Definitions and Keywords

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20 Φεβ 2013 (πριν από 4 χρόνια και 3 μήνες)

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Bioavailability Constraints in the Uptake of Oil
& Hydrocarbons by Microorganisms



Prof. Suparna Mukherji


Centre for Environmental Science & Engineering

IIT, Bombay

Definitions and Keywords


NAPLs/Oils :
Oil comprises of a series of paraffins,
aromatics and asphaltenes which are long chain
hydrocarbons, hence is immiscible in water. Oil spills on
soil or water are toxic, carcinogenic, and hazardous to
the environment.


NAPL: Non
-
aqueous phase liquids


Being immiscible in aqueous phase their bioavailability
to the microorganisms is hindered and hence a major
challenge for bioremediation.






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Definitions and Keywords


Bioavailability:
availability to microorganisms, it is
dependent on mass transfer rates i.e. rate of transfer of
pollutants (oils & hydrocarbons) to the aqueous phase.


Bioavailability limitations can be overcome by microbial
adherence to oil and direct interfacial uptake of
components from the oil phase; and by release of
surfactants that cause pseudosolubilization or
emulsification of oil.


Surfactants:
surface active agents, long chain
amphiphillic molecules, can be anionic, cationic,
zwitterionic, and non ionic, classified as chemical
surfactants and biosurfactants depending upon their
origin.






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Definitions and Keywords


Micellization
: Micellar solubilisation occurs when the
surfactant concentration exceeds CMC (critical micelle
concentration), aqueous solubilisation is enhanced by
incorporation of hydrophobic molecules into the
surfactant micelles.


Sorption:
transfer from solution phase onto a solid
matrix, includes both


Adsorption: accumulation at the interphase


Absorption: uniform distribution in the solid phase




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INSTRUCTIONS SLIDE

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Questionnaire

1
.
How does the surfactant influence the surface tension?

Answers: (a)

increases


(b)

decreases



(c)

no
effect


(d)


none of these

2
. Bioavailability constraint of oils is due to

Answers: (a)

hydrophobicity


(b)

immissibility in aqueous
phase (c) hydrophilicity (d)


both (a) & (b)


3
. Micelle formation by surfactants occurs at concentration

Answers: (a) does not occur ( b)

above CMC




(c) below CMC

(d) none of these


4
. Bioavailability limitations can be avoided by

(a) Use of surfactants ( b) direct uptake by microorganisms (c) both
a) & b) d) none





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Links

for further reading

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Singh, A., Van Hamme, J.D., Ward, O.P., 2007. Surfactants in microbiology and
biotechnology: Part 2. Application aspects. Biotechnology Advances 25, 99
-
121.



Volkering, F., Breure, A.M., Rulkens, W.H., 1998. Microbiological aspects of
surfactant use for biological soil remediation. Biodegradation 8, 401
-

417.



Surfactant Science Series: a series of books describing the nature , behaiviour,
mechanisms, & applications related to surfactants.












Thank you