Thus, microalgae can be a powerful source of oil (biodiesel production). However, microalgae biosynthesize long-chain polyunsaturated fatty acids in particular
omega-6 family (ω À 6) such as γ-linolenic acid, arachidonic acid, and omega-3
family (ω À 3) as eicosapentaenoic acid and docosahexaenoic acid. These longchain polyunsaturated fatty acids are essential fatty acids and also well-known for
their nutraceuticals properties (healthy and disease prevention) (Andrade et al.
2018).
The investigation of the production of essential fatty acids, such as omega 3, 6,
and 9, was studied by Abdo et al. (2015) by using the microalgae species
Chlamydomonas variabilis, Chlorella vulgaris, Haematococcus pluvialis, and Spirulina platensis. The species Chlamydomonas variabilis showed the highest lipid
content (21%) with 29.24% of omega 6, whereas Haematococcus pluvialis showed
the lower lipid content (10%) with 14.83% of omega 6. The species Chlorella
vulgaris and Spirulina platensis showed the presence of omega 3, respectively,
21.17% and 4.9%. Spirulina platensis was the only one that showed the presence
of omega 9 (3.22%). Hence, the species Chlamydomonas variabilis and Chlorella
vulgaris are recommended healthy range.
Considering the biorefinery concept, a recent study evaluated the growth of
Crypthecodinium cohnii, a heterotrophic marine microalga, in the presence of
volatile fatty acids, such as acetic butyric or propionic acids, which are released in
high amounts through the dark fermentation by using biowastes. They also evaluated
the ability of the microalgae to convert volatile fatty acids in high-added-value like
docosahexaenoic acid, the most known omega-3 fatty acids. After 60 h of fed-batch
cultivation, they observed the docosahexaenoic acid content of 29.8% of total fatty
acids (Chalima et al. 2019).
4.5.3 Phenolic Compounds
Phenolic compounds are defined as low-molecular-weight compounds. Their structures have at least one phenol unit (Rosa et al. 2019; Sánchez-Salgado et al. 2019).
Recent studies are shown that phenolic compounds are produced by photosynthetic organisms (Wilson et al. 2017), and thus, microalgae have drawn attention as a
source of high-value-added molecules. In this sense, Spirulina spp. are the most
commercial sources of microalgae phenolics (Klejdus et al. 2009; Machu et al. 2019;
Kumar et al. 2019). Table 4.4 shows some phenolic compounds obtained from
different species of microalgae.
The humans’ long life is also related to antioxidant-rich feed whose compounds
are produced by photosynthetic organisms (Wilson et al. 2017), and phenolic
compounds are a very important class of antioxidants molecules, such as flavonoids
(isoflavones, flavanones, flavonols, and dihydrochalcones) that can be found in
microalgae (Klejdus et al. 2010). Thus, microalgae molecules can play an important
role in repairing or preventing oxidative damages caused by free radicals
4 Phycoremediation: A Sustainable Biorefinery Approach
113
omega-6 family (ω À 6) such as γ-linolenic acid, arachidonic acid, and omega-3
family (ω À 3) as eicosapentaenoic acid and docosahexaenoic acid. These longchain polyunsaturated fatty acids are essential fatty acids and also well-known for
their nutraceuticals properties (healthy and disease prevention) (Andrade et al.
2018).
The investigation of the production of essential fatty acids, such as omega 3, 6,
and 9, was studied by Abdo et al. (2015) by using the microalgae species
Chlamydomonas variabilis, Chlorella vulgaris, Haematococcus pluvialis, and Spirulina platensis. The species Chlamydomonas variabilis showed the highest lipid
content (21%) with 29.24% of omega 6, whereas Haematococcus pluvialis showed
the lower lipid content (10%) with 14.83% of omega 6. The species Chlorella
vulgaris and Spirulina platensis showed the presence of omega 3, respectively,
21.17% and 4.9%. Spirulina platensis was the only one that showed the presence
of omega 9 (3.22%). Hence, the species Chlamydomonas variabilis and Chlorella
vulgaris are recommended healthy range.
Considering the biorefinery concept, a recent study evaluated the growth of
Crypthecodinium cohnii, a heterotrophic marine microalga, in the presence of
volatile fatty acids, such as acetic butyric or propionic acids, which are released in
high amounts through the dark fermentation by using biowastes. They also evaluated
the ability of the microalgae to convert volatile fatty acids in high-added-value like
docosahexaenoic acid, the most known omega-3 fatty acids. After 60 h of fed-batch
cultivation, they observed the docosahexaenoic acid content of 29.8% of total fatty
acids (Chalima et al. 2019).
4.5.3 Phenolic Compounds
Phenolic compounds are defined as low-molecular-weight compounds. Their structures have at least one phenol unit (Rosa et al. 2019; Sánchez-Salgado et al. 2019).
Recent studies are shown that phenolic compounds are produced by photosynthetic organisms (Wilson et al. 2017), and thus, microalgae have drawn attention as a
source of high-value-added molecules. In this sense, Spirulina spp. are the most
commercial sources of microalgae phenolics (Klejdus et al. 2009; Machu et al. 2019;
Kumar et al. 2019). Table 4.4 shows some phenolic compounds obtained from
different species of microalgae.
The humans’ long life is also related to antioxidant-rich feed whose compounds
are produced by photosynthetic organisms (Wilson et al. 2017), and phenolic
compounds are a very important class of antioxidants molecules, such as flavonoids
(isoflavones, flavanones, flavonols, and dihydrochalcones) that can be found in
microalgae (Klejdus et al. 2010). Thus, microalgae molecules can play an important
role in repairing or preventing oxidative damages caused by free radicals
4 Phycoremediation: A Sustainable Biorefinery Approach
113