These systems are more appropriated for cells that cannot compete and grow in
difficult environments and for the obtaining of pharmaceutical and food products
(Safi et al. 2014). To increase lipid productivity in microalgae, growth conditions
like nitrogen on nutrients limitation are applied (Mata et al. 2010).
2.1.3 Heterotrophic Growth
The heterotrophic culture of microalgae is interesting, due to the fact that it is
expected that growth rates and productivity are major in comparison with autotrophic growth. Additionally, the biomass production using these systems allows a
simple and low-cost harvesting (Chen 1996). Nevertheless, one of the main limitations of this type of cultures is the high-cost attached to carbon source (glucose or
acetate), in comparison with another nutrients in the medium, added to the competition of these sources with food sector (Liang et al. 2009). Given this situation, it
is of great interest to find a cheap carbon source, with the aim to make these cultures
competitive when used on a commercial level (Abad and Turon 2012). For this
reason, many studies have been focused on the analysis of microalgae growth in
agroindustrial residues such as molasses, glycerol, and pig manure (Leesing and
Kookkhunthod 2011). Almost it has been demonstrated that microalgae culture can
be used for wastewater treatment with high organic and salt levels (Perez-Garcia
et al. 2011).
2.1.4 Mixotrophic Growth
In this type of cultures, microorganisms as microalgae can be able to get metabolic
energy from both, photosynthesis and carbon organics sources (Chen et al. 2011). It
has been reported a high cellular density in mixotrophic cultures for C. vulgaris,
demonstrating that these microalgae can grow in this type of cultures (Liang et al.
2009).
3 Process of Harvesting
To consider the lipids obtained from microalgae a viable raw material, it is necessary to have in mind the harvesting method to use. This stage can represent a
20–30% of the total cost for biomass obtaining (Rawat et al. 2011) that implies a
cumulative high energetic demand for biodiesel production (Dassey and Theegala
2012). These difficulties are mainly associated to the small size of the microalgae
and their suspension stability in aqueous media, as a result of negative charges.
Additionally, the organic material and low concentration of the streams treated that
come from diluted cultures makes difficult this stage (Liu et al. 2013). The harvesting process can be classified into physical, chemical, and biological methods.
184
D. L. Restrepo-Serna et al.
difficult environments and for the obtaining of pharmaceutical and food products
(Safi et al. 2014). To increase lipid productivity in microalgae, growth conditions
like nitrogen on nutrients limitation are applied (Mata et al. 2010).
2.1.3 Heterotrophic Growth
The heterotrophic culture of microalgae is interesting, due to the fact that it is
expected that growth rates and productivity are major in comparison with autotrophic growth. Additionally, the biomass production using these systems allows a
simple and low-cost harvesting (Chen 1996). Nevertheless, one of the main limitations of this type of cultures is the high-cost attached to carbon source (glucose or
acetate), in comparison with another nutrients in the medium, added to the competition of these sources with food sector (Liang et al. 2009). Given this situation, it
is of great interest to find a cheap carbon source, with the aim to make these cultures
competitive when used on a commercial level (Abad and Turon 2012). For this
reason, many studies have been focused on the analysis of microalgae growth in
agroindustrial residues such as molasses, glycerol, and pig manure (Leesing and
Kookkhunthod 2011). Almost it has been demonstrated that microalgae culture can
be used for wastewater treatment with high organic and salt levels (Perez-Garcia
et al. 2011).
2.1.4 Mixotrophic Growth
In this type of cultures, microorganisms as microalgae can be able to get metabolic
energy from both, photosynthesis and carbon organics sources (Chen et al. 2011). It
has been reported a high cellular density in mixotrophic cultures for C. vulgaris,
demonstrating that these microalgae can grow in this type of cultures (Liang et al.
2009).
3 Process of Harvesting
To consider the lipids obtained from microalgae a viable raw material, it is necessary to have in mind the harvesting method to use. This stage can represent a
20–30% of the total cost for biomass obtaining (Rawat et al. 2011) that implies a
cumulative high energetic demand for biodiesel production (Dassey and Theegala
2012). These difficulties are mainly associated to the small size of the microalgae
and their suspension stability in aqueous media, as a result of negative charges.
Additionally, the organic material and low concentration of the streams treated that
come from diluted cultures makes difficult this stage (Liu et al. 2013). The harvesting process can be classified into physical, chemical, and biological methods.
184
D. L. Restrepo-Serna et al.