Preprint volume - SIBM

Pre-print Volume - Posters
VARIOUS TOPICS
R. MALAVENDA, C. RIZZO, A. LO GIUDICE, L. MICHAUD, M. DE DOMENICO, V. BRUNI
Department of Animal Biology and Marine Ecology, University of Messina,
Viale Ferdinando Stagno d’Alcontres, 31 – 98166 Messina, Italia.
rmalavenda@unime.it
SCREENING FOR BIOSURFACTANT PRODUCTION
BY ANTARCTIC MARINE BACTERIA
SCREENING PER LA PRODUZIONE DI BIOSURFATTANTI
AD OPERA DI BATTERI MARINI ANTARTICI
Abstract - This study was carried out on 403 Antarctic marine bacteria. Hemolytic and emulsification
activities, production of stable emulsion, surface tension reduction and CTAB assay were used to select
biosurfactant-producing bacteria. Acinetobacter sp. 11/4 resulted the best promising strain with 56.60% of
a stable emulsion value when growing at 15 °C in presence of soybean oil as carbon source, and 10.9
mN/m of surface tension at 15 °C on tetradecane.
Key-words: biosurfactants, emulsifiers, hydrocarbon degradation, bioremediation.
Introduction - Research on microbial emulsifying agents has been mainly focused on
mesophilic bacteria. Conversely, few publications report on emulsifiers and surfactants
produced by psychrophilic and psychrotrophic bacteria (Lo Giudice et al., 2010).
Isolation of indigenous cold-adapted microorganisms, which produce specific
molecules that increase emulsification of hydrocarbons, could have promising
applications for bioremediation purposes. In addition, the introduction of non-native
species to Antarctica is forbidden by the Antarctic Treaty and, therefore, the eventual
utilization of autochthonous microrganisms is requested. Microbes adapted to Antarctic
conditions may be valuable as bioaugmentation agents also in other cold climates.
In this context, the aim of the present work was to investigate the capacity of native
Antarctic bacteria to produce biosurfactants under different conditions of temperature
and substrate.
Materials and methods - This study was carried out on 403 bacterial strains belonging
to the Italian Collection of Antarctic Bacteria (CIBAN) of the National Antarctic
Museum (MNA) “Felice Ippolito” kept in our laboratory at the University of Messina.
Bacterial strains were preliminary grown at 4 °C in a mineral medium supplied with
crude oil (Arabian Light, Sigma) as a sole carbon source. Oil-degrading isolates were
selected for further analyses aimed at individuating biosurfactant producers, as follows.
Strains were inoculated in a mineral medium with soybean oil (2%) and incubated by
shaking under aerobic conditions for two weeks at 15°C. pH values and bacterial
growth were measured during the assay. During all the growth phase, cell suspensions
were tested for the eventual presence of biosurfactants by using the emulsification
assay (EA), the detection of E24 index (Tuleva et al., 2002), the measure of the surface
tension (ST) according to the Wilhelmy method with a digital tensiometer TSD
(Gibertini), the CTAB and Blood Agar (BA) assays (Fiebig et al., 1997). Strains
identification was carried by the 16S rDNA sequencing according to Michaud et al.
(2004). The most promising isolate were than tested to evaluate the biosurfactant
production during their growth at 4 and 15 °C in the presence of soybean oil or
tetradecane as a carbon source.
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
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