2.3 Aquatic Organisms
21
the nutrients for growth and metabolism. Light is therefore as important for aquatic
algae life as it is for terrestrial plants.
Algae can either be macroalgae or microalgae. There a thousands of species of
both microalgae and macroalgae. Microalgae are photosynthetic, mostly unicellular, microscopic organisms, while macroalgae also called seaweeds are multicellular, photosynthesizing organisms. Algae can either be heterotrophic, autotrophic or
mixotrophic. Autotrophic algae can fix inorganic CO 2 from the atmosphere through
photosynthesis and produce storage carbohydrates while heterotrophic algae can
fix small organic molecules into lipids and proteins while mixotrophic algae can
do both. This makes algae potentially suitable for the production of both biodiesel
and bioethanol, since the lipids can be taking through transesterification and carbohydrates can be saccharified and fermented. Algae have been explored for several
decades for potential commercial production of third-generation biofuel (Nigam and
Singh 2010)
Algae are of particular environmental and economic importance for several reasons. They are able to accumulate carbohydrate at a much faster rate than land plants
due to much higher photosynthetic efficiency. They can grow in wastewater with
high nitrogen content unlike terrestrial plants, and they take up CO 2 at a much faster
rate. Algae can also grow in a variety of environments from saline to fresh, from high
turbulence ocean water to slow flowing municipal wastewater (John et al. 2010).
Microalgae are more compliant to genetic engineering for the optimization of
desired output than higher plants being microscopic in nature. They are more susceptible to control of metabolic pathways and DNA alteration (Rosenberg et al.
2008). Microalgae make for good third-generation biofuel as they contain both lipid
and starch, for the production of biodiesel and bioethanol, respectively. Furthermore,
microalgae does not contain lignin and hemicellulose (Mahapatra and Ramachandra 2013), which makes the process of extraction of the fermentable carbohydrates
less expensive and rigorous as these biopolymers are more complex to saccharify.
Like macroalgae. The microalgae also has the ability to remediate wastewater by
removing sulfur and nitrates (Lv et al. 2017). Microalgae can be found in fresh and
saltwater. Example of freshwater microalgae is the Chlorococcum sp.
Green, brown and red algae are distinguished from one another based on their
cellular structures and composition. While the cell walls of brown algae contain
alginates and fucoidan with laminarin as reserve photosynthetic pigment, red algae
contain agar and carrageenan as their cell wall polysaccharide alongside cellulose,
those of green contain ulvan in their cell wall and starch within their chloroplast.
Diatoms are eukaryotic microalgae that belong to the group of plankton and benthic
algae. Their skeleton is made of amorphous silica, and some diatoms are photosynthetic while others are not. They can be found in both marine and freshwater (Chetia
et al. 2017).
Algae can either be sourced from natural stocks; some fishermen simply dive into
the sea to pick algae by hand. Algae can also be cultivated in open sea or aquaculture.
There are three main methods of cultivating algae as illustrated in Fig. 2.6. These are
broadcast, off button, and longline methods.
21
the nutrients for growth and metabolism. Light is therefore as important for aquatic
algae life as it is for terrestrial plants.
Algae can either be macroalgae or microalgae. There a thousands of species of
both microalgae and macroalgae. Microalgae are photosynthetic, mostly unicellular, microscopic organisms, while macroalgae also called seaweeds are multicellular, photosynthesizing organisms. Algae can either be heterotrophic, autotrophic or
mixotrophic. Autotrophic algae can fix inorganic CO 2 from the atmosphere through
photosynthesis and produce storage carbohydrates while heterotrophic algae can
fix small organic molecules into lipids and proteins while mixotrophic algae can
do both. This makes algae potentially suitable for the production of both biodiesel
and bioethanol, since the lipids can be taking through transesterification and carbohydrates can be saccharified and fermented. Algae have been explored for several
decades for potential commercial production of third-generation biofuel (Nigam and
Singh 2010)
Algae are of particular environmental and economic importance for several reasons. They are able to accumulate carbohydrate at a much faster rate than land plants
due to much higher photosynthetic efficiency. They can grow in wastewater with
high nitrogen content unlike terrestrial plants, and they take up CO 2 at a much faster
rate. Algae can also grow in a variety of environments from saline to fresh, from high
turbulence ocean water to slow flowing municipal wastewater (John et al. 2010).
Microalgae are more compliant to genetic engineering for the optimization of
desired output than higher plants being microscopic in nature. They are more susceptible to control of metabolic pathways and DNA alteration (Rosenberg et al.
2008). Microalgae make for good third-generation biofuel as they contain both lipid
and starch, for the production of biodiesel and bioethanol, respectively. Furthermore,
microalgae does not contain lignin and hemicellulose (Mahapatra and Ramachandra 2013), which makes the process of extraction of the fermentable carbohydrates
less expensive and rigorous as these biopolymers are more complex to saccharify.
Like macroalgae. The microalgae also has the ability to remediate wastewater by
removing sulfur and nitrates (Lv et al. 2017). Microalgae can be found in fresh and
saltwater. Example of freshwater microalgae is the Chlorococcum sp.
Green, brown and red algae are distinguished from one another based on their
cellular structures and composition. While the cell walls of brown algae contain
alginates and fucoidan with laminarin as reserve photosynthetic pigment, red algae
contain agar and carrageenan as their cell wall polysaccharide alongside cellulose,
those of green contain ulvan in their cell wall and starch within their chloroplast.
Diatoms are eukaryotic microalgae that belong to the group of plankton and benthic
algae. Their skeleton is made of amorphous silica, and some diatoms are photosynthetic while others are not. They can be found in both marine and freshwater (Chetia
et al. 2017).
Algae can either be sourced from natural stocks; some fishermen simply dive into
the sea to pick algae by hand. Algae can also be cultivated in open sea or aquaculture.
There are three main methods of cultivating algae as illustrated in Fig. 2.6. These are
broadcast, off button, and longline methods.