314 Marine Macro- and Microalgae: An Overview
Cyclotella sp.) show that the fatty acid composition closely matches the profile of menhaden oil and their
protein composition has an amino acid composition similar to fishmeal (Fig. 7). Additionally, eukaryotic
microalgae are a rich source of many vitamins; levels in four microalgae from different genera are higher
than that found in a commercial menhaden meal (Fabregas and Herrero 1990).
Studies evaluating the use of biomass from marine eukaryotic algae as a fishmeal replacement for
valuable species such as Atlantic salmon have shown promising results at levels of replacement around
10%. For example, Cellana showed that algal protein from two marine microalgae strains that were
selected for biofuel (not aquafeed) production was suitable as a fishmeal replacement for salmon at
levels up to 10% (Kiron et al. 2012). Replacement of fishmeal in diets of Atlantic cod with a mixture of
30% microalgae (Nannochloropsis and Isochrysis) resulted in a reduction in feeding, possibly because
of reduced palatability (Walker and Berlinsky 2011). Additional research, therefore, is required in order
to identify microalgae strains with the optimum biomass composition coupled with digestibility and
palatability levels that will allow an eventual complete replacement of fishmeal and fish oil. For example,
the ProAlgae 2012 initiative (Kleivdal 2012) is supporting research to identify preferred microalgae
strains suitable for cold water cultivation for Norwegian aquaculture.
The acceptance by manufacturers of microalgae biomass as an alternative feed ingredient will
depend on having data for available nutrient utilization and efficiency in growing fish. The NOAA/USDA
report “Future of Aquafeeds” (Rust et al. 2011) emphasizes that research is required on the suitability of
algae biomass (either whole cells or secondary streams resulting from extraction of high-value products)
so that manufacturers can properly formulate feeds. Success also depends on creating a reliable supply at
the scale and cost needed for aquafeed manufacturing.
In summary, because of needed replacements for wild-caught fish meal and microalgae’s nutritional
characteristics, expansion in the use of microalgal meal in aquafeeds will result in environmental benefits
including the recovery of wild fisheries that are currently under pressure.
Nutrition for humans
Spirulina has been part of the human diet for, at least, centuries. Diaz del Castillo (in Ciferri 1983)
described the sale of dried Spirulina in the Tenochtitlan (today’s Mexico City) market some 500 yr
ago as human food. Dangeard (in Ciferri 1983) also described the use of Spirulina as human food in
the area around Lake Chad in Africa early in the 20th century. Today, Spirulina products (Arthrospira
sp.) are widely available. The biomass of the Arthrospira cyanobacterium has long been recognized
as an excellent source of protein for humans based on its amino acid composition (Habib et al. 2008).
Furthermore, on a land utilization basis, it is probably the most efficient phototrophic source of proteins
for humans (Ahsan et al. 2008). Commercial Spirulina plants (Fig. 1) have been operating in the US
since the early 1980s. Smaller plants have been built since across the world (see, for example, Yun-Ming
et al. 2011). Spirulina capacity is believed to represent the largest share of the global microalgal market
(Benemann 2010).
Habib et al. (2008) summarize a number of reports and conclude that Spirulina has the potential
to produce protein with a much smaller environmental footprint than many other food crops. Spirulina
production from commercial farms ranges from 10 to 40 tons per hectare per year. Due to its high protein
content it yields 20, 40, and over 200 times more protein per unit area than soy, corn, or beef respectively.
Because of its ability to use non-potable non-fresh water it would not require use of water otherwise
destined for people or agricultural crops. Additionally, it uses only about 2100 L of water per kg of
protein produced which is about 25%, 17%, and 2% of the water used for soy, corn, and beef respectively.
Further, cultivation can be carried out on land not suitable to agriculture. Thus, Spirulina represents an
excellent protein source.
Other microalgae, although with a somewhat lower protein concentration, would be expected to
have similar environmental advantages over conventional protein sources (Chacón-Lee and GonzálezMariño 2010). Chlorella, Dunaliella, Haematococcus, Schizochytrium, Scenedesmus, Aphanizomenon,
Odontella, and Porphyridium are noted not only for their protein content but an array of other nutritional
benefits such as polyunsaturated fatty acids, polysaccharides, and carotenoid pigments. In spite of the
Cyclotella sp.) show that the fatty acid composition closely matches the profile of menhaden oil and their
protein composition has an amino acid composition similar to fishmeal (Fig. 7). Additionally, eukaryotic
microalgae are a rich source of many vitamins; levels in four microalgae from different genera are higher
than that found in a commercial menhaden meal (Fabregas and Herrero 1990).
Studies evaluating the use of biomass from marine eukaryotic algae as a fishmeal replacement for
valuable species such as Atlantic salmon have shown promising results at levels of replacement around
10%. For example, Cellana showed that algal protein from two marine microalgae strains that were
selected for biofuel (not aquafeed) production was suitable as a fishmeal replacement for salmon at
levels up to 10% (Kiron et al. 2012). Replacement of fishmeal in diets of Atlantic cod with a mixture of
30% microalgae (Nannochloropsis and Isochrysis) resulted in a reduction in feeding, possibly because
of reduced palatability (Walker and Berlinsky 2011). Additional research, therefore, is required in order
to identify microalgae strains with the optimum biomass composition coupled with digestibility and
palatability levels that will allow an eventual complete replacement of fishmeal and fish oil. For example,
the ProAlgae 2012 initiative (Kleivdal 2012) is supporting research to identify preferred microalgae
strains suitable for cold water cultivation for Norwegian aquaculture.
The acceptance by manufacturers of microalgae biomass as an alternative feed ingredient will
depend on having data for available nutrient utilization and efficiency in growing fish. The NOAA/USDA
report “Future of Aquafeeds” (Rust et al. 2011) emphasizes that research is required on the suitability of
algae biomass (either whole cells or secondary streams resulting from extraction of high-value products)
so that manufacturers can properly formulate feeds. Success also depends on creating a reliable supply at
the scale and cost needed for aquafeed manufacturing.
In summary, because of needed replacements for wild-caught fish meal and microalgae’s nutritional
characteristics, expansion in the use of microalgal meal in aquafeeds will result in environmental benefits
including the recovery of wild fisheries that are currently under pressure.
Nutrition for humans
Spirulina has been part of the human diet for, at least, centuries. Diaz del Castillo (in Ciferri 1983)
described the sale of dried Spirulina in the Tenochtitlan (today’s Mexico City) market some 500 yr
ago as human food. Dangeard (in Ciferri 1983) also described the use of Spirulina as human food in
the area around Lake Chad in Africa early in the 20th century. Today, Spirulina products (Arthrospira
sp.) are widely available. The biomass of the Arthrospira cyanobacterium has long been recognized
as an excellent source of protein for humans based on its amino acid composition (Habib et al. 2008).
Furthermore, on a land utilization basis, it is probably the most efficient phototrophic source of proteins
for humans (Ahsan et al. 2008). Commercial Spirulina plants (Fig. 1) have been operating in the US
since the early 1980s. Smaller plants have been built since across the world (see, for example, Yun-Ming
et al. 2011). Spirulina capacity is believed to represent the largest share of the global microalgal market
(Benemann 2010).
Habib et al. (2008) summarize a number of reports and conclude that Spirulina has the potential
to produce protein with a much smaller environmental footprint than many other food crops. Spirulina
production from commercial farms ranges from 10 to 40 tons per hectare per year. Due to its high protein
content it yields 20, 40, and over 200 times more protein per unit area than soy, corn, or beef respectively.
Because of its ability to use non-potable non-fresh water it would not require use of water otherwise
destined for people or agricultural crops. Additionally, it uses only about 2100 L of water per kg of
protein produced which is about 25%, 17%, and 2% of the water used for soy, corn, and beef respectively.
Further, cultivation can be carried out on land not suitable to agriculture. Thus, Spirulina represents an
excellent protein source.
Other microalgae, although with a somewhat lower protein concentration, would be expected to
have similar environmental advantages over conventional protein sources (Chacón-Lee and GonzálezMariño 2010). Chlorella, Dunaliella, Haematococcus, Schizochytrium, Scenedesmus, Aphanizomenon,
Odontella, and Porphyridium are noted not only for their protein content but an array of other nutritional
benefits such as polyunsaturated fatty acids, polysaccharides, and carotenoid pigments. In spite of the