4.6 Drying and Disruption Techniques
Photoautotrophic microalgae usually have a low concentration of biomass (0.5–4 g/
L, dry basis) suspended in a large volume of water (Chatsungnoen and Chisti 2016).
Thus, biomass harvesting is a process that involves the separation of microalgae
from the water media, where it is considered successful when achieving up to 20% of
solids at the end of the process (Kadir et al. 2018). The harvesting can be performed
using solid–liquid separation processes, such as physical, chemical, and biological
methods (Fig. 4.5). However, the disadvantages of these techniques are related to the
high cost, the high energy consumption, and the long extraction period (Wang et al.
2015). On the other hand, autoflocculation can occur similarly to bioflocculation,
having the advantages of being a low-cost method, with no cell damage, non-toxic to
microalgae biomass, high separation efficiency; the disadvantages are related to the
occurrence of alterations in cellular composition or microbiological contamination
(Christenson and Sims 2011; Zhou et al. 2012). After harvesting, the microalgae
biomass needs to be submitted to a disruption process to obtain the bioproduct for
subsequent application.
After the separation, to obtain the bioproduct for subsequent application, the
microalgae cell biomasses need to be disrupted (intracellular molecules). Currently,
a variety of cell disruption processes are available. In general, they can be categorized into mechanical and non-mechanical techniques of microalgal cellular disruption (Fig. 4.6). Cell wall destruction by a nonspecific technique is usually achieved
by mechanical forces such as solid-shear forces (Yap et al. 2015), liquid-shear forces
(Halim et al. 2012), energy through waves (Zheng et al. 2011), and currents (Goettel
et al. 2013). Non-mechanical methods frequently involve cell lysis with chemical
compounds (Kim et al. 2016) or enzymatic agents (Zheng et al. 2011). These
methods are considered more advantageous than mechanical processes since cells
are often only perforated or permeabilized rather than being shredded. Chemical and
enzymatic methods depend on selective interaction of the cell wall or membrane
Centrifugation
Gravity sedimentation
Filtration
Flotation
Electricity assisted techniques
Physical
Chemical
Harvesting techniques
Biological
Flocculation and coagulation
Bioflocculation and autoflocculation
Fig. 4.5 Separation methods applied on microalgae harvesting processes
124
W. Michelon et al.
Photoautotrophic microalgae usually have a low concentration of biomass (0.5–4 g/
L, dry basis) suspended in a large volume of water (Chatsungnoen and Chisti 2016).
Thus, biomass harvesting is a process that involves the separation of microalgae
from the water media, where it is considered successful when achieving up to 20% of
solids at the end of the process (Kadir et al. 2018). The harvesting can be performed
using solid–liquid separation processes, such as physical, chemical, and biological
methods (Fig. 4.5). However, the disadvantages of these techniques are related to the
high cost, the high energy consumption, and the long extraction period (Wang et al.
2015). On the other hand, autoflocculation can occur similarly to bioflocculation,
having the advantages of being a low-cost method, with no cell damage, non-toxic to
microalgae biomass, high separation efficiency; the disadvantages are related to the
occurrence of alterations in cellular composition or microbiological contamination
(Christenson and Sims 2011; Zhou et al. 2012). After harvesting, the microalgae
biomass needs to be submitted to a disruption process to obtain the bioproduct for
subsequent application.
After the separation, to obtain the bioproduct for subsequent application, the
microalgae cell biomasses need to be disrupted (intracellular molecules). Currently,
a variety of cell disruption processes are available. In general, they can be categorized into mechanical and non-mechanical techniques of microalgal cellular disruption (Fig. 4.6). Cell wall destruction by a nonspecific technique is usually achieved
by mechanical forces such as solid-shear forces (Yap et al. 2015), liquid-shear forces
(Halim et al. 2012), energy through waves (Zheng et al. 2011), and currents (Goettel
et al. 2013). Non-mechanical methods frequently involve cell lysis with chemical
compounds (Kim et al. 2016) or enzymatic agents (Zheng et al. 2011). These
methods are considered more advantageous than mechanical processes since cells
are often only perforated or permeabilized rather than being shredded. Chemical and
enzymatic methods depend on selective interaction of the cell wall or membrane
Centrifugation
Gravity sedimentation
Filtration
Flotation
Electricity assisted techniques
Physical
Chemical
Harvesting techniques
Biological
Flocculation and coagulation
Bioflocculation and autoflocculation
Fig. 4.5 Separation methods applied on microalgae harvesting processes
124
W. Michelon et al.