47
bonate, and, especially, volatile organic compounds (VOCs) (Jacob-Lopes et al.
2010).
Volatile organic compounds are compounds of low molecular weight, high vapor
pressure, and low boiling point, promoting the rapid passage from the liquid or solid
phase to the gaseous phase and can be desorbed and dispersed at the water-air interface (Jerković et al. 2018). The metabolic profile of these compounds assumes an
important category in the volatolomic branch, one of the new research fields in the
“omic” sciences (Achyuthan et al. 2017).
Depending on the species, photosynthetic activity, and the growing circumstance, microalgae and cyanobacteria have been reported as a prosperous source for
the production of VOC blends with up to 15 carbon atoms belonging to distinct
chemical classes, such as alcohol, aldehydes, ketones, esters, terpenes, hydrocarbons, and sulfurized compounds (Santos et al. 2016b; Hosoglu 2018). However,
there is a scarcity of consolidated information about how these compounds are
formed, which could help identify them and target the most appropriate industrial
application sector. According to Jacob-Lopes and Franco (2013), the elucidation of
VOC formation occurs through the global CO 2 sequestration rates associated with
the carbon mass balances, which shows the possible routes of carbon fractions
incorporation. Still, according to these authors, about 90% of the carbon-based
compounds generated in microalgal processes are represented by the release of
VOCs, which could be profitable if they were collected adequately by efficient
recovery systems.
Therefore, the objective of this chapter was to provide a comprehensive view of
the biological conversion of CO 2 into VOCs. Here, we cover topics related to the
characteristics of microalgae and photosynthetic metabolism, the VOC biosynthesis
mechanism, the culture systems, the environmental implications, and, finally, the
insights on industrial applications.
2.2 Microalgae and Photosynthetic Metabolism
Microalgae are a group of living microorganisms widely known on the terrestrial
surface, whose screening comprises approximately 72,500 species. The classification of microalgae has undergone many changes over the years. Currently, the
taxonomic division patterns rely upon their morphophysiological and structural
characteristics, dividing these organisms into 16 classes (Cyanophyceae,
Rhodophyceae,
Chlorophyceae,
Charophyceae,
Euglenophyceae,
Raphidophyceae,
Xanthophyceae,
Bacillariophyceae,
Chrysophyceae,
Haptophyceae, Phaeophyceae, Dinophyceae, Cryptophyceae, Synurophyceae,
Eustigmatophyceae, and Glaucophyceae), but the most abundant in nature are the
golden algae (Chrysophyceae), the green algae (Chrysophyceae), and the diatoms
(Bacillariophyceae). Concerning biotechnological exploitation, the green algae,
the cyanobacteria (Cyanophyceae), and the diatoms are the most relevant (JacobLopes et al. 2019).
2 Biological Conversion of Carbon Dioxide into Volatile Organic Compounds
bonate, and, especially, volatile organic compounds (VOCs) (Jacob-Lopes et al.
2010).
Volatile organic compounds are compounds of low molecular weight, high vapor
pressure, and low boiling point, promoting the rapid passage from the liquid or solid
phase to the gaseous phase and can be desorbed and dispersed at the water-air interface (Jerković et al. 2018). The metabolic profile of these compounds assumes an
important category in the volatolomic branch, one of the new research fields in the
“omic” sciences (Achyuthan et al. 2017).
Depending on the species, photosynthetic activity, and the growing circumstance, microalgae and cyanobacteria have been reported as a prosperous source for
the production of VOC blends with up to 15 carbon atoms belonging to distinct
chemical classes, such as alcohol, aldehydes, ketones, esters, terpenes, hydrocarbons, and sulfurized compounds (Santos et al. 2016b; Hosoglu 2018). However,
there is a scarcity of consolidated information about how these compounds are
formed, which could help identify them and target the most appropriate industrial
application sector. According to Jacob-Lopes and Franco (2013), the elucidation of
VOC formation occurs through the global CO 2 sequestration rates associated with
the carbon mass balances, which shows the possible routes of carbon fractions
incorporation. Still, according to these authors, about 90% of the carbon-based
compounds generated in microalgal processes are represented by the release of
VOCs, which could be profitable if they were collected adequately by efficient
recovery systems.
Therefore, the objective of this chapter was to provide a comprehensive view of
the biological conversion of CO 2 into VOCs. Here, we cover topics related to the
characteristics of microalgae and photosynthetic metabolism, the VOC biosynthesis
mechanism, the culture systems, the environmental implications, and, finally, the
insights on industrial applications.
2.2 Microalgae and Photosynthetic Metabolism
Microalgae are a group of living microorganisms widely known on the terrestrial
surface, whose screening comprises approximately 72,500 species. The classification of microalgae has undergone many changes over the years. Currently, the
taxonomic division patterns rely upon their morphophysiological and structural
characteristics, dividing these organisms into 16 classes (Cyanophyceae,
Rhodophyceae,
Chlorophyceae,
Charophyceae,
Euglenophyceae,
Raphidophyceae,
Xanthophyceae,
Bacillariophyceae,
Chrysophyceae,
Haptophyceae, Phaeophyceae, Dinophyceae, Cryptophyceae, Synurophyceae,
Eustigmatophyceae, and Glaucophyceae), but the most abundant in nature are the
golden algae (Chrysophyceae), the green algae (Chrysophyceae), and the diatoms
(Bacillariophyceae). Concerning biotechnological exploitation, the green algae,
the cyanobacteria (Cyanophyceae), and the diatoms are the most relevant (JacobLopes et al. 2019).
2 Biological Conversion of Carbon Dioxide into Volatile Organic Compounds