BIOLOGICAL AND ECONOMICAL IMPORTANCE OF ALGAE K R.pptx

1. BIOLOGICAL AND ECONOMICAL IMPORTANCE OF ALGAE
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As primary producers
 Algae form organic food molecules from carbon dioxide and water through the
process of photosynthesis, in which they capture energy from sunlight.
 Similar to land plants, algae are at the base of the food chain, and, given that
plants are virtually absent from the oceans, the existence of nearly all marine
life—
including whales, seals, fishes, turtles, shrimps, lobsters, clams, octopuses, sea
stars, and worms—ultimately depends upon algae
 In addition to making organic molecules, algae produce oxygen as a by-product of
photosynthesis.
 Algae produce an estimated 30 to 50 percent of the net global oxygen available to
humans and other terrestrial animals for respiration
 Most algae possess chlorophyll a. As primary producers, they use the sunlight
energy to convert inorganic substances into simple organic compounds, and,
provide the principal basis of food webs on the Earth. Furthermore, they produce
oxygen that is essential for heterotrophic organisms.
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• Because of their photosynthetic abilities the algae are the primary producers of
the aquatic environments. They provide food and energy to the animal life,
produce oxygen and take up carbon dioxide produced during respiration which is
injurious for living organisms especially fishes.
• Ecologically, algae are at the base of the food chain. They are the beginning of the
transfer of solar energy to biomass that transfers up trophic levels to the top
predators.
• The larger algae provide a habitat habitat for fish and other invertebrate animals. A
great example of this is Macrocystis, which is a keystone species in a giant kelp
forest.
• As algae die, they are consumed by organisms called decomposers (mostly fungi
and bacteria). The decomposers feed on decaying plants and consume the high-
energy molecules essentially remineralizing the biomass into lower-energy
molecules that are used by other organisms in the food web
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Economic imporatnce of Algae
 Food: Large number of algae have entered into the diets of human beings from
ancient times
 The earliest records are those of the Chinese, who mentioned such food plants as
Laminaria and Gracilaria in their ‘materia medica’ several thousand years ago.
 The ancient inhabitants of Japan ate Porphyra as a healthful supplement to their
rice diet.
 Its use became widespread, not only in Japan, but in China in course of time.
Kombu, a Japanese food is prepared from stipes of species of Laminaria.
 The most diversified dietary use of seaweeds was developed by the Polynesians
and reached its peak in Hawaii, where during the nineteenth century at least 75
species were separately named and used regularly as food in that island world.
 The Hawaiians called them ‘limu’ and considered them a necessary staple of their
daily diet.
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• Perhaps the best known and most widely used food alga in Western Europe in
recent centuries was Irish moss, or carragheen (Chondrus chrispus), which was
cooked with milk, seasoned with vanilla or fruit, and made into a highly palatable
dish known, as blancmanges.
• Man, thus obtains carbohydrates, vitamins (algae are especially rich in vitamins A
and E, and they contain some C and D), and inorganic substances, e.g., iodine
(goiter is unknown among the people who eat seaweeds), not to mention the
benefits of the mild laxative action of the ingested algae.
• In Japan, powdered Chlorella ellipsoidea has been used successfully mixing with
green tea.
• In Germany and in the United States considerable work is being carried out on the
suitability of mass cultures of Chlorella as an alternative source of animal feed and
of human vegetable food.
• The common algae used as food include chlorella, lamianria, chondria, porphyra,
spirulina, ulva
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 Biofuel production: There are generally two types of biofuels: ethanol (or
biopetrol) made from carbohydrates (sugars) and biodiesel made from lipids (fats)
 Biofuels can be derived from biological material like plants, animal fats, and other
sources. However, plant-based feedstock has attracted significant interest to
sustainably meet current and future fuel demands
 In recent years, biofuel production from algae has attracted the most attention
among other possible products
 This can be explained by the global concerns over depleting fossil fuel reserves and
climate change. Furthermore, increasing energy access and energy security are
seen as key actions for reducing poverty thus contributing to the Millennium
Development Goals.
• Algae have a great potential of producing ethanol due to low content of lignin and
hemicellulose as compared to lignocellulosic plants
• In addition to low lignin content, macroalgae are known to have high sugars
content (~50%) which can be fermented for production of ethanol
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• The marine red algae like Gelidium and Gracilaria are rich source of agar, a
carbohydrate (polymer of galactose and galactopyranose
• The release of simple sugars from agar is quite difficult, thus, current research
should focus to develop methods of saccharification from agar.
• Saccharification is a process of breakdown of complex carbohydrates into simple
monomers. The enzymatic hydrolysis is very specific, requires less energy and mild
conditions
• The enzyme cellulase cleaves the bonds of cellulose into glucose and hemicel-
• lulase cleave the bonds of hemicelluloses into mannose, xylulose, glucose,
galactose and arabinose.
• The ethanol industry uses cellulase and hemicellulase from fungus Trichoderma
reesei
• The development of efficient method for release of glucose from cellulose would
also lead to enhance ethanol yields during fermentation
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• There are reports that blue-green algae like Spirogyra sp. and Chlorococum sp.
accumulate starch and also have high content of polysaccharides in their complex
cell walls. The Chlorella vulgaris, a microalga is also known to accumulate high
content of starch (37% of dry weight). The accumulated starch can be used for
production of ethanol
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 Medicine (Therapeutic uses):
 ANTIOXIDANT PROPERTY OF MARINE ALGAE: Antioxidants play prominent role in
the later stages of cancer development. The most powerful water soluble
antioxidants found in algae are polyphenols, phycobiliproteins and vitamins
 Oxidative processes promote carcinogenesis. The antioxidants may be able to
cause the regression of premalignant lesions and inhibit their development into
cancer
 It is found that , several algal species have prevented oxidative damage by
scavenging free radicals and active oxygen and hence able to prevent the
occurrence of cancer cell formation
 These Antioxidants are considered key compounds to fight against various diseases
and ageing processes
 Polyphenols in marine brown algae are called phlorotannins and known to act as
potential antioxidants.
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• ANTICANCER ACTIVITY OF MARINE ALGAE: Marine macro-algae belongs to the
most interesting algae group because of their wide range spectrum of biological
activities such as antimicrobial , antiviral , antifungal, anti-allergic , anticoagulant ,
anticancer , antifouling and antioxidant activities
• They produce variety of chemically active metabolites in their surroundings as a
weapon to protect themselves against other settling organisms
• Many marine algae produce antibiotic substances capable of inhibiting bacteria,
viruses, fungi, and other pibionts. The antibiotic characteristic is dependent on
factors like that particular alga, the microorganisms, the season, and the growth
conditions
• ANTIVIRAL PROPERTIES OF MARINE ALGAE: Vaccines are very successful in
controlling many viral diseases, yet some diseases are not controlled by
vaccination. Some synthetic antiviral compounds were developed for treatment of
active herpetic infections, were not effective for the treatment of latent infections
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• The concept of antiviral compounds with pharmaceutical value could not be
accepted easily. Some plants and algae extracts were tested on different viruses
including the herpes viruses
• In some of these experiments different species of brown algae were tested for
their antiviral activity.
• Other uses: Alginates is used in the medicine industry for its haemostatic nature
• Antibacterial agent chlorellin is extracted from chlorella this antibacterial agent is
used to control coliforms and other related intestinal Bacteria
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Role of algae in heavy metal removal
 Algae can effectively remove metals from multi-metal solutions. Dead cells sorb
more metal than live cells.
 Various pretreatments enhance metal sorption capacity of algae. CaCl2
pretreatment is the most suitable and economic method for activation
of algal biomass.
 Many algae have immense capability to sorb metals, and there is considerable
potential for using them to treat wastewaters.
 Metal sorption involves binding on the cell surface and to intracellular ligands. The
adsorbed metal is several times greater than intracellular metal.
 Carboxyl group is most important for metal binding. Concentration of metal and
biomass in solution, pH, temperature, cations, anions and metabolic stage of the
organism affect metal sorption.
 Algae can effectively remove metals from multi-metal solutions. Dead cells sorb
more metal than live cells. Various pretreatments enhance metal sorption capacity
of algae.
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• CaCl2 pretreatment is the most suitable and economic method for activation of
algal biomass.
• Algal periphyton has great potential for removing metals from wastewaters. An
immobilized or granulated biomass-filled column can be used for several
sorption/desorption cycles with unaltered or slightly decreased metal removal
• Algae require certain heavy metals for their normal functioning, these include iron
for photosynthesis and chromium for metabolism.
• Many researchers found that the Sargassum brown algae has a high adsorption
capacity to remove heavy metals such as Cu, Ni, Cd, Pd, Cr, Sm, and Pr from their
solution efficiently due to its cell wall structure that is rich in active bioadsorption
sites
• potential use of three green algae (Cladophora glomerata, Enteromorpha
intestinalis and Microspora amoena) dry biomass as a biosorbent to remove Cr(VI)
from aqueous solutions.
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• Bioadsorption is an adsorption process that aims to remove or recover organic and
inorganic substances in aqueous solutions using a biological material that may
include live or dead microorganisms and their components, seaweed, vegetables,
industrial waste, agricultural waste, and natural waste as adsorptive medium
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Immobilized algae
 Algae are a largely untapped source of potentially useful biotransformations.
 Where algal immobilization is appropriate in exploiting this potential, methods fall
into two categories: active entrapment and invasive adsorption
 The use of microalgae in biotechnology has been increased in recent years, these
organisms being implicated in food, cosmetic, aquaculture and pharmaceutical
industries
 but small size of single cells implies a problem in the application of
biotechnological processes to those organisms.
 Cell immobilization techniques have been developed in order to solve those
problems.
 An immobilized cell is defined as a cell that by natural or artificial means is
prevented from moving independently of its neighbours to all parts of the aqueous
phase of the system under study
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• Frequent uses of immobilized algal cells are the nutrients, metal and organic
pollutant removal from aquatic media, culturing for metabolite production,
improvement of culture collections handling, measurement of toxicity, obtaining of
energy (via Hydrogen or electricity) and co-immobilization system production for
different purposes
• Immobilized algae have been investigated for their potential use for the uptake of
nitrogen and phosphorus
• The algal cells immobilized in carrageenan and alginate beads had the efficiency to
remove nitrogen and phosphorus from wastewater as the free suspended cells
• Immobilized Scenedesmus was found to be capable of removing 90% of the
ammonium within four hours and 100% of phosphate within two hours from a
typical effluent
• Immobilization of biomass also provides protection to cells from metal toxicity
• It is recommended that beads should be in the size range between 0.7 and 1.5
mm, corresponding to the size of commercial resins meant for removing metal
ions
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• Significant uptake of Co, Zn and Mn was also recorded for Chlorella salina cells
immobilized in alginate
• The interest in utilizing algae for wastewater treatment has been increased due to
many advantages. Algae-wastewater treatment system offers a cost-efficient and
environmentally friendly alternative to conventional treatment processes such as
electrocoagulation and flocculation.
• In this biosystem, algae can assimilate nutrients in the wastewater for their growth
and simultaneously capture the carbon dioxide from the atmosphere during
photosynthesis resulting in a decrease in the greenhouse gaseousness.
• Furthermore, the algal biomass obtained from the treatment process could be
further converted to produce high value-added products.
• However, the recovery of free suspended algae from the treated effluent is one of
the most important challenges during the treatment process as the current
methods such as centrifugation and filtration are faced with the high cost
• Immobilization of algae is a suitable approach to overcome the harvesting issue.
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Labeled Algae
 The marine flagellate Pavlova lutheri is a microalga known to be rich in long-chain
polyunsaturated fatty acids (LC-PUFAs) and able to produce large amounts of n-3
fatty acids, such as eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid
(DHA, 22:6n-3)
 As no previous study had attempted to measure the metabolic step of fatty acid
synthesis in this alga, we used radiolabeled precursors to explore the various
desaturation and elongation steps involved in LC-PUFA biosynthesis pathways.
 The incorporation of (14)C-labeled palmitic ([1-(14)C] 16:0) and dihomo-γ-linolenic
([1-(14)C] 20:3n-6) acids as ammonium salts within the cells was monitored during
incubation periods lasting 3, 10 or 24h.
 Total lipids and each of the fatty acids were also monitored during these
incubation periods.
 The main purpose of radiolabeling to study the lipids and fatty acids in the algae
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Algal Blooms
 An algal bloom or algae bloom is a rapid increase or accumulation in the
population of algae in freshwater or marine water systems
 And is often recognized by the discoloration in the water from their pigments
 Algal bloom commonly refers to rapid growth of microscopic, unicellular algae, not
macroscopic algae. An example of a macroscopic algal bloom is a kelp forest
 Algal blooms are the result of a nutrient, like nitrogen or phosphorus from fertilizer
runoff, entering the aquatic system and causing excessive growth of algae
 An algal bloom affects the whole ecosystem. Consequences range from the benign
feeding of higher trophic levels, to more harmful effects like blocking sunlight from
reaching other organisms, causing a depletion of oxygen levels in the water, and,
depending on the organism, secreting toxins into the water.
 The process of the oversupply of nutrients leading to algae growth and oxygen
depletion is called eutrophication
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• Blooms that can injure animals or the ecology are called "harmful algal blooms"
(HAB), and can lead to fish die-offs, cities cutting off water to residents, or states
having to close fisheries.
• blue-green algae, and cyanobacteria are examples of harmful algal blooms that
can have severe impacts on human health, aquatic ecosystems, and the economy.
• Effects of algal blooms
 Produce extremely dangerous toxins that can sicken or kill people and animals
 Create dead zones in the water
 Raise treatment costs for drinking water
 Problematic for industries which depends on fresh water
 Causes of algal blooms
 Nutrients: Nutrients promote and support the growth of algae and Cyanobacteria.
The eutrophication (nutrient enrichment) of waterways is considered as a major
factor. The main nutrients contributing to eutrophication are phosphorus and
nitrogen.
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• In the landscape, runoff and soil erosion from fertilized agricultural areas and
lawns, erosion from river banks, river beds, land clearing (deforestation), and
sewage effluent are the major sources of phosphorus and nitrogen entering water
ways.
• Temperature: Early blue–green algal blooms usually develop during the spring
when water temperature is higher and there is increased light. The growth is
sustained during the warmer months of the year. Water temperatures above 25°C
are optimal for the growth of Cyanobacteria. At these temperatures, blue–green
algae have a competitive advantage over other types of algae whose optimal
growth temperature is lower (12-15°C).
• In temperate regions, blue–green algal blooms generally do not persist through
the winter months due to low water temperatures. Higher water temperatures in
tropical regions may cause blue–green algal blooms to persist throughout the year
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• Light: Blue–green algae populations are diminished when they are exposed to long
periods of high light intensity (photo-inhibition) but have optimal growth when
intermittently exposed to high light intensities. These conditions are met under
the water surface where light environment is fluctuating.
• Even under low light conditions, or in turbid water, blue–green algae have higher
growth rates than any other group of algae. This ability to adapt to variable light
conditions gives cyanobacteria a competitive advantage over other algal species.
• Stable Conditions: Most of blue–green algae prefer stable water conditions with
low flows, long retention times, light winds and minimal turbulence; other prefer
mixing conditions and turbid environments.
• Drought, water extraction for irrigation, human and stock consumption and the
regulation of rivers by weirs and dams all contribute to decreased flows of water in
our river systems. Water moves more slowly or becomes ponded, which
encourages the growth of algae.
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• Harmful algal blooms can occur in lakes, reservoirs, rivers, ponds, bays and coastal
waters, and the toxins they produce can be harmful to human health and aquatic
life. ... Harmful algal blooms release toxins that contaminate drinking water,
causing illnesses for animals and humans
Algal toxins
 Algal toxins are toxic substances released by some types of algae when they are
present in large quantities (blooms) and decay or degrade.
 Many bloom forming species of algae are capable of producing biologically active
secondary metabolites which are highly toxic to human health and other animals
 Cyanobacteria can produce different type of Cyanotoxins which belongs to four
major classes namely Neurotoxins, Hepatotoxins, Cytotoxins, Dermatotoxins and
Lipo polysaccharides.
 Of the more than 50 genera of blue green algae at least 8 have exhibited toxic
characteristics of these include Anabaena sp., Aphanizomenon
sp., Coelosphaerium sp., Gleotrichia sp., Lyngbea sp., Nodularia sp., and Nostoc sp.
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28. Contd..
• Neurotoxins are produced by different genera of Cyanobacteria
including Anabaena sp, Aphanizomenon sp, Microcystis sp, Planktothrix sp, Raphid
opsis sp, Cylindrospermium sp, Phormidium sp, and Oscillatoria sp.
• Neurotoxins of Oscillatoria sp. and Anabaena sp. have been responsible for animal
poisoning
• Neurotoxins usually cause acute effects in vertebrates including rapid paralysis of
the peripheral skeletal and respiratory muscles. Neurotoxins affect the nervous
system of the animals.
• Hepatotoxins:The cyclic penta peptide Nodularin is most commonly produced
from the filamentous, planktonic, Cyanobacterium, Nodularia spumigena.
• Nodularin is a potent hepatotoxin for humans and other animal. It induces liver
hemorrhage in mice, when it injected in artificial way.
• The toxic effects of nodularin are primarily associated with the hepatic cells due to
active transport of the toxin to liver via the bile acid, multi specific organic anion
transporters
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• Saxitoxins: Saxitoxins are heterocyclic guanidine neurotoxins act like carbamate
pesticides produced by different fresh water algae like Anabaena
circinalis, Aphanizomenon., Aphanizomenon gracilie., Lyngbea wolleri are
responsible for shell fish poisoning.
• Blooms of these toxic species have led to mass kills of fish, native mammals and
live stock as well as the contamination of fresh water resources.
• Paralytic shell fish poisoning symptoms generally onset with in 30 min of ingestion
and invariably begin with a tingling or burning of lips, tounge and throat increase
to total numbness of face
• The saxitoxin causes several health problems in humans include perspiration,
vomiting, diarrhea. In case of acute poisoning numbness may be spread to neck
and extremities and progress to muscular weakness, loss of motor coordination,
and finally leads to paralysis
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30. Contd..
• Anatoxins: There are three families of cyanobacterial neurotoxins are known
namely Anatoxin-a and Homoanatoxin-a, Anatoxin-a(s), Saxitoxin
• Anatoxin-a is one of the neurotoxic alkaloids tht have been produced from
cyanobacteria include Anabaena, Planktothrix,(Oscillatoria), Aphanizomenon,
Cylindrospermum, Microcystis spp.
• Skin irritations were a frequent symptoms found in an epidemiological study by
Pilotto et al (1997).
• Microcystins: Microcystins produced by Microcystis aeruginosa., Microcystis
viridis., Aphanizomenon flos-aquae., Oscillatoria
haplosporium and Anabaena species are associated with Microcystins.
• M.aeruginosa are most frequently associated with the algal blooms and
associated with hepatotoxicity.
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