207
is of particular significance for environmental applications, e.g., for biosequestration and bioconcentration of heavy metals from wastewater.
Accumulation of pigments and changes in fatty acid profile are common effects
for attached or entrapped cells as compared with free (suspended) microalgae (Lau
et al. 1998). Chlorophyll content of Chlorella vulgaris cells immobilized in carrageenan gel was twice higher than in suspended culture (Lau et al. 1998). Cells of
Botryococcus braunii and B. protuberans immobilized in alginate beads contain
more chlorophylls, carotenoids, and lipids during the stationary growth phase in
comparison with free cells (Singh 2003). Co-immobilized bacteria Azospirillum
brasilense and Chlorella spp. promoted pigment and lipid accumulation (de-Bashan
et al. 2002).
Higher specific production rates of immobilized microalgal cells as compared to
suspended ones have been investigated for the production of secondary metabolites.
Immobilization of Dunaliella salina in agar-agar resulted in significant enhancement of glycerol production in comparison with free cells (Thakur and Kumar
1999). Thus, agar entrapment of the marine diatom Haslea ostrearia augmented the
production of marennin, a blue-green pigment demanded by commercial culturing
of oysters (Lebeau et al. 1998). Ammonia production by Mastigocladus laminosus
was significantly increased when the cells were confined in polyvinyl sheets
(Brouers and Hall 1986).
The improvement of photosynthetic productivity was proved for several species
of cyanobacteria immobilized in the hydrated latex coatings (Bernal et al. 2014).
H 2 -producing green algae (Kosourov and Seibert 2009; Song et al. 2011) and heterocystous cyanobacteria (Leino et al. 2012; Touloupakis et al. 2016) entrapped
within thin calcium alginate sheets and beads demonstrated the increased H 2 -
production yields compared to suspended microalgae.
It was revealed that in the free cells, hydrogen production was largely achieved
by the nitrogenase enzyme system, but in immobilized cells, it was essentially
hydrogenase mediated, particularly when calcium alginate was used for entrapment
of cells (Touloupakis et al. 2016). It was found that this shift was not because of
nitrogenase inhibition by immobilization since the enzyme activity and stability
were both increased. Immobilization of Anabaena azollae and Mastigocladus laminosus in polyvinyl or polyurethane carriers resulted in enhancement and/or stabilization of H 2 photoproduction rate (Brouers and Hall 1986). Hydrogen production
by immobilized Anabaena sp. was increased threefold likely due to decreased cell
growth and better protection against shear stress (Kayano et al. 1981).
It was supposed that the impaired mass transfer, e.g., limited nutrient availability,
augments the yield of target substances, e.g., secondary metabolites such as reserve
lipids or secondary carotenoids. The net result of it is channeling of photofixed carbon, ATP, and NADPH to the production of the desired end products instead of cell
multiplication (Lukavský 1988).
Nevertheless, there are many examples where immobilized cultures demonstrate
unchanged or even lower rate of metabolite accumulation as compared to suspended
cultures. For example, polysaccharide production by Porphyridium is reduced by
7 Biotechnological Applications of Immobilized Microalgae
is of particular significance for environmental applications, e.g., for biosequestration and bioconcentration of heavy metals from wastewater.
Accumulation of pigments and changes in fatty acid profile are common effects
for attached or entrapped cells as compared with free (suspended) microalgae (Lau
et al. 1998). Chlorophyll content of Chlorella vulgaris cells immobilized in carrageenan gel was twice higher than in suspended culture (Lau et al. 1998). Cells of
Botryococcus braunii and B. protuberans immobilized in alginate beads contain
more chlorophylls, carotenoids, and lipids during the stationary growth phase in
comparison with free cells (Singh 2003). Co-immobilized bacteria Azospirillum
brasilense and Chlorella spp. promoted pigment and lipid accumulation (de-Bashan
et al. 2002).
Higher specific production rates of immobilized microalgal cells as compared to
suspended ones have been investigated for the production of secondary metabolites.
Immobilization of Dunaliella salina in agar-agar resulted in significant enhancement of glycerol production in comparison with free cells (Thakur and Kumar
1999). Thus, agar entrapment of the marine diatom Haslea ostrearia augmented the
production of marennin, a blue-green pigment demanded by commercial culturing
of oysters (Lebeau et al. 1998). Ammonia production by Mastigocladus laminosus
was significantly increased when the cells were confined in polyvinyl sheets
(Brouers and Hall 1986).
The improvement of photosynthetic productivity was proved for several species
of cyanobacteria immobilized in the hydrated latex coatings (Bernal et al. 2014).
H 2 -producing green algae (Kosourov and Seibert 2009; Song et al. 2011) and heterocystous cyanobacteria (Leino et al. 2012; Touloupakis et al. 2016) entrapped
within thin calcium alginate sheets and beads demonstrated the increased H 2 -
production yields compared to suspended microalgae.
It was revealed that in the free cells, hydrogen production was largely achieved
by the nitrogenase enzyme system, but in immobilized cells, it was essentially
hydrogenase mediated, particularly when calcium alginate was used for entrapment
of cells (Touloupakis et al. 2016). It was found that this shift was not because of
nitrogenase inhibition by immobilization since the enzyme activity and stability
were both increased. Immobilization of Anabaena azollae and Mastigocladus laminosus in polyvinyl or polyurethane carriers resulted in enhancement and/or stabilization of H 2 photoproduction rate (Brouers and Hall 1986). Hydrogen production
by immobilized Anabaena sp. was increased threefold likely due to decreased cell
growth and better protection against shear stress (Kayano et al. 1981).
It was supposed that the impaired mass transfer, e.g., limited nutrient availability,
augments the yield of target substances, e.g., secondary metabolites such as reserve
lipids or secondary carotenoids. The net result of it is channeling of photofixed carbon, ATP, and NADPH to the production of the desired end products instead of cell
multiplication (Lukavský 1988).
Nevertheless, there are many examples where immobilized cultures demonstrate
unchanged or even lower rate of metabolite accumulation as compared to suspended
cultures. For example, polysaccharide production by Porphyridium is reduced by
7 Biotechnological Applications of Immobilized Microalgae