kumar et al. 2015). To upgrade this method, many modifications have been proposed, one of those is the addition of 1 M NaCl to avoid
denatured lipids. With this method, extraction yields upon 95% from total lipid
content had been obtained, with the possibility for using it in both dry and wet algal
biomass (Pragya et al. 2013).
9 Biofuels from Microalgae: Energy and Exergy Analysis for the …
187
drying is considerable (Taher et al. 2014). On the other hand, if wet biomass is
used, the cell rupture is realized in the solution where the microalgae were cultivated (Ghasemi Naghdi et al. 2016) and better energy efficient is achieved, but lipid
extraction yield is low (Taher et al. 2014).
4.1 Organic Solvent Extraction
Lipid extraction with organic solvents is based on the interaction between long
hydrophobic chains of fatty acids and neutral lipids through van der Waals forces,
forming globules in the cytoplasm (Medina et al. 1998), which in presence of a
nonpolar solvent form a solvent–lipid complex, that leave the cell due to a concentration gradient (Halim et al. 2012). Similar mechanism is applied for the
extraction of polar lipids when polar solvents like alcohols are used, due to the
interruption of hydrogen bonds (Pragya et al. 2013). An ideal solvent must have
certain characteristics like non-toxic, cheap, volatile, and selective compound
(Rawat et al. 2011).
4.2 Soxhlet Extraction
This method has the advantage that the cells are in constant contact with fresh
organic solvent, avoiding the equilibrium limitation present in batch processes with
solvents (Mubarak et al. 2015). It has been demonstrated that using this method, it
is possible to recover almost all the microalgae lipids, been the reference method to
compare with another extraction methods (Prommuak et al. 2012).
4.3 Bligh and Dyer’s Method
The Bligh and Dyer’s method is one of the most common methods for lipid
extraction, using 1:2 chloroform/methanol (v/v); the lipids in the chloroform phase
are separated (Ranjith Kumar et al. 2015). To upgrade this method, many modifications have been proposed, one of those is the addition of 1 M NaCl to avoid
denatured lipids. With this method, extraction yields upon 95% from total lipid
content had been obtained, with the possibility for using it in both dry and wet algal
biomass (Pragya et al. 2013).
9 Biofuels from Microalgae: Energy and Exergy Analysis for the …
187