96 Marine Macro- and Microalgae: An Overview
Ye 2007), and polysaccharide flocculants produced by Alcaligenes cupidus KT201 (Toeda and Kurane
1991) and Bacillus mucilaginosus (Lian et al. 2008). Among these bioflocculants, poly (γ-glutamic acid)
(PGA), is an extracellular product of Bacillus subtilis (Yokoi et al. 1996) and Bacillus licheniformis
(Shih et al. 2001) which can be produced industrially via fermentation (Zheng et al. 2012) and is used
commercially as a microbial flocculant in wastewater treatment (Taniguchi et al. 2005). PGA is an anionic
water-soluble homo-polyamide consisting of D- and L-glutamic acid monomers connected by amide
linkages with α-amino and γ-carboxyl groups (Bajaj and Singhal 2011). The flocculating properties of
PGA when applied to the harvest of both marine and freshwater microalgae were recently investigated
(Zheng et al. 2012). The flocculating efficiency of PGA was achieved at an optimum concentration of
22.03 mg/L, with a biomass of 0.57 g/L and a salinity of 11.56 g/L for the marine C. vulgaris. For
the freshwater algae Chlorella protothecoides the maximum efficiency was achieved with 19.82 mg/L
PGA and 0.60 g/L biomass. The application of the optimized flocculation methods to Nannochloropsis
occulata LICME 002, Phaeodactylum tricornatum, C. vulgaris LICME 001, and Botryococcus braunii
LICME 003 gave no less than 90% flocculation efficiency and a concentration factor of 20.
In another study, the harvesting of Nannochloropsis sp. was performed using 20 mL/L mung bean
protein extract (MBPE). After 2 hr of settling time, the flocculation efficiency was found to be above 92%
(Kandasamy et al. 2017).
Ndikubwimana et al. (2016) performed bioflocculation studies both in pilot scale and in situ with
the freshwater microalgae Desmodesmus brasiliensis and a bacterial broth bioflocculant produced by
Bacillus licheniformis CGMCC2876 containing γ-PGA. In both cases, the flocculation efficiency was
greater than 98%.
Bioflocculation. As can be seen from above, some of the polymers are synthesized by bacteria; hence, the
possibility to use concomitant bacterial cultures instead of pure polymers as flocculating agent emerges,
as these co-cultured bacteria could produce extracellular polymeric substances (EPS) that would induce
flocculation (Toeda and Kurane 1991). Lee et al. (2009) investigated a microbial induced flocculation of
the marine microalgae Pleurochrysis carterae. Average recovery efficiency over 90% and a concentration
factor of 226 were achieved at a low concentration of organic substrate (0.1 g/L) and long mixing time
(24 hr). Characterization of flocculating bacteria revealed the presence of Pseudomonas stutzeri and
Bacillus cereus, but could not exclude the presence of other bacteria. The EPS excreted by the bacterial
culture was not identified.
Excellent growth of Nannochloropsis oceanica IMET1 was observed in Permian groundwater (Wang
et al. 2012) at three different temperatures: 15, 25, and 30
o
C. Interestingly, the algal cells aggregated at the
highest temperature, whereas they remained as single cells at the two other temperatures. This led to the
isolation of a new bacterium designated as HW001, which showed the ability to aggregate N. oceanica
IMET1 after three days of incubation. This bacterium was also capable of aggregating the microalgae
N. oceanica CT-1, T. suecica, and Tetraselmis chuii. Furthermore, the addition of the bacterium to the
algal culture did not affect the lipid content or the lipid composition.
Salim et al. (2011) investigated the sedimentation kinetics and recovery efficiency of Nannochloropsis
oleoabundans, a non-flocculating microalga with T. suecica, a flocculating microalga. It was demonstrated
that the combination of both the algae improved the sedimentation of the non-flocculating microalga and
that by increasing the amount of flocculating algae, it was possible to double the sedimentation rate of
N. oleoabundans. The presence of the flocculating microalga in the final biomass concentrate did not
impact the further downstream processing of the microalga of interest as the reported lipid contents for
T. suecica and N. oleoabundans were 18–26 and 36–42% DW, respectively. N. oculata cultures exposed
to a water-soluble extract of senescent cultures of Skeletonema marinoi showed flocculation as formation
of groups of cells could be observed microscopically (Taylor et al. 2012). The recovery efficiency was
91.2% after 2 hr and increased to 95.3% by 6 hr, which was a significant compared to control cultures. As
increasing levels of polyunsaturated aldehydes were detected in the growing media of S. marinoi prior
to the decline of diatom blooms, it was hypothesized that the diatom-derived polyunsaturated aldehyde
decadienal could be responsible for this flocculation event. However, when applying this aldehyde to the
N. oculata cultures no flocculation was induced, suggesting that other compound(s) in the water-soluble
extract of S. marinoi was responsible for the flocculation event.
Ye 2007), and polysaccharide flocculants produced by Alcaligenes cupidus KT201 (Toeda and Kurane
1991) and Bacillus mucilaginosus (Lian et al. 2008). Among these bioflocculants, poly (γ-glutamic acid)
(PGA), is an extracellular product of Bacillus subtilis (Yokoi et al. 1996) and Bacillus licheniformis
(Shih et al. 2001) which can be produced industrially via fermentation (Zheng et al. 2012) and is used
commercially as a microbial flocculant in wastewater treatment (Taniguchi et al. 2005). PGA is an anionic
water-soluble homo-polyamide consisting of D- and L-glutamic acid monomers connected by amide
linkages with α-amino and γ-carboxyl groups (Bajaj and Singhal 2011). The flocculating properties of
PGA when applied to the harvest of both marine and freshwater microalgae were recently investigated
(Zheng et al. 2012). The flocculating efficiency of PGA was achieved at an optimum concentration of
22.03 mg/L, with a biomass of 0.57 g/L and a salinity of 11.56 g/L for the marine C. vulgaris. For
the freshwater algae Chlorella protothecoides the maximum efficiency was achieved with 19.82 mg/L
PGA and 0.60 g/L biomass. The application of the optimized flocculation methods to Nannochloropsis
occulata LICME 002, Phaeodactylum tricornatum, C. vulgaris LICME 001, and Botryococcus braunii
LICME 003 gave no less than 90% flocculation efficiency and a concentration factor of 20.
In another study, the harvesting of Nannochloropsis sp. was performed using 20 mL/L mung bean
protein extract (MBPE). After 2 hr of settling time, the flocculation efficiency was found to be above 92%
(Kandasamy et al. 2017).
Ndikubwimana et al. (2016) performed bioflocculation studies both in pilot scale and in situ with
the freshwater microalgae Desmodesmus brasiliensis and a bacterial broth bioflocculant produced by
Bacillus licheniformis CGMCC2876 containing γ-PGA. In both cases, the flocculation efficiency was
greater than 98%.
Bioflocculation. As can be seen from above, some of the polymers are synthesized by bacteria; hence, the
possibility to use concomitant bacterial cultures instead of pure polymers as flocculating agent emerges,
as these co-cultured bacteria could produce extracellular polymeric substances (EPS) that would induce
flocculation (Toeda and Kurane 1991). Lee et al. (2009) investigated a microbial induced flocculation of
the marine microalgae Pleurochrysis carterae. Average recovery efficiency over 90% and a concentration
factor of 226 were achieved at a low concentration of organic substrate (0.1 g/L) and long mixing time
(24 hr). Characterization of flocculating bacteria revealed the presence of Pseudomonas stutzeri and
Bacillus cereus, but could not exclude the presence of other bacteria. The EPS excreted by the bacterial
culture was not identified.
Excellent growth of Nannochloropsis oceanica IMET1 was observed in Permian groundwater (Wang
et al. 2012) at three different temperatures: 15, 25, and 30
o
C. Interestingly, the algal cells aggregated at the
highest temperature, whereas they remained as single cells at the two other temperatures. This led to the
isolation of a new bacterium designated as HW001, which showed the ability to aggregate N. oceanica
IMET1 after three days of incubation. This bacterium was also capable of aggregating the microalgae
N. oceanica CT-1, T. suecica, and Tetraselmis chuii. Furthermore, the addition of the bacterium to the
algal culture did not affect the lipid content or the lipid composition.
Salim et al. (2011) investigated the sedimentation kinetics and recovery efficiency of Nannochloropsis
oleoabundans, a non-flocculating microalga with T. suecica, a flocculating microalga. It was demonstrated
that the combination of both the algae improved the sedimentation of the non-flocculating microalga and
that by increasing the amount of flocculating algae, it was possible to double the sedimentation rate of
N. oleoabundans. The presence of the flocculating microalga in the final biomass concentrate did not
impact the further downstream processing of the microalga of interest as the reported lipid contents for
T. suecica and N. oleoabundans were 18–26 and 36–42% DW, respectively. N. oculata cultures exposed
to a water-soluble extract of senescent cultures of Skeletonema marinoi showed flocculation as formation
of groups of cells could be observed microscopically (Taylor et al. 2012). The recovery efficiency was
91.2% after 2 hr and increased to 95.3% by 6 hr, which was a significant compared to control cultures. As
increasing levels of polyunsaturated aldehydes were detected in the growing media of S. marinoi prior
to the decline of diatom blooms, it was hypothesized that the diatom-derived polyunsaturated aldehyde
decadienal could be responsible for this flocculation event. However, when applying this aldehyde to the
N. oculata cultures no flocculation was induced, suggesting that other compound(s) in the water-soluble
extract of S. marinoi was responsible for the flocculation event.