Abstract:
Seventeen bacterial strains were isolated from the rhizosphere soil of an Egyptian salt marsh plant and
screened for biosurfactant production. 76.5 % of the bacterial strains were found to produce biosurfactants, they
were identified as Bacillus spp (4 strains) and Pseudomonas spp (9 strains), of which P. aeruginosa was represented
by 6 strains. From the preliminary experiment, (Bacillus SH 20, SH 26 and Pseudomonas aeruginosa SH 29, SH 30)
were the most active biosurfactant producers. The four main active biosurfactant producers were selected and
studied. The results showed that P. aeruginosa SH 29 represents a good candidate for the production of the
biosurfactants when grown on both nutrient broth (NB) and inorganic salt media (ISM) supplemented with waste
frying oil. On the other hand Bacillus spp (SH 20 and SH26) were active biosurfactant producers when grown on
molasses. Waste frying oil and molasses represent good, cheap and easily available substrates which have the
advantage of reducing the production cost and help economic production of biosurfactants. The results of using
different vegetable oils varied with the variation of media and bacterial strains. Olive oil was promising followed by
sunflower oil and soybean oil. All of the four bacterial strains were able to emulsify the studied hydrocarbon oils and
vegetable oils but with different E24 values. Bacillus spp SH 20, SH 26 produced the highest E24 values for
petroleum oil (84.4 ± 5.2 and 75.0 ± 5.6 % respectively). This was followed by P. aeruginosa SH 30 (66.7 ± 3.8 %)
and P. aeruginosa SH 29 (62.0 ± 3.4 %). The results also showed that the produced biosurfactants in the present
study were stable at 0-121 °C, pH 1-14 values and at different concentrations of NaCl. An attempt was made to
isolate the biosurfactant produced by P. aeruginosa SH 29 when grown in waste frying oil (2% w/v). The production
yield of this crude product was estimated as 2.8 g/L. This crude material was selected and kept for further
purification and studies. Accordingly, the four bacterial strains may be useful in petroleum industry (e.g petroleum
recovery, cleaning of oil storage tanks and recovery of oil from oily sludge) and they may help in bioremediation of
oil contaminated sites.
[Ali Diab and Shereen Gamal El Din. Production and Characterization of Biosurfactants Produced by Bacillus
spp and Pseudomonas spp Isolated from the Rhizosphere Soil of an Egyptian Salt Marsh Plant. Nat Sci
2013;11(5):103-112]. (ISSN: 1545-0740). http://www.sciencepub.net.
