BIOACCUMALATION AND
BIOSORPTION
TECHNIQUES IN BIOREMEDIATION
5/7/2015
THURSDAY
SUBMITTED TO: SIR IMRAN
SUBJECT: ENVIRONMENTAL BIOTECHNOLOGY
CONTENTS
PAGE 1:
CONTENTS
PAGE 2:
BIOREMEDIATION (INTRODUCTION)
PAGE 3:
IMPORTANCE AND LIMITATIONS
PAGE 4:
BIOSORPTION
PAGE 5:
MECHANISMS AND FACTORS AFFECTING BIOSORPTION
PAGE 6:
APPLICATIONS OF BIOSORPTION
PAGE 7:
APPLICATIONS OF BIOSORPTION
PAGE 8:
BIOACCUMALATION
PAGE 9:
FACTORS AFFECTING BIOACCUMALATION
PAGE 10: APPLICATIONS OF BIOACCUMALATION
PAGE 11: REFERENCES
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BIOREMIDIATION
Bioremediation is the use of living organisms, primarily microorganisms, to degrade
environmental contaminants into less toxic forms. Research has demonstrated that there are
very few environments where microbes have not been able to survive, adapt, and indeed,
thrive. Microbes are able to utilize a near infinite combination of electron donors and electron
acceptors to drive their metabolism. In addition to these redox (oxidation / reduction)
reactions, they have also developed a myriad of other strategies enabling them to detoxify
their environment. Bioremediation applies these principles to select a suitable combination of
microbial community activity, electron donor / acceptor / contaminant concentrations and
other physical and practical parameters to remediate / recover a targeted pollutant.
More recently, the advances in the field of genetic engineering have allowed scientists to
attempt to create artificial strains of organisms, specifically designed to break down and
remove highly toxin, harmful or radioactive waste. Though still in its infancy, such a
breakthrough has proven ground-breaking in bioremediation strategies.
VARIOUS METHODS OF BIOREMEDIATION
Bioremediation techniques can generally be divided into two categories: in situ and ex situ. The
former involves treating the contaminated area on site while the latter involves removing it to
an alternative location for treatment. The varying methods and branches of bioremediation are
manifold and distinct, but some of them include:
Bio augmentation: The introduction of strains which are known to have
decompositional properties into a contaminated area.
Bio stimulation: The addition of organic or inorganic compounds to cause indigenous
organisms to effect remediation of the environment, e.g. fertilizer, surfactants.
Bioleaching: This is aimed at extracting precious or polluting metals from their ore
through the introduction of living organisms.
Bio sorption: Passive concentration and binding of contaminants onto cellular structures
of biomass.
Bioaccumulation: Accumulation of substances, such as pesticides, or other chemicals by
active concentration into an organism.
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IMPORTANCE OF BIOREMEDIATION TECHNIQUES:
• It is a natural process. Microbes able to degrade the contaminant increase in numbers when
the contaminant is present, however when the contaminant is degraded, the biodegradative
population declines. The residues for the treatment are usually harmless products.
• Bioremediation also requires a very less effort and can often be carried out on site, often
without causing a major disruption of normal activities. This also eliminates the need to
transport quantities of waste off site and the potential threats to human health and the
environment that can arise during transportation.
• Bioremediation is also a cost effective process as it lost less than the other conventional
methods that are used for clean-up of hazardous waste.
• It also helps in complete destruction of the pollutants, many of the hazardous compounds
can be transformed to harmless products, and this feature also eliminates the chance of future
liability associated with treatment and disposal of contaminated material.
• It does not use any dangerous chemicals. The nutrients added to make microbes grow are
fertilizers commonly used on lawns and gardens. Because bioremediation changes the harmful
chemicals into water and harmless gases, the harmful chemicals are completely destroyed..
Limitations of Bioremediation:• Bioremediation is limited to those compounds that are biodegradable. Not all compounds
are susceptible to rapid and complete degradation.
• There are some concerns that the products of biodegradation may be more persistent or
toxic than the parent compound. Biological processes are often highly specific. Important site
factors required for success include the presence of metabolically capable microbial
populations, suitable environmental growth conditions, and appropriate levels of nutrients and
contaminants.
• It is difficult to extrapolate from bench and pilot-scale studies to full-scale field operations.
• Research is needed to develop and engineer bioremediation technologies that are
appropriate for sites with complex mixtures of contaminants that are not evenly dispersed in
the environment. Contaminants may be present as solids, liquids, and gases.
• Bioremediation often takes longer than other treatment options, such as excavation and
removal of soil or incineration.
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BIOSORPTION
Biosorption is a physio-chemical process that occurs naturally in certain biomass which allows
it to passively concentrate and bind contaminants onto its cellular structure. Biosorption can be
defined as the selective sequestering of metal soluble species that result in the immobilization
of the metals by microbial cells.
The major advantages of biosorption using microbial, algal and fungal species over
conventional treatment methods include:

Low cost

High efficiency

Minimization of chemical and biological sludge

No additional nutrient requirement

Regeneration of bio sorbent

Possibility of metal recovery.
PROCESS
The biosorption process involves a solid phase (sorbent or biosorbent; biological material) and
a liquid phase (solvent, normally water) containing a dissolved species to be sorbed (sorbate,
metal ions). Due to higher affinity of the sorbent for the sorbate species, the latter is attracted
and bound there by different mechanisms.
Biosorbent material: Strong biosorbent behavior of certain micro-organisms towards
metallic ions is a function of the chemical make-up of the microbial cells. One type of
biosorbent consists of dead and metabolically inactive cells, another type may contain living
and metabolically active microbial cells.
Biosorption mechanisms:
Physical adsorption: Physical adsorption takes place with the help of vander Waals' forces.
It is hypothesized that uranium, cadmium, zinc, copper and cobalt biosorption by dead biomasses of algae, fungi and yeasts takes place through electrostatic interactions between the
metal ions in solutions and cell walls of microbial cells.
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Ion Exchange: Cell walls of microorganisms contain polysaccharides and bivalent metal ions
exchange with the counter ions of the polysaccharides. For example, the alginates of marine
algae occur as salts of K+, Na+, Ca2+, and Mg2+. These ions can exchange with counter ions
such as CO2+, Cu2+, Cd2+ and Zn2+ resulting in the biosorptive uptake of heavy metals.
Complexation: The metal removal from solution may also take place by complex formation
on the cell surface after the interaction between the metal and the active groups. Complexation
was found to be the only mechanism responsible for calcium, magnesium, cadmium, zinc,
copper and mercury accumulation by Pseudomonas syringae. Micro­organisms may also
produce organic acids (e.g., citric, oxalic, gluonic, fumaric, lactic and malic acids), which may
chelate toxic metals resulting in the formation of metal-lo-organic molecules. Metals may be
bio-sorbed or complexed by carboxyl groups found in microbial polysaccharides and other
polymers.
Precipitation: Microbes may react in the presence of toxic metal producing compounds,
which favor the precipitation process. Or it may be a consequence of the chemical interaction
between the metal and the cell surface.
FACTORS AFFECTING BIOSORPTION PROCESS:

pH seems to be the most important parameter in the biosorptive process: it affects the
solution chemistry of the metals, the activity of the functional groups in the biomass and
the competition of metallic ions

Biomass concentration in solution seems to influence the specific uptake, some
hypothesis suggest that an increase in biomass concentration leads to interference
between the binding sites, whereas others suggest a direct relation between biomass
and bio sorption.

Types and concentrations of sorbent: the removal of one metal ion may be
influenced by the presence of other metal ions. For example: cobalt uptake by different
microorganisms seemed to be completely inhibited by the presence of uranium, lead,
mercury and copper
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APPLICATIONS OF BIOSORPTION
METAL BEARING WASTE WATER TREATMENT
The microbial cells are immobilized in a chemical matrix then exposed to sorbent particles,
finally, the desorption of metals is done to make the process economically sound by
regenerating biomass adsorptive capability. Usually the metals are recovered by leaching with
a desorbing agent, such as dilute acid or chelating compounds.
COMMERCIAL NAME
FOR BIOSORBENT
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Bonds formation between metals, amino and carboxyl groups of cell wall polysaccharides:

Copper biosorption by the bacterium Zoogloea ramigera and alga Chlorella vulgaris.

Chromium biosorption by fungus Ganoderma lucidum and Aspergillus niger.

The brown alga Sargassum fluitans has been found particularly effective in binding
heavy metal ions of gold, cadmium, copper and zinc. More specifically, it is the
properties of cell wall constituents, such as alginate and fucoidan, which are chiefly
responsible for heavy metal chelation.
Ion exchange method supporting bioadsorption:

Copper bioadsorption by fungus Ganoderma lucidium and Aspergillus niger
BIOSORPTION OF RADIOACTIVE ISOTOPES
Uranium is one of the most seriously threatening heavy metals because of its high toxicity and
some radioactivity. Excessive amounts of uranium have found their ways into the environment
through the activities associated with the nuclear industry posing a threat in some surface and
ground waters, and have attracted creation of new techniques for its removal.
Various non-living biomass has been used for the removal of uranium by biosorption.
Organisms such as:

The fresh water green algae, Chlorella regularis and Chlorella vulgaris. The marine
algae are capable of biologically concentrating various radionuclides such as radium,
thorium and uranium.

Other common examples include the yeast Saccharomyces cerevisiae and bacteria
Pseudomonas aeruginosa.
Recombinant bacteria for metal removal:


A highly specific lead-binding peptide was displayed on Escherichia coli, and lead
adsorption characteristics of the recombinant bacteria were enhanced significantly. Cell
surface-displayed peptide was expressed under the control of an arabinose promoter
expressing recombinant genes and using outer membrane protein C as an anchoring
motif.
A novel cell surface display system was developed by employing Escherichia coli outer
membrane protein C (OmpC) as an anchoring motif. Polyhistidine peptides could be
successfully displayed on the seventh exposed loop of OmpC. Recombinant cells
displaying polyhistidine could adsorb up to 32.0 micromol of Cadmium Cd(2+) per g
(dry weight) of cells.
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BIOACCUMALATION
DEFINITION:
“Bioaccumulation means an increase in the concentration of a chemical in
biological organism over time as compared to chemical’s concentration in the environment.”
Compounds accumulate in living things any time they are taken up and stored faster then they
are broken down (metabolized) or excreted.
THE BIOACCUMULATION PROCESS:
Bioaccumulation is a normal and essential process for the growth and nurturing of organisms.
All animals, including humans, and microorganisms daily bio accumulate many vital nutrients,
Such as vitamins A, D and K, Trace minerals, Essential fats and amino acids.
Because bioaccumulation is the net result of the interaction of uptake, storage and elimination
of a chemical, these parts of the process will be examined further.
UPTAKE:
Bioaccumulation begins when a chemical passes from the environment into a microorganism's
cells. Uptake is a complex process which is still not fully understood. Scientists have learned
that chemicals tend to move, or diffuse, passively from a place of high concentration to one of
low concentration. The force or pressure for diffusion is called the chemical potential, and it
works to move a chemical from outside to inside an organism.
STORAGE:
The same factors affecting the uptake of a chemical continue to operate inside a microorganism, hindering a chemical's return to the outer environment. Some chemicals are
attracted to certain sites, and by binding to proteins or dissolving in fats, they are temporarily
stored.
ELIMINATION
Another factor affecting bioaccumulation is whether a microorganism can break down and/or
excrete a chemical. The biological breakdown of chemicals is termed metabolism. This ability
varies among individual microorganisms and species and also depends on characteristics of the
chemical itself.
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FACTORS AFFECTING BIOACCUMULATION:
 BINDING:
Some chemicals bind to specific sites in the body of microorganism, prolonging their stay,
whereas others move freely in and out.
 TIME:
The time between uptake and eventual elimination of a chemical directly affects
bioaccumulation. Chemicals that are immediately eliminated, for example, do not bio
accumulate.
 DURATION OF EXPOSURE:
Similarly, the duration of exposure is also a factor in bioaccumulation. Most exposures to
chemicals in the environment vary continually in concentration and duration, sometimes
including periods of no exposure. In these cases, equilibrium is never achieved and the
accumulation is less than expected.
 VARIATION BETWEEN INDIVIDUAL MICROORGANISM/SPECIE:
Bioaccumulation varies between individual microorganisms as well as between species. Large,
fat, long-lived individuals or species with low rates of metabolism or excretion of a chemical
will bio accumulate more than small, thin, short-lived organisms. Thus, an old lake trout may
bio accumulate much more than a young bluegill in the same lake.
 LIPOPHILIC:
Some chemicals do not mix well with water. They are called lipophilic, meaning "fat loving," or
hydrophobic, meaning "water hating." In either case, they tend to move out of water and enter
the cells of an organism, where there are lipophilic microenvironments.
 WATERSOLUBILITY:
One factor important in uptake and storage is water solubility; the ability of a chemical to
dissolve in water. Usually, compounds that are highly water soluble have a low potential to bio
accumulate and do not leave water readily to enter the cells of a microorganism. Once inside,
they are easily removed unless the cells have a specific mechanism for retaining them.
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APPLICATIONS OF BIOACCUMALATION
REMOVAL OF HEAVY METALS FROM WATER, SOIL OR SEDIMENT
Bacterial strains were isolated from soil, sediment and water samples of metal contaminated
industrial area and investigated the heavy metal resistance and bioaccumulation potential of
the isolates. Cadmium resistance studies of the bacterial isolates showed that out of 164
isolates collected most of them showed low resistance (<500µg/ml) and many isolates showed
high resistance of >1500µg/ml. Ten bacterial genera were represented in soil and 11 from
water, while only 5 bacterial genera were recorded from sediment samples. Bacillus,
pseudomonas and Enterobacter were found in soil, sediment and water samples. Results of
cadmium removal study revealed that with increase in time, the biomass of the
selected Pseudomonas sp. increased. Correspondingly, with increase in biomass, the cadmium
bioaccumulation was also increased. Relatively an Increased removal of cadmium was observed
in the first day of the experiment. About 40% of the cadmium in the experimental flask was
reduced while only 5% reduction occurs in the control flasks till the end of the experiment
(74hours). Comparatively cadmium showed higher reduction at pH 7. From the results, it could
be concluded that the selected bacterial isolates possessed potential in respect of
bioaccumulation activity and thus, appeared to be an appropriate nominee in bioremediation
processes.
HEAVY METAL REMOVAL FROM INDUSTRIAL WASTES AND
CONVERSION INTO NON-TOXIC FORMS
The mercury produced during many industrial processes has started accumulated in the
surrounding area. The bacterial strains isolated from those areas were able to active
accumulate mercury in their cells and then convert the mercury into methyl mercury and then
to volatile mercury thus reducing the mercury pollution from the environment by using
method of bioaccumulation.
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SUBMITTED BY:
Risham Hussain
Maimoona Ashfaq
Ayesha Ilyas
Neelam Faraz
Waseem Abbas
REFERENCES:
 BIOREMEDIATION, SMALL SOLUTIONS TO BIG PROBLEMS by
Prof. Esta van Heerden and Dr. Peter Williams
 Bioremediation: Features, Strategies and applications by Shilpi
Sharma, (Asian Journal of Pharmacy and Life Science).
 Environmental Biotechnology by Lawrence K. Wang and Yung
Tse Hung.
 Environmental biotechnology, Theory and Applications by
Gareth M. Evans and Judith C. Furlong.
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