13 Process Intensification Aspects of Extraction …
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be attributed to the fact that increase in power increases the temperature resulting
in structural changes in the astaxanthin (Zhao et al. 2009). MAE was also reported
to be efficient in another study performed on pigment extraction from Arthrospira
platensis using mixture of methanol/ethyl acetate/light petroleum in 1:1:1 ratio under
conditions of 1 bar as pressure, 400 W as power, temperature of 50 °C and 15 min
as the treatment time resulting in 629 μg/mg yield of total carotenoids (EsquivelHernández et al. 2016). Overall it can be concluded from the studies reported that
MAE is an effective extraction process giving significant benefits for the pigment
extraction in terms of lesser processing time and chemical requirements.
13.3.7 Ultrasound Assisted Extraction (UAE)
Ultrasound (US) assisted extraction is a process in which an ultrasound wave of
18–200 kHz frequency is passed through a liquid medium producing rarefaction and
compression cycles. During the rarefaction cycle, formation of micro-scale cavities occurs which grow to a particular size and implode during compression cycle.
Implosion of these cavities results in generation of local hotspots having temperature in range of 1000–10,000 K and pressure in the range of 100–1000 bar alongwith physical effects of turbulence and micro streaming (Gogate and Pandit 2000).
US generated physical effects help in pigment extraction by disruption of cell wall
and membranes along-with enhanced diffusion of solvents into micro algal cells.
UAE offers potential to reduce process time and required chemicals making pigment
extraction process economical. UAE is generally performed using different reactor
configurations (US horn, US bath and continuous US flow cell) depending upon the
processing volumes. We now present an overview of different studies that reported
the intensification obtained using UAE.
Pigment extraction from Nannochloropsis sp. using UAE applied at 24 kHz
frequency and 400 W power for 7.5 min was reported to result in maximum total
chlorophyll yield which was 9 folds higher than that obtained using conventional
process of extraction (Parniakov et al. 2015). Another study performed on UAE of
pigments from Phormidium autumnale reported yield of pheophytin a
as 371 μg/g
of and that of chlorophyll as 159.3 μg/g using ethyl acetate as solvent followed
by second stage application of methanol under optimum conditions of frequency
of 20 kHz, 50% amplitude and 20 min (Cichoski et al. 2016). Study performed
by Macías-Sánchez et al. (2008) on extraction of total carotenoids from lyophilised
D. salina using N,N-dimethylformamide (DMF) as the solvent reported significantly
higher yields of carotenoids as 27.7 μg/mg as compared to SFE which gave 15 μg/mg
as the yield of carotenoids. Fucoxanthin extraction from Dunaliella tertiolecta was
performed using UAE at 12.2 W power for 5 min and yield of pigment obtained was
reported as 4.49 ± 0.08 μg/mg which was similar to that of conventional extraction process but a significant reduction in extraction time was reported for the UAE
(Pasquet et al. 2011). Study performed by Jaeschke et al. (2016) on carotenoid extraction from Heterochlorella luteoviridis using UAE (20 kHz frequency, 50 W/cm
2
319
be attributed to the fact that increase in power increases the temperature resulting
in structural changes in the astaxanthin (Zhao et al. 2009). MAE was also reported
to be efficient in another study performed on pigment extraction from Arthrospira
platensis using mixture of methanol/ethyl acetate/light petroleum in 1:1:1 ratio under
conditions of 1 bar as pressure, 400 W as power, temperature of 50 °C and 15 min
as the treatment time resulting in 629 μg/mg yield of total carotenoids (EsquivelHernández et al. 2016). Overall it can be concluded from the studies reported that
MAE is an effective extraction process giving significant benefits for the pigment
extraction in terms of lesser processing time and chemical requirements.
13.3.7 Ultrasound Assisted Extraction (UAE)
Ultrasound (US) assisted extraction is a process in which an ultrasound wave of
18–200 kHz frequency is passed through a liquid medium producing rarefaction and
compression cycles. During the rarefaction cycle, formation of micro-scale cavities occurs which grow to a particular size and implode during compression cycle.
Implosion of these cavities results in generation of local hotspots having temperature in range of 1000–10,000 K and pressure in the range of 100–1000 bar alongwith physical effects of turbulence and micro streaming (Gogate and Pandit 2000).
US generated physical effects help in pigment extraction by disruption of cell wall
and membranes along-with enhanced diffusion of solvents into micro algal cells.
UAE offers potential to reduce process time and required chemicals making pigment
extraction process economical. UAE is generally performed using different reactor
configurations (US horn, US bath and continuous US flow cell) depending upon the
processing volumes. We now present an overview of different studies that reported
the intensification obtained using UAE.
Pigment extraction from Nannochloropsis sp. using UAE applied at 24 kHz
frequency and 400 W power for 7.5 min was reported to result in maximum total
chlorophyll yield which was 9 folds higher than that obtained using conventional
process of extraction (Parniakov et al. 2015). Another study performed on UAE of
pigments from Phormidium autumnale reported yield of pheophytin a
as 371 μg/g
of and that of chlorophyll as 159.3 μg/g using ethyl acetate as solvent followed
by second stage application of methanol under optimum conditions of frequency
of 20 kHz, 50% amplitude and 20 min (Cichoski et al. 2016). Study performed
by Macías-Sánchez et al. (2008) on extraction of total carotenoids from lyophilised
D. salina using N,N-dimethylformamide (DMF) as the solvent reported significantly
higher yields of carotenoids as 27.7 μg/mg as compared to SFE which gave 15 μg/mg
as the yield of carotenoids. Fucoxanthin extraction from Dunaliella tertiolecta was
performed using UAE at 12.2 W power for 5 min and yield of pigment obtained was
reported as 4.49 ± 0.08 μg/mg which was similar to that of conventional extraction process but a significant reduction in extraction time was reported for the UAE
(Pasquet et al. 2011). Study performed by Jaeschke et al. (2016) on carotenoid extraction from Heterochlorella luteoviridis using UAE (20 kHz frequency, 50 W/cm
2