In photobioreactor systems, high costs are involved in providing continuous
intense illumination, system sterilization, to scale-up and operate the reactors
[27]. To make microalgae production in photobioreactors more competitive, more
innovative system configurations along with optimization of already available technology are much needed and important.
4 Modes of Cultivation
Conventional microalgal growth techniques depend on cultivation of phototrophic
algae in open ponds or indoor in photobioreactors. These techniques are normally
not cost-effective because of high operating costs, culture inefficiency, light insufficiency, and low biomass production. Several studies have stated that microalgal
growth via heterotrophic and mixotrophic methods is cost-effective [28–30]. A lot of
microalgal strains are having the ability to utilize organic carbon sources in
mixotrophy (light) or heterotrophy (dark) and grow. These modes of microalgal
cultivation also play a major role in boosting the production of essential fatty acids.
4.1 Heterotrophic Cultivation
Some microalgae species can be grown in dark conditions, utilizing an organic
carbon substrate rather than CO 2 and light to supply energy to the cells growth.
The advantages associated with the heterotrophic microalgae cultivation are exclusion of light requirements, easier bioreactor operation, increased growth rates, and
improved lipid and protein production.
The organic carbon resources that these algae could metabolize are lactate,
ethanol, acetate, pyruvate, C6 sugars, amino acids, C5 monosaccharides, disaccharides, and glycerol [31]. However the high cost of these carbon sources represents
the main downside of this operation mode. Previous studies have demonstrated that
glucose occupies major of the total medium cost (80%) [32]. Therefore it is imperative to find other low-cost carbon sources. Indeed, recent studies have focused on
the utilization of cheap carbon sources like food waste hydrolyzate or whey permeate for microalgal cultivation [33, 34].
Heterotrophic growth mode has produced elevated lipid content owing to their
high rate of algal growth and cell concentrations [35]. When compared with photoautotrophic conditions, the oils produced under heterotrophic were more saturated,
making them apt for biodiesel manufacture. The class and quantity of biodiesel
produced depends on the ability of strain to effectively uptake the given carbon
source, grow, and accumulate oil [36]. However, new researches on cheap carbon
sources are desired for the improvement of cost-efficient processes for food, feed,
and biofuel production.
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intense illumination, system sterilization, to scale-up and operate the reactors
[27]. To make microalgae production in photobioreactors more competitive, more
innovative system configurations along with optimization of already available technology are much needed and important.
4 Modes of Cultivation
Conventional microalgal growth techniques depend on cultivation of phototrophic
algae in open ponds or indoor in photobioreactors. These techniques are normally
not cost-effective because of high operating costs, culture inefficiency, light insufficiency, and low biomass production. Several studies have stated that microalgal
growth via heterotrophic and mixotrophic methods is cost-effective [28–30]. A lot of
microalgal strains are having the ability to utilize organic carbon sources in
mixotrophy (light) or heterotrophy (dark) and grow. These modes of microalgal
cultivation also play a major role in boosting the production of essential fatty acids.
4.1 Heterotrophic Cultivation
Some microalgae species can be grown in dark conditions, utilizing an organic
carbon substrate rather than CO 2 and light to supply energy to the cells growth.
The advantages associated with the heterotrophic microalgae cultivation are exclusion of light requirements, easier bioreactor operation, increased growth rates, and
improved lipid and protein production.
The organic carbon resources that these algae could metabolize are lactate,
ethanol, acetate, pyruvate, C6 sugars, amino acids, C5 monosaccharides, disaccharides, and glycerol [31]. However the high cost of these carbon sources represents
the main downside of this operation mode. Previous studies have demonstrated that
glucose occupies major of the total medium cost (80%) [32]. Therefore it is imperative to find other low-cost carbon sources. Indeed, recent studies have focused on
the utilization of cheap carbon sources like food waste hydrolyzate or whey permeate for microalgal cultivation [33, 34].
Heterotrophic growth mode has produced elevated lipid content owing to their
high rate of algal growth and cell concentrations [35]. When compared with photoautotrophic conditions, the oils produced under heterotrophic were more saturated,
making them apt for biodiesel manufacture. The class and quantity of biodiesel
produced depends on the ability of strain to effectively uptake the given carbon
source, grow, and accumulate oil [36]. However, new researches on cheap carbon
sources are desired for the improvement of cost-efficient processes for food, feed,
and biofuel production.
146
B. Srinivasan and G. Kulshreshtha