4.4 Microwave Extraction
Due to the heat generated by the interaction between water (a polar fluid) and the
electric field produced by microwaves, vapor is generated next to the cell. This
action breaks the cell wall and releases the compounds that are inside the
microalgae (Ghasemi Naghdi et al. 2016). The heating with microwaves is very fast
allowing short times for the lipid extraction (Dai et al. 2014).
4.5 Ultrasound Extraction
This method is based on the rupture of the cell through the cavitation produced
from the collapse of microbubbles generated by the ultrasound waves. These
bubbles are near of the cell wall and when they collapse, a shock wave is created,
breaking the cell wall, releasing the internal compounds of the microalgae
(Ghasemi Naghdi et al. 2016). The study of the ultrasound method has been
combined with the use of organic solvents or solvent-free with the aim of has a
clean and environmental process (Adam et al. 2012).
4.6 Supercritical Fluids
The extraction using supercritical fluids is a new green technology with the
potential to substitute other types of extraction like the extraction with organic
solvents. The use of supercritical fluids has a series of advantages due to the fluid
properties like favorable mass transfer that facilities the input to the cell inside, their
property variability with operational conditions and that the extracted lipids do not
require a posterior stage of purification because are solvent-free (Halim et al. 2012).
4.7 Ionic Liquids Extraction
Ionic liquids are salts that have a melting point under 100 °C that due to unique
properties like their thermal stability, high selectivity, solubility, and non-volatile
characteristics, which are called to be an alternative for the use of organic solvents
(Kim et al. 2012). It has been found that the ionic liquids with a high hydrophobicity and high acidity have better extraction yields (Yu et al. 2016).
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D. L. Restrepo-Serna et al.
Due to the heat generated by the interaction between water (a polar fluid) and the
electric field produced by microwaves, vapor is generated next to the cell. This
action breaks the cell wall and releases the compounds that are inside the
microalgae (Ghasemi Naghdi et al. 2016). The heating with microwaves is very fast
allowing short times for the lipid extraction (Dai et al. 2014).
4.5 Ultrasound Extraction
This method is based on the rupture of the cell through the cavitation produced
from the collapse of microbubbles generated by the ultrasound waves. These
bubbles are near of the cell wall and when they collapse, a shock wave is created,
breaking the cell wall, releasing the internal compounds of the microalgae
(Ghasemi Naghdi et al. 2016). The study of the ultrasound method has been
combined with the use of organic solvents or solvent-free with the aim of has a
clean and environmental process (Adam et al. 2012).
4.6 Supercritical Fluids
The extraction using supercritical fluids is a new green technology with the
potential to substitute other types of extraction like the extraction with organic
solvents. The use of supercritical fluids has a series of advantages due to the fluid
properties like favorable mass transfer that facilities the input to the cell inside, their
property variability with operational conditions and that the extracted lipids do not
require a posterior stage of purification because are solvent-free (Halim et al. 2012).
4.7 Ionic Liquids Extraction
Ionic liquids are salts that have a melting point under 100 °C that due to unique
properties like their thermal stability, high selectivity, solubility, and non-volatile
characteristics, which are called to be an alternative for the use of organic solvents
(Kim et al. 2012). It has been found that the ionic liquids with a high hydrophobicity and high acidity have better extraction yields (Yu et al. 2016).
188
D. L. Restrepo-Serna et al.