Preprint volume - SIBM

Pre-print Volume - Posters
VARIOUS TOPICS
C. RIZZO, B. CALDARONE, M. DE LUCA, M. DE DOMENICO, E. DE DOMENICO
Department of Animal Biology and Marine Ecology, University of Messina, Salita Sperone, 31 - 98166 Messina,
Italia.
carmen.rizzo@unime.it
EVALUATION OF DIFFERENT CARBON SOURCE
FOR BIOSURFACTANT PRODUCTION
UTILIZZO DI DIFFERENTI FONTI DI CARBONIO
PER LA PRODUZIONE DI BIOSURFATTANTI
Abstract – A study was carried out to investigate biosurfactant production under different growth
conditions by oil degrading bacteria isolated from oil contaminated water samples of Mediterranean Sea.
Two strains of Pseudomonas sp. and a strain of Acinetobacter calcoaceticus were inoculated in mineral
medium (ONR 7a) with three different type of carbon sources in order to detect the use of different
substrate for biosurfactant and bioemulsifiers production. Both hydrocarbon and vegetable oil substrate
were useful for biosurfactant production showing specificity with each strain.
Key-words: Biosurfactants, emulsifiers, hydrocarbons, bioremediation.
Introduction – Biosurfactants (SURFace ACTive ageNTS) are complex polymers
produced on living surfaces, mostly microbial cell surfaces, with amphiphilic
molecular structure, consisting of a hydrophilic and a hydrophobic domain. Due to
their molecular structure, biosurfactants have the properties of reducing surface
tension, stabilizing emulsions, promoting foaming (Georgiou et al., 1992; Desai,
1997). In recent years natural biosurfactant have attracted attention because of their
low toxicity, biodegradability, ecological acceptability and therefore potential
application in environmental protection.
Hydrocarbon-contaminated sites are the most promising for the isolation of
biosurfactant producing microbes, because they synthesize surface active agents during
growth on water-
insoluble substrates. When microorganisms are cultivated on n-alkanes or other
hydrocarbons, biosurfactant are accumulated in the culture medium. Their activity as
emulsifiers may facilitate mass transfer on the surface of microorganism (Kitamoto et
al., 2002). Biosurfactants can be produced by microbial fermentation processes using
cheaper agrobased substrates and waste materials (Mukherjee et al., 2006). This aspect
is very important because the production of microbial surfactants on a commercial
scale has not been realized because of their low yields and high production costs.
The aim of this work was to analyze three different bacterial strains for their ability to
produce biosurfactants when grown under different carbon source conditions.
Materials and methods – Two strains of Pseudomonas sp. and 1 strain of
Acinetobacter calcoaceticus (isolated from oil contaminated water samples of
Mediterranean Sea) were inoculated in mineral medium (ONR 7a) with three different
type of carbon sources: tetradecane, glucose and soybean oil. The growth was recorded
and measured spectrophotometrically as values of OD600. Several independent tests
were used for the detection of biosurfactants (rhamnolipids) or bioemulsifiers.
Qualitative biosurfactant activity assay was performed using a preliminary
emulsification test; then a larger emulsification test was performed to detect E24 index.
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