Part B | 9.1
258 Part B Tools and Methods in Marine Biotechnology
ing marine organisms as cell factories for biological synthesis of these compounds. Marine organisms
can be broadly classified into two categories, those
requiring an organic carbon source for growth (heterotrophs) and those that rely on photosynthesis for
growth (phototrophs). This chapter focuses solely on
phototrophic marine organisms. Phototrophic marine
organisms comprise a vast group that includes photosynthetic bacteria, cyanobacteria, microscopic algae
(microalgae), and seaweeds (macroalgae).
9.1.1 Phototrophic Marine Organisms:
A Diverse Source
of Valuable Natural Products
A marine natural product is defined as any valuable
material that is biologically produced by a marine organism. This section overviews natural products of
current or future value commercial value from phototropic marine organisms, with a particular focus on
marine algae.
Phototrophic marine algae are particularly diverse
sources of natural products, as detailed in several reviews [9.1–8]. The biosynthesis of natural compounds
by phototrophic marine organisms falls into two categories. The first category comprises organic compounds
biologically synthesized through primary metabolism.
Primary metabolism represents a system of biochemical pathways that are essential for cell growth and
reproduction. For example, the biosynthesis of sugars,
amino acids, nucleic acids, proteins, ribonucleic acid
(RNA), and deoxyribonucleic acid (DNA), are usually
associated with primary metabolism in phototrophic
marine organisms. The second category comprises organic compounds derived from secondary metabolism.
Biochemical pathways within secondary metabolism
are not essential for cell growth or reproduction but
serve some specialized function in time of need, for
example, lipids for chemical energy storage, or bioactive chemical defense compounds to avoid being eaten
by other organisms. In general, secondary metabolites
are the source of pharmacologically-active compounds.
Natural products derived from marine organisms do not
have to be in a pure form. Often, the cell biomass itself
or extracts of the cell biomass are valuable. These extracts, which can include both primary and secondary
metabolites of human nutritional value, are called nutraceuticals.
Microalgae are a promising future platform for the
production of advanced biofuels, as discussed in several recent reviews and papers [9.9–15]. Microalgae
are single-celled photosynthetic organisms that grow,
reproduce themselves, and biosynthesize energy-dense
molecules through metabolic processes that utilize only
sunlight, atmospheric CO 2 , water, and macronutrients –
principally nitrogen and phosphorous – as inputs. The
variety of lipids biosynthesized within the algae, which
can constitute up to 50 wt% of the algal biomass, can be
chemically converted to liquid transportation fuels such
as biodiesel ( C 14 C 22 fatty acid methyl esters)
or green diesel by catalytic processes [9.16]. Relative
to oil-bearing land plants for biodiesel production, algae can thrive on saline waters not suitable for food
production, and have much higher production rates.
Furthermore, algal biofuel production systems can be
sited on non-arable land because the organisms are
grown in water within engineered systems (e.g., open
ponds or enclosed photobioreactors), not in soil.
Other than algal biofuels, commercially important
natural products from phototrophic marine organisms
fall into five categories:
1. Nutritional supplements or nutraceuticals
2. Specialty pigments
3. Industrial polysaccharides
4. Products for aquaculture
5. Pharmaceutical compounds.
Examples of commercial natural products from
phototrophic marine organisms are provided in Table 9.1. Commercial natural products include betacarotene, the polyunsaturated fatty acids (PUFAs) EPA
and DHA, Spirulina dried biomass, astaxanthin (an
aquaculture feed supplement), and the hydro-colloids.
Most of the products listed in Table 9.1 are primary
metabolites, although some polyunsaturated fatty acids
and polysaccharides can also be produced as a consequence of secondary metabolism. Discussions of the
metabolic pathways associated with the biological synthesis of each of these compounds within the cell are
beyond the scope of this chapter.
Phototrophic marine organisms will play a major
role in emerging marine biotechnology revolution because they are a rich source of novel drugs for the
future. Below, a few exciting new pharmaceutical candidates from cyanobacteria, microalgae, and macroalgae are overviewed.
Marine cyanobacteria and microalgae offer a diverse array of pharmaceutical candidates. For example,
a sulfolipid from the filamentous marine cyanobacteria Lyngbya sp. is in preclinical trials for treatment
against the human immunodeficiency virus (HIV). The
thiazoline-containing lipid Curacin A from Lyngbya
258 Part B Tools and Methods in Marine Biotechnology
ing marine organisms as cell factories for biological synthesis of these compounds. Marine organisms
can be broadly classified into two categories, those
requiring an organic carbon source for growth (heterotrophs) and those that rely on photosynthesis for
growth (phototrophs). This chapter focuses solely on
phototrophic marine organisms. Phototrophic marine
organisms comprise a vast group that includes photosynthetic bacteria, cyanobacteria, microscopic algae
(microalgae), and seaweeds (macroalgae).
9.1.1 Phototrophic Marine Organisms:
A Diverse Source
of Valuable Natural Products
A marine natural product is defined as any valuable
material that is biologically produced by a marine organism. This section overviews natural products of
current or future value commercial value from phototropic marine organisms, with a particular focus on
marine algae.
Phototrophic marine algae are particularly diverse
sources of natural products, as detailed in several reviews [9.1–8]. The biosynthesis of natural compounds
by phototrophic marine organisms falls into two categories. The first category comprises organic compounds
biologically synthesized through primary metabolism.
Primary metabolism represents a system of biochemical pathways that are essential for cell growth and
reproduction. For example, the biosynthesis of sugars,
amino acids, nucleic acids, proteins, ribonucleic acid
(RNA), and deoxyribonucleic acid (DNA), are usually
associated with primary metabolism in phototrophic
marine organisms. The second category comprises organic compounds derived from secondary metabolism.
Biochemical pathways within secondary metabolism
are not essential for cell growth or reproduction but
serve some specialized function in time of need, for
example, lipids for chemical energy storage, or bioactive chemical defense compounds to avoid being eaten
by other organisms. In general, secondary metabolites
are the source of pharmacologically-active compounds.
Natural products derived from marine organisms do not
have to be in a pure form. Often, the cell biomass itself
or extracts of the cell biomass are valuable. These extracts, which can include both primary and secondary
metabolites of human nutritional value, are called nutraceuticals.
Microalgae are a promising future platform for the
production of advanced biofuels, as discussed in several recent reviews and papers [9.9–15]. Microalgae
are single-celled photosynthetic organisms that grow,
reproduce themselves, and biosynthesize energy-dense
molecules through metabolic processes that utilize only
sunlight, atmospheric CO 2 , water, and macronutrients –
principally nitrogen and phosphorous – as inputs. The
variety of lipids biosynthesized within the algae, which
can constitute up to 50 wt% of the algal biomass, can be
chemically converted to liquid transportation fuels such
as biodiesel ( C 14 C 22 fatty acid methyl esters)
or green diesel by catalytic processes [9.16]. Relative
to oil-bearing land plants for biodiesel production, algae can thrive on saline waters not suitable for food
production, and have much higher production rates.
Furthermore, algal biofuel production systems can be
sited on non-arable land because the organisms are
grown in water within engineered systems (e.g., open
ponds or enclosed photobioreactors), not in soil.
Other than algal biofuels, commercially important
natural products from phototrophic marine organisms
fall into five categories:
1. Nutritional supplements or nutraceuticals
2. Specialty pigments
3. Industrial polysaccharides
4. Products for aquaculture
5. Pharmaceutical compounds.
Examples of commercial natural products from
phototrophic marine organisms are provided in Table 9.1. Commercial natural products include betacarotene, the polyunsaturated fatty acids (PUFAs) EPA
and DHA, Spirulina dried biomass, astaxanthin (an
aquaculture feed supplement), and the hydro-colloids.
Most of the products listed in Table 9.1 are primary
metabolites, although some polyunsaturated fatty acids
and polysaccharides can also be produced as a consequence of secondary metabolism. Discussions of the
metabolic pathways associated with the biological synthesis of each of these compounds within the cell are
beyond the scope of this chapter.
Phototrophic marine organisms will play a major
role in emerging marine biotechnology revolution because they are a rich source of novel drugs for the
future. Below, a few exciting new pharmaceutical candidates from cyanobacteria, microalgae, and macroalgae are overviewed.
Marine cyanobacteria and microalgae offer a diverse array of pharmaceutical candidates. For example,
a sulfolipid from the filamentous marine cyanobacteria Lyngbya sp. is in preclinical trials for treatment
against the human immunodeficiency virus (HIV). The
thiazoline-containing lipid Curacin A from Lyngbya