Produccion De Biosurfactante

Production of Biosurfactant Using Different Hydrocarbons by
Pseudomonas aeruginosa EBN-8 Mutant
Zulfiqar Ali Razaa,b, Muhammad Saleem Khana, Zafar M. Khalidb,*, and
Asma Rehmanb
a
b

National Centre of Excellence in Physical Chemistry, University of Peshawar, Peshawar
25120, Pakistan
Environmental Biotechnology Division, National Institute for Biotechnology and Genetic
Engineering(NIBGE), P.O. Box 577, Faisalabad, Pakistan. Fax: 92-41-2 65 14 72.
E-mail: zmkhalid@yhaoo.com

* Author for correspondence and reprint requests
Z. Naturforsch. 61 c, 87Ð94 (2006); received May 30/July 28, 2005
The present investigation dealt with the use of previously isolated and studied gamma-ray
mutant strain Pseudomonas aeruginosa EBN-8 for the production of biosurfactant by using
differenthydrocarbon substrates viz. n-hexadecane, paraffin oil and kerosene oil, provided
in minimal medium, as the sole carbon and energy sources. The batch experiments were
conducted in 250 mL Erlenmeyer flasks, containing 50 mL minimal salt media supplemented
with 1% (w/v) hydrocarbon substrate, inoculated by EBN-8 and incubated at 37 ∞C and
100 rpm in an orbital shaker. The sampling was done on24 h basis for 10 d. The surface
tension of cell-free culture broth decreased from 53 to 29 mN/m after 3 and 4 d of incubation
when the carbon sources were paraffin oil and n-hexadecane, respectively. The largest reduction in interfacial tension from 26 to 0.4 mN/m was observed with n-hexadecane, while critical
micelle dilution was obtained as 50 ¥ CMC for paraffin oil as carbon source. Whengrown
on n-hexadecane and paraffin oil, the EBN-8 mutant strain gave 4.1 and 6.3 g of the rhamnolipids/L, respectively. These surface-active substances subsequently allowed the hydrocarbon
substrates to disperse readily as emulsion in aqueous phase.
Key words: Biosurfactant, Hydrocarbons, Pseudomonas aeruginosa

Introduction
Biosurfactants are a structurally diverse class of
compoundsconsisting of a hydrophobic portion,
which usually consists of saturated or unsaturated
(hydroxy) fatty acids or fatty alcohols, and a hydrophilic portion, which is composed of mono-, oligo- or polysaccharides, amino acids or peptides or
carboxylate or phosphate groups (Lang and Wullbrandt, 1999). The major classes of biosurfactants
are: glycolipids, phospholipids, neutral lipids, fatty
acids,lipopolysaccharides, lipoproteins-lipopeptides, flavolipids, complete cell surface itself and
those not fully characterized (Bodour et al., 2004;
Desai and Banat, 1997). Biosurfactants are extracellular macromolecules produced by bacteria,
yeast and fungi, and in particular by natural and
recombinant bacteria when grown on different
carbon sources. The microbial surfactants have
gained attentionin recent years due to their commercial importance, diverse desirable characteristics such as biodegradability, selectively effectiveness, low toxicity, ecological acceptability and their
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ability to be produced from cheaper substrates
(Ishigami, 1997; Makkar and Cameotra, 1997).
They are finding vast potential applications in environmental protection,petroleum, food, mining,
agriculture, pharmaceutical, textile, leather and
other industries (Banat et al., 2000; Desai and Banat, 1997). Biosurfactants create micro-emulsions
in which micelle formation occurs where hydrocarbons can be solubilized in water and vice versa
(Ashtaputre and Shah, 1995; Haditirto et al., 1989).
They mainly reduce surface and interfacial tensions
both in aqueous solutionsand hydrocarbon mixtures, therefore increasing the aqueous concentrations of poorly soluble compounds which lead to
improving the accessibility of these substrates to
the microorganisms (Banat, 1995). These emulsification properties have been demonstrated to enhance the hydrocarbon degradation in the environment, hence making them potential tool for the
oil spill pollution control (Banat et...