Essay: Seaweed ( macroalgae): an omnipotent source for sustainable life – a review

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  • Seaweed ( macroalgae): an omnipotent source for sustainable life - a review
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abstract
the consequent reduction of land resources by human activities such as pollution, over exploitation,
industrialization, migration etc has lead man to search for other alternative ways to meet the demands for
well being. when this has been the existing situation in most of the developing countries, marine resources
like seaweeds which are known for its potentially strong bioactive compounds can be the best fit to fulfill
numerous requirements such as nutritious food, biofuels, biofertilizers, pharmacueticals to cure different
diseases and other industrial applications. besides many research works done regarding seaweeds this review
provides thorough knowledge about the potentials and wide range applications of seaweed, a marine
macroalgae.
key words: seaweed , compositional variation, free radical scavenging, seaweed polysaccharides ,
apoptosis induction, seaweed nanoparticles.
contents
1 introduction
1.1 morphology and diversity
1.2 occurrence and distribution
1.3 cutivation and harvesting
1.3.1 red algae
1.3.2 brown algae
1.3.3 green algae
2 biochemical composition
3 properties
3.1 antioxidant activity
3.2 anticancer activity
3.3 antimicrobial activity
3.4 antiviral activity
3.5 anti inflammatory activity
4 applications of seaweed
4.1 biofuels
4.1.1 bioethanol
4.1.2 biodiesel
4.1.3 biogas
4.1.4 biobutanol
4.2 polysaccharides of seaweeds
4.2.1 agar
4.2.2 alginates
4.2.3 carrageenan
4.2.4 fucoidan
4.2.5 laminarin
4.3 pharmaceutical application
4.4 seaweed nanoparticles
4.5 seaweed in waste water treatment
4.6 seaweed as beauty promoters
4.7 seaweed as animal feed
4.8 seaweed as biofertiliser
5 economic importance
6 conclusion
acknowledgements
reference
1.Introduction
seaweed which is a macroalgae seen in various form , color and occur along the coastal line in marine
habitat and indian as a peninsular nation has got wide distribution of seaweeds compared to other countries.
several harvesting techniques and cultivation methods for red, brown and green algae were in practice
depending upon the species and other environmental factors. the biochemical components of seaweed such
as carbohydrates, proteins, vitamins, fat, mineral are numerous and their composition experiences seasonal
variation. the various compounds such as sulfated polysaccharides , fucoxanthin, carrageeanans, agarans,
terepenoids etc and organic extracts such as methanolic, ethanolic and butanolic extracts of different
seaweeds posses antioxidant, antiviral , antinflammatory, anticancer activity against various pathogens and
diseases. seaweed compounds extracted and processed are being used as various biofuels.
1.1 Morphology and diversity
‘algae have a great variety of forms, sizes and colors. some are simple colonies with many cells; some are
filamentous, tubular, meshed, membranous or saccate algae. some are more delicate and complex, such as,
sargassum having structures similar to roots, stems and leaves of plants as well as differentiated air bladders
which help the algae floating to water surface to be able to absorb more sunlight. nevertheless, although
algae may have different forms, their internal structures are composed of similar cells with simple
differentiation instead of true roots, stems or leaves. seaweeds are grouped into three based on colour:green
algae (chlorophyta), brown algae(phaeophyta),red algae(rhodophyta),blue-green algae (cyanophyta) which
are being harvested and utilized for several purposes[1]. the thallus(the algal body),lamina or blade(a
flattened leaf-like structure), stipe(a stem-like structure) , holdfast(a basal structure provides attachment to a
surface) forms the parts of a seaweed which is shown in the figure 1.
1.2 Occurrence and distribution
in india it has been reported that there are 271 genera and 1153 species of marine algae found along
indian coast. seaweed is particularly available in abundant in three areas: the worm northern waters around
the kermadec and three king island, the cook straight kaikoura coast region in central new zealand and the
south in an area encompassing fiordland,stewart island and the otagocoast[2]. the figure 2 & 3 [3] shows the
different kinds of species distribution that includes chlorophyta, phaeophyta, rhodophyta and cyanophyta
across various coastal lines in the world. india has got the maximum number of species along her coastal
line compared to other countries. as far as indian coastal line is concerned tamilnadu has recorded the
maximum number of species and distribution varies according to species.
1.3 Cultivation and harvesting
the physical, chemical and biological parameters should be investigated before cultivation. apart from
this, the general environmental factors that influence the cultivation and harvesting processes are location,
water and land quality, fauna, climatic factor, marketing accessibility, farm management operations,
industrial and domestic pollution. depending upon the properties and natural environment of individual
seaweed species or species in groups , the harvesting methods are selected. the seaweed culture methods that
are in practice are off-bottom method, raft method, horizontal culture method, mixed culture method, long
line method[slide 111]. it is noted that the major problem faced by the seaweed industry is the lack of
efficient harvesting technique. let us see the viable harvesting that has been used from the past.
1.3.1. Red algae
the culturing method varies between species to species and for instance the red algae are generally seen
in deep waters and are much smaller in size compared to the brown algae. in addition, the harvesting of red
algae is expensive and involves complexity and it was reviewed that two planting techniques were
commonly used for red algal farming. one is the direct method that involves the direct burial of the thalli
into the sandy bottom using different types of tools and the other is the plastic tube method which
consists of fastening bundles of thalli to plastic tubes filled with sand, which anchor the algae to the sea
bottom [4]. it was estimated from the experience gained from subtidal farms that hand-pulling of thalli has
given more production rather than the use of tools[5]. mechanized harvesting that uses power-driven barges
equipped with reciprocating underwater mowers(cropping vessels) were used for cultivating macrocystis
that grows in large beds. similar cropping equipments were used to harvest ascophyllum species which
grows at high tide (booth, e., in firth, 1969) [6].
1.3.2 Brown algae
the predominant species porphyra yezoensis, porphyra tenera grow in the inner parts of estuaries and
bays and can survive in high salt conditions whereas porphyra pseadolinearis grows in the deeper waters.
the concochelis ‘spore culture technique was used to cultivate these porphyra (nori) species[7]. the rope
cultivation and stone techniques??were used in japan to cultivate the brown alga undaria or ” wakame”. the
“collector strings” that are hung in the water for the sporophytes of undaria to grow and tanks were used for
seedling. as an expansion of past technique,along with natural beds a new substrate of rocks exploded with
dynamite was also used to grow undaria. (tamura, 1966).[8] production of hybrid varieties of undaria was
also made possible by crossing closely related species. (saito, 1971)[9]. to harvest laminaria that grows only
on hard, rocky ocean bottoms , reciprocating cutters mounted on dredges or a system of continuous grapnels
were used and the development of techniques for cutting the normal 2-yr growth period to harvest down to 1
yr was researched to increase the production (hasegawa, 1972).[10]it was reported that in norwegain coastal
area the sugar kelp saccharina latissima was cultivated by integrating with salmon((salmo salar)
aquaculture and the growth was seemed to be good in late autumn and in spring[11].
1.3.3 Green algae
green algae may be found in marine or freshwater habitats, and some even thrive in moist soil. the
green macro algae were cultivated in outdoor tanks and the biocrude was obtained through hydrothermal
liquefaction in batch reactor[12]. also, the green algae were cultivated in ponds, open lagoons and in cages.
it was reported that the oedogonium species has given the maximum yield followed by derbesia , ulva
species[13].
?? 2. Biochemical composition
the composition of seaweeds varies depending upon season ,density and other environmental factors.
compared to vegetables , fruits, pulses and cereals, seaweed records the maximum content of carbohydrates,
proteins, vitamins ,minerals, fat, fibre, ash, moisture. earlier work has revealed that the different species
gathered from similar area, family, environmental factors showed greater variations with respect to their
elemental composition[22]. also it has been observed that red seaweed contains thirty times more potassium
than bananas, 200 times more iron than beetroot, the nori seaweed constitute twice the protein than meat
and the hijiki seaweed contains twice the amount of calcium compared to full-cream milk. further ,it was
noted that 15,000 novel compounds were chemically determined and algae are considered to be the
predominant source for novel biologically active compounds that is required for human nutrition[57]. while
seasonal variations are of great concern, it was showed that the phaeophyta and rhodophyta recorded the
maximum biomass during summer, and cholorophyta was maximum during autumn season[20]. the table 1
shows the composition of some commercially important seaweeds.
3. Properties
it was reviewed that seaweeds are rich in bioactive compounds that promotes and some of the species
to say are. laminaria species., fucus species., ascophyllum nodosum, chondrus crispus, porphyra species.,
ulva species., sargassum species, gracilaria species. and palmaria palmate [85]. since chemical
preservatives were proved to cause deleterious health hazards like cancer, asthma etc seaweeds have been
known to be the safe and promising replace as food additives that has antimicrobial , antioxidant
properties[86]. also it was identified that many secondary metabolites from the marine source with
effective antibacterial, antifungal and antiviral activities which are being used as antibiotics and drugs to
treat various infectious diseases[87]. and bioactive compounds of marine macro algae are known to have
diverse mechanism of action against diseases. in addition to this ,red ,brown and green macro algae were
detected to contain compounds with cytostatic, antiviral, antihelminthic, antifungal and antibacterial
activities [88].
3.1 Antioxidant activity
algae are antioxidant in nature because of their non enzymatic antioxidant components
reducedglutathione(gsh),ascorbicacidalphatocopherol,betacarotenoids,flavonoids,hydroines,pycocyanin,proli
ne,mannitol,myoinosi-tol,phenolics,polyamines[89].the antioxidants can inhibit the intiation of the
oxidative chain reaction and thus prevent cell damage caused by =reactive oxygen species (ros)[90]. the
antioxidant molecules can destroy free radicals by donating hydrogen atoms or by electron donation . in
most of the cases dpph had been used as a free radical to evaluate reducing substances rather than nitric
oxide, deoxyribose , hydrogen peroxide, abts. the dpph radical scavenging activity was evaluated using an
esr(electron spin resonance) spectrometer.[91]. from the earlier works done it was reported that the
extracts of species such as hijika fusiformis, cladosiphon okamuranus, undaria pinnatifida, and sargassum
fulvellum were known to possess effective dpph radical scavenging activity [93,94]. also carotenoids have
radical scavenging which helps to keep up health and in prevention of disease whereas fucoxanthin has
been reported to effectively scavenge chemically-generated free radicals like dpph[95,96]. based on
quenching rate constants it was shown that the radical scavenging activity of fucoxanthin and its metabolite
fucoxanthinol were higher than that of ??-tocopherol and lower than ??-carotene[97]. fucoxanthin(fx) , an
orange colored carotenoid belonging to non pro-vitamin carotenoids which is also known as xanthophylls
are present in edible brown seaweeds such as undaria pinnatifida , hijikia fusiformis , laminaria japonica
and sargassum fulvellum possess significant antioxidant activity [102,103]. sulfated polysaccharides(sp)
are the compounds found in the extracellular matrix of seaweeds that has got antioxidant property and the
well known sp are carragenans , agarans, xylase, galactose, mannose, fucan, fucoidan[99]. based on the
rheological behavior ,the polysaccharide content and the methanol extract of red algae gracillaria biridae
and gracilaria verrucosa were reported to posses antioxidant property[100,101]. further it was noted that
the water extract of laminaria species had higher antioxidant activity than its ethanol extract[92]. thus high
levels of oxidative stress leads to many harmful diseases such as atherosclerosis, parkinson’s disease,
alzheimer’s disease, acute myocardial infarction, chronic fatigue syndrome and fibromyalgia. fx was
estimated as an effective tool to prevent and treat these diseases[98].
3.2 Anticancer activity
cancer being a fatal disease has become a major health problem worldwide mainly because of
bad food habits. the conventional chemotheraphy or radiotheraphy treatment to control tumors and reduce
the risk of mortality rates has resulted in other ill-effects such as long term side effects, destruction of
healthy tissues etc. several types of carcinomas such as prostate cancer, leukemia, colon cancer, breast
cancer, liver cancer, melanoma, lymphoma are in existence[104]. in a quest to cure and uproot cancer,
seaweeds were identified as the best source that has antitumor properties. the seaweed compounds or
extracts undergo several types of mechanisms against the cancer cells and some of them are apoptosis
induction, inhibition of tumor invasion, hyaluronidase activity inhibition., anti-angiogenic activity.
regulation of mammary gland integrity[105]. polysaccharides present in the cell wall of macroalgae
contain immunomodulatory and anticancer effects and are most considered in the medical areas of
study[106]. sulfated polysaccharides from brown species viz., sargassum, laminaria, ecklonia inhibited
growth of sarcoma-180 cells and acted as antitumor against l-1210 leukemia.[107-109]. further fucoidan or
fucose containing sulfated polysaccharides(fcsp) and mapk(mitogen activated protein kinase) along with
fcsp in brown seaweeds found to enhance and augment macrophage mediated immune signaling molecules
production and thereby induced apoptosis[110]. breast cancer ranks the second most common cancer in the
world and is the major cause for mortality in women[111]. as a remedy for this ,the methanol extract of
sargassum muticum activity against proliferation of breast cancer cell lines were evaluated for its apoptosis
property[112]. also the combination of seaweed porphyra dentate , ??-sitosterol and campesterol was
known to reduce the tumor size considerably[113]. nextly the colorectal cancer which affects both men and
women , their cancer cell lines proliferation could be inhibited by the extracts of laminarian species and
ulva faciata by apoptosis induction mechanism[114-116]. further more based on dosage the anti tumor and
anti metastatic activities of fucoidan isolated from fucus evanescens were studied. alginates and palmitic
acid from the species sargasum vulgare(brown algae) and amphiroa zonata (red algae) were also reported to
posses antitumor property[117,118].
3.3 Antimicrobial activity
The antimicrobial activity mainly depends upon the algal species taken and the extraction method followed.
the antimicrobial compound extracted from a biological source is generally by means of attacking the cell
wall and cell membrane of the target organism. further it disrupts the electron transport chain , coagulates
protein and nucleic acid synthesis[119]. among seaweed species the ethyl acetate extracts of sargassum
species have strong antimicrobial activity against bacteria and fungi than the water extract and the activity is
due to the presence of meroterepenoids[120]. the brown alga stoechospermum marginatum was active
against bacterial strains klebsiella and vibrio cholerae whereas the green alga cladophora prolifera was
bacteriocidal against saccharomyces aureus and vibrio cholera [121,122]. it was found that the extracts of
red algae gracilaria fisheri inhibits the pathogen vibrio harveyi which affects the shrimp population [123].
also the butanolic extracts of the seaweeds ulva lactuca and sargassum wightii exhibited considerable
inhibition zone against the shrimp pathogen vibrio parahaemolyticus[124]. the phlorotannins of ascophllum
nodosum was more active against the escherichia coli strain than the condensed or terrestrial tannins[125].
the dichloromethane extracts of several seaweed has showed significant antibacterial action against fish
pathogens such as asparagopsis armata , falkenbergia rufolanosa [126]. the dimethyl sulfoxide(dmso)
extracts of seaweed species and their antiprotozoal activity against plasmodium species has been studied and
the selectivity index was the parameter used to evaluate the activity[127] . the same dmso extract of
sargassum longifolium showed inhibitory activity against various bacterial strains whereas the acetic acid
extract showed maximum inhibition against proteus species and minimum activity against streptocccus
species [128]. the antifungal activity against phythium phanidermatam and colletotrichumcapsici was
maximum in ulva fasciata [130]. ultimately nanoparticles which is the most welcomed compound because
of its size and viability was found to be extracted as silver nanoparticles from ulva lactuca by agar well
diffusion method and it was analysed for its antibacterial activity[129].
3.4 Antiviral activity
Aids is a fatal disease caused by human immunodeficiency virus (hiv) which belongs to retro virus family
and has no effective treatment till date. the antiviral activity of seaweeds depends on the dosage and time.
apart from other causes the herpes simplex virus (hsv-1) and hsv-2 which causes infection in mouth ,face
and genital area was also identified as a major risk factor for human immunodeficiency virus(hiv)[131,132]
and the antiviral activity against these virus has been conferred with sqds(sulfoquinovosyldiacylglycerol)
fractions extracted from sargassum vulgare[133]. also the bioactive alginates from sargassum species has
antiviral property and it was studied that the extracts of this species acted against the viruses human tcell
lymphotropic virus type1(htlv1) and human immunodeficiency virustype1(hiv-1)[134-136]. the fucoidan
polysaccharide was against hiv and human cytomegalovirus (hcmv) while its derivative galactofuran
extracted from the seaweed adenocystis utricularis showed inhibitory action towards the retro viruses (hsv)
1 and 2[137]. further the diterpenes isolated from the dictyota species exerted antiviral action and
galactofucan sulfate extract from undaria pinnatifida worked against hsv-1, hsv-2 and hcmv( human cyto
megalovirus)[138,139]. considering plant viruses the seaweed polysaccharides such as fucans, laminarin,
alginates , ulvans obtained from fucus vesiculosus, laminaria digitatum, lessonia species, ulva species
respectively, when injected into tobacco plants , protected against tobacco mosaic virus(tmv) by inducing
jasmonic acid (ja) and salicylic acid(sa) signaling pathways[140].
3.5 Anti inflammatory activity
the inflammatory response is an auto defensive mechanism that is met with huge leukocyte production and
the inflammatory reactions are generally due to the presence of ros , nitric oxideand other factors which
results in tissue damage[142]. caulerpin an alkaloid extracted from caulerpa racemosa was found to exhibit
anti-inflammatory properties[143] and this compound act by suppressing the antigen , histamine secretion ,
lymphocyte and natural killer cell proliferation[141]. the sulfated polysaccharides play a major role in
treating inflammation. also it was demonstrated that the fucans of fucus species ,laminarian species on
injection into rats reduced the peritoneal inflammation by leukocyte inhibition[144]. the ulvan
polysaccharides of ulva rigida also exerted anti inflammation by reducing immune stimulation[145]. the
fucoxanthin from seaweeds was active against inflammation and allergic reactions by degranulating the mast
cells which secretes histamine[146]. it is noted that the carrageeanan produced from eucheuma or chondrus
or hypnea species was used to analyse anti-inflammatory activity[147].
4. Applications of seaweed
4.1.Biofuels
after cultivation and harvesting, the macroalgal biomass must be pre-treated for most biofuel.applications.
the first step of pre-treatment is to remove foreign objects and debris such as stones,sand, snails, or other
litter that may be caught in the biomass either manually or by washing in many cases, chopping or milling is
then required to increase the surface area/volume ratio [148[19]].finally, the biomass should be dewatered to
20%’30% to increase shelf life and reduce transportation costs in situations where it must be stored for long
periods or transported over long distances before further processing.the principal energy process considered
for seaweed is fermentation, either anaerobic digestion (ad),to create biogas, or ethanol fermentation. other
thermochemical options for macroalgae utilizationinclude direct combustion, gasification, pyrolysis and
liquefaction. [149][18] for better understanding about the production of biofuel from the algal biomass is
made through the figure.
4.1.1 Bioethanol:
generally, bioethanol is produced from wood, grasses, and other inedible parts of plant but it is a tedious
process to make sugar monomers. in order to overcome this, marine algae can be used as source for
bioethanol production. algae contain large quantities of carbohydrate biomass and high photon conversion
efficiency for bioethanol production[150][4][151][5]in addition, marine algae has buoyant property which
can simplify the process of bioethanol production by neglecting the pre-treatment steps[152][6]it is noted
that in japan they use 4.47 million sq.km for harvesting sargassumhorneri for bioethanol
production[153][7]ulvareticulataa macroalgaewhich can grow quickly was said to posses the potential to
produce bioethanol [154][2].it is reported that other species such as padina japonica, sphacelariarigidula,
dictyosphaeriacavernosa, sargassumpolyphyllum have appreciable dry weight content [155][3].brown
seaweed laminariahyperboreahas high amount of soluble carbohydrate[156][8] bioethanol from algae was
known to reduce greenhouse gas emission by 85% over reformulated gasoline[157][1]
4.1.2.Biodiesel:
biodiesel can be made from oils within the algae and it is noted that the macroalgae contains oil with in its
cell. there are different varieties of macroalgae which contain oil once grown, the oil is removed from the
macroalgae using chemicals or by squeezing oil out of the cells using scientific equipment. then the oil is
used as an ingredient in biodiesel. this oil is changed chemically from plant oil to biodiesel. the finished
product can be used on its own as pure biodiesel but is normally mixed with ordinary diesel and used
directly in cars.biodiesel is an alternative biodegradable energy source which has less co2 and no emission
[158][9]. oil extraction from algae and transesterification process are the two major steps involved in
biodiesel production and the brown seaweed ascophyllum nodosum has high oil content compared to the
species such as sargassum, codium,ulva ,enteromorpha[159][10]
4.1.3.Biogas
seaweeds can be subjected to anaerobic digestion for the production of methane gas it was estimated that
the methane yield from anaerobic digestion of seaweed was 0.12 n/ch4/g[160][11] saccharina latissima is a
brown seaweed rich in carbohydrate was anaerobically digested for biogas production.it was reported that
two process parameters such as steam explosion and thermal pretreatment method for biomass degradation
seemed to affect the biogas yield in general the brown algae are more easily degraded than the green algae,
and the green are more easily degraded than the red. [161][12] anaerobic digestion has been the most
efficient method for the production of biogas rather than fermentation and thermal treatment[162][13] the
biogas yield from certain species viz ,saccorhiza polyschides, ulva species, laminaria digitata, fucus
serratus and saccharina latissima,are discussed in the following table 3[163][16] despite the variations in
the quantity and material ratios, the ratio between the methane produced and the input chemical oxygen
demand was reported to be stable[164][17]
4.1.4.Biobutanol
butanol is a very competitive renewable biofuel for use in internal combustion engines and has been a boom
to mankind. while comparing fuel properties it indicates that n-butanol is potent enough to remove the
drawbacks brought by low-carbon alcohols or biodiesel. the applications of butanol as a biofuel are
considered as three aspects, and they are as combustion experimentors in some well-defined burning
reactors, as gasoline in spark ignition engine, as diesel fuel in compression ignition engine. from these
demonstration that butanol is estimated effective as a second generation biofuel, from the viewpoints of
combustion characteristics, engine performance, and exhaust emissions[165][20] ulva lactuca was
considered as the reserve species for acetone butanol ethanol (abe) fermentation.[166][14]the fermentation
done with the bacterial strains such as clostridium beijerinkii , clostridium saccharoper butylacetonium and
the algal carbohydrate resulted in the production of biobutanol.the yield and the concentration of biobutanol
obtained from media were 0.29g butanol/g sugar and 4g/litre respectively.[167][15]
4.2. Polysaccharides of seaweed
seaweed polysaccharide is known for their varied functions and structures. they constitute natural sugars
and sugar acids similar to land plants and in animals polysaccharides. as three polysaccharides contain
hexose sugar, glucose, galactose and mannose, they have identical chemical formula, shape, properties and
specific atomic orientation.[168][32]
4.2.1 Agar
agar is the most ancient phycocolloid found in japan and discovered by minoya tarozaemon in 1658 and first
time manufactured in monument.[169][23] agar is the major component of the cell-wall of certain red algae
,which are the members of families gelidiaceae,gelidiellaceae and gracilariceae.[170][21]agar consists of a
chain of 9-p galactopyranose units linked in 1,4 bonds with a sulphated l.galactose.in order to increase the
yield and gel strength of agar, an alkaline treatment was done with sodium hydroxide for nearly one hour at
the rate of 2 to 3 % alkali solution of 20,000 1/tonne at 90??c .[171][22]also the sun-bleached seaweed was
washed well in water and soaked for 24 h and then ground to a pulp and rinsed again in water.and then the
pulp was then extracted with water under pressure for 2 h after bringing the ph to 6 by adding of acetic acid.
the agar gel was subjected to freeze thawing and bleached with naclo before drying in a current of hot
air.??[172][25] it is insoluble in cold water but soluble in boiling water. when agar was cooled to 34-43??c it
forms a firm gel and does not melt further below 85??.[173][24] in food technology agar is used as gelling
and thickening agent in the confectionary and bakery industries, as stabilizer in the preparation of cheese
and for salad dressings. in fish and meat industry, agar is applied for canned products, as a protective coating
to avoid shaking during transport of these products. the agarose polycolloid play a prominent role in the dna
research and gel electrophoresis further agar is widely used in pharmaceutical industry as laxatives as drug
vehicle and as a medium for bacterial and fungal cultures. and also used as an ion exchanger in the ion
exchange resins [174][26]
4.2.2 Alginate:
algin or alginic acid is a membrane mucilage and a major constituent of all alginates and the trade name is
for sodium alginate.. alginic acid is obtained from brown seaweed species such as
ecklonia,macrocysiis,undaria, laminaria and duruillea from temperate area and turbinaria,sargassum, cysto
seira and harmophysa from the tropical areas. Alginic acid which is the major polysaccharide of the brown
seaweeds consists of unbranched chains comprising of contiguous fl-l,4-1inked d-mannuronic acid and
blocks of contiguous e-l,4-1inked l-guluronic acid [175][33]. the proportions of d-mannuronic acid and l-
guluronic acid varies between different species and from different parts of the same weed [176][34]
alginates are found in both the intercellular region and the cell walls and it does biological functions
structural and ion exchange type. also it was extracted from the spices laminaria digitata by alkaline
extraction protocol[177][31][178][35].the molecular weight of alginate ranges generally between 500 and
1000kda [179][27] as discussed earlier the alginate composition of different seaweed species are
ascophylum nodosum, (22’30%); laminaria digitata fronds (25’44%); laminaria digitata stipes( 35’47%);
laminaria hyperborea fronds( 17’33%); laminaria hyperborean stipes, (25’38%) [180][28] alginate
contents ranges between 17 and 45% are extracted in sargassum species. [181][29]. in industries the
alginates are extracted from brown seaweed sargassum turbinarioides by cutting the thallus with a knife
near the rizoid and the algae were washed and sun- dried at ambient temperature and stored in aerated bags.
[182][30] japanese work on the brown seaweed has revealed that alginate is subjected to polymerization in
the cytoplasm and then transported to the cell surface.[183][36] it has observed d-mannuronic acid
precursor of polymannuronic acid that while separating from the brown seaweed, fueus gardneri in young
tissue. they identified the presence of trace quantity of a gdp-guluronic acid[184][37]. further on extracting
epimerase from pelvetia canaliculata the convertion of polymannuronic acid into a mixed poly-d-
mannuronic-l-guluronic polymer has been witnessed by tritium incorporation[185][38] in beverages
alginates acts as clarifying agents for making wines and liquor where as it acts as foam stabilizer in leger
beer and malt beer.[186][39].artificial casings are made with alginates as poses to ensure longer shelf life in
sausage undustries and it alginates are used in the form of gel for deep freezing of fish, meat and poultry
products in western countries [187][40]
4.2.3 Carrageenan
carrageenan is a sulphated polymer obtained from various red seaweeds and it differs from agar in its high
sulphate and ash content.. the major difference between the agars and carrageenan is that the former contains
d- and l-galactose units whereas the latter consists entirely of the d-sugar.[188][32] they are commercially
important hydrophilic colloids present in the matrix of red seaweeds (rhodophyta) and does structural
function also they are considered as high sulfated galactans and as strong anionic polymers[189][41].
seaweed species kappaphycus and eucheuma chondrus crispus,gigarttna stellate,iridaea,hypnea species
have high content of carrageenan. [190][42] carrageenan can be recovered to either by direct drying on
steam-heated rolls or by precipitation of the carrageenan from solution by 2-propanol or other alcohols. it is
to be noted that in the past alcohol precipitation method was used to recover carrageenan from irish moss.
[191][43] commercially three types of carrageenan are available they are??kappa-,??iota-, and??lambda-
carrageenan. furcellaran which is similar to kappa carrageenan a preferred product for use in milk pudding
powders.[192][44] the iota-carrageenan is used in dessert gel formulations affords gels.,where as lambda
carraaginan is being and used to thicken dairy product. in food industry,carrageenan is also being used
bakery, confectionery and in culinary works. carrageenan is also called ‘painters’because because of its
wide range use in paint manufacturing and in stabilising pigments carrageenan gel beads are the excellent
media for enzyme entrapment which in turn catalysis the synthesis and conversion processes.
4.2.4 Fucoidan
fucoidan??is a??sulfated??polysaccharide found mainly in various species of’? brown??seaweed??and ??fucoidan is
used as??dietary supplements.[193][46]fucoidan is class of sulfated, fucose rich, polysaccharides found in the
fibrillar cell walls and intercellular spaces of brown seaweeds. fucose-containing sulfated polysaccharides
(fcsps) consist of a backbone of (1’3)- and (1’4)-linked ??-l-fucopyranose residues, that may be organized
in stretches of(1’3)-??-fucan or of alternating ??(1’3)- and ??(1’4)-bonded??l-fucopyranose
residues.??[194][45]apart from fucose and sulfate groups fucoidans also contain galactose, xylose, mannose
and other uronic acid.[195][47][196][48][197][49]fucoidan was extracted using dilute acetic acid from
various species of??laminaria??and??fucus??[198][59]. fucoidans were reported to possess various biological such
as anti-inflammatory, anticoagulant, antithrombotic [199][50][200][51], antiviral including anti-hiv
[201][52][202][53], immunomodulatory [203][54], antioxidant [204][55], and antitumor [205][56]. fucoidan
from laminaria species were found to inhibit a variety of dna and rna enveloped viruses and also useful in
elucidation of mammalian sperm and egg [206][57] the “fucan” extracted from pelvetia canaliculata had a
very strong affinity for magnesium which in turn can assist the contact of their fronds with seawater. it was
also studied that pelvetia canalieulata, since grows on the higher part of the shores have a high “fucan”
content.[207][58]
4.2.5 Laminarin
??laminarin?? is a storage??glucan?? found in??brown algae and is used as a carbohydrate food reserve similar to
diatoms.[208][60] laminaran is ??-glucan it induce anti-apoptotic and anti-tumoral activities[209][61] this is
a water-soluble polysaccharide containing approximately 20-25 glucose units. it has two types of chains
namely , g-chains terminated at the reducing end with glucose and m-chains terminated by mannitol
[210][62] in addition the laminaran, , from eisenia bicyclis, may contain 1,6-1inked units in the chains, or
the chains may be branched at c-6.[211][63] it was that the mannitol and laminaran are active metabolites
which can be interconverted[212][64]. have shown that laminaran isolated from the cytoplasm of developing
zygotes of fucus species decreased during the first 7 hours of wall assembly while the content in cellulose in
the wall increased laminarin structure and composition vary according to algae species[213][65] based on
the degree of polymerization the molecular weight of laminarin has been found as 5000da approximately
[214][66]
4.3 Pharmaceutical application of seaweed
seaweed has been the most inspired bioresource as far as pharmaceuticals is concerned and pharmaceutical
interest. because of the high nutrient content, seaweed has been used as food throughout asia japan china
rome to treat various health disorders. the romans used seaweed in the treatment of wounds, burns, and
rashes [215][67] in scotland physicians used dried seaweed stem to drain abdominal wall abscesses and they
also inserted seaweed into the cervix to treat dysmenorrhea.??seaweed was also employed intravaginally for
vaginal atresia and was used urethrally and rectally for strictures [216][67][217][68][218][69] traditional
chinese medicine includes use of the brown alga laminaria in the treatment of cancer. the ancient egyptians
used seaweed to treat breast cancer. Seaweeds are being extensively used in cardiovascular conditions as it
can reduce cholestrol level. in general alginates from seaweeds has been used in wound dressings and as
fillers in tablets ,pills and as ointment base whereas seaweed carrageenan acts as good emulsifiers in
mineral oil and drug preparations. saccharina japonica and undaria pinnatifida was analysed to contain
fucoidan which can destruct cancer cells. also complete wipe out of cancer cells by fucoidan treatment has
been demonstrated in japan. it is noted that cancer mortality rates and breast cancer rates are considerably
low in japan because of seaweed consumption??[219][70]&[220][71]. seaweed extracts being a source of
calcium, magnesium, selenium and other minerals has been evaluated to treat
osteoarthritis[221][72]&[222][73]. and it was reported that intake of seaweed powder 5g/day ,12g/day and
4-6g/day in diet controls cholesterol , hypertension , metabolic syndrome respectively[223][74]&[224][75].
iodine rich seaweeds like asparagopsis tcudjirmis, sarconema species was reported to cure
hypothyroidism(goitre). also seaweed extracts was known to stimulate b lymphocytes and macrophages that
in turn modulates immune response[225][79]&[226][80].
4.4 Seaweed nanoparticles
algal nano particles are known as bio nano factories as they are highly stable, easy to handle and avoids cell
maintenance. added to this, metal nano particles from seaweed have excellent potential in biomedical
applications[227][81]. benign nanoparticle synthesis which is nontoxic has been an emerging trend in
todays world[228][78]. ecofriendly gold nanoparticles synthesized from turbinaria conoides was confirmed
to be associated with carboxylic, amine, and polyphenolic groups by fourier transform-infrared
spectroscopy [229][77]. green seaweed caulerpa peltata, red hypnea valencia , brown sargassum
myriocystum seaweeds were used to synthesize zinc oxide nanoparticles and they can be used in effluent
treatment process to reduce microbes.[230][82]. silver nanoparticles from sargassum tenerrimum along
with the presence of phytochemicals as reducing agents was foung to have excellent antimicrobial
activity[231][83]. further report identified that fe3o4 nanoparticles obtained from sargassum muticum
which contain sulfated polysaccharides as the reducing agent was determined to have antimicrobial
potential, stabilizing capacity and this on fabrication came out with other metal oxides[232][84].
4.5 seaweed in wastewater treatment
the two major areas of waste water treatment in which seaweed has its prominent role to play are one is to
treat sewage and agricultural wastes to exploit nitrogen- phosphorous wastes and the other is to remove toxic
metals from industrial effluent and it was suggested to be a boon in coastal areas[233][85]. alginates
extracted from the seaweed sargassum sinicola??was used to co-immobilize the microalgae chlorella
sorokiniana??and the bacterium azospirillum brasilense which promotes growth to be employed in waste
water treatment[234][86]. seaweeds were used in wastewater treatment because of its ability to absorb
nutrients and heavy metal ions that are toxic. also seaweeds were suggested as biological indicator of marine
pollution like eutrophication on considering its capacity to take up ammonia in the nitrogen form and
phosphorous. despite varying concentration and type seaweeds such as sargassum,??laminaria??,??ecklonia,
??ulva and??enteromorpha were identified as indicators of heavy metal pollution[235][87].
4.6 seaweed as beauty promotors
seaweeds possess potentials to stimulate blood circulation and revitalize , nourish and eliminate toxins of the
skin. seaweed bath is one such instance that has been in practice in ireland with fucus serratus species
promoted to treat rheumatism and arthritis. also all the required nutrients, aminoacids and oils were found to
be absorbed by the skin in seaweed bath[236][89]. an irish company has been established to produce
seaweed powder from ascophyllum nodosum for the cosmetic and algotheraphy and it was said to improve
damaged hair by means of ionic interactions with the proteins of hair[237][90]. also seaweeds enzymes were
found to heal dandruff and stimulate hair follicles for hair growth[238][88]. silicon from seaweeds were
analysed to have anti- wrinkle effect on facial skin and other anticellulite preparations from seaweeds has
been used in the form of creams and lotions for hip, thigh and neck[239][89].
4.7 seaweed as animal feed
to produce seaweed meal for use in animal feed, brown seaweeds are collected,dried, and milled. because it
contains large amount of protein and carbohydrates. in norway, where seaweed meal has been produced for
animal feeds since the 1960s,and also the usage of seaweed for animal feed by european for horses and it
was fed regularly to domestic animals in iceland, france, and norway. [240][95]
seaweed meal is considered to have 30 percent??of the nutritive value of grains. seaweed meal can be added
to poultry diets in a ratio of up to 5 to 15 percent??of the diet, depending on the species of seaweed and the
species and age of the animal. another main use of seaweed in the diet is as a pellet binder including
seaweed as up to 3 percent??of the diet improves the hardness of the pellet. with duck diets, brown seaweeds
can be included as up to 12 percent of the starter diet and up to 15 percent of the finisher diet without
adversely affecting growth performance of animals or meat quality. in addition, to that feeding seaweed
meal and sardine oil together to chickens results in reduced levels of egg cholesterol and increased omega-3
fatty acid levels with no adverse effect on taste.besides seaweed meal, other forms of seaweedalso can be
beneficial to animals. for example, intactof brownseaweed,likeascophyllumnodosum, as well as seaweed
extracts, have been used to promote prebiotic activity in pigs. prebiotic compounds are indigestible
compounds that induce the growth and activity of beneficial microorganisms in the digestive tract. growth
or activity of these microorganisms, in turn, has health benefits for the animal.
for a long time, animals such as sheep, cattle and horses that lived in coastal areas have eaten seaweed,
especially in those european countries where occupied with large brown seaweeds were washed ashore.
today the availability of seaweed for animal feed has been increased with the production of seaweed meal
,dried seaweed that has been milled to a fine powder. norway was among the early producers of seaweed
meal, using??ascophyllumnodosum,becauseascophylllumnodosum contains the large amount of nutritive
value it has been said in topic of biochemical composition early in this review and it also provided ascorbic
acid, tocopherols, a suite of b-vitamins, and mineral elements including iodine to chickens, hogs, sheep, and
dairy cows[96]and also ascophyllum??is so accessible, it is the main raw material for seaweed meal and most
experimental work to measure the effectiveness of seaweed meal has been done on this seaweed. the
seaweed used for meal must be freshly cut.the wet seaweed is passed through hammer mills with
progressively smaller screens to reduce it to fine particles. these are passed through a drum dryer starting at
700-800??c and exiting at no more than 70??c.a seaweed that grows in the eulittoral zone so that it can be cut
and collected when exposed at low tide.??france has used??laminariadigitata, iceland
both??ascophyllum??and??laminaria??species, and the united kingdom.when compare to other species
ascophyllum is wieldy used species for animal feeding ,and we already discussed some of the main features
of ascophyllumin addition to that
analysis shows that it contains useful amounts of minerals (potassium, phosphorus, magnesium, calcium,
sodium, chlorine and sulphur), trace elements and vitamins. trace elements are essential elements needed by
humans and other mammals in smaller quantities than iron (approximately 50 mg/kg body weight), and
include zinc, cobalt, chromium, molybdenum, nickel, tin, vanadium, fluorine and iodine. because most of
the carbohydrates and proteins are not digestible, the nutritional value of seaweed has traditionally been
assumed to be in its contribution of minerals, trace elements and vitamins to the diet of animals.
ascophyllum??is a very dark seaweed due to a high content of phenolic compounds. it is likely that the protein
is bound to the phenols, giving insoluble compounds that are not attacked by bacteria in the stomach or
enzymes in the intestine.??alariaesculenta??is another large brown seaweed, but much lighter in colour and it
also a wieldy used seaweed species some experimental trials said that it has been found to be more effective
than??ascophyllum??meal. but it is lack of protein digestibility that is a distinct drawback to??ascophyllum??meal
providing a useful energy content.??in preparing compound feedstuffs, farmers may be less concerned about
the price per kilogram of an additive; the decisive factor is more likely to be the digestibility and nutritive
value of the additive.
the seaweed meal is probably only really beneficial to sheep and cattle. certainly the size of the industry has
diminished since the late 1960s and early 1970s, when norway alone was producing about 15 000 tonnes of
seaweed meal annually. there are many companies in australia, canada, ireland, norway, united kingdom
and united states of america advocating the use of seaweed meal as a feed additive for sheep, cattle, horses,
poultry, goats, dogs, cats, emus and alpacas. the horse racing industry seems to be especially targeted. one
interesting report from a united states of america university states that the immune system of some animals
is boosted by feeding a particular canadian seaweed meal. obviously the industry is still active.
the brown seaweeds macrocystispyriferaand sargassum species.recently have been evaluated as extenders or
fodder supplements in goat and sheep diets. ten 43-week-old nubian goats were fed balanced diets and ten
were fed diets in which sun-dried sargassumspecies. flour replaced 25% of the ration[241][97]
4.8 seaweed as a biofertilizer
seaweeds have been used to nourish worn out soil around coastal areas and also seaweed fertilizers have
gathered interest among the worldwide cultivators so as to implement sustainable and green
agriculture[242][92].use of seaweed fertilizer stimulated root volume ,plant growth and even promoted fruit
development thus resuted in the production of high quality agricultural products[243][91]. further it was
revealed that the use of seaweed fertilizer improved germination and disease resistant capacity in
plants[244][93]. water and alkaline extracts of ascophyllum nodosum has given tomatoes of appreciable
mass and also yielded good quality fruits[245][94].
5. Economic importance
from all the seaweed potentials studied it is evident that the globalization of seaweed and seaweed derived
products can improve the economic status of various countries all over the world. the european, eastern and
southeast asian countries are the major cultivators and users of seaweed [246][151]. according to fao 2014
chile tops the global natural seaweed producers and it was estimated as one of the first agar producers in the
world[247][150]. various seaweeds are being harvested for human consumption and other nutrceutical and
industrial uses and patagonia is one such place where all the seaweeds are harvested and has been
commercialized[248][148]. the red seaweeds are harvested for agar and carrageeanan industries whereas the
brown species for alginates industries[249][149]. it is to be noted that rapid growth is seen in japan and
korea is mainly because of seaweed production and the increasing demands as an edible product. the 2010
estimate has shown that the global seaweed production was 19 million tons and it accounts for us $5.7
billion[250][152].
6 .Conclusion
seaweed thus serves as a sustainable feedstock and an ecofriendly resource for various purposes. also many
bioactive compounds and pharmacologically active substances have been isolated from macroalgae and put
into use in various forms. nowadays seaweeds are under threat in developing nations because of human
settlements, natural barriers and lack of awareness. hence awareness about the importance of harvesting
and commercialization of seaweeds and products should be effectively promoted in developing nations. the
cultivators should be well trained to know the different harvesting techniques , the parameters and
specificity involved in growing various classes of species. india , since it has got long coastal line with rich
availability of seaweed species , if encouraged and promoted with financial aids by the government,
malnutrition and poverty can be uprooted to the maximum extent.

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