292
R. Halim
12.4.2 β-Carotene Recovery
Table 12.4 provides a summary of previous studies that have investigated β-carotene
recovery from microalgal biomass (Abu-Rezq et al. 2010; Herrero et al. 2006;
Marchal et al. 2013; Pour Hosseini et al. 2017; Rammuni et al. 2019; Thoisen et al.
2017; Viskari and Colyer 2003). The table reports the biomass pretreatment (cell
rupture) and extraction method used in the studies as well as the key findings obtained
from them. As can be seen in the table, Dunaliella salina was the species used in all of
the studies. D. salina cells are able to accumulate significant amounts of β-carotene
(up to 13 wt% of biomass) as droplets in their chloroplast stroma under certain
environmental stresses (e.g. high temperature, high light intensity, high salinity and
nitrogen starvation astaxanthin). The cells do not have rigid cell walls. Instead, each
cell is encapsulated by a thick mucilaginous coating that is composed primarily of
glycoproteins.
Similar to astaxanthin recovery from H. pluvialis, β-carotene recovery from
D.salina also follows a two-step cell rupture and extraction formula. During the
cell rupture step, the biomass is subjected to a mechanical pretreatment (such as
bead milling) in order to rupture the cells. This was then followed by a subsequent
extraction step where pressurised solvent (such as acetone, ethanol, or hexane) or
supercritical carbon dioxide is used to extract pigments from the biomass. However,
since D. salina lacks cell walls, their cells tend to rupture more easily than other
microalgal cells with rigid cell walls (e.g. H. pluvialis). For this reason, a dedicated biomass pretreatment (or cell rupture) step is often not needed as the cells are
readily ruptured to release their intracellular pigments upon solvent contact during
the extraction step. This automatic cell rupture simplifies β-carotene recovery from
D.salina into a single-step extraction procedure. As can be seen in Table 12.4, the
pretreatment or cell rupture step was omitted in the majority of studies that have
previously attempted to optimise β-carotene recovery from D. salina.
12.4.3 Phycobiliprotein Recovery
Since phycobiliproteins are water-soluble pigments, they do not require the use of
organic solvent or supercritical carbon dioxide for their recoveries (Furuki et al. 2003;
Lawrenz et al. 2011; Thoisen et al. 2017). The recovery process for phycobiliproteins
therefore entails a combined cell rupture and extraction process, whereby the biomass
is first suspended in the aqueous extraction solvent (such as water, phosphate buffer,
culture medium or ionic liquid) before being subjected to a mechanical cell rupture
step (such as ultrasonication, high-pressure homogenisation, bead milling, grinding
and nitrogen cavitation) to liberate the phycobiliproteins to the aqueous solvent.
Tables 12.5 and 12.6 provide a summary of previous studies examining phycobiliprotein recovery (both phycoertyhrin and phycocyanin) from microalgal and cyanobacterial biomass. The tables report the cell rupture and the extraction methods used
R. Halim
12.4.2 β-Carotene Recovery
Table 12.4 provides a summary of previous studies that have investigated β-carotene
recovery from microalgal biomass (Abu-Rezq et al. 2010; Herrero et al. 2006;
Marchal et al. 2013; Pour Hosseini et al. 2017; Rammuni et al. 2019; Thoisen et al.
2017; Viskari and Colyer 2003). The table reports the biomass pretreatment (cell
rupture) and extraction method used in the studies as well as the key findings obtained
from them. As can be seen in the table, Dunaliella salina was the species used in all of
the studies. D. salina cells are able to accumulate significant amounts of β-carotene
(up to 13 wt% of biomass) as droplets in their chloroplast stroma under certain
environmental stresses (e.g. high temperature, high light intensity, high salinity and
nitrogen starvation astaxanthin). The cells do not have rigid cell walls. Instead, each
cell is encapsulated by a thick mucilaginous coating that is composed primarily of
glycoproteins.
Similar to astaxanthin recovery from H. pluvialis, β-carotene recovery from
D.salina also follows a two-step cell rupture and extraction formula. During the
cell rupture step, the biomass is subjected to a mechanical pretreatment (such as
bead milling) in order to rupture the cells. This was then followed by a subsequent
extraction step where pressurised solvent (such as acetone, ethanol, or hexane) or
supercritical carbon dioxide is used to extract pigments from the biomass. However,
since D. salina lacks cell walls, their cells tend to rupture more easily than other
microalgal cells with rigid cell walls (e.g. H. pluvialis). For this reason, a dedicated biomass pretreatment (or cell rupture) step is often not needed as the cells are
readily ruptured to release their intracellular pigments upon solvent contact during
the extraction step. This automatic cell rupture simplifies β-carotene recovery from
D.salina into a single-step extraction procedure. As can be seen in Table 12.4, the
pretreatment or cell rupture step was omitted in the majority of studies that have
previously attempted to optimise β-carotene recovery from D. salina.
12.4.3 Phycobiliprotein Recovery
Since phycobiliproteins are water-soluble pigments, they do not require the use of
organic solvent or supercritical carbon dioxide for their recoveries (Furuki et al. 2003;
Lawrenz et al. 2011; Thoisen et al. 2017). The recovery process for phycobiliproteins
therefore entails a combined cell rupture and extraction process, whereby the biomass
is first suspended in the aqueous extraction solvent (such as water, phosphate buffer,
culture medium or ionic liquid) before being subjected to a mechanical cell rupture
step (such as ultrasonication, high-pressure homogenisation, bead milling, grinding
and nitrogen cavitation) to liberate the phycobiliproteins to the aqueous solvent.
Tables 12.5 and 12.6 provide a summary of previous studies examining phycobiliprotein recovery (both phycoertyhrin and phycocyanin) from microalgal and cyanobacterial biomass. The tables report the cell rupture and the extraction methods used