3 Phycobiliproteins in Microalgae: Occurrence …
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3.6.4 Carbon and Nitrogen Stress
The carbon and nitrogen ratio is crucial for the growth and development of cyanobacteria and that plays a distinguished role in the production of value-added compounds
or PBPs. Generally, carbon sources such as fructose, glucose, glycerol, and sucrose
are used for the large scale production of cyanobacteria (Kovaˇ c et al. 2017). It has
been reported that addition of glucose with optimum light condition play a significant role in increasing the concentration of PC in cyanobacteria Moreover, high
concentration of glucose and glycerol exhibit increase in the production of PBPs in
Anabaena C2 and Spirulina S2 strains (Kovaˇ c et al. 2017). Khattar et al. (2015) have
also found sucrose as another good carbon source for the growth of Anabaena fertilissima than glucose and fructose. Cyanobacteria require range of nitrogen components
such as NO 3− , NH 4 or carbamide, and NaNO 3 for their growth and development.
The cyanobacterium Fischerella sp. produced more amounts of PBPs under nitrate
or ammonium medium as compared to nitrogen-free growth media (Soltani et al.
2007). Hemlata and Fatma (2009) have reported about the toxicity of ammonium in
growth medium, which reduces growth that leads to cell death in Spirulina platensis,
Nostoc sp., Calothrix sp. PCC7601, and Nodularia spumigena (Belkin and Boussiba
1991, Liotenberg et al. 1996).
3.6.5 Metal Stress
Heavy metals play a leading role to induce toxicity of undesirable pollutants on
an organism. The toxicity of heavy metals may further increase due to their nonbiodegradable nature and ability to enter into the food chain. Heavy metals severely
affect normal physiological processes by interference of essential enzyme activity
and pigment-protein developmental process (Bertrand and Guary 2002). Micronutrient heavy metals include boron, manganese, zinc, molybdenum, copper, and cobalt
required in very low quantities. Boron is a rare metal and keenly required by plants,
but has no role in the growth of fungi as well as animals. Anderson and Jordan
(1961) found that boron required for the dinitrogen fixation in Azotobacter. Boron
is an essential micronutrient for rapid growth and development in nitrogen-deprived
condition in certain cyanobacteria like Nostoc muscorum, Calothrix parietina, and
Anabaena cylindrica (Gerloff 1968). The boron-induced growth of cyanobacteria
may signify rapid synthesis of PBPs. Manganese and zinc are essential elements for
the growth of cyanobacteria particularly in different enzymatic reactions involved
in photosynthetic processes (Casarett and Doull 1980). Metal-induced changes in
the arrangement and structure of the light-harvesting complex in cyanobacteria have
been well documented (Sersen and Kralova 2001). Murthy and Mohanty (1991) have
found that energy transfer from PC to chlorophyll a (Chl a) is rapidly inhibited by
heavy metals. This eventually could study the effects of cadmium on three different
57
3.6.4 Carbon and Nitrogen Stress
The carbon and nitrogen ratio is crucial for the growth and development of cyanobacteria and that plays a distinguished role in the production of value-added compounds
or PBPs. Generally, carbon sources such as fructose, glucose, glycerol, and sucrose
are used for the large scale production of cyanobacteria (Kovaˇ c et al. 2017). It has
been reported that addition of glucose with optimum light condition play a significant role in increasing the concentration of PC in cyanobacteria Moreover, high
concentration of glucose and glycerol exhibit increase in the production of PBPs in
Anabaena C2 and Spirulina S2 strains (Kovaˇ c et al. 2017). Khattar et al. (2015) have
also found sucrose as another good carbon source for the growth of Anabaena fertilissima than glucose and fructose. Cyanobacteria require range of nitrogen components
such as NO 3− , NH 4 or carbamide, and NaNO 3 for their growth and development.
The cyanobacterium Fischerella sp. produced more amounts of PBPs under nitrate
or ammonium medium as compared to nitrogen-free growth media (Soltani et al.
2007). Hemlata and Fatma (2009) have reported about the toxicity of ammonium in
growth medium, which reduces growth that leads to cell death in Spirulina platensis,
Nostoc sp., Calothrix sp. PCC7601, and Nodularia spumigena (Belkin and Boussiba
1991, Liotenberg et al. 1996).
3.6.5 Metal Stress
Heavy metals play a leading role to induce toxicity of undesirable pollutants on
an organism. The toxicity of heavy metals may further increase due to their nonbiodegradable nature and ability to enter into the food chain. Heavy metals severely
affect normal physiological processes by interference of essential enzyme activity
and pigment-protein developmental process (Bertrand and Guary 2002). Micronutrient heavy metals include boron, manganese, zinc, molybdenum, copper, and cobalt
required in very low quantities. Boron is a rare metal and keenly required by plants,
but has no role in the growth of fungi as well as animals. Anderson and Jordan
(1961) found that boron required for the dinitrogen fixation in Azotobacter. Boron
is an essential micronutrient for rapid growth and development in nitrogen-deprived
condition in certain cyanobacteria like Nostoc muscorum, Calothrix parietina, and
Anabaena cylindrica (Gerloff 1968). The boron-induced growth of cyanobacteria
may signify rapid synthesis of PBPs. Manganese and zinc are essential elements for
the growth of cyanobacteria particularly in different enzymatic reactions involved
in photosynthetic processes (Casarett and Doull 1980). Metal-induced changes in
the arrangement and structure of the light-harvesting complex in cyanobacteria have
been well documented (Sersen and Kralova 2001). Murthy and Mohanty (1991) have
found that energy transfer from PC to chlorophyll a (Chl a) is rapidly inhibited by
heavy metals. This eventually could study the effects of cadmium on three different