170
8 Ulvans
Marine algae are of great economical significance as they are a source of valuable
biomaterials: polyphenols, polyunsaturated fatty acids, proteins, polysaccharides and
pigments. All of which are useful in the pharmaceutical, cosmetics, food, biotechnology and microbiology fields. Some of the advantages of polymers sourced from
algae include the higher biomass yield of algae compared to terrestrial plants similarly used as biorefinery crops, the use of aquatic rather than land space for their
cultivation, removal of CO 2 from the atmosphere and uptake of eutrophying nutrients
from the water. On the other hand, issues such as competition with algae used for
food and relatively high cost of algae as feedstock pose a challenge in commercial
production of ulvan.
This chapter reviews ulvan as an aquatic sourced biopolymer, its source, extraction
process, environmental issues surrounding its production and the present state of
commercial ulvan production. In so doing it furthers the goal of the book to highlight
the diverse range of biopolymers in the aquatic ecosystem, the present issues as well
as their environmental and economic significance.
8.2 Occurrence in Nature
Green marine algae such as Ulva amoricana and Ulva rigida and Ulva enteromorpha
are the known sources of ulvan which forms a part of the cell wall alongside other cell
wall polysaccharides such as mannan, xylan and cellulose (Misurcova et al. 2012).
These green algae contain around 38–54% Ulvan by dry weight (Michel and Czjzek
2014) (8–29% Lahaye and Robic 2007), while others report between 9 and 36% by
dry mass in Ulva species (Kidgell et al. 2019). Ulvan producing species include U.
rigida, Ulva pertusa, Enteromorpha, Ulva intestinalis (Tabarsa et al. 2018), E. linza,
E. clathrata (Tabarsa et al. 2018), Ulva ohnoi (Fernández-Díaz et al. 2017). The
green algae Ulva species are rapid-growing species to the extent that they can result
in algae blooms under uncontrolled growth in the wild aquatic habitat (Kidgell et al.
2019). Figure 8.1 is a schematic representation of Ulva within the green algae cell
wall. Ulvan exists in a matrix with other cell wall polymers such as cellulose proteins
and glucuronan.
Sulfated polysaccharides are also found in animals, and however, plants do not
produce sulfated polysaccharides. Examples of sulfated polysaccharides of animals
are glycosaminoglycans (GAGs) and proteoglycans (Scharnweber et al. 2015). Much
of the studies on bioactivity of ulvans have explored mimicking the functions of these
animal sulfated polysaccharides as it is expected that the similarity in structure will
manifest as similarity in bioactivity. The plant macromolecule rhamnogalacturonans
and rhamnolipids in phytopathogenic bacterium (Varnier et al. 2009) are the components of these organisms which have the closest similarity with ulvans of green
algae.
8 Ulvans
Marine algae are of great economical significance as they are a source of valuable
biomaterials: polyphenols, polyunsaturated fatty acids, proteins, polysaccharides and
pigments. All of which are useful in the pharmaceutical, cosmetics, food, biotechnology and microbiology fields. Some of the advantages of polymers sourced from
algae include the higher biomass yield of algae compared to terrestrial plants similarly used as biorefinery crops, the use of aquatic rather than land space for their
cultivation, removal of CO 2 from the atmosphere and uptake of eutrophying nutrients
from the water. On the other hand, issues such as competition with algae used for
food and relatively high cost of algae as feedstock pose a challenge in commercial
production of ulvan.
This chapter reviews ulvan as an aquatic sourced biopolymer, its source, extraction
process, environmental issues surrounding its production and the present state of
commercial ulvan production. In so doing it furthers the goal of the book to highlight
the diverse range of biopolymers in the aquatic ecosystem, the present issues as well
as their environmental and economic significance.
8.2 Occurrence in Nature
Green marine algae such as Ulva amoricana and Ulva rigida and Ulva enteromorpha
are the known sources of ulvan which forms a part of the cell wall alongside other cell
wall polysaccharides such as mannan, xylan and cellulose (Misurcova et al. 2012).
These green algae contain around 38–54% Ulvan by dry weight (Michel and Czjzek
2014) (8–29% Lahaye and Robic 2007), while others report between 9 and 36% by
dry mass in Ulva species (Kidgell et al. 2019). Ulvan producing species include U.
rigida, Ulva pertusa, Enteromorpha, Ulva intestinalis (Tabarsa et al. 2018), E. linza,
E. clathrata (Tabarsa et al. 2018), Ulva ohnoi (Fernández-Díaz et al. 2017). The
green algae Ulva species are rapid-growing species to the extent that they can result
in algae blooms under uncontrolled growth in the wild aquatic habitat (Kidgell et al.
2019). Figure 8.1 is a schematic representation of Ulva within the green algae cell
wall. Ulvan exists in a matrix with other cell wall polymers such as cellulose proteins
and glucuronan.
Sulfated polysaccharides are also found in animals, and however, plants do not
produce sulfated polysaccharides. Examples of sulfated polysaccharides of animals
are glycosaminoglycans (GAGs) and proteoglycans (Scharnweber et al. 2015). Much
of the studies on bioactivity of ulvans have explored mimicking the functions of these
animal sulfated polysaccharides as it is expected that the similarity in structure will
manifest as similarity in bioactivity. The plant macromolecule rhamnogalacturonans
and rhamnolipids in phytopathogenic bacterium (Varnier et al. 2009) are the components of these organisms which have the closest similarity with ulvans of green
algae.