SEAWEEDS AND THEIR APPLICATIONS

BY S.BARATHY SELVARANIII M.Sc., MARINE BIOTECHNOLOGY

• Seaweeds are a fascinating and diverse group of organisms living in the earth's oceans.

• You can find them attached to rocks in the intertidal zone, washed up on the beach, in giant underwater forests, and floating on the ocean's surface.

• They can be very tiny, or quite large, growing up to 30 metres long!

• Seaweeds are marine algae: saltwater-dwelling, simple organisms that fall into the somewhat outdated, but still useful, category of "plants".

• Seaweeds are plants because they use the sun's energy to produce carbohydrates from carbon dioxide and water (this is called photosynthesis). They are simpler than the land plants mainly because they absorb the nutrients that they require from the surrounding water and have no need for roots or complex conducting tissues.

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• Seaweeds are also called macro-algae. This distinguishes them from micro-algae (Cyanophyceae), which are microscopic in size, often unicellular, and are best known by the blue-green algae that sometimes bloom and contaminate rivers and streams.

• Three groups of seaweeds are recognised, according to their pigments that absorb light of particular wavelengths and give them their characteristics.

STRUCTURE OF SEAWEEDS

• Holdfasts

• stipe

• blades

• floats

• thallus

CONT….• Instead of roots seaweeds have holdfasts, which attach them to the sea floor. A

holdfast is not necessary for water and nutrient uptake, but is needed as an anchor. Holdfasts are made up of many fingerlike projections called haptera.

The stalk or stem of a seaweed is called a stipe. The function of the stipe is to support the rest of the plant. The structure of the stipe varies among seaweeds; they can be flexible, stiff, solid, gas-filled, very long (20 metres), short, or completely absent.

The leaves of seaweeds are called blades. The main function of the blades is to provide a large surface for the absorption of sunlight. In some species the blades also support the reproductive structures of the seaweed. Some seaweeds have only one blade, which may be divided, while other species have numerous blades.

Many seaweeds have hollow, gas-filled structures called floats or pneumatocysts. These help to keep the photosynthetic structures of the seaweed buoyant so they are able to absorb energy from the sun.

The term thallus refers to the entire plant body of a seaweed.

REPRODUCTION INSEAWEEDS

• Seaweeds reproduce in a variety of ways. Lower types reproduce asexually. More advanced kinds produce motile zoospores that swim off, anchor themselves, and grow into new individuals, or they reproduce sexually by forming sex cells (gametes) that, after fusing, follow the same pattern. Sometimes pieces of a seaweed break off and form new plants; in a few species there is a cycle of asexual and sexual reproduction foreshadowing the alternation of generations characteristic of plants

Types of Seaweeds

• PHAEOPHYCEAE – Brown algae

• CHLOROPHYCEAE – Green algae

• RHODOPHYCEAE – Red algae

PHAEOPHYCEAECHARACTERISTICS :

#Marine water species

# Xanthophyll pigment, which masks the other chlorophyll and carotenoid pigments.

#food reserves are polysaccharides

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• Brown seaweeds are usually large, and range from the giant kelp that is often 20 m long, to thick, leather-like seaweeds from 2-4 m long, to smaller species 30-60 cm long

CHLOROPHYCEAE

CHARACTERISTICS :

#Also a marine water species

#Chlorophyll a & b

#food reserves are starch

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• Green seaweeds are also small, with a similar size range to the red seaweeds.

Green seaweeds are found on both sandy and rocky beaches. Many can tolerate low salinity and will colonise areas where rivers meet the sea. The green colour of the seaweed is due to the green pigment chlorophyll required for the photosynthesis of light.

RHODOPHYCEAE

• Red seaweeds are usually smaller, generally ranging from a few centimetres to about a metre in length; however, red seaweeds are not always red: they are sometimes purple, even brownish red .

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• The red colour of the seaweeds is due to the larger amount of red phycoblin pigments overriding the green pigment chlorophyll.

• The pigments that colour it red have a purpose, enabling the seaweeds to photosynthesis light from a specific part of the light spectrum. Within the group of phycoblins two pigments are of importance phycoerythrin and phycocyanin. Phycoerythrin absorbs green, yellow and red light while phycocyanin absorbs blue, green and yellow light. These parts of the spectrum are the type of light that penetrates the deepest in sea water. The red pigments absorb the light but chlorophyll is still required to process it.

APPLICATIONS

• Used as a food• Used as a medicine• Used as a soil fertilizer & conditioner• Alginophytes • Agarophytes• Carrageenan• Animal feed • Fish feed

USED AS A FOOD• Food from brown seaweeds comes

mostly from the genera Laminaria, Undaria and Hizikia.

• Porphyra species are the largest source of food from red seaweeds. Dulse (Palmaria palmata, formerly Rhodymenia palmata) is another red seaweed used as food.

• Sea Lettuce Ulva lactuca - This is a green seaweed which looks similar to a lettuce leaf and is edible.

Medicinal uses• RESPIRATORY TREATMENT

Red algae containing carrageenan have been used for respiratory ailments, especially intractable sinus infections and lingering pneumonias. ANTIVIRAL RED SEAWEEDS Strong antiviral activity has been observed in a variety of heavily modified carrageenans and research continues on how to use this in commercial medications. One carrageenan derivative showed strong anti-HIV activity when delivered as a contraceptive vaginal foam.

cont….• HORMONES IN SEAWEEDS

Melatonin is abundant in many seaweeds, up to 1000 times the amounts found in land plants. This may explain some of the calming effects of eating seaweeds. There may be some useful therapeutic opportunities using seaweed-sourced melatonin.• Thyroid Hormones in Seaweeds

Brown seaweeds are the only known non-animal sources of thyroid hormones.

The presence of organically-bound iodine in brown seaweeds as thyroid hormones may explain some of the effects of eating some brown seaweeds.

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• ESSENTIAL FAT AND VITAMINS IN SEAWEEDSMost seaweeds are rich in vitamins, especially the B vitamins, including B12.

They also have significant amounts (1-3%)of Omega-3 fatty acids. Nori, in particular has 3% omega-3 fatty acids and large amounts of vitamins A and C.

cont….

• CARRAGEENAN INHIBITION OF PAPILLOMA VIRUS INFECTION

Carrageenan is an easily extracted, sulfated unbranched polygalactose red algal polymer. It is used in thousands of patented applications in food and cosmetic products and in sexual lubricants.

SEAWEEDS AS MEDICINE • Seaweeds as the Best Dietary Sources of Essential Minerals• All essential minerals are provided by dietary seaweeds. No

land plant even remotely approaches seaweeds as sources of metabolically-required minerals. Seaweeds are 20-50% dry weight mineral(Kazutosi, 2002). The elements abundant in seaweeds include: potassium, sodium, calcium, magnesium, zinc, copper, chloride, sulfur, phosphorous, vanadium, cobalt, manganese, selenium, bromine, iodine, arsenic, iron, and fluorine.

AGAR

• Most agar is extracted from species of Gelidium and Gracilaria

Gelidium Gracilaria

cont….• Food grade agar• A short and simplified description of the extraction of agar from

seaweeds is that the seaweed is washed to remove foreign matter and then heated with water for several hours. The agar dissolves in the water and the mixture is filtered to remove the residual seaweed. The hot filtrate is cooled and forms a gel (jelly) which contains about 1 percent agar. The gel is broken into pieces, and sometimes washed to remove soluble salts, and, if necessary, it can be treated with bleach to reduce the colour. Then the water is removed from the gel, either by a freeze-thaw process or by squeezing it out using pressure. After this treatment, the remaining water is removed by drying in a hot-air oven. The product is then milled to a suitable and uniform particle size.

cont….• Bacteriological agar• This can only be made from species of Gelidium because the

resulting agar has a low gelling temperature (34-36°C) that allows the addition of other materials to the agar with a minimum risk of heat damage. Gracilaria and Gelidiella give agars that gel at 41°C or higher.

• "Bacto" agars must not contain anything that might inhibit the growth of bacteria, such as trace metals, soluble carbohydrates or proteins, nor should they contain any bacterial spores. They must not interact with any materials that must be added as nutrients for the bacteria under study. The gels must be strong and have good clarity.

cont….• Agarose• Agar can be divided into two principal components: agarose and

agaropectin. Agarose is the gelling component; agaropectin has only a low gelling ability. There are several methods of producing agarose; many rely on removing the agaropectin from the agar. There are only a small number of processors who produce purified, high quality agarose for a small but growing market, mainly in biotechnology applications. These processors use good quality agar as their starting material rather than seaweed, and are often not in the seaweed processing business.

ALGINATE

• Ascophyllum, Durvillaea, Ecklonia, Laminaria, Lessonia, Macrocystis and Sargassum,

Ascophyllum Durvillaea

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• The uses of alginates are based on three main properties.

• The first is their ability, when dissolved in water, to thicken the resulting solution

• The second is their ability to form gels.• The third property of alginates is the ability to form

films of sodium or calcium alginate and fibres of calcium alginates.

TEXTILE PRINTING

• In textile printing, alginates are used as thickeners for the paste containing the dye. These pastes may be applied to the fabric by either screen or roller printing equipment. Alginates became important thickeners with the advent of reactive dyes. These combine chemically with cellulose in the fabric. Many of the usual thickeners, such as starch, react with the reactive dyes, and this leads to lower colour yields and sometimes by-products that are not easily washed out. Alginates do not react with the dyes, they easily wash out of the finished textile and are the best thickeners for reactive dyes. Alginates are more expensive than starch and recently starch manufacturers have made efforts to produce modified starches that do not react with the reactive dyes, so it is becoming a more competitive market.

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• Alginate derivatives of alginic acids, are used commercially for toothpaste, soaps, ice cream, tinned meats, fabric printing etc.,

• It forms a stable viscous gel in water, and its primary function in the above applications is as a binder, stabilizer, emulsifier,, or moulding agent.

CARRAGEENAN

• Most carrageenan is extracted from Kappaphycus alvarezii and Eucheuma denticulatum

• . The original source of carrageenan was Chondrus crispus, and this is still used to a limited extent.

• Betaphycus gelatinum is used for a particular type of carrageenan.

Kappaphycus alvarezii. Betaphycus gelatinum

cont….• There are several carrageenans, differing in their chemical structure

and properties, and therefore in their uses. The carrageenans of commercial interest are called iota, kappa and lambda.

• Their uses are related to their ability to form thick solution or gels, and they vary as follows.

• Iota- Elastic gels formed with calcium salts.Clear gel with no bleeding of liquid (no synaeresis).Gel is freeze/thaw stable.

Kappa- Strong, rigid gel, formed with potassium salts.Brittle gel forms with calcium salts.Slightly opaque gel, becomes clear with sugar addition.Some synaeresis.

Lambda- No gel formation, forms high viscosity solutions.

USES & PROPERTIES • Processed Meat, Poultry & Seafood - Water binding, increased product yields, improved texture, fat

replacement, meat/seafood analog binding, tolerant to high levels of salt.• Dairy (Chocolate Milk, Frozen Desserts, UHT Milks, Flans, Puddings, Low Fat Cheese, Cheese Analogs)

- Provides cocoa suspension, milk stability, emulsion stability, milk gelling.• Cold Milk Powders (Diet powder mixes, Nutritional beverage mixes) - Provides body and mouthfeel,

suspends solids.• Water gel Desserts - Provides wide range of textures and flavor release, all without the need for

refrigeration.• Toothpaste - Provides structure without masking flavors, resistant to enzymatic breakdown.• Pharmaceutical -- provides animal-free capsules (soft and hard).• Petfoods - Binds water, provides structure and prevents fat separation in canned retorted products,

excellent binding.• Air Freshener Gels - Provides structure and controlled release of active ingredients such as per fume in

a water gel base.• Beer Fining -- acts as a process aid in beer manufacture to produce good clarity.

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• Wastewater treatment• There are two main areas where seaweeds have

the potential for use in wastewater treatment. • The first is the treatment of sewage and some

agricultural wastes to reduce the total nitrogen- and phosphorus-containing compounds before release of these treated waters into rivers or oceans.

• The second is for the removal of toxic metals from industrial wastewater.

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• Fertilizers and soil conditioners• Animal feed• Fish feed• Biomass for fuel• Cosmetics• Integrated aquaculture

REFERENCES• www.fao.org/docrep/006/y4765e/y4765e0c.htm • www.bcb.uwc.ac.za/envfacts/seaweeds/index.htm • http://www.oceanlink.info/biodiversity/seaweeds/seaweeds.html• www.ryandrum.com/seaweeds.htm • www.uoflife.com/wc/studentpapers/seaweed.htm -

www.infoplease.com/ce6/sci/A0861006.htm • http://www.shemberg.com.ph/carrageenan.html