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10 Aquatic Plants and Algae Proteins
extraction of algal protein using the enzymes which break down the polysaccharides
within the fiber, thereby making the protein available for extraction.
Animals fed with diet which included algae as a protein source have shown
improvement in immune system, increased productivity and improved quality of
meat and milk. This has been observed in a variety of commercially bred animals
such as steers used for beef and pigs used for pork (Allen et al. 2001; Saker et al. 2001;
Montgomery et al. 2001; Braden et al. 2004; Gatrell et al. 2014). In poultry, chicken
broilers fed with microalgae Spirulina show improved fertility and a more aesthetically pleasing egg yolk color (Zahroojian et al. 2013). However, these attributes are
not directly linked with the protein content. The improvement in egg yolk color is
thought to be due to the presence of beta carotene (Anderson et al. 1991). In aquaculture, both microalgae and macroalgae are used as feed for aquaculture animals such
as mollusks, sea bream and shrimps (Müller-Feuga 2013). They also act to regulate
the nutrient and mineral content in the water (Chuntapa et al. 2003).
Aquatic plants such as water fern, duckweed and American pondweed have been
used as animal feed as a protein source as well as other nutrients. Some aquatic plants
such as duckweed species, Lemna gibba, have relatively high protein content. For
example, a crude protein content of 21.5% was measured for L. gibba, while green
algae species, U. lactuca, was 17.2% in the same study (Aguilera-Morales et al.
2018). Both the duckweed and U. lactuca contained eight of the essential amino
acids necessary for fish feed.
10.7.5 Antihypertensive
The antihypertensive properties of compounds can be measured by their ability to
inhibit the activity of the angiotensin-converting enzyme (ACE I). This enzyme
converts the inactive angiotensin into an active ACE I which is then converted to ACE
II which caused constriction of the cardiac blood vessels leading to hypertension.
Bioactive peptides act as antihypertensive agents by preventing the conversion of
inactive ACE to the active ACE I, which in turn prevents the formation of ACE II
(Seca and Pinto 2018; Daskaya-Dikmen et al. 2017).
Another therapeutic approach to hypertension is the enhancement of vasodilation
to reduce blood pressure. Like flow in a channel, as the vessel is widened, the pressure
in the vessel is reduced. Vasodilation is facilitated by the enzyme bradykinin through
a series of processes. The body’s natural control system releases the appropriate
enzyme in response to the pressure in the blood vessels. A normal blood pressure
is therefore dependent on this control system, where the vasoconstricting enzymes
and substrates are working in conjunction with the vasodilating enzymes to maintain
homeostasis. Angiotensin I is also thought to be responsible for degradation of the
bradykinin, thus preventing vasodilation (Daskaya-Dikmen et al. 2017). Therefore,
by inhibiting the angiotensin enzyme, vasodilation is also promoted.
The antihypertensive properties shown by these peptides are absent in the parent
proteins. These parent proteins need to be broken down into the peptide forms before
10 Aquatic Plants and Algae Proteins
extraction of algal protein using the enzymes which break down the polysaccharides
within the fiber, thereby making the protein available for extraction.
Animals fed with diet which included algae as a protein source have shown
improvement in immune system, increased productivity and improved quality of
meat and milk. This has been observed in a variety of commercially bred animals
such as steers used for beef and pigs used for pork (Allen et al. 2001; Saker et al. 2001;
Montgomery et al. 2001; Braden et al. 2004; Gatrell et al. 2014). In poultry, chicken
broilers fed with microalgae Spirulina show improved fertility and a more aesthetically pleasing egg yolk color (Zahroojian et al. 2013). However, these attributes are
not directly linked with the protein content. The improvement in egg yolk color is
thought to be due to the presence of beta carotene (Anderson et al. 1991). In aquaculture, both microalgae and macroalgae are used as feed for aquaculture animals such
as mollusks, sea bream and shrimps (Müller-Feuga 2013). They also act to regulate
the nutrient and mineral content in the water (Chuntapa et al. 2003).
Aquatic plants such as water fern, duckweed and American pondweed have been
used as animal feed as a protein source as well as other nutrients. Some aquatic plants
such as duckweed species, Lemna gibba, have relatively high protein content. For
example, a crude protein content of 21.5% was measured for L. gibba, while green
algae species, U. lactuca, was 17.2% in the same study (Aguilera-Morales et al.
2018). Both the duckweed and U. lactuca contained eight of the essential amino
acids necessary for fish feed.
10.7.5 Antihypertensive
The antihypertensive properties of compounds can be measured by their ability to
inhibit the activity of the angiotensin-converting enzyme (ACE I). This enzyme
converts the inactive angiotensin into an active ACE I which is then converted to ACE
II which caused constriction of the cardiac blood vessels leading to hypertension.
Bioactive peptides act as antihypertensive agents by preventing the conversion of
inactive ACE to the active ACE I, which in turn prevents the formation of ACE II
(Seca and Pinto 2018; Daskaya-Dikmen et al. 2017).
Another therapeutic approach to hypertension is the enhancement of vasodilation
to reduce blood pressure. Like flow in a channel, as the vessel is widened, the pressure
in the vessel is reduced. Vasodilation is facilitated by the enzyme bradykinin through
a series of processes. The body’s natural control system releases the appropriate
enzyme in response to the pressure in the blood vessels. A normal blood pressure
is therefore dependent on this control system, where the vasoconstricting enzymes
and substrates are working in conjunction with the vasodilating enzymes to maintain
homeostasis. Angiotensin I is also thought to be responsible for degradation of the
bradykinin, thus preventing vasodilation (Daskaya-Dikmen et al. 2017). Therefore,
by inhibiting the angiotensin enzyme, vasodilation is also promoted.
The antihypertensive properties shown by these peptides are absent in the parent
proteins. These parent proteins need to be broken down into the peptide forms before