Phycology and economic importance of algae

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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 Neurotoxins are produced by different genera of Cyanobacteria
including Anabaena sp, Aphanizomenon sp, Microcystis sp, Planktothrix sp, Ra
phidopsis 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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 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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