274
R. Halim
(respectively at 6, 1.6 and 1.3 wt% of carbohydrates) (Baudelet et al. 2017; Desai
et al. 2016).
12.1.3.2 Cell Wall of Chlorella Sp
Since there are dramatic interspecies (between species) and intraspecies (the same
species but grown under different conditions) variations in Chlorella cell walls, it is
difficult to describe a representative Chlorella cell wall. Nevertheless, three distinct
classes of Chlorella wall structures have been identified (Fig. 12.1b): type 1 is bilayered with a microfibrillar inner layer and a TLS outer layer, type 2 is bilayered without
the TLS layer and type 3 is a single microfibrillar layer (Baudelet et al. 2017). The
cell wall of C vulgaris UTEX 395 is a type-2 configuration with long hair-like fibres
protruding out of the outer layer. In terms of composition, Chlorella cell wall generally comprises 22–25 wt% hemicellulose and 60–66 wt% rigid non-alkali soluble
wall fraction. The main neutral sugar monosaccharides found in the rigid fraction
are glucosamine, galactose and rhamnose (Baudelet et al. 2017).
12.1.3.3 Cell Wall of Dunaliella Salina
D.salina lacks a cell wall. Instead of a rigid cell wall, the cell’s plasmalemma is
covered by a thick electron-dense mucilaginous coating composed of lysozymesensitive glycoproteins. The genus Dunaliella is known to secrete large amounts of
exopolysaccharides (EPS) under certain environmental conditions (e.g. salt stress)
(Baudelet et al. 2017).
12.1.3.4 Cell Wall of Spirulina Platensis
The cell wall of Spirulina platensis consists of four longitudinal layers with recurrent
ingrowths of a three-layered septum (Fig. 12.1c) (Van Eykelenburg 1977). L1 and
L3 are fibrillar in nature and composed of a glucose polysaccharide known as β-1,2,glucan. L2 contains peptidoglycan that confers the cells with structural strength and
the ability to counteract osmotic pressure, while L4 has a structure analogous to the
cell wall of gram-negative bacteria. The thickness of each layer ranges from 10 to
15 nm and the whole wall is roughly 60 nm in thickness.
12.2 Biomass Pretreatment
The purpose of biomass pretreatment or cell disruption is to rupture cell walls in
order to liberate intracellular products and improve their accessibilities to extracting
solvents. The release of intracellular products from the biomass enhances their mass
R. Halim
(respectively at 6, 1.6 and 1.3 wt% of carbohydrates) (Baudelet et al. 2017; Desai
et al. 2016).
12.1.3.2 Cell Wall of Chlorella Sp
Since there are dramatic interspecies (between species) and intraspecies (the same
species but grown under different conditions) variations in Chlorella cell walls, it is
difficult to describe a representative Chlorella cell wall. Nevertheless, three distinct
classes of Chlorella wall structures have been identified (Fig. 12.1b): type 1 is bilayered with a microfibrillar inner layer and a TLS outer layer, type 2 is bilayered without
the TLS layer and type 3 is a single microfibrillar layer (Baudelet et al. 2017). The
cell wall of C vulgaris UTEX 395 is a type-2 configuration with long hair-like fibres
protruding out of the outer layer. In terms of composition, Chlorella cell wall generally comprises 22–25 wt% hemicellulose and 60–66 wt% rigid non-alkali soluble
wall fraction. The main neutral sugar monosaccharides found in the rigid fraction
are glucosamine, galactose and rhamnose (Baudelet et al. 2017).
12.1.3.3 Cell Wall of Dunaliella Salina
D.salina lacks a cell wall. Instead of a rigid cell wall, the cell’s plasmalemma is
covered by a thick electron-dense mucilaginous coating composed of lysozymesensitive glycoproteins. The genus Dunaliella is known to secrete large amounts of
exopolysaccharides (EPS) under certain environmental conditions (e.g. salt stress)
(Baudelet et al. 2017).
12.1.3.4 Cell Wall of Spirulina Platensis
The cell wall of Spirulina platensis consists of four longitudinal layers with recurrent
ingrowths of a three-layered septum (Fig. 12.1c) (Van Eykelenburg 1977). L1 and
L3 are fibrillar in nature and composed of a glucose polysaccharide known as β-1,2,glucan. L2 contains peptidoglycan that confers the cells with structural strength and
the ability to counteract osmotic pressure, while L4 has a structure analogous to the
cell wall of gram-negative bacteria. The thickness of each layer ranges from 10 to
15 nm and the whole wall is roughly 60 nm in thickness.
12.2 Biomass Pretreatment
The purpose of biomass pretreatment or cell disruption is to rupture cell walls in
order to liberate intracellular products and improve their accessibilities to extracting
solvents. The release of intracellular products from the biomass enhances their mass