4 Recovery of lipids and other products
Generally, the process of drying followed by disruption and solvent extraction is
used for the recovery of desired products including the lipids from microalgae.
Drying can be performed based on sun drying, spray drying, drum drying, and
freeze drying. Sun drying is the most affordable option and can be employed
effectively in biofuels production while spray drying hampers the overall economics
of process when used for biofuels or protein production. Drum drying and freeze
drying are also not the most viable options considering the application of biofuel
production. After drying process, the dried biomass is subjected to disruption
depending on the nature of desired product to be recovered or cell wall strength of
microalgae, which affects the recovery. Disruption is carried out by mechanical
processes (bead mills, autoclave, cell homogenizer, spray drying, ultrasound, etc.)
and non-mechanical processes (using organic solvents, freezing, acid and osmotic
shock, alkali, and enzyme treatment).
Microwave and ultrasound are emerging potential technologies which can be
employed in the cell disruption process, also giving process intensification benefits.
Application of Process intensification approaches helps this process to be performed
with the achievement of economic feasibility. It has been reported that microwave
and ultrasound are the technologies which result in higher amount of disruption as
compared to other available technologies (Prabakaran and Ravindran 2011).
Table 1 illustrates a few examples in which the ultrasound has been employed as a
effective process for disruption of biomass.
Table 1 Ultrasound use for disruption of microalgae
Specie
Biomass
concentration
(g/L)
Frequency
(kHz)
Time
(min)
Yield of lipid
Reference
Chlorella sp. 5
50
15
156.6 mg/L
Prabakaran and
Ravindran
(2011)
C. vulgaris
5
10
5
6.1–8.8 mg/L
Lee et al.
(2010)
C. vulgaris
2.5
–
17.5
2.9 times increase in
lipid content
Zheng et al.
(2011)
N. oculata
5
20
30
Increase in oil
recovery to 0.24%
from 0.15%
Adam et al.
(2012)
4 Process Intensification of Biofuel Production …
65
Generally, the process of drying followed by disruption and solvent extraction is
used for the recovery of desired products including the lipids from microalgae.
Drying can be performed based on sun drying, spray drying, drum drying, and
freeze drying. Sun drying is the most affordable option and can be employed
effectively in biofuels production while spray drying hampers the overall economics
of process when used for biofuels or protein production. Drum drying and freeze
drying are also not the most viable options considering the application of biofuel
production. After drying process, the dried biomass is subjected to disruption
depending on the nature of desired product to be recovered or cell wall strength of
microalgae, which affects the recovery. Disruption is carried out by mechanical
processes (bead mills, autoclave, cell homogenizer, spray drying, ultrasound, etc.)
and non-mechanical processes (using organic solvents, freezing, acid and osmotic
shock, alkali, and enzyme treatment).
Microwave and ultrasound are emerging potential technologies which can be
employed in the cell disruption process, also giving process intensification benefits.
Application of Process intensification approaches helps this process to be performed
with the achievement of economic feasibility. It has been reported that microwave
and ultrasound are the technologies which result in higher amount of disruption as
compared to other available technologies (Prabakaran and Ravindran 2011).
Table 1 illustrates a few examples in which the ultrasound has been employed as a
effective process for disruption of biomass.
Table 1 Ultrasound use for disruption of microalgae
Specie
Biomass
concentration
(g/L)
Frequency
(kHz)
Time
(min)
Yield of lipid
Reference
Chlorella sp. 5
50
15
156.6 mg/L
Prabakaran and
Ravindran
(2011)
C. vulgaris
5
10
5
6.1–8.8 mg/L
Lee et al.
(2010)
C. vulgaris
2.5
–
17.5
2.9 times increase in
lipid content
Zheng et al.
(2011)
N. oculata
5
20
30
Increase in oil
recovery to 0.24%
from 0.15%
Adam et al.
(2012)
4 Process Intensification of Biofuel Production …
65