Algae are an assemblage of organisms that share common characteristic such as auto trophic, photosynthetic thallophytes.
Source of Nutrition
Many of the edible algal forms are rich in proteins,vitamins and resources. Kelps, brown algae eg species of laminaria are rich sources of iodine. These algae can accumulate iodine in concentration10,000 times greater than found in sea water.
Spirulina contains about 65% proteins and is also rich in carotenes. It can be grown in wastewater. It is mass cultured in Mexico Taiwan and India. Because of its high nutritive value it has been identified as a source of single cell protein (SCP).
Chlorella is another single cell alga that grows very rapidly. It is rich in proteins , lipids and contains many vitamins in high concentration.
Gracilaria is used in preparing a tasty dessert. Ulva lactuca and gelidiella acerosa are cooked with other vegetables like spinach is cooked in India.
Among seaweeds, Porohyra is important. It contains 30- 35% proteins, 40 — 45% carbohydrates and is rich in vitamins. The sheets are toasted and cut into pieces and are eaten with rice, raw fish or some vegetables. They are also used for flavouring soups and in ‘sushi’. In Japan porphyria called as Nori.
Undaria a brown alga is used in Japan for extracting an edible product called wakeme. A list of edible seaweeds of indian coasts is given below.
Source of Animal Feed
Spirulina , chlorella and many types of seaweeds are cultured on commerical scale for human consumption because of their high nutritive value. These can be used as fodder for livestock or can be used as a supplement to their regular feed .
The seaweed used as fodder are Rhodymenia, Laminaria, Alaria, Fucus, Ascophyllum, Macrocytis and Sagrassum .
According to the some reports the milk of cows fed with seaweeds had high fat content than those fed on conventional fodder.
Treatment of wastewater
Sewage Treatment involves broadly the following two stages:
- In the first stage, diluted sewage is allowed to decompose in the absence of air (anaerobic digestion) by anaerobic microorganism. When it gets partially digested the methane gas (biogas) is produced .
- In the second stage the sludge is vigorously aerated with air or oxygen so that complete oxidation May take place. This process can be best be don economically and profitably by using algae. Some algae used are Chlorella, Scenedesmus, Spirulina, Chlamydomonas and Oscillatoria. During photosynthesis they produce oxygen that helps aerobic microorganism to breakdown organic matter completely. The algal biomass produced can profitably used for other purpose like feed for cattle or poultry.
Bio fertiliser
Some of the algal bio fertilizer that are being developed and used successfully in India and abroad are discussed below.
- Seaweed :-
Seaweeds compost is rich in minerals kike potassium, phosphate, sulphate and trace elements. Several vegetables crops like bhindi, brinjal, tapioca, cucurbits are found to be benefited by this manure.
2. Blue green algae:-
Nitrogen fixing cyanobacteria can be grown in shallow puddles or metals pans in summers wherever sunlight and water are available in plenty.
Cyanobacteria are also added to the paddy fields immediately after the transplantation of seedling. They multiply rapidly and supply nitrogen and other nutrients to the plants directly or by their decay.
Blue green algae are also used in the reclamation of udar lands.
Source of Energy
Algal biomass is found quite suitable for use in biogas plants for producing methane gas. It can be fermented in anaerobic digesters as sole substrate or along with the sewage sludge.
Algae having potential for energy production are: Spirulina, botryococcus, braunii, sargassum tenerrium, Alteromonas gracilis, Chlamydomonas, Dunaliella, Anabaena (for hydrogen).
Algae sunthesis energy rich molecules like long chain hydrocarbons, glycerol and lipids. When some algae are grown without nitrogen and silicon, there is an increase in the synthesise.
Industrial Applications
A variety of compounds are obtained from seaweeds and these are Phycocolloids, Diatomite and pigments.
The economically important seaweeds in India include species of red algae such as — Gelidiella acerosa, Gracilaria edulis, Gracilaria corticata, Gracilaria foliifera, Gracilaria crassa, Hypnea musciformis, Hypnea Valentiae, Hypnea pannosa
Medical uses
Some algae have antibacterial, antiviral and antipyretic properties. They are used for wound healing treatment of heart disease, gout, goiter, hypertension, gall stone, bowel movement, skin disease and as vermifuge.