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A. Pérez-Gálvez and J. Fontecha
Here, the objective is to disrupt the natural barriers (cell walls and organellar lipoprotein associations) to enhance the transfer of the lipids to the solvent(s) phase. Disruption could be performed by physical, chemical, or enzymatic methods and the choice
is made according to the strength of the natural barrier, which is species-dependent.
Hence, those microalgae with trilayered cell walls (Haematococcus pluvialis) need
intensive, and high energy cost, procedures to produce successful disruption, while
softer treatments are enough to achieve a high extraction yield in other species.
According to literature, most of the disruption methods applied in the extraction
of lipids from microalgae are physical as the use of chemical protocols involve the
application of strong acidic or basic solvents that are unappropriated for carotenoid
analysis, while the use of enzyme-based technologies is not cost-effective at the lab
scale. Indeed, the reader should keep in mind that the techniques applied in the downstream processing for carotenoid isolation from algal biomass are not necessarily
suitable for analysis at the lab.
Mechanical grinding is among the most commonly used techniques for cell disruption (Hu et al. 2013; Taucher et al. 2016). The solid shear produces mechanical
damage in the cell tissues by collisions with the mortar side walls and among cells.
This pre-treatment increases its efficiency when the biomass has been previously
dehydrated (by filtering or freeze-drying). The disruption yielding of this procedure
has been rated to 93% of cells (McMillan et al. 2013). Solid shear could be performed
with a blender, rendering a fast disruption of the cells by physical collisions of the
cells with the blades and among them, and when the blend is made in a stainlesssteel flask, disruption is extended to the collisions with the side walls. This method
is easily scaled-up for semi-pilot and industrial processing of biomass (McMillan
et al. 2013). Mechanical grinding could be complemented at the lab with alternating
cycles of ultrasonication, so that the extraction is even faster but monitoring of the
temperature should be made at the ultrasonication step (Halim et al. 2013).
Other pre-treatment alternatives are available for routine in the lab, but their
application is aimed for processing of the biomass at the industrial scale. Pulsed and
moderate electric fields and high-pressure homogenization are physical methods
for disruption of the cells and assist the extraction of lipophilic algal compounds.
The technologies based on the application of electric fields require optimization
of the conditions according to the cell characteristics (Vito et al. 2008) and even
the intensity could be tailored to promote the selective extraction of the intracellular compounds (Carullo et al. 2018) and retention of their bioactivity value (Grimi
et al. 2014; Sánchez-Moreno et al. 2005), although the extraction rates are lower in
comparison with other pre-treatment alternatives (Lai et al. 2014). This is the case of
high-pressure homogenization, a technology with a significant relevance for largescale disruption of cells, and that yields a non-selective release of the cellular contents
and small debris. This fact means a handicap for subsequent processing stages at the
industrial level because purification of added-value compounds will require further
separation processes (Balasundaram et al. 2009). Operating pressure, nozzle diameter, and number of passes are conditions that should be optimized to reduce the
energy requirements and increase the performance of the disruption process, while
the monitoring of the temperature is mandatory to avoid undesirable degradation
A. Pérez-Gálvez and J. Fontecha
Here, the objective is to disrupt the natural barriers (cell walls and organellar lipoprotein associations) to enhance the transfer of the lipids to the solvent(s) phase. Disruption could be performed by physical, chemical, or enzymatic methods and the choice
is made according to the strength of the natural barrier, which is species-dependent.
Hence, those microalgae with trilayered cell walls (Haematococcus pluvialis) need
intensive, and high energy cost, procedures to produce successful disruption, while
softer treatments are enough to achieve a high extraction yield in other species.
According to literature, most of the disruption methods applied in the extraction
of lipids from microalgae are physical as the use of chemical protocols involve the
application of strong acidic or basic solvents that are unappropriated for carotenoid
analysis, while the use of enzyme-based technologies is not cost-effective at the lab
scale. Indeed, the reader should keep in mind that the techniques applied in the downstream processing for carotenoid isolation from algal biomass are not necessarily
suitable for analysis at the lab.
Mechanical grinding is among the most commonly used techniques for cell disruption (Hu et al. 2013; Taucher et al. 2016). The solid shear produces mechanical
damage in the cell tissues by collisions with the mortar side walls and among cells.
This pre-treatment increases its efficiency when the biomass has been previously
dehydrated (by filtering or freeze-drying). The disruption yielding of this procedure
has been rated to 93% of cells (McMillan et al. 2013). Solid shear could be performed
with a blender, rendering a fast disruption of the cells by physical collisions of the
cells with the blades and among them, and when the blend is made in a stainlesssteel flask, disruption is extended to the collisions with the side walls. This method
is easily scaled-up for semi-pilot and industrial processing of biomass (McMillan
et al. 2013). Mechanical grinding could be complemented at the lab with alternating
cycles of ultrasonication, so that the extraction is even faster but monitoring of the
temperature should be made at the ultrasonication step (Halim et al. 2013).
Other pre-treatment alternatives are available for routine in the lab, but their
application is aimed for processing of the biomass at the industrial scale. Pulsed and
moderate electric fields and high-pressure homogenization are physical methods
for disruption of the cells and assist the extraction of lipophilic algal compounds.
The technologies based on the application of electric fields require optimization
of the conditions according to the cell characteristics (Vito et al. 2008) and even
the intensity could be tailored to promote the selective extraction of the intracellular compounds (Carullo et al. 2018) and retention of their bioactivity value (Grimi
et al. 2014; Sánchez-Moreno et al. 2005), although the extraction rates are lower in
comparison with other pre-treatment alternatives (Lai et al. 2014). This is the case of
high-pressure homogenization, a technology with a significant relevance for largescale disruption of cells, and that yields a non-selective release of the cellular contents
and small debris. This fact means a handicap for subsequent processing stages at the
industrial level because purification of added-value compounds will require further
separation processes (Balasundaram et al. 2009). Operating pressure, nozzle diameter, and number of passes are conditions that should be optimized to reduce the
energy requirements and increase the performance of the disruption process, while
the monitoring of the temperature is mandatory to avoid undesirable degradation