Algae – future from the sea

technique • market
Algae – future from the sea
Dominika KĘPSKA*, Łukasz OLEJNIK – Faculty of Biotechnology and Food Sciences, Lodz University
of Technology, Łódź, Poland
Please cite as: CHEMIK 2014, 68, 10, 967–972
General characteristics
Algae, seaweed, or Phykoi are just a few names of a large group of
aquatic organisms. They belong to the group of autotrophic, usually
avascular and thallus plant organisms, prochlorofits and bacteria
[1]. Algae in the far east have been valued from ancient times as
an extremely attractive source of food, as well as raw materials in
cosmetics and herbal medicine. In the west, they were appreciated at
the end of 19th and 20th century, when British researchers found a large
amount of iodine and alginic acid (currently used as a gelling agent) in
them [2]. Their origin and taxonomy is still under investigation, as well
as their connexion with Embryophyta. 11 clusters and over 20,000
species of organisms belonging to several separate kingdoms (plants,
protista and bacteria) of diverse structure and shape, systematized
in 1993 by A. J . Szweykowskich [1] are hidden under the name of
algae. Classification of algae is complicated because of their large
morphological differentiation. The most important features to be taken
into consideration are: construction of cells, cell wall composition
and color of biomass [2]. Eukaryotic algae are glaucophytes, bundles,
euglenoids, chrysophyta (Chrysophyta) and golden algae, haptophytes
(Prymnesiophyceae, Haptophyceae) xanthophytes (Xanthophyceae),
diatoms and eustigmatophyceae (Eustigmatophyta), cryptomonads,
brown algae, red algae and green algae [1]. Many of these organisms
are fished out of the sea and other natural, water reservoirs or further
cultured. The ones that are most widely used are brown algae, red
algae and green algae [3]. Each species has a different morphology and
properties. The size of algae organisms depends on the species and
ranges from microscopic organisms such as microalgae, to reaching
several tens of meters long (macroalgae and seaweed) [4]. Most
of algae produce thallus, which is composed of the same or less
differentiated cells. In order to facilitate the absorption of mineral
salts from the environment, it is transformed into pseudo-leaves and
pseudo-stem, as well as pseudo-roots, allowing to anchor to the
bottom, or other surface [5].
Chemical compounds
One of the first scientists who decided to try to investigate the
chemical composition of algae was prof. Claude Chasse. It turned out
that algae are a source of valuable substances for our body. These
organisms contain large amounts of proteins, lipids, carbohydrates,
vitamins and micronutrients [6]. The main ingredient of algae biomass
is water, which constitutes about 75–90% of their fresh wet weight.
A large share of compounds found in algae are mineral salts and
carbohydrates (30–50%). Carbohydrates constitute the majority of
the dry weight of algae, which predominate polysaccharides (about
60%). These include: mucopolysaccharides composed of amino
sugars and uronic acid, hyaluronic acid, chondroitin sulfate, alginic
acid, carrageenans, agar and other natural hydrocolloids. Proteins
found in algae represent about 7–15% of their dry weight. They
are mainly glycoproteins and metalloproteins containing exogenous
amino acids [7]. Algae are also a source of essential fatty acids (EFAs),
which include eicosapentaenoic acid (EPA), arachidonic acid, as well as
rare γ-linolenic acid (GLA). Algae also contain polyphenols (exhibiting
Corresponding author:
Dominika KĘPSKA, e-mail: [email protected]
970 •
antioxidant and anti-inflammatory activity), biogenic compounds
(with antibacterial properties), natural dyes (which are protecting
algae against UV damage) and vitamins (B1, B2, B5, B6, B12, C, E,
A and D). Algae are also rich in macro-and micronutrients present in
easily assimilable form as complex and organometallic compounds.
These elements include iron, copper, bromine, zinc, iodine, calcium,
magnesium, and manganese [8].
Usage and properties
This amount of ingredients allows the use of algae in various
industries, especially food, cosmetic and pharmaceutical [7]. Cosmetics
and creams made based on algae provide the skin with nutrients and
accelerate the regeneration of the skin, heal scars, causing tightening
and brightening of skin. Sugars present in algae are highly moisturizing
and protective action, but also stimulate blood and lymph circulation
and metabolic processes, which occur in the cells [6]. Also support the
penetration of micro- and macronutrients to the skin. Lipids contribute
to the restoration and protection of epidermis. Vitamins and minerals
cause strengthening of the walls of blood vessels and normalize the
functioning of the sebaceous glands in the skin, regenerate and firm the
skin [2]. Because of its high nutritional qualities, algae are commonly used
in food production. As a supplement to the daily diet, are particularly
valued in China and Brittany, where they are caught in large quantities
[8]. Algae are a rich source of proteins, exogenous amino acids and
vitamins necessary for proper functioning of human body. Spirulina,
Chlorella and recently discovered Aphanizomenon flosaquae are mainly
used in diet supplementation. Consumption of these algae allows
to supplement diet with nutritious protein and causes detoxification
of the body, has a protective effect on the mucous membrane of the
stomach and supports digestion processes. Also has a positive effect
on memory and concentration, helps in diabetes, rheumatism and high
blood pressure treatment. Prevents the formation of viral, fungal and
bacterial infections [5]. Compounds derived from algae are also used
for medical purposes, such as inhibit the inflammation, relieve pain and
reduce fever, prevent psoriasis, osteoporosis and weaken anxiety [9].
Algae are not only a rich source of diverse and valuable substances, but
also a very important part of ecosystems. They serve as food for aquatic
organisms (listed at the beginning of most food chains in the aquatic
system) and also enrich the water tanks with oxygen and regulate
access to sunlight [10]. Among the many useful products derived from
algae, this article discusses only a few, such as agar, alginate, biofuels and
biosorbents, which are used in wastewater treatment.
Agar
Agar is a structural polysaccharide of seaweeds, consisting
essentially of residues D and L-galactose, part of which is esterified
with sulfuric acid. Due to the presence of these acid groups agar
bind cations of calcium, magnesium, potassium and sodium. Agar
preparations are generally odorless, though sometimes they may have
a slight characteristic aroma. Agar is available in the form of fibers or
flakes and granules, or powder. Depending on the degree of purity,
its color varies from light yellow through yellow-gray, to orange. Agar
influenced by water swells, forming for hot-sticky, gelatinous, colloidal
solutions, which are solidified after cooling [11]. For this reason, it is
used in the cosmetics industry, for the production of fat-free creams
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Alginate
Alginate is present in all types of Phaeophycaea. As a structural
polysaccharide provides rigidity of algae and, thanks to a strong
hydrophilicity and water binding ability, prevents seaweeds from
drying out during the outflow [14]. Alginate is a linear copolymer
composed of residues of: α-L-guluronic acid and β-D-mannuronic
acid, linked by glycoside bonding. Construction of alginate, which
depends on the species of algae and growth conditions, determines
its gelling properties. Molecules predominantly of mannuronic acid
form more flexible and soft gels, while the superiority of guluronic
acid form more rigid gels [15]. The viscosity of colloidal solutions
of alginate depends on its molecular weight as well. Alginate is
used as an additive to food products, including processed meat and
fruit products, and as a stabilizer for ice cream [14]. Advantage of
alginate is that it’s gel structure can be modified by using calcium
ions. In the presence of these cations, alginate chains are linked
together, forming a characteristic molecular structure, called eggsin-box model [5,16].
A very popular food additive is sodium alginate with the symbol E
401 [15]. It is a tasteless and odorless sodium salt of alginic acid. With
good water binding ability it is used as a thickener, gelling agent or
stabilizer for marzipan masses, fruit fillings, low-fat mayonnaise, frozen
fish products, canned vegetables, concentrates, jellies and marmalades.
Sodium alginate is also added as a clarifying substance for juice, musts,
wine or mead [13], as well as the fulfillment of tablets [5].
Alginate from brown algae is obtained by extraction of algae
biomass with dilute base solutions, in which alginic acid can be dissolved.
The resulting thick mass is then treated with inorganic acids in order
to obtain free alginic acid. Alginate is also used for immobilization,
mainly encapsulation of chemical compounds, and its fibers are used in
the textile industry as an admixture of synthetic fibers. Currently, these
fibers are also used in biomedical engineering, mainly as a modern
wound dressings [5].
Application of algae as an alternative energy source
Microalgae are characterized by rapid growth of their biomass
[17] and absorbing large amounts of CO2 during photosynthesis [18].
Due to these properties, algae can be used as a renewable energy
source [12]. Diversity of biofuels obtained from algae depends
on the individual components of the cells, which are used for this
purpose. As a result of anaerobic biomass fermentation – biomethane
can be obtained, from algae oil – biodiesel, and after biomass
saccharification and fermentation – bioethanol [3]. Breeding of algae,
under conditions appropriate to their needs, may be carried out in
bioreactors or ponds. Determining factors of biomass productivity
are: temperature (optimum at 20–30°C), light intensity (preferably
sunlight, making it possible to reduce the cost of electricity) and the
accessibility of CO2 and minerals (mainly nitrogen, phosphorus, iron
and silicon) [17,10]. It is important to provide a source of phosphorus
in excess, due to its ability to forming complexes with iron ions, which
limits the availability of this element for growing organisms [3]. Algae
biomass can be generated in the continuous, open culture (ponds) or
closed (photobioreactors) [19]. A pond can be a shallow canal formed
by a closed recirculation loop with a turbine (which is responsible
for mixing and circulation, preventing from algae sedimentation). At
the end of the recirculation loop (behind the turbine), the biomass is
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collected [3]. Higher biomass yield, however, associated with higher
costs can be achieved by the use of vertical – columnar, cylindrical
or panel (flat) light-transmissive photobioreactors [10]. Twilight
zone and self-shadowing (formation of the outer, middle and inner
layers of algae from the most intense light until its absence), might
be avoided by using special panels that emit red light. Appropriate
lighting of microorganisms can be achieved as well by adjusting the
rate of aeration and circulation of medium that guarantees a specific
frequency of cell circulation between areas of greater and lesser
exposure to the light in the reactor [18]. Not without significance is
the control of O2 and CO2 in the bioreactor – too high concentration
of the first factor leads to the inhibition of photosynthesis, and the
second – to changes in pH and growth inhibition [3]. Losses in culture,
associated with the utilization of energy through the overnight
microorganism’s breathing can be offset by a controlled decrease
of temperature in the bioreactor [20]. Separation of biomass from
the culture suspension occurs through the filtration or centrifugation.
Obtained biomass is subjected to thermochemical changes (pyrolysis,
hydrogenation, carried out in the liquid state, gasification) which leads
to biooils and biochemical (fermentation, transesterification), giving the
bioethanol and biodiesel. Pyrolysis is a high temperature, anaerobic,
chemical decomposition process, which occurs in the absence of
catalyst, allowing the conversion of biomass into biofuel, charcoal
and gaseous fraction. The hydrogenation is the joining the hydrogen
to an unsaturated bond in a compound . In case of algae, it takes place
in an autoclave under high-pressure and temperature, in the presence
of a solvent and a catalyst (usually nickel, platinum, palladium, copper)
and leads to the formation of liquid fuel. Gasification is a thermal
conversion of biomass into gas. It runs in two stages. At the beginning
by degassing biofuel – flammable gas and mineral residue is produced
(it applies in oxygen deficiency and a relatively low temperature).
In the second stage (high temperature and excess of oxygen)
afterburning in the chamber and combustion of resulting gas takes
place. As a result of saccharification of polysaccharide derived from
algae and alcoholic fermentation, bioethanol is obtained. Alcoholic
fermentation is carried out using the Saccharomyces–cerevisiae yeast,
and after the end of it, bioethanol is separated by distillation [18].
On the other hand, in order to obtain biodiesel, transesterification
(alcoholysis) of biooil is used. In this process free fatty acids obtained
by hydrolysis of triglycerides, react with alcohol (usually methanol),
resulting in the formation of fatty acid methyl esters (biodiesel) and
glycerol as a by-product [3]. Nowadays, very high production costs of
biofuels are the biggest problem in popularizing this form of energy.
However, the development of biotechnology, genetic engineering, as
well as the deepening oil crisis, should help the improvement of the
economy and the development of these processes in the future[18].
Application of seaweed in the wastewater treatment
Many studies have confirmed the existence of groups of
microorganisms, characterized by their ability to bind heavy
metals [4]. These include fungi, yeasts, bacteria [4] and algae [10].
Biosorption, besides environment detoxification, allows recovery
of valuable metals, such as silver or gold. Interestingly, adsorption
of ions, of radioactive elements such as uranium is also possible [4].
Immobilization (on a water-insoluble carrier) of microorganisms
further increases the efficiency of the removal of heavy metals
from the water environment and improves the conditions of
sedimentation. Immobilization of biosorbents facilitates their
reuse (cycles repeated up to dozens of times), which in turn
leads to a significant costs reduction [15]. Dead biomass is more
likely to be used as biosorbent, because it does not require the
maintenance of sterile conditions and satisfaction of nutritional
needs [5]. Macroalgae for wastewater treatment are usually
acquired through direct harvesting from natural reservoirs (oceans,
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technique • market
or masks. It improves the spreadability of these preparations, as well as
increases their adhesion [12]. Agar is also used as a thickener, stabilizer
and emulsifier [11]. In the food industry, it is used as a substitute for
animal gelatin. The gelling and thickening properties of agar are used
in production of: non-fermented milk beverages, salad dressings, jams,
jellies, pastry, etc [13]. In laboratories agar acts as a medium solidifying
ingredient for bacterial or tissue cultures in vitro [11].
technique • market
seas, lakes, ponds, rivers), with special combine, or in the traditional
way – manually. Here is also a possibility to develop the biomass of
algae, which need to be removed from the water, especially during
blooms [4]. As biological material binding metal ions can be used
also waste biomass from various industries such as pharmaceutical
(biomass after production of antibiotics), biotechnology or food
(biomass remaining after fermentation processes) [4, 15].
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*Dominika KĘPSKA – student of master’s program: 2nd year of biotechnology and 1st year of management. Research interests: industrial and medical
biotechnology.
e-mail: [email protected]
Łukasz OLEJNIK – student of master’s program: 2nd year of biotechnology and 1st year of management. Research interests: issues connected
with food, microbiology and environment.
Z prasy światowej – innowacje: odkrycia, produkty
i technologie
From the world press - innovation: discoveries, products and technologies
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szereg pozytywnych zmian, m.in. złagodzenie skutków zmian klimatycznych, oszczędność środków i możliwość dystrybucji w wielu różnych
lokalizacjach. Biopaliwa, w tym biodiesel, odgrywają również kluczową
rolę w działalności przemysłowej i rolniczej, zapewniają nowe źródła dochodu. Łańcuch produkcji prowadzący od uprawy nasion do sprzedaży
biodiesla na rynku można podzielić na dwa obszary: w pierwszym rolnicy
uprawiają rośliny energetyczne i sprzedają nasiona na rynku; w drugim
fabryki zajmujące się przetwórstwem nasion kupują je i wykorzystują
do produkcji biodiesla. Włoscy i kanadyjscy naukowcy prezentują na łamach czasopisma Bioresource Technology innowacyjną metodę produkcji
biodiesla, w której wykorzystują proces synergii dwóch różnych technologii. Głównym celem jest maksymalizacja dochodu rolników i zwiększenie stabilności systemu konwersji przez centralizację wszystkich etapów
w jednym miejscu. Połączenie procesów zgazowania i konwersji biodiesla wykazało wysoką skuteczność. Minimalna powierzchnia wymagana
do wprowadzenia proponowanej technologii wynosi 15 ha dla elektrowni o 7 kW. Biorąc pod uwagę koszt systemu, ok. 50 tys. EUR, czas zwrotu
inwestycji wynosi 5 lat. (kk)
(Giulio Allesina, Simone Pedrazzi, Sina Tebianian, Paolo Tartarini: Biodiesel and
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972 •
Filtracja biotrickling
Metan, charakteryzujący się 20-krotnie wyższym potencjałem cieplarnianym niż CO2, jest obecnie drugim najbardziej niebezpiecznym
gazem cieplarnianym. Stężenia atmosferyczne CH4 w 2011 r. przekroczyło poziom sprzed rewolucji przemysłowej o 150%. Od 50 do 65%
całkowitej emisji CH4 ma podłoże antropogeniczne. W związku z tym
na całym świecie prowadzone są intensywne badania nad rozwojem
i optymalizacją przyjaznych środowisku technologii redukcji emisji metanu. Gazy o zawartości metanu poniżej 30% są tradycyjnie spalane,
jednak proces ten jest opłacalny, gdy stężenie CH4 przekracza 20%.
Niestety, ponad 50% z antropogenicznego CH4 jest emitowanych
w stężeniach poniżej 3%. Technologie biologiczne stanowią obiecujące rozwiązania dla przetwarzania rozcieńczonych gazów wylotowych,
a tak zwana filtracja biotrickling jest jedną z najbardziej opłacalnych
konfiguracji, z uwagi na swoją wytrzymałość i niskie koszty operacyjne. Naukowcy z University of Valladolid w Hiszpanii proponują
maksymalizację wydajności filtrów biotrickling poprzez zwiększenie
transportu masy wynikające z zastosowania zaawansowanych technologii recyklingu. (kk)
(José M. Estrada, Raquel Lebrero, Guillermo Quijano, Rebeca Pérez, Ivonne FigueroaGonzález,, Pedro A. García-Encina, Raúl Muńoz: Methane abatement in a gas-recycling
biotrickling filter: Evaluating innovative operational strategies to overcome mass transfer
limitations. Chemical Engineering Journal 253 (2014) 385–393)
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