Because of their simpler structure than those of higher plants, microalgae can
achieve much higher photosynthetic efficiencies than terrestrial plants. Thus, a
larger share of the captured solar energy is stored through the accumulation of
carbohydrates inside the cell. Similarly, microalgae biomass production occurs in
relatively short times, much lower compared to terrestrial plants used in the production of the first- and secondgeneration bioethanol. The possibility of recovering
the microalgal several times or continuously, depending on the type of bioreactor
used for biomass production. Thus, there is an abundant and inexpensive source of
biomass for the production of bioethanol. Considering the potential of microalgae
use, the great diversity of species, and the different possible conditions of cultivation, the knowledge of the physiology and metabolism of these microorganisms
becomes imperative for the development of new industrial processes.
The microalgae serve as raw material for different types of biofuels, among them
methane, hydrogen, biodiesel, and bioethanol, which could be used together or
substituting the gasoline in light vehicles (Mata et al. 2010). Since global consumption of light fossil fuels is greater than the consumption of diesel heavy
vehicles, researches’ efforts on microalgae bioethanol production should be
increased, an economically interesting alternative.
The selection of the appropriate microalgae species for the production of biofuels is an important factor for the success of the productive process as a whole. The
desirable characteristics for a microalgae to be potential organism to biofuels
production are tolerate shear stresses found in the reactors (especially in closed
photobioreactors), to be dominant in relation to contaminant microorganism strains,
large CO 2 absorption capacity in photoautotrophic systems (high photosynthetic
efficiency), tolerate large temperature variations resulting from daily and seasonal
cycles, low nutrient requirement, potential of high value-added coproducts in
addition to the desired product, present a short productive cycle and
self-flocculation to facilitate the recovery stage of the microalgal biomass.
The use of microalgae and cyanobacteria for the production of the
third-generation biofuels has many advantages over higher plants in view of producing the first- and second-generation biofuels, mainly due to their faster growth
under several conditions, including in wastewater. The biochemical composition of
microalgae grown under normal conditions, that is, without nutrient limitation,
primarily encompasses proteins (30–50%), carbohydrates (20–40%), and lipids
(8–15%). Microalgae present several compounds in their cells, such as lipids,
carbohydrates, proteins, and pigments, in different concentrations. This chemical
profile directly reflects the nature of the microorganism (as its species or lineage),
the influence of the chosen culture conditions, and the stage of growth of the
culture. In this way, the same microalgae species can present different compositions
when handling the specified factors (Zepka et al. 2008). For the production of the
third-generation bioethanol, one should select a microalgae species with the ability
to produce high concentrations of carbohydrates instead of lipids as energy reserve
compound (Mussatto et al. 2010).
11 Biofuels from Microalgae: Bioethanol
231
achieve much higher photosynthetic efficiencies than terrestrial plants. Thus, a
larger share of the captured solar energy is stored through the accumulation of
carbohydrates inside the cell. Similarly, microalgae biomass production occurs in
relatively short times, much lower compared to terrestrial plants used in the production of the first- and secondgeneration bioethanol. The possibility of recovering
the microalgal several times or continuously, depending on the type of bioreactor
used for biomass production. Thus, there is an abundant and inexpensive source of
biomass for the production of bioethanol. Considering the potential of microalgae
use, the great diversity of species, and the different possible conditions of cultivation, the knowledge of the physiology and metabolism of these microorganisms
becomes imperative for the development of new industrial processes.
The microalgae serve as raw material for different types of biofuels, among them
methane, hydrogen, biodiesel, and bioethanol, which could be used together or
substituting the gasoline in light vehicles (Mata et al. 2010). Since global consumption of light fossil fuels is greater than the consumption of diesel heavy
vehicles, researches’ efforts on microalgae bioethanol production should be
increased, an economically interesting alternative.
The selection of the appropriate microalgae species for the production of biofuels is an important factor for the success of the productive process as a whole. The
desirable characteristics for a microalgae to be potential organism to biofuels
production are tolerate shear stresses found in the reactors (especially in closed
photobioreactors), to be dominant in relation to contaminant microorganism strains,
large CO 2 absorption capacity in photoautotrophic systems (high photosynthetic
efficiency), tolerate large temperature variations resulting from daily and seasonal
cycles, low nutrient requirement, potential of high value-added coproducts in
addition to the desired product, present a short productive cycle and
self-flocculation to facilitate the recovery stage of the microalgal biomass.
The use of microalgae and cyanobacteria for the production of the
third-generation biofuels has many advantages over higher plants in view of producing the first- and second-generation biofuels, mainly due to their faster growth
under several conditions, including in wastewater. The biochemical composition of
microalgae grown under normal conditions, that is, without nutrient limitation,
primarily encompasses proteins (30–50%), carbohydrates (20–40%), and lipids
(8–15%). Microalgae present several compounds in their cells, such as lipids,
carbohydrates, proteins, and pigments, in different concentrations. This chemical
profile directly reflects the nature of the microorganism (as its species or lineage),
the influence of the chosen culture conditions, and the stage of growth of the
culture. In this way, the same microalgae species can present different compositions
when handling the specified factors (Zepka et al. 2008). For the production of the
third-generation bioethanol, one should select a microalgae species with the ability
to produce high concentrations of carbohydrates instead of lipids as energy reserve
compound (Mussatto et al. 2010).
11 Biofuels from Microalgae: Bioethanol
231