25th International Meeting on Organic Geochemistry IMOG 2011

P-141
Biosurfactants – a green alternative to synthetic surfactants
Gunhild Bødtker 1 , Ina Hvidsten 2 , Tanja Barth 2
1 Uni CIPR, Uni Research, UoB, Bergen, Norway, 2 Petroleum and Colloid Chemistry Research Group,
Department of Chemistry, UoB, Bergen, Norway (corresponding author:gunhild.bodtker@uni.no)
Surfactants are amphiphilic compounds that have a
wide range of application in commercial production of
food, cosmetics and pharmaceuticals in addition to
applications in agriculture and petroleum industry.
The steady demand for new specialty surfactants
have lead to an increased interest in biologically
produced surfactants, termed biosurfactants. In
addition to being generally nontoxic, biosurfactants
tend to be more effective (low critical micelle
concentration, CMC) and stable than synthetic
biosurfactants. They are also biodegradable and
environmentally friendly, thus fitting the definition of
currently sought-after ―green chemicals‖. The
properties of biosurfactants have high commercial
value, as are reflected in the recent years increase in
research interest [2].
Biosurfactants may be produced by animals, plants
and microorganisms, but are most often associated
with bacteria growing on water-immiscible oily
substrates such as high-molecular-weight
hydrocarbons. Biosurfactant production is initiated as
a response to the presence of specific substrates
(e.g. hydrocarbons) and requires multi-component
enzymes for its synthesis. They may be cell-bound or
excreted into the surrounding environment.
Biosurfactants are a diverse group of biomolecules
varying in composition from low molecular-weight
glycolipids and lipopeptides to high-molecular-weight
lipopolysaccharides, proteins and lipoproteins (figure
1). The amphiphilic composition of biosurfactants,
which orients these molecules towards both
hydrophilic and hydrophobic phases, gives
tensioactive properties that reduce surface and
interfacial tensions. Extracellular biosurfactants have
emulsifying properties that form oil-in-water emulsions
that leaves the oil accessible for uptake and
degradation by bacteria. Cell-bound biosurfactants on
the other hand, enables bacteria to be situated at the
oil/water interface. Subsequent exponential growth at
the interface leads to a corresponding exponential
reduction of the interfacial tension (IFT). Growthdependent
reduction in oil/water IFT is believed to be
one of the key mechanisms in microbial enhanced oil
recovery (MEOR).
We are in the process of isolating and characterizing
biosurfactants produced by oil-degrading bacteria
isolated from petroleum environments with regard to
their molecular structure and physiochemical
properties. Present research is focusing on the very
efficient biosurfactants produced by a new
Actinobacterium. This oil field bacterium is able to
reduce oil/water IFT by close to ~10 4 while growing at
an n-dodekan/water interface at ~20 o C [1].
Characterization of cold-loving oil-degrading bacteria
from geoactive sites in the arctic region show high
potential for long-chained n-alkane degradation,
which suggests production of cold adapted
biosurfactants. Our overall aim is to assess
biosurfactants as candidates for development of
green chemicals for the oil industry. The major
challenges related to the commercial use of
biosurfactants are the high-cost production compared
to synthetic surfactants, and their biodegradability that
may lead to loss of efficiency during application.
Fig. 1 Structures of biosurfactants [2]
References
1.Kowalewski E, Rueslåtten I, Gilje E, Sunde
E, Bødtker G, Lillebø BLP, Torsvik T, Stensen JÅ,
Bjørkvik B, and Strand KA (2005) Interpretation of
microbial oil recovery from laboratory experiments.
13th European Symposium on Improved Oil
Recovery, Budapest, Hungary 25-27 April
2.Soberón-Chávez G Biosurfactants: From Genes to
Applications (2011) Springer-Verlag Berlin,
Heidelberg
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