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PROCESOS DE TRANSFORMACIÓN
DE CONTAMINANTES
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HIDRÓLISIS
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FOTÓLISIS
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OXIDACIÓN-REDUCCIÓN
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TRANSFORMACIÓN MICROBIANA
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TRANSFORMACIÓN EN
ORGANISMOS SUPERIORES
BIOREMEDIATION
Bioremediation is the use of biological systems (mainly
microoganisms) for the removal of pollutants from aquatic
or terrestrial systems. It is based on the extremely diverse
metabolic potential of natural microbial communities. A
challenge in this area is the existence of xenobiotics, i.e.
compounds produced by chemical synthesis for industrial
or agricultural purposes and having no counterparts in the
natural world. It may be possible to remove bottlenecks in
environmental cleanup by selecting soil microorganisms
which have developed new properties in response to the
introduction of xenobiotics, and then combining different
metabolic activities in the same microorganisms for the
degradation of a particular target compound.
“In situ”: polluted soil is treated in its original place
“Ex situ”: polluted soil is removed and treated somewhere
else
Bioremediation may include the introduction of
microorganisms (bioaugmentation), ventilation and/or,
adding nutrient solutions (biostimulation)
EVOLUTION OF MICROBIAL WORLD
Microorganisms are the most versatile and
adaptable forms of life on Earth, and they have
existed here for some 3.5 billions years. For the
first 2 billions years of their existence, bacteria
alone ruled the biosphere, colonizing every
accessible ecological niche from glacial ice to the
hydrothermal vents of the deep sea bottoms
What they did?
-Developed the major metabolic pathways
characteristic of all living organism today
-Changed earth transforming its anaerobic
atmosphere to one rich in oxygen
-Created an environment to sustain more
complex forms of life
-Adapted to an even-changing world leading to
selection of new metabolic activities
Biodegradability of a substituted aromatic compounds is
affected by the modification or removal of one or more
substituent groups in order to allow the hydroxylation of
two adjacent carbons, followed by the ring cleavage.
Factors which affect biodegradability
A) Molecule:
•polymerization and branching
•presence of hydrolysis resistant bonds
•chemical structure:
•concentration
•water solubility
•heterocyclic, aromatic and polycyclic
residues
•chloro and nitro substituents
•physical properties
•toxicity
B) Environment:
•bioavailibility
•pH, pO2, temperature, redox potential
•ionic composition and concentration
•presence of organic and inorganic nutrients
•presence of adequate microbial populations
Characteristics
Biodegradation
effect
Examples
Such synthetic novel compounds produced by
chemical synthesis for industrial or agricultural
purposes, have no counterparts in the natural
world and then are called “xenobiotics”
How to circumvent bottlenecks in environmental
cleanup from xenobiotics?
-By selecting soil microorganisms which have
developed new properties in response to the
introduction of xenobiotics
-By combining different metabolic abilities in the
same microorganism for the degradation of a
particular target compound
BACTERIA CAPABLE OF OXIDIZING PAH
Organism
Substrate
Pseudomonas
NAPH, PHEN, ANTH
Flavobacteria
PHEN, ANTH
Alcaligenes
PHEN
Aeromonas
NAPH, PHEN
Vibrio
Beijerenckia
PHEN
NAPH, PHEN, ANTH, BA, B(a)P
Bacillus
NAPH
Nocardia
PHEN, ANTH
Corynebacteria
NAPH ANTH=
Note:
NAPH= naphtalene, PHEN= pheanthrene,
anthracene, BA= benz(a)anthracene, B(a)P= benzo(a)pyrene
Micrococcus
PHEN
Different genetic mechanisms may be involved in the
evolution of metabolic pathways in general and in the
process of adaptation of microorganisms to xenobiotic
substrates in particular:
i) gene transfer
ii) mutational drift
iii) genetic recombination and transposition
Degradative plasmids code different catabolic segments
which probably have been aggregated on a plasmid during
the evolution through the recruitment of genes from
different microorganisms, leading to the selection of
microorganisms with new catabolic abilities.
Strategies for the development of
microorganisms with new degradative abilites
• Selection of microorganisms from soils or
sediments able to degrade environmental pollutants
• “In vivo” creation of hybrid degradative pathways
through assembling of pre-existing catabolic segments
transferred from one microorganism to another one
• “In vitro” construction of new
pathways through genetic engineering
degradative
• Avoid the substrate channelling in useless catabolic
pathways which produce toxic products.
Development of microorganisms able to degrade
recalcitrant compounds
Recalcitrant pollutant molecules
The problem
Characterization of the catabolic elements with
the capacity to transform apolar chloro and
nitroaromatic compounds
Analysis
Optimization of catabolic elements to increase
the transformation efficiency
feedback Optimization
Development of bacterial strains for the
biodegradation of recalcitrant pollutants
feedback
Validation of degradative abilities in microcosmos
Validation
Bacterial strains able to efficiently degrade
recalcitrant pollutants
Solution
PREVENTING POLLUTION AND SAVING
NON-RENEWABLE RESOURCES
Another way to protect the environment is to avoid
pollution by replacing chemical pesticides and industrial
compounds with environmentally friendly substitutes.
Examples of environmental prevention include:
• the use of microbial enzymes in activities such as leather
processing, textile desizing, the production of washing
powders;
• the use of microbial insecticides;
• the use of plant-growth-promoting bacteria to reduce the
use of chemical fertilizers;
• the use of microorganisms to control plant pathogens, so
as to reduce the use of fungicides and nematocides;
• the use of biopolymers to save non-renewable resources
like fossil fuels.