2.3.2 Closed Systems
The photobioreactors allow the culture of a single species of microalgae for long
periods of cultivation (Molina Grima et al. 1999). Among the various types of
photobioreactors for monocultures cultivation, the tubular photobioreactors are the
most suitable for large-scale production of microalgae.
The tubular photobioreactors consist of a set of transparent tubes, usually glass
or plastic (Chisti 2007). The tubes have typically a diameter less than or equal to
0.1 m. This parameter is limited in order to allow the penetration of light inside the
tube, thus guaranteeing light availability to the whole culture. Culture circulates
within the tubes, passing by a reservoir (degassing column) and returns again to the
tubes, as shown in Fig. 3. There are other variants of photobioreactors; however,
they are not usually applied (Carvalho et al. 2006; Molina Grima et al. 1999; Pulz
2001; Tredici 2002).
Some of the advantages of photobioreactors are: (i) the control of cultivation
conditions (pH, agitation, concentration of CO 2 and oxygen—O 2 ) is facilitated;
(ii) the reduction of water and CO 2 losses; (iii) the possibility of operating with high
cell concentrations and volumetric productivities; and (iv) the reduction of contamination by other microorganisms (Li et al. 2008). However, the photobioreactors
have some drawbacks, among them the overheating of the culture, the accumulation
of O 2 and the high costs of construction.
2.4 Microalgal Applications
The microalgae biomass can be used to generate added-value products. The biomass applicability varies depending on the used microalgae species (Spolaore et al.
2006). Currently, there are numerous commercial applications for microalgae, such
Fig. 3 Tubular photobioreactor (adapted from Chisti 2007)
42
A. P. de Carvalho Lopes et al.
The photobioreactors allow the culture of a single species of microalgae for long
periods of cultivation (Molina Grima et al. 1999). Among the various types of
photobioreactors for monocultures cultivation, the tubular photobioreactors are the
most suitable for large-scale production of microalgae.
The tubular photobioreactors consist of a set of transparent tubes, usually glass
or plastic (Chisti 2007). The tubes have typically a diameter less than or equal to
0.1 m. This parameter is limited in order to allow the penetration of light inside the
tube, thus guaranteeing light availability to the whole culture. Culture circulates
within the tubes, passing by a reservoir (degassing column) and returns again to the
tubes, as shown in Fig. 3. There are other variants of photobioreactors; however,
they are not usually applied (Carvalho et al. 2006; Molina Grima et al. 1999; Pulz
2001; Tredici 2002).
Some of the advantages of photobioreactors are: (i) the control of cultivation
conditions (pH, agitation, concentration of CO 2 and oxygen—O 2 ) is facilitated;
(ii) the reduction of water and CO 2 losses; (iii) the possibility of operating with high
cell concentrations and volumetric productivities; and (iv) the reduction of contamination by other microorganisms (Li et al. 2008). However, the photobioreactors
have some drawbacks, among them the overheating of the culture, the accumulation
of O 2 and the high costs of construction.
2.4 Microalgal Applications
The microalgae biomass can be used to generate added-value products. The biomass applicability varies depending on the used microalgae species (Spolaore et al.
2006). Currently, there are numerous commercial applications for microalgae, such
Fig. 3 Tubular photobioreactor (adapted from Chisti 2007)
42
A. P. de Carvalho Lopes et al.