Algae are very primitive aquatic plants of kingdom Plantae. They don't have plant parts like roots, stems, leaves or fruits but have filamentous or nonfilamentous thallus or body. Algal classification is based on type of photosynthetic pigment present. Three classes of algae are Green, Brown and Red algae. Chlorophyll a and Î²-carotenes are present in all three types but other photosynthesis pigments are different. Green algae contain chlorophyll b, and xanthophylls; brown algae contain chlorophyll e and fucoxanthine; red algae have phycocyanin and phycoerythrin as pigments. Habitat of green algae (Spirogyra, Oedogonium) is fresh water or terrestrial while as brown (Sargassum, Laminaria) and red algae (Porphyra, Gelidium) are marine forms. The reserved food material of green algae is starch; mannitol and laminarin is present in brown algae; red algae have Floridian and starch as stored food. Blue green algae (BGA) or cyanobacteria were excluded and placed in kingdom Monera as they possess prokaryotic cellular organization and functions.
Biotechnological importance of algae:
o Algae as renewable energy source; Chlorella, Dunaliella, Gracilaria and Sargassum produce fuels like diesel, gasoline, methane, butanol, ethanol and aviation fuel.
o They can grow on land or water (arid/saline/alkaline/marshy) unsuitable for crop cultivation.
o They scavenge green house gases and can be used for carbon dioxide mitigation.
o Algae are cheap source for waste water treatment and biogas production.
o Genetically engineered algae are used to enhance biofuel production and as source of protein and vitamin rich food and fodder.
o Algae are used as biofertilizer for crops as rich source of nitrogen, phosphorous, potassium, iodine, iron, calcium, silica and vitamins.
o Algae have been recommended for pesticide and heavy metal bioremediation.
o Algae are used in formation of biosolar cells.
o Algae as food; Alaria, Laminaria, Sargassum, Porphyra is popular as food in Japan and Europe.
o Algal storage materials like starch, gelatin and lipids are used as gelling agents in jellies, ice-creams, confectioneries and bacteriological media.
o Algae have therapeutic importance; Chlorellin from Chlorella is broad spectrum antibiotic.
o Algal pigments have antioxidant properties and therefore used in formulation of age proofing cosmetics.
Growth in laboratory: In laboratory, algae are cultivated under aseptic conditions and controlled physical parameters like pH, temperature, light intensity, shaking of growth medium and incubation time. Algae being photoautotrophic, they are grown in broth or agar medium supplemented with micronutrients like magnesium, nitrate, calcium and iron. The incubation is always carried out in illuminated growth chamber for about 7-15 days till algal growth is visualized. Identification is carried out with the help of standard classification manual.
Algal farming: Algal cultivation is cheap as compared to other economic crops. Algae do not require prepared and fertilized land for their growth. They can grow on marginal land like salinated or drought affected hard soils. They also grow in waste water effluents or sewage or even waste water from nuclear reactors. They can be grown in open ponds or bioreactor tanks or closed ponds or tanks covered inside shade nets. Algae are cultivated on large scale in photobioreactors. Reactors are plastic pumps containing nutrient water for algal growth. Carbon dioxide is supplied intermittently to enhance algal biomass. Algae when grown in closed system are protected from air borne microbial contamination, particularly fungal spores which can be pathogenic to algae.
Genetic engineering of algae for enhanced fuel production:
Today, the world is facing critical fuel crisis and exploitation of novel fuel resources is in express progress. Marine and terrestrial algae are potential producers of fuels equivalent to fossil fuels like diesel, gasoline and jet fuel. Molecular biology tools are in use for identification and characterization of algal cell. Molecular markers have been used to study algal photosynthesis, pigment synthesis, respiration, storage granules and reproduction. Genetic engineering techniques have made it possible to enhance the fuel production in cyanobacteria but the same is in very primitive stage for true algae. The main constrain is no availability of suitable carrier vector (plasmid or virus) for the insertion of desired external gene sequences into algal genome. So there is a great scope for molecular biologists to overcome this constrain or to innovate novel method to engineer the algal genome for enhanced fuel production.
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