Algae-A Nutritional Food Source:
To fulfill demand of growing global population, there is steady explore for novel food sources. Approx 90% of food is got from land. Although aquaculture, its potential has not been completely explore. Among marine organisms - algae seem to be one of capable food resources. Several edible synthesize some necessary polyunsaturated fatty acids that are hardly ever synthesized in higher plants or animals. Algae develop rapidly and their farming can be performed in brackish water, fresh water, and shallow coastal areas and also in open sea. So, it is worthwhile to search algae and algal products which have potential food value. Idea of including algae in human diet is fairly new in Nigeria but in maritime countries algae and alagal products are daily consumed along with other food items. Consumption of seaweed by coastal Japanese people dates back to 600 B.C. and by Chinese 6th century A.D. Approx 160 species of algae are utilized as commercially significant food sources.
Spirulina has approx 65% proteins and is also rich in carotenes. It can be dveloped in wastewater. It is mass cultured in Mexico, Taiwan and India. Due to its high nutritive value it has been recognized as source of single cell protein (SCP), as appropriate supplement to vegetarian meal. It can be supplemented in diet of children to curb malnutrition widespread in developing countries. Natives of Mexico and Africa have long utilized it. Another single cell, rapidly growing alga is chlorella. It contain a potential food value as it is in lipids, proteins and has several vitamins in high concentration. It nutritive value is approximately equal to that of soyabean and spinach. In Taiwan, Japan and other South East Asian countries it is developed as health food having 'a cure-all property, Taiwan alone produces 1500 tons (dry weight) annually. After harvesting cells are washed and pigments are extracted. Dried algal mass is ground and stored in powdered form. Marine algal foods are both conventional and delicacy in Japan, Korea, Philippines, china and Thailand. Several species of algae like Gelidiella Laurencia, Enteromorpha, Caulerpa Ulva lactuca, and Gracilaria are eaten raw as salad, Gracilaria is utilized in preparing tasty dessert. Gelidiella acerosa and Ulva lactuca are cooked with other vegetables like spinach is cooked in Nigeria.
Among seaweed, one of the most significant is portphyra. It has 30-35% proteins, 40-5% carbohydrates and rich in vitamins. Mature prophyra is harvested, dried and pressed in sheets. Sheets are toadsed and cut in pieces and eaten with rice, raw fish or some vegetables. They are also utilized for flavoring soups and in 'sushi'. In Japan porphyra (called nori) farming is performed over 60,000 hectare area in sea by either placing concrete blocks on sea floor to improve seaweed growth or on bamboorope network or raft like network of bamboos. In North Atlantic coast palmaria known as dulse and portphyra called layer are most extensively utilized seaweed. In pacific countries and Asia the huge variety of seaweed are harvested are harvested as foraging shore and are consumed as food. Undularia is utilized in Japan for extracting the edible product known as Wakame.
Algae - A Source of Animal Feed:
Chlorella and several seaweed are commercially cultured for human consumption due to their high nutritive value. These can also be utilized directly as folder for livestock or supplemented with regular feed. During World war I when fodder was in short supply, seaweed were. Tried as cattle feed and quality of milk was found to be unaltered. After that seaweed based stock feed factories were set up in Denmark, France, Norway, Germany and USA. According to few reports milk of cows fed with seaweed is rich in fat content than these fed on conventional fodder. Seaweed are utilized either directly as folder for livestock or added in powdered from to regular feed of cattle, pigs, sheep, fish and poultry.
Use of Algae for Waste Water Treatment:
Waste water from lavatories, bathrooms and kitchens of homes has large amount of organic material and is usually called as sewage. Sewage is foul smelling but rich in nutrients. If it is discharged into ponds, lakes or rivers the development of different kinds of bacteria and viruses is encouraged resulting in epidemics of disease such as cholera, gastro-enteritis. Typhoid, viral jaundice etc. in cities amount of sewage made is certainly very large. It requires to be treated to get rid of most of organic matter and nutrients before water is reused or disposed of into river or lake. Sewage treatment engages generally following two stages:
In first stage, diluted sewage is permitted to decompose in absence of air (anaerobic digestion) by anaerobic micro-organisms. When it gets partly digested methane gas (biogas) is made. In second stage sludge is strongly aerated with air or oxygen so that complete oxidation may occur. This procedure can best be completed economically and profitably by using algae. Few algae utilized are chlorella, scenedesmus chlamydomonas, Oscillatoria. In shallow ponds, exposed to bright sunlight algae develop profusely. In photosynthesis they make oxygen which assists aerobic microorganisms to breakdown organic matter entirely. Water of oxidation ponds can be safely utilized for horticultural or agricultural purposes. Algal biomass made can be profitably employed for other purposes such as feed for cattle or poultry.
Algae as bioaccumulator of Toxic Pollutants:
It has been seen that algae can collect as much several thousand folds of pesticides and toxic metals like Zn, Hg, Cd, Cu, Pb widespread in industrial effluents. Therefore algae can be utilized for treatment of industrial effluents to eliminate toxic pollutants. Algal biomass therefore attained can be utilized for biogas production instead of feeding to animals.
Use of Algae as Biofertiliser:
With raise in population, it has become essential to increase yield of crop plants and this has resulted in large scale use of chemical fertilizers. It is only lately that people have recognized harmful effects of such fertilizer on environment particularly on solid. Chemical fertilizers are produce in factories from non-renewable sources like crude oil and natural gas that may not be available after some time when exhausted.
Being soluble in water much of fertilizer added to crop is liberally washed down by irrigation water or rain and reaches water resources such as ponds, lakes and rivers. This bring about development of algae and bacteria leading to harsh water pollution, besides, these unwanted side effects, chemical fertilizers influence chemical and physical properties of soil so as to make it unfit for growing crops. Usually, farmers use farmyard manure (FYM), made from agricultural wastes. Though they are good as soil conditioner they are poor in nutrients. In recent years, number of organic nutrient-rich fertilizers of biological origin termed bio fertilizers has become popular. Some of algal bio fertilizers which are being developed and utilized successfully are provided below:
In coastal areas where seaweed are washed ashore, they are accumulated and composed like farmyard manure, seaweed compost is rich in mineral such as phosphate, postassium, sulphate and trace elements, many vegetable crops such as cassava (tapioca) cucurbits; fruits such as lemon: trees like palm and papaya are found to has advantage by this manure. Extracts of seaweed (seaweed boiled in water) have been discovered stimulatory for germination and seeding development of red gram tomato and other plants. Extracts are commercially available in few countries under name of Algofert (Norway) and SM3 (England). Similar water extracts of common cyanobacteria such as Cylindropermum, Calothrix, Anabaena, Aulorsira are also found advantageous for development and yield of crop and vegetable plants.
Blue-green Algal Bio-fertilizers:
Wherever sunlight and water are available, nitrogen-fixing cyanobacteria can be developed in summer on shallow puddles or metal pans. Thick mats which grow within a week or so are dried and kept in bags. This is abundantly growing one's own fertilizer during summer season when field is empty without crop. Such dry algal material is rich source of nitrogen and phosphorus besides many other significant elements. Agircultural departments supply kits to farmers to produce their fertilizer. Nitrogen-fixing cyanobacteria are also directly added to rich paddies immediately after transplantation of rice seedlings. They multiply rapidly and supply directly or by decay nitrogen and other nutrients to rice plants.
Azolla is water fern, extremely common in ponds In Vietnam, China and other south East Asian countries; it is grown and utilized as fertilizer and also as feed for cattle and poultry. Azolla has symbiotic nitrogen-fixing cyanobacter-Anabaena in leaf pockets and grows rapidly when inoculated in rice fields. It can be grown separately and composted, stored and added to crops if required.
Algae - a Source of Energy:
Fossil fuel reserves such as coal, peat, rice oil products (hydrocarbons) and natural gas on earth are limited. At present, they are consumed at much faster rate than before because of rapid increase in industrialization. Unluckily, they are non-renewable and it is evelauted that they will soon be depleted. So serious efforts are being prepared to find alternate renewable sources of energy Algae are recognized as one such potential source.
Algae biomass is discovered fairly appropriate for use in biogas plants for making methane gas. It can be fermented in anaerobic digesters as sole substrate or along with sewage sludge. It has been illustrated that Spirulina when added to sewage sludge doubles production of methane.
Algae synthesize energy-rich molecules like long chain hydrocarbons glycerol and lipids. When few algae are developed without nitrogen and silicon, there is increase in synthesis. These energy rich chemicals can be converted in petrol and diesel. Glycerol required in pharamaceutical industry is produced by Astromosnas gracilis, Chlamydomonas and Dunaliella.
Though, glycerol is not good liquid fuel as it is highly oxygenated, it can be converted to other liquid fuels such as ethanol, butanol and propane-diol that can be utilized as substitute for petrol. In Brazil ethanol is utilized in place of petrol and in USA it is added to gasoline and sold as gasohol. Another potential alga is Botryococcus branii that under saline circumstances produces long chain hydrocarbons comprising fatty acids. In Sumatra, oil extracted from this alga.
The chance of hydrogen production bu cyanobacteria has drawn much attention, as they can produce hydrogen in presence of light completely in nitrogen free atmosphere. Hydrogen along with air is utilized in fuel cells to produce electricity without polluting atmosphere.
Another interesting possibility that has been productively explore is sustained photo-production of ammonia from nitrate by cyanobacteria. This needs inhibition of enzyme glutamate synthetase. As a result, alga produces ammonia at high rates with fairly high efficiency.
Industrial Application of Algae:
The large numbers of algal products have verified to be of great commercial use. Variety of compounds attained from seaweed is given below:
Algmic acid, agar and carrageenans are high molecular weight polysaccharides and have colloidal properties. They are constituents of cell wall of mainly red and brown seaweed. They are utilized as viscofiers and lubricants in food, paper, textile, drug and caustic industries. As there are no synthetic substitutes of non-algal sources to get them seaweed are of great value.
Alganic Acid: In cell wall of algae, alginic acid is present in form of algainates-Na, K, Ca, Nh4 salts of alginic acid. As sodium salt is soluble in water, extraction. They are also utilized for making flame-proof fabrics and plastic articles. This polymer can absorb large quantities of water so it is utilized as highly absorbent gauze in internal operations to stop bleeding efficiently. Owing to the non-toxic and colloidal property it is utilized for making antibiotic capsules
Uses of Algainates:
Jams, jellies and sauces, cosmetics, textile and
Ice creams, milk shakes and squashes
For the preparation of paints and polishes
Surface coating agents
For flame proof fabrics, plastics
In surgical operations
Gelatinous substance agar, is well known for solidification of culture media in microbiology and tissue culture. It is mixture of agarose and agaropectin and is extracted from approx 80 algal species of seaweed. Commonly utilized aglae are Gracilaria and Gelidium. Like alginic acid it is also utilized in manufacture of puddings, ice creams jellies and soups. As stabilizer or emulsifier it is utilized in cosmetics, leather and pharmaceutical industries. Due to its laxative property it is utilized for treatment of constipation.
The major sources of carrageenan are chondrus crispus (usually called as Irish moss) and Eucheuma spp. Polysaccharides in carrangeenan are sulphated. Like alginic acid and agar, it is utilized in dairy industry and in textile, cosmetics, leather, pharmaceutical and brewing industries.
Diatoms contain firm silicified cell walls. Complete cell wall of diatom is called as frustule. The fossilized frustules of diatoms are usually called as diatomite or diatomaceous earth. They create sedimentary rock and serve as biogenic silica sources, because of high porosity, low density, large area, low abrasion capacity and chemically inert nature, diatomite are utilized in industry.
Uses of diatomite are given below:
For clearing lubricating oil and available fuels, for refining sugar.
In boilers, furnaces, refrigerator, for making soundproof rooms
In sourcing and polishing powders like tooth powder, bleaching powder, glass cleaners, plains and vanishes.
In battery boxes.
Controller of burn and friction in match heads and cigars, for packing explosive materials.
In handling and packing of hazardous materials.
You know that one of criteria for classifying algae is presence of photosynthetic pigments- chlorophylls, carotenes, xanthophylls and fucoxanthin which impart distinct colors- blue, red, green, yellow, golden, brown etc. to them. Such pigments are extracted on commercial scale and are utilized for different objective Dunaliella and Spirulina are rich sources of Bcarotene, precursor of vitamin A. in comparison of other sources of Bcarotene microalgae present many benefits. They need short generation time for development and can be grown in sewage water. Amount of B-carontene in them is in high concentration. B-carotene has been recognized as anticancer drug. B-carotene and other pigments (like xanthophylls, cantaxanthin and zeaxanthin) are utilized as food colorant. For e.g. B-carotene is utilized for coloring soft drinks and margaring and cantaxanthin is utilized for coloring chicken skin, gold fish skin and egg yolk.
Medical uses of Algae:
Few algae illustrate antibacterial, antiviral and antipyretic properties. They are utilized for wound healing, treatment of heart disease, gall stone, goiter, gout, bowels movement, hypertension, skin diseases and as vermifuge.
Advantageous uses of algae in medicine are given below:
Medicinal uses of Algae:
Kainic Acid (Dignenea)
Diagnostic tool in understanding
The nature of seizure In epilepsy
Decoction of some seaweed
Binding agent for medicinal
Fucoidin and agar
Companies which have establish large scale industries to use algal potential for range of products are: Dupont and Sohio (USA), Thapar Corporation (India), Kairin and Dainpa (Japan), siam Algae Company (Bangkok), Wester Biotechnology Ltd. (Austtralia).
Dangerous Effects of Algae:
Fast growth of algae in water reservoirs (algal bloomd) leads to eutrophication. Water reservoir is no more appropriate for recreational - swimming, coating or fishing activities. In cloudy weather algae deplete oxygen of water and suffocate fish and other aquatic animal. Fish die as they get choked in mouth and gills when intertwined in large masses of algal filaments. At times, you may have suffer strange odor and taste in drinking water supply. This could be because of certain algae that impart fishy, grassy, musty or some other odor, and sweet or bitter taste to water. Odor and taste are due to metabolic and/or decomposition products of algae. Only few cells of alga (of Division Chrysophyta) are adequate to provide bad taste and stinking smell to supply, filters get blocked and severe economic losses happen.
Few algae make toxins that enter humans and animal directly or by food chains. For instance, the person can get poisoned on consumption of oysters or fish which feed on toxic dinoflagellates. This algal toxin inhibits nerve transmission and therefore results in paralysis and even may cause death, ingestion of toxin algae with drinking water or in swimming may cause gastric problems, skin infections or respiratory disorders. Alga Prototheca disease, protothecosis that manifests in form of skin lesions, inflammation around joints and defective lesions, infamination around joints and defective leucocytes in humans. Persons working with diatomeacous earth experience algal silicosis. Arsenic poisoning is caused by extreme consumption of seaweed. Affected person experiences skin rashes blistering and inflammation. Fresh water blue-green algae generate alkaloids that are nerotoxins.
Dermatitis (skin inflammation)
Lyngbya mjuscula, Chlorella
Chlorella, Oscillatoria, Anabactena, Cymnodium spp
Excessive consumption of seaweed
Lyngbya major, Chlorella, Oscillatoria, Anabaena
Control of Algal Nuisance:
Chemical and biological technique can be utilized to manage undesirable development of algae. Many algicides are known like copper sulphate, quinones, phenols and other which selectively kill algae. Algae growth can also be handled by introducing appropriate crustaceans or fish fingerlings in affected reservoir. Certain viruses that kill blue-green and green algae are also helpful for control.
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