EXTRACTION OF FLUORENE FROM SOIL USING BIOSURFACTANTS FROM L.
pentosus
1
X. Vecino , R. Devesa-Rey,2J. M. Cruz 1, A. Moldes*1.
1
Chemical Engineering Department. University of Vigo, School of Industrial
Engineering (EEI). Campus As Lagoas, Marcosende. 36310 Vigo – Pontevedra, Spain.
2
Defense University Center, Escuela Naval Militar, University of Vigo. Plaza de España
2, 36920 Marín-Pontevedra, Spain.
*amoldes@uvigo.es
The elimination of polycyclic aromatic hydrocarbons (PAHs) from soils is limited by the
poor solubility of these hydrophobic contaminants in water, this fact prevent the
spontaneous biodegradation of these contaminants by the natural microbial biomass of
soil. Thus, it is necessary to add onto the soil surface-active agents that increase the
solubilisation of hydrophobic contaminants; allowing the extraction of these
contaminants in aqueous solution during ex situ treatments, or improving their
biodegradation by the microbial biomass of soil.
The use of environmental friendly surfactants for the extraction of PAHs from soil is an
area of great potential. Microbial molecules that are able to reduce the surface tension
of media are named biosurfactants. These surface-active compounds are biological
substances that exhibit good surface-active properties, and they are significantly less
toxic than synthetic petroleum-based surfactants.
This study proposes the use of biosurfactants obtained by fermentation of sugars from
trimming vineyard using L. pentosus, named BSL, to extract fluorene from
contaminated soil. Results were compared with those obtained using chemical
surfactants: sodium dodecyl sulfate (SDS) and Tween 20.
Biosurfactant from L. pentosus was obtained by growing L. pentosus cells in sugars
from trimming vineyards. Once the sugars were depleted, L. pentosus cells were
recovered by centrifugation from the fermentation media, washed twice in
demineralized water, and resuspended in phosphate buffer saline (PBS: 10 mM
KH2PO4/K2HPO4 and 150 mM NaCl with pH adjusted to 7.4) in order to extract the
biosurfactants. Following, soil was contaminated with 500 ppm of fluorene and
incubated in presence and absence of surfactants (BSL; SDS or Tween 20).
Experiments were carried out in Erlenmeyer flasks using a solid/liquid ratio of 1:10; at
room temperature during 24 h. Liquid phase contained the surfactant at its critical
micellar concentration. The fluorene extracted in the aqueous phase was measured
using a spectrophotometer at 240 nm, by dissolving the samples in acetonitrile: water
(1:1).
Results showed that BSL was able to extract 80 % of fluorene; whereas Tween 20 only
extracted 13 % and SDS extracted 100 % of fluorene contained into the soil. Thus, it
can be concluded that the biosurfactant obtained from L. pentosus is a potential
surface-active compound to extract PAHs from soil, with a close capability to SDS.