3. • The quality of life on the Earth is linked inextricably to
the overall quality of the environment.
• Unfortunately , a large amount ranging from raw sewage
to nuclear waste dumped into the ecosystem thereby
posing a serious problem for survival of mankind itself
• New technologies for waste disposal that use high-
temperature incineration and chemical decomposition
(e.g., base-catalyzed dechlorination, UV oxidation) have
The earth we abuse and the living things we kill
4. BUT WHY BIOREMEDIATION?
Ø Conventional methods to mitigate toxic
substances in soil or ground water via human
activities include pump and treat systems, soil
vapour extraction, incineration, and
Ø Utility of each of these conventional methods
suffers from recognizable drawbacks and may
involve some level of risk.
Ø These methods are complex, uneconomical, and
lack public acceptance.
5. Ø The scenerio has led focused efforts towards
harnessing modern-day bioremediation process as a
vAccording to E.K. Nyer, the term “bioremediation”
refers to all biochemical reactions of natural
attenuation, which includes all biotic and abiotic
processes used to reduce contaminant levels.
Biodegradation is the primary mechanism to reduce
biodegradable contaminants by employing organisms
like bacteria, fungi, algae or plants.
6. ENZYMATIC BIOREMEDIATION
• Bioremediation technologies rely on the activity of
microbial or plant enzymes involved in the metabolic and
catabolic transformation of a variety of organic
• To date, contaminants have been exposed to enzymatic
degradation primarily by stimulating microbial growth in
• The extracellular activity of enzymes is expected to be
increasingly exploited in future bioremediation
• Enzymes can be obtained in large quantities from microbial
populations grown under optimal conditions and without
exposure to toxic chemicals.
7. WHY ENZYMES FOR BIOREMEDIATION ?
v Enzymes present advantages over traditional technologies, and also over
v Enzymes are not inhibited by inhibitors of microbial metabolism.
v They can be used under extreme conditions .
v They are active in the presence of microbial predators or antagonists.
v They act against a given substrate (microorganisms may prefer more easily
degradable compounds than the pollutant).
v They are more mobile than microorganisms because of their smaller size
(Gianfreda and Bollag, 2002).
All these characteristics render enzymes eco-friendly catalysts as well as
8. MAJOR ENZYMES USED IN BIOREMEDIATION
• Their main producers are bacteria, fungi, mainly white-rot fungi, plants and microbe-
• Enzymes from white rot fungi have been found to be very capable of degrading a large
number of different contaminants.
• White rot fungi are unique among eukaryotes because they are able to cleave the
carbon-carbon bonds in contaminants such as PAHs.
• During the secondary metabolism of plant life, white rot fungi produces and secretes
LiP, manganese peroxidase (MnP) and laccase.
• Each of the enzymes can catalyze the one-electron oxidation of phenols and non-
• This results in the production of cation-radical intermediates, which can be used to
futher oxidize non-phenolitic substrates.
• They play a key role in the metabolism of organic compounds by
increasing their reactivity or water solubility or bringing about
cleavage of the aromatic ring.
• Oxygenases have a broad substrate range and are active against a
wide range of compounds, including the chlorinated aliphatics.
• Generally the introduction of O2 atoms into the organic molecule
by oxygenase results in cleavage of the aromatic rings.
10. • Halogenated organic compounds comprise the largest groups
of environmental pollutants .
• It is due to the widespread use as herbicides, insecticides,
fungicides, hydraulic and heat transfer fluids, plasticizers.
• The degradation of these pollutants is achieved by specific
oxygenases. Oxygenases also mediate dehalogenation
reactions of halogenated methanes, ethanes, and
ethylenes in association with multifunctional enzymes [