250
M. M. Maroneze et al.
11.5.2 β-Carotene Production Process
β-Carotene was the first high-value product commercially produced from a
microalgae (Borowitzka 2013). The most important source for the natural production of β-carotene is the halophilic green microalgae D. salina, which can contain up
to 14% of dw as β-carotene (Borowitzka 2018). The estimated market in 2019 was
about 200 USD million for β-carotene from D. salina, based on a CAGR of 3.3%.
The estimated cost of its production is about USD 105.0/kg, and the selling price is
about USD 790/kg (Jacob-Lopes et al. 2019; Hu 2019).
In D. salina, adverse environmental conditions like nitrogen limitation, high
salinity, low temperature, and high luminosity favor the β-carotene biosynthesis. As
the carotenogenic pathway of microalgae appears to be similar to that of plants, it is
believed that the generation of reactive oxygen species (ROS) triggers the accumulation of β-carotene. The ROS induction by applied stress conditions acts as messenger
molecules for biosynthesis (Ye et al. 2008; Von Alvensleben and Heimann 2018).
Although the β-carotene inductors conditions in D. salina have become clear, via
that leading to this response still has not been adequately elucidated (Paliwal et al.
2017). To date, the known genes involved in the β-carotene biosynthetic pathway are
PSY, PDS, ZDS, and β-LCY (Ramos et al. 2011).
Recent researches are focused on the coordinated expression of multiple enzymes
and the regulation of specific enzymes that control the flow to the desired product
(Varela et al. 2016). An example of this approach would be the positive regulation
of β-LCY accompanied by the down-regulation of ε-LCY is desired to promote βcarotene accumulation, so that the conversion of lycopene to α-carotene does not
occur (Li et al. 2019). In this sense, considerable efforts are being devoted to the
massive accumulation of carotenoids in D. salina (Galarza et al. 2018).
Currently, at a commercial scale, the cultivation of D. salina is based on
autotrophic growth in saline media containing inorganic nutrients, with CO 2 as the
carbon source. Generally, these production plants are located in semidesert regions
(i.e., Hutt Lagoon, Western Australia, Whyalla, Israel), where solar irradiance is
maximal, cloudiness is minimal, the climate is warm, and hypersaline water is
available (Del Campo et al. 2007).
The optimum salinity for growth lies between 18 and 22% NaCl, while a higher
salinity at or around 27% of NaCl is ideal for carotenogenesis (Borowitzka et al.
1984). As β-carotene is an intracellular product, which accumulates in oil globules in
the chloroplasts, it is necessary to find a balance between the production of biomass
and the production of carotenoids. The maximum β-carotene yield occurs at an
intermediate salinity, but it is advisable to use salinity above the ideal level to avoid
protozoan predators and non-carotenogenic microalgal competitors, as Dunaliella
viridis (Raja et al. 2007). D. salina also has a high-temperature tolerance, with
optimal growth in temperatures around 28 °C (Borowitzka 2018).
Due to the adverse cultivation conditions employed, open ponds are the most used
commercial systems. Among the different open system projects, extensive unmixed
ponds and raceway ponds are the most employed. These cultivation systems are also
M. M. Maroneze et al.
11.5.2 β-Carotene Production Process
β-Carotene was the first high-value product commercially produced from a
microalgae (Borowitzka 2013). The most important source for the natural production of β-carotene is the halophilic green microalgae D. salina, which can contain up
to 14% of dw as β-carotene (Borowitzka 2018). The estimated market in 2019 was
about 200 USD million for β-carotene from D. salina, based on a CAGR of 3.3%.
The estimated cost of its production is about USD 105.0/kg, and the selling price is
about USD 790/kg (Jacob-Lopes et al. 2019; Hu 2019).
In D. salina, adverse environmental conditions like nitrogen limitation, high
salinity, low temperature, and high luminosity favor the β-carotene biosynthesis. As
the carotenogenic pathway of microalgae appears to be similar to that of plants, it is
believed that the generation of reactive oxygen species (ROS) triggers the accumulation of β-carotene. The ROS induction by applied stress conditions acts as messenger
molecules for biosynthesis (Ye et al. 2008; Von Alvensleben and Heimann 2018).
Although the β-carotene inductors conditions in D. salina have become clear, via
that leading to this response still has not been adequately elucidated (Paliwal et al.
2017). To date, the known genes involved in the β-carotene biosynthetic pathway are
PSY, PDS, ZDS, and β-LCY (Ramos et al. 2011).
Recent researches are focused on the coordinated expression of multiple enzymes
and the regulation of specific enzymes that control the flow to the desired product
(Varela et al. 2016). An example of this approach would be the positive regulation
of β-LCY accompanied by the down-regulation of ε-LCY is desired to promote βcarotene accumulation, so that the conversion of lycopene to α-carotene does not
occur (Li et al. 2019). In this sense, considerable efforts are being devoted to the
massive accumulation of carotenoids in D. salina (Galarza et al. 2018).
Currently, at a commercial scale, the cultivation of D. salina is based on
autotrophic growth in saline media containing inorganic nutrients, with CO 2 as the
carbon source. Generally, these production plants are located in semidesert regions
(i.e., Hutt Lagoon, Western Australia, Whyalla, Israel), where solar irradiance is
maximal, cloudiness is minimal, the climate is warm, and hypersaline water is
available (Del Campo et al. 2007).
The optimum salinity for growth lies between 18 and 22% NaCl, while a higher
salinity at or around 27% of NaCl is ideal for carotenogenesis (Borowitzka et al.
1984). As β-carotene is an intracellular product, which accumulates in oil globules in
the chloroplasts, it is necessary to find a balance between the production of biomass
and the production of carotenoids. The maximum β-carotene yield occurs at an
intermediate salinity, but it is advisable to use salinity above the ideal level to avoid
protozoan predators and non-carotenogenic microalgal competitors, as Dunaliella
viridis (Raja et al. 2007). D. salina also has a high-temperature tolerance, with
optimal growth in temperatures around 28 °C (Borowitzka 2018).
Due to the adverse cultivation conditions employed, open ponds are the most used
commercial systems. Among the different open system projects, extensive unmixed
ponds and raceway ponds are the most employed. These cultivation systems are also