Uses of Seaweeds

Seaweeds are used in many maritime countries as a source of food, for industrial applications and as a fertiliser.
The present uses of seaweeds are as human foods, cosmetics, fertilisers, and for the extraction of industrial gums and chemicals. They have the potential to be used as a source of long- and short-chain chemicals with medicinal and industrial uses. Marine algae may also be used as energy-collectors and potentially useful substances may be extracted by fermentation and pyrolysis.

As food :The sea weeds are also used as food in the regions of Far East and Australia. The inhabitants of the Hawaii island consume large quantities of sea weeds. The indigenous people of chile use large quantities of Durvillea antarctica and some species of Ulva. The natives of New Zealand use certain green sea weeds in preparation of salad and soups.
The people of China and Japan consume the sea weeds on large scale. The people living on the sea coasts in these countries commonly use fresh sea weeds as food. The most important food species in Japan are Nori (Porphyra species), Kombu (Laminaria species), and Wakame (Undaria pinnatifida). In japan porphyra tenera happens to be one of the most important edible algae and a product by the name of amanori and Asakusa- Nori are made from it.

The use of kelps ("kombu" in Japan; "haidai" in China) dates back to at least the 5th century in China. The main species used is Laminaria japonica (Laminariales), but 8-11 other species are used also, mainly in Japan.

Plants are dried after harvesting and either cut into strips or powdered. In Japan, kombu is used in the preparation of fish, meat dishes, soups and also as a vegetable with rice. Powdered kombu is employed either in sauces and soups or is added to rice in the same way as curry. Some kinds are used in making an infusion similar to tea.

Another kelp, Undaria pinnatifida (Laminariales), is widely used in Japan (where it is known as "wakame") and China ("qundai-cai") as food. In Japan this species is a more important crop than Laminaria both in value and production.
The harvested algae are dried after washing in freshwater. After resoaking the plant material is used as an additive to soups (wakame soup is served with virtually every meal in Japan); toasted (Yaki-wakame); used half resoaked, with boiled rice; and coated in sugar and tinned (Ito-wakame).

Nori is a red alga, Porphyra spp. (Bangiophyceae). Nori is sold in sheets that may be toasted to give a green colour and then flaked and added to sauces, soups and broths. Sometimes it is just soaked and eaten. Small, dry nori sheets are used to wrap cold rice balls, which make a popular lunch-time snack for Japanese children. The food value of nori lies in its high protein content (25-35% of dry weight), vitamins and mineral salts, especially iodine. Its vitamin C content is about 1.5 times that of oranges and 75% of the protein and carbohydrates are digestible by humans, which is very high for seaweeds.

As a source of vitamins. Seaweeds are the richest source of vitamins. The vitamins A, B and E are found abundantly in sea weeds. The vitamin B essentially required for the development of human body is found in great abundance in almost all phaeophyceae. The cod liver oil is the rich source of vitamin A, which is acquired from sea weeds. Vitamin E is equally important for human beings which is found in many seaweeds.

Several vitamins except ascorbic acid have been reported from Chlorella. The vitamins found in Chlorella are-thiamin, niacin, pyridoxine, pantothenic acid, chlorine, biotin, vitamin B and lipoic acid.

Various red algae have been used in the Mediterranean as sources of dying agents and as anthelmintic and other health remedies since pre-Christian times

As a source of agar. The best agar is manufactured from Gelidium of Rhodophyceae, which is also called vegetative agar, Japan produces the largest quantity of agar. It produces 95% of the world production. Agar is also obtained from several other marine algae, the yield of agar, setting temperature and gel strength of the product from ten species belonging to Gelidium, Sarconema, Hypnea and Gracilaria were obtained by Thivy (1951). Japan is the chief agar producing country and it exports agar to most of the countries of the world.

The agar is used in several ways. It is employed in the preparation of ice crem, jellies, desserts etc., in sizing the textiles and clearing many liquids. It is also used in preparing shaving creams, cosmetics and shoe polishes. The agar has constantly been used in biological laboratories for media preparation.

In India, agar resources, as annual yield of dry sea weeds of Chilka Lake have been estimated by Mitra (1946) to be about 4.06-5.08 metric tons, of Cape Comorin by Koshy and John (1948). Thivy (1957) about one metric ton, and of the Pamban area as estimated by Thivy (1957) about seven metric tons. Other large quantities are in Kathiawar peninsula end estuaries, the resources of the Andamans are believed to be considerable.

Cosmetics, Medicines and minerals.There are several medicinal properties of seaweeds. Algae rich in iodine such as Asparagopsis taxiformis, Sarconema spp. can be used for controlling goitre disease caused by enlargement of thyroid glands. Many bioactive compounds can be obtained from seaweeds.

Several diseases caused by vitamin deficiency such as vitex, asthma, tooth decay etc., may be eradicated, if flour of the sea weeds is added to the food. Iodine is the most important element to enable the thyroid glands to secrete the thyrosin which contains 60% iodine. It controls the general development of the animal. Sea weeds are the best source of iodine for human beings. Several important sea weed medicinal preparations are prepared in various countries, i.e., Kelpeck is prepared from kelps in Chicago; Burbank Vegetable tablets are sea weed preparations from United States. Kelpamalt is a sea weed medicinal preparation from New York (U.S.A.); Isokelp is prepared in California; Parakelp and Manamar are other medicinal sea weed American preparations. An antibiotic drug Chlorellum is also obtained from algae.

About fortyfive elements are found in a sea weed Macrocystis pyrifera. In addition to these elements vitamins are also found. No other food contains such a great abundance of minerals and vitamins.

Alginic acid, algin and mannitol. The alginic acid is manufactured from the cell wall of phaeophyceae. It is insoluble in water and hard when dry. Sodium alginate is used in sizing material for water proof material, dyes, buttons, handles, combs and many of such things. This is also used as a sterilizer in daily use.

The algin is found in the form of calcium alginate and alginic acid. The fucaceae are the chief source of algin in india. Yields of algin varying from 15.6 to 19.2 percent on air dry matter were estimated for fucaceae and 10. Percent for padina. A yield of 9. Percent of mannitol from Sargassum tenerrimum and 73% from S. wightii have been reported.

The use of seaweed extract in cosmetics is a major international trend at present. The elements contained in seaweeds act in harmony with the human body, heping t achieve, beauty and relaxation. In cosmetology, it is important to know the biochemical composition and potential use of cosmentics. The extract can be used in 2 ways : either as an agent in preparation of products or as therauptic agent itself. Alginates of different viscocity servea as thickening and dispersing agents n cream, jellies, liquid emulsions, lotions, compact powders, toothpasste, soaps etc.Manufacture of soaps and alums. By burning sea weeds on the sea coast, the alkalies are prepared from sea weed ashes. These alkalies are employed in the manufacture of soaps and alums.

Some countries have even industries to process sea weeds into suitable cattle feed. The manufacture of cattle feed from sea weeds is made principally from brown algae and the processed food is fed to cattle, poultry and even pigs. It has seen recorded that dried sea weeds served as cattle food have enhanced the milk-yielding and egg-laying capacity of cattle and poultry respectively.

Used as fertilizers. Due to the presence of potassium chloride (KCI) in sea weeds, they are used as fertilizers in many countries, such as Japan, France, United States, England and South India.

Seaweeds are used in different parts of the world as fertilizer for various land crops. In India, freshly collected and cast ashore seaweeds are used as manure for coconut plantation either directly or in the form of compost in coastal areas of Tamil Nadu and Kerala. Seaweed manure has been found superior to farm yard manure.

Sea weeds are as a store-house of the important potash, ionic sulphate, trace elements and growth substances, besides having every other element and radical required by plants. Seaweed manure seems to increase resistance to disease. Most of the nutrients including nitrogen compounds are in ionic form and a quick absorption by crops takes place and relatively little is left to be broken down by soil microflora, thus preventing acid conditions of the soil arising from the fermentation. In general the minerals diffuse out from the seaweed thallus rapidly. Yet another feature is that sea weed manure holds water and air at the same time and improves the soil in both respects. Like other manures sea weeds have a similar role but also contribute the required potassium, sulphur, phosphorus and calcium.

The liquid seaweed fertilizer obtained from seaweed extract is used as foliar spray for inducing faster growth and yield in leafy and fleshy vegetables, fruits, orchards and horticultural plants.