Oxydation of oleic acid to (E)-10-hydroperoxy-8-octadecenoic and (E)-10-hydroxy-8-octadecenoic acids by Pseudomonas sp. 42A2

Thirty years with three-dimensional structures of lipoxygenases

The X-ray crystal structures of soybean lipoxygenase (LOX) and rabbit 15-LOX were reported in the 1990s. Subsequent 3D structures demonstrated a conserved U-like shape of the substrate cavities as reviewed here. The 8-LOX:arachidonic acid (AA) complex showed AA bound to the substrate cavity carboxylate-out with C10 at 3.4 Å from the iron metal center. A recent cryo-electron microscopy (EM) analysis of the 12-LOX:AA complex illustrated AA in the same position as in the 8-LOX:AA complex. The 15- and 12-LOX complexes with isoenzyme-specific inhibitors/substrate mimics confirmed the U-fold. 5-LOX oxidizes AA to leukotriene A4, the first step in biosynthesis of mediators of asthma. The X-ray structure showed that the entrance to the substrate cavity was closed to AA by Phe and Tyr residues of a partly unfolded α2-helix. Recent X-ray analysis revealed that soaking with inhibitors shifted the short α2-helix to a long and continuous, which opened the substrate cavity. The α2-helix also adopted two conformations in 15-LOX. 12-LOX dimers consisted of one closed and one open subunit with an elongated α2-helix. 13C-ENDOR-MD computations of the 9-MnLOX:linoleate complex showed carboxylate-out position with C11 placed 3.4 ± 0.1 Å from the catalytic water. 3D structures have provided a solid ground for future research.

Use of Stress Signals of Their Attached Bacteria to Monitor Sympagic Algae Preservation in Canadian Arctic Sediments

Based on the strong aggregation of sympagic (ice-associated) algae and the high mortality or inactivity of bacteria attached to them, it was previously hypothesized that sympagic algae should be significant contributors to the export of carbon to Arctic sediments. In the present work, the lipid content of 30 sediment samples collected in the Canadian Arctic was investigated to test this hypothesis. The detection of high proportions of trans vaccenic fatty acid (resulting from cis-trans isomerase (CTI) activity of bacteria under hypersaline conditions) and 10S-hydroxyhexadec-8(trans)-enoic acid (resulting from 10S-DOX bacterial detoxification activity in the presence of deleterious free palmitoleic acid) confirmed: (i) the strong contribution of sympagic material to some Arctic sediments, and (ii) the impaired physiological status of its associated bacterial communities. Unlike terrestrial material, sympagic algae that had escaped zooplanktonic grazing appeared relatively preserved from biotic degradation in Arctic sediments. The expected reduction in sea ice cover resulting from global warming should cause a shift in the relative contributions of ice-associated vs. pelagic algae to the seafloor, and thus to a strong modification of the carbon cycle.

Dual Behavior of Long-Chain Fatty Acids and Their Cyclooxygenase/Lipoxygenase Metabolites on Human Intestinal Caco-2 Cell Growth

Etiology of colorectal cancer (CRC) is related, at least in part, with nutritional profile and epidemiological data indicating a key role of dietary fat on CRC pathogenesis. Moreover, inflammation and eicosanoids produced from arachidonic acid might have a pivotal role in CRC development. However, the effect of specific fatty acids (FAs) on intestinal epithelial cell growth is not completely studied now. By this reason, the aim of this work is to unravel the effect of different saturated and unsaturated long-chain fatty acids (LCFA) and some LCFA metabolites on CRC cell line growth and their possible mechanisms of action. Our results demonstrated that oleic acid is a potent mitogenic factor to Caco-2 cells, at least in part, through 10-hydroxy-8-octadecenoic synthesized by lipoxigenase pathway, whereas polyunsaturated FAs such as eicosapentaenoic (EPA) acid has a dual behavior effect depending on its concentration. A high concentration, EPA induced apoptosis through intrinsic pathway, whereas at low concentration induced cell proliferation that could be related to the synthesis of eicosanoids such as prostaglandin E₃ and 12-hydroxyeicosapentaenoic acid and the subsequent induction of mitogenic cell signaling pathways (ERK 1/2, CREB, p38α). Thus, this study contributes to understand the complicated relationship between fat ingest and CRC.

Bacterial Biotransformation of Oleic Acid: New Findings on the Formation of γ-Dodecalactone and 10-Ketostearic Acid in the Culture of Micrococcus luteus

Microbial conversion of oleic acid (1) to form value-added industrial products has gained increasing scientific and economic interest. So far, the production of natural lactones with flavor and fragrance properties from fatty acids by non-genetically modified organisms (non-GMO) involves whole cells of bacteria catalyzing the hydration of unsaturated fatty acids as well as yeast strains responsible for further β-oxidation processes. Development of a non-GMO process, involving a sole strain possessing both enzymatic activities, significantly lowers the costs of the process and constitutes a better method from the customers' point of view regarding biosafety issues. Twenty bacteria from the genus of Bacillus, Comamonas, Dietzia, Gordonia, Micrococcus, Pseudomonas, Rhodococcus and Streptomyces were screened for oxidative functionalization of oleic acid (1). Micrococcus luteus PCM525 was selected as the sole strain catalyzing the one-pot transformation of oleic acid (1) into natural valuable peach and strawberry-flavored γ-dodecalactone (6) used in the food, beverage, cosmetics and pharmaceutical industries. Based on the identified products formed during the process of biotransformation, we clearly established a pathway showing that oleic acid (1) is hydrated to 10-hydroxystearic acid (2), then oxidized to 10-ketostearic acid (3), giving 4-ketolauric acid (4) after three cycles of β-oxidation, which is subsequently reduced and cyclized to γ-dodecalactone (6) (Scheme 1). Moreover, three other strains (Rhodococcus erythropolis DSM44534, Rhodococcus ruber PCM2166, Dietzia sp. DSM44016), with high concomitant activities of oleate hydratase and alcohol dehydrogenase, were identified as efficient producers of 10-ketostearic acid (3), which can be used in lubricant and detergent formulations. Considering the prevalence of γ-dodecalactone (6) and 10-ketostearic acid (3) applications and the economic benefits of sustainable management, microbial bioconversion of oleic acid (1) is an undeniably attractive approach.

Algicidal hydroxylated C18 unsaturated fatty acids from the red alga Tricleocarpa jejuensis: Identification, synthesis and biological activity

Bioassay-guided separation of a methanol extract of Tricleocarpa jejuensis by monitoring algicidal activity against the red tide phytoplankton Chattonella antiqua led to the isolation of an active fraction consisting of a mixture of four isomeric compounds. The active compounds were identified as (E)-9-hydroxyoctadec-10-enoic acid (1), (E)-10-hydroxyoctadec-8-enoic acid (2), (E)-11-hydroxyoctadec-12-enoic acid (3) and (E)-12-hydroxyoctadec-10-enoic acid (4) by NMR, IR and mass spectral data. The structures were confirmed by comparison of the NMR and MS data with those of authentic samples of 1-4 obtained by unambiguous syntheses. Synthesized hydroxy acids 1-4 and related compounds were assessed for algicidal activity against C. antiqua and it was found that all of 1-4 had high activity (>80% mortality at 24 h) at a concentration of 20 μg/mL. A structure-activity relationship study using 11 related compounds revealed that the presence of the hydroxyl group is important for the activity and the double bond may be replaced with a triple bond.

Extra Virgin Olive Oil Minor Compounds Modulate Mitogenic Action of Oleic Acid on Colon Cancer Cell Line

Experimental and clinical findings suggest that olive oil has a protective effect, whereas oleic acid consumption induces colorectal cancer (CRC). Considering this apparent contradiction and that olive oil is a complex mix of fatty acids, mainly oleic acid and minor compounds such as phenolic compounds, lignans, hydrocarbons, and triterpenes, we study its effects on intestinal epithelial cell growth. Our results show that oleic acid (1-100 μM) but not elaidic acid induced DNA synthesis and Caco-2 cell growth (2-fold higher than cells without growth factors, p < 0.05). These effects were inhibited by 5-lipoxygenase inhibitors as well as the leukotriene antagonist (p < 0.05), suggesting the implication of this pathway in this mitogenic action. Hydroxytyrosol, oleuropein, pinoresinol, squalene, and maslinic acid (0.1-10 μM) reverted DNA synthesis and Caco-2 cell growth induced by oleic acid. These effects were not the consequence of the cell cycle arrest or the impairment of cell viability with the exception of hydroxytyrosol and maslinic acid that induced cell detachment and apoptosis (35.6 ± 2.3 and 43.2 ± 2.4%, respectively) at the higher concentration assayed. Oleuropein effects can be related with hydroxytyrosol release as a consequence of oleuropein hydrolysis by Caco-2 cells (up to 25%). Furthermore, hydroxytyrosol modulates the arachidonic acid cascade, and this event can be associated with its antimitogenic action. In conclusion, oleic acid and oleic acid in the presence of olive oil representative minor components have opposite effects, suggesting that the consumption of seed oils, high oleic acid seed oils, or olive oil will probably have different effects on CRC.

Yield and kinetic constants estimation in the production of hydroxy fatty acids from oleic acid in a bioreactor by Pseudomonas aeruginosa 42A2

We modelled the production of hydroxy fatty acids from oleic acid by Pseudomonas aeruginosa 42A2 in a bioreactor with a non-dispersive aeration system. First, we designed an adapted wetted-wall gas-absorption column, offering a k La value of 39.9 h(-1), to enhance oxygen absorption in the culture media and prevent foam formation. Then, we analysed different kinetic models to simulate the yield coefficients and the kinetic constants in this bacterial transformation. Monod model fitting (μ max1 = 0.51 h(-1), K S1 = 1.60 C-mol l(-1), μ max2 = 0.12 h(-1), K S2 = 0.035 C-mol l(-1), and k 2 = 0.033 h(-1)) showed a good accuracy with the experimental data sets and was chosen for its simplicity. Lastly, mass balances were carried out to establish the stoichiometry of this biotransformation with the following yield coefficients, Υ X/OA, Υ X/(10S)-HPOME and Υ (10S)-HPOME/(7S10S)-HPOME of 0.172, 0.347 and 2.388 C-mol C-mol(-1), respectively.

Unveiling the genes responsible for the unique Pseudomonas aeruginosa oleate-diol synthase activity

Pseudomonas aeruginosa displays the ability to perform bioconversion of oleic acid into a class of hydroxylated fatty acids known as oxylipins. A diol synthase activity is responsible for such a conversion, which proceeds through the dioxygenation of oleic acid to release hydroperoxide 10-H(P)OME ((10S)-hydroxy-(8E)-octadecenoic acid), followed by conversion of the hydroperoxide intermediate into 7,10-DiHOME ((7S,10S)-dihydroxy-(8E)-octadecenoic acid), both of which accumulate in the culture supernatant. Several mutants of P. aeruginosa PAO1 were analyzed for the production of 10-H(P)OME and 7,10-DiHOME and two of them (ORFs PA2077 and PA2078), unable to release hydroxylated fatty acids, were detected and selected for further analysis. Involvement of ORFs PA2077 and PA2078 in oleate-diol synthase activity was confirmed, and their respective role in the conversion of oleic acid was analyzed by mutation complementation. Activity restoration revealed that gene PA2077 codes for the 10S-dioxygenase activity (10S-DOX) responsible for the first step of the reaction, whereas PA2078 encodes for the (7S,10S)-hydroperoxide diol synthase enzyme (7,10-DS) which allows the conversion of 10-H(P)OME into 7,10-DiHOME. Heterologous expression of both enzymes separately showed that no hetero-complex formation is required for enzymatic activity. Bioinformatics and RT-PCR analysis revealed that both genes constitute a new fine regulated oleate-diol synthase operon, originated by a gene duplication event followed by neofunctionalization for environmental adaptation, being unprecedented in prokaryotes.

Production of 10(S)-hydroxy-8(E)-octadecenoic and 7,10(S,S)-hydroxy-8(E)-octadecenoic ethyl esters by Novozym 435 in solvent-free media

Novozym 435, lipase B from Candida antarctica, was used in this study for the production of ethyl esters. For the first time, trans-hydroxy-fatty acid ethyl esters were synthesized in vitro in solvent-free media. We studied the effects of the substrate-ethanol molar ratio and enzyme synthetic stability of the biocatalyst. To determine the structure of the formed compounds, Fourier transformed infrared spectroscopy, nuclear magnetic resonance, and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry were used, three less time-consuming structural techniques. trans-Hydroxy-fatty acid ethyl esters were synthesized with a reaction yield of 90 % or higher with optimal reaction conditions.

Overproduction, purification, and characterization of extracellular lipoxygenase of Pseudomonas aeruginosa in Escherichia coli

Lipoxygenase (LOX; EC 1.13.11.12,) is an enzyme that is widely used in food industry to improve aroma, rheological, or baking properties of foods. In this study, we described the expression and characterization of Pseudomonas aeruginosa LOX in Escherichia coli. The recombinant LOX was successfully expressed and secreted by E. coli using its endogenous signal peptide. When induced with 1 mM isopropyl β-D-1-thiogalactopyranoside (final concentration) at 20 °C for 47 h, the titer of the recombinant enzyme reached 3.89 U/mL. In order to characterize the catalytic properties, the recombinant LOX was purified to homogeneity on Q High Performance and Mono Q5/50GL sequentially. The molecular weight of the LOX was estimated as 70 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The Km and Vmax of the recombinant enzyme were 48.9 μM and 0.226 μmol/min, respectively. The purified enzyme exhibited a maximum activity at 25 °C and pH 7.5. High-performance liquid chromatography analysis of the linoleic acid hydroperoxides produced by recombinant LOX revealed that the LOX from P. aeruginosa falls into linoleic acid 13(S)-LOX. To the best of our knowledge, this is the first report on the overexpression of extracellular LOX in microorganisms, and the achieved LOX yield is the highest ever reported.

Biochemical characterization of the oxygenation of unsaturated fatty acids by the dioxygenase and hydroperoxide isomerase of Pseudomonas aeruginosa 42A2

We have studied oxygenation of fatty acids by cell extract of Pseudomonas aeruginosa 42A2. Oleic acid ((9Z)-18:1) was transformed to (10S)-hydroperoxy-(8E)-octadecenoic acid ((10S)-HPOME) and to (7S,10S)-dihydroxy-(8E)-octadecenoic acid (7,10-DiHOME). Experiments under oxygen-18 showed that 7,10-DiHOME contained oxygen from air and was formed sequentially from (10S)-HPOME by isomerization. (10R)-HPOME was not isomerized. The (10S)-dioxygenase and hydroperoxide isomerase activities co-eluted on ion exchange chromatography and on gel filtration with an apparent molecular size of approximately 50 kDa. 16:1n-7, 18:2n-6, and 20:1n-11 were also oxygenated to 7,10-dihydroxy fatty acids, and (8Z)-18:1 was oxygenated to 6,9-dihydroxy-(7E)-octadecenoic acid. A series of fatty acids with the double bond positioned closer to ((6Z)-18:1, (5Z,9Z)-18:2) or more distant from the carboxyl group ((11Z)-, (13Z)-, and (15Z)-18:1) were poor substrates. The oxygenation mechanism was studied with [7S-(2)H]18:1n-9, [7R-(2)H]18:2n-6, and [8R-(2)H]18:2n-6 as substrates. The pro-R hydrogen at C-8 was lost in the biosynthesis of (10S)-HPODE, whereas the pro-S hydrogen was lost and the pro-R hydrogen was retained at C-7 during biosynthesis of the 7,10-dihydroxy metabolites. Analysis of the fatty acid composition of P. aeruginosa revealed relatively large amounts of (9E/Z)-16:1 and (11E/Z)-18:1 and only traces of 18:1n-9. We found that (11Z)-18:1 (vaccenic acid) was transformed to (11S,14S)-dihydroxy-(12E)-octadecenoic acid and to a mixture of 11- and 12-HPOME, possibly due to reverse orientation of (11Z)-18:1 at the active site compared with oleic acid. The reaction mechanism of the hydroperoxide isomerase suggests catalytic similarities to cytochrome P450.

Liquid chromatography/tandem mass spectrometric analysis of 7,10-dihydroxyoctadecenoic acid, its isotopomers, and other 7,10-dihydroxy fatty acids formed by Pseudomonas aeruginosa 42A2

Pseudomonas aeruginosa is an opportunistic pathogen, which oxidizes oleic acid to 7(S),10(S)-dihydroxy-8(E)-octadecenoic acid (7,10-(OH)(2)-18:1) of biological and industrial interest. Electrospray tandem mass spectrometric (MS/MS) analysis of hydroxylated fatty acids usually generates characteristic fragments containing the carboxylate anion and formed by alpha-cleavage at the oxidized carbon. These fragments indicate the positions of the hydroxyl group. In contrast, liquid chromatography (LC)/MS/MS analysis of 7,10-(OH)(2)-18:1 yielded a series of other ions with structural information. To study the fragmentation mechanism, we prepared (2)H- and (18)O-labeled isotopomers. We also performed MS(3) analysis of the major ions, and for comparison we generated the corresponding 7,10-dihydroxy metabolites of 16:1n-7, 18:2n-6, and 20:1n-11 with a protein extract of P. aeruginosa. The MS/MS spectra of 7,10-(OH)(2)-18:1 and its isotopomers, 7,10-(OH)(2)-16:1, and 7,10-(OH)(2)-20:1, contained a series of prominent fragments that all hold the omega end. The 8,9-double bond was not essential for this fragmentation, as 7,10-(OH)(2)-18:0, and its isotopomers, formed essentially the same fragments in the lower mass range. In contrast, 7,10-dihydroxy-8(E),12(Z)-octadecadienoic acid (7,10-(OH)(2)-18:2) fragmented by alpha-cleavage at the oxidized carbons with formation of carboxylate anions. Our results demonstrate that C(16)-C(20) fatty acids with a 7,10-dihydroxy-8(E) functionality undergo charge-driven fragmentation after charge migration to the omega-end, whereas the main ions of 7,10-(HO)(2)-18:2 retain charge at the carboxyl group.

Regiospecific enzymatic oxygenation of cis-vaccenic acid in the marine phototrophic bacterium Erythrobacter sp. strain MG3

The fatty acid composition of the marine phototrophic bacterium Erythrobacter sp. strain MG3 was analysed. The involvement of an unusual enzymatic peroxidation of the allylic carbon 10 of cis-vaccenic acid in this strain was confirmed. This process, which seems to be a characteristic of some aerobic and anaerobic phototrophic bacteria, appeared to also act on the allylic carbon 10 of octadeca-5,11-dienoic acid. Enzymatic degradation of 10-hydroperoxyoctadec-11(cis)-enoic acid resulting from the peroxidation of cis-vaccenic acid mainly involves reduction to the corresponding hydroxy acid (probably catalysed by peroxygenases) and cleavage to the corresponding oxoacid, which is then biohydrogenated. Abiotic degradation of this hydroperoxide involves allylic rearrangement to 10-hydroperoxyoctadec-11(trans)-enoic and 12-hydroperoxyoctadec-10(trans)-enoic acids and cyclisation to the very unusual 7,10-epoxyoctadec-11(cis)-enoic acid. Several tests carried out at different periods of growth and under different growth conditions allowed to show that the induction of this enzymatic peroxidation process strongly depends on the physiological state of the cells and is enhanced during C-limitation and at low temperatures.

Production of 7, 10-dihydroxy-8(E)-octadecenoic acid from triolein via lipase induction by Pseudomonas aeruginosa PR3

Hydroxy fatty acids (HFA) have gained importance because of their special properties such as higher viscosity and reactivity compared with other non-hydroxy fatty acids. The bacterial isolate Pseudomonas aeruginosa (PR3) was reported to produce mono-, di-, and trihydroxy fatty acids from different unsaturated fatty acids. Of those, 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) was produced with high yield from oleic acid by PR3. Up to now, the substrates used for microbial HFA production were free fatty acids. However, it is possible to utilize triacylglycerides, specifically triolein containing three oleic groups, as a substrate by microbial enzyme system involved in HFA production from oleic acid. In this study we used triolein as a substrate and firstly report that triolein could be efficiently utilized by PR3 to produce DOD. Triolein was first hydrolyzed into oleic acid by the triolein-induced lipase and then the released oleic acid was converted to DOD by PR3. Results from this study demonstrated that natural vegetable oils, without being intentionally hydrolyzed, could be used as efficient substrates for the microbial production of value-added hydroxy fatty acids.

Cloning and expression of a lipoxygenase from Pseudomonas aeruginosa 42A2

In order to produce (S) 10-monohydroxy-8E-octadecenoic acid (MHOD) from oleic acid, a full-length probable lipoxygenase cDNA from Pseudomonas aeruginosa 42A2 was cloned and expressed in Escherichia coli BL21(DE3). The recombinant protein was purified by affinity chromatography to electrophoretic homogeneity and specifically stained. Its molecular mass was 70 kDa. The activity of the rec-LOX with oleic acid was about 30% of that of the preferred substrate, linoleic acid (100%). Bacterial LOX forms a new subfamily in the lipoxygenase phylogenetic tree.

GC-MS structural characterization of fatty acids from marine aerobic anoxygenic phototrophic bacteria

The FA composition of 12 strains of marine aerobic anoxygenic phototrophic bacteria belonging to the genera Erythrobacter, Roseobacter, and Citromicrobium was investigated. GC-MS analyses of different types of derivatives were performed to determine the structures of the main FA present in these organisms. All the analyzed strains contained the relatively rare 11-methyloctadec-12-enoic acid, and three contained 12-methyl-octadec-11-enoic acid, which has apparently never been reported before. High amounts of the very unusual octadeca-5,11-dienoic acid were present in 9 of the 12 strains analyzed. A FA containing a furan ring was detected in three strains. Analytical data indicated that this FA was 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid. A very interesting enzymatic peroxidation of the allylic carbon 10 of cis-vaccenic acid was observed in three strains. Deuterium labeling and GC-MS analyses enabled us to demonstrate that this enzymatic process involves the initial dioxygenase-mediated formation of 10-hydroperoxyoctadec-11(cis)-enoic acid, which is then isomerized to 10-hydroperoxyoctadec-11(trans)-enoic acid and converted to the corresponding hydroxyacids and oxoacids. Different biosynthetic pathways were proposed for these different compounds.

The opportunistic pathogen Pseudomonas aeruginosa carries a secretable arachidonate 15-lipoxygenase

In mammals, lipoxygenases play key roles in inflammation by initiating the transformation of arachidonic acid into potent bioactive lipid mediators such as leukotrienes and lipoxins. In general, most bacteria are believed to lack lipoxygenases and their polyunsaturated fatty acid substrates. It is therefore of interest that an ORF (PA1169) with high homology to eukaryotic lipoxygenases was discovered by analysis of the whole-genome sequence of the opportunistic bacterial pathogen Pseudomonas aeruginosa. Using TLC and liquid chromatography-UV-tandem mass spectrometry (LC-UV-MS-MS), we demonstrate that PA1169 encodes a bacterial lipoxygenase (LoxA) that converts arachidonic acid into 15-hydroxyeicosatetraenoic acid (15-HETE). Although mammalian lipoxygenases are cytoplasmic enzymes, P. aeruginosa LoxA activity is secreted. Taken together, these results suggest a mechanism by which a pathogen-secreted lipoxygenase may modulate host defense and inflammation via alteration of the biosynthesis of local chemical mediators.

Regiospecific enzymatic oxygenation of cis-vaccenic acid during aerobic senescence of the halophilic purple sulfur bacterium Thiohalocapsa halophila

A regiospecific oxygenation of the allylic carbon 10 of cis-vaccenic acid has been observed in senescent cells of the halophilic purple sulfur bacterium Thiohalocapsa halophila incubated under aerobic conditions in darkness. The results obtained strongly suggest that these enzymatic processes involve the initial dioxygenase-mediated formation of 1 O-hydroperoxyoctadec-cis-11-enoic acid, which is not accumulated in the cells of T. halophila owing to its high cytotoxic properties. Deuterium labeling and GC-MS analyses enabled us to demonstrate that subsequent enzymatic conversions of this allylic hydroperoxide involved reduction, cleavage, isomerization, and saturation reactions. Some of the specific oxidation products thus formed could constitute potential T. halophila biomarkers.

Screening and production of rhamnolipids by Pseudomonas aeruginosa 47T2 NCIB 40044 from waste frying oils

World production of oils and fats is about 2.5 million tonnes, 75% of which are derived from plants. Most of them are used in the food industry for the manufacture of different products, or directly as salad oil. Great quantities of waste are generated by the oil and fat industries: residual oils, tallow, marine oils, soap stock, frying oils. It is well known that the disposal of wastes is a growing problem and new alternatives for the use of fatty wastes should be studied. Used frying oils, due to their composition, have great potential for microbial growth and transformation. The use of economic substrates such as hydrophobic wastes meets one of the requirements for a competitive process for biosurfactant production. In the Mediterranean countries, the most used vegetable oils are sunflower and olive oil. Here we present a screening process is described for the selection of micro-organism strains with the capacity to grow on these frying oils and accumulate surface-active compounds in the culture media. From the 36 strains screened, nine Pseudomonas strains decreased the surface tension of the medium to 34-36 mN/M; the emulsions with kerosene remained stable for three months. Two Bacillus strains accumulated lipopeptide and decreased the surface tension to 32-34 mN/m. Strain Ps. aeruginosa 47T2 was selected for further studies. The effect of nitrogen and a C/N of 8. 0 gave a final production of rhamnolipid of 2.7 g l-1 as rhamnose, and a production yield of 0.34 g g-1.