Abstract: AIMS: To study the growth inhibitory properties of a series of phytosphingosine (PHS) and phytoceramide (PHC) analogues. METHODS AND RESULTS: A panel of two yeast (Candida albicans and Saccharomyces cerevisiae) and six moulds (Aspergillus repens, Aspergillus niger, Penicillium chrysogenum, Cladosporium cladosporioides, Arthroderma uncinatum and Penicillium funiculosum) has been used in this study. A series of new PHS and PHC analogues differing at the sphingoid backbone and the functional group at C1 position were synthesized. CONCLUSIONS: Among PHS analogues, 1-azido derivative 1c, bearing the natural D-ribo stereochemistry, showed a promising growth inhibitory profile. Among PHC analogues, compound 12, with a bulky N-pivaloyl group and a Z double bond at C3 position of the sphingoid chain, was the most active growth inhibitor. Minimal inhibitory concentration values were in the range of 23-48 micromol l(-1) for 1c and 44-87 micromol l(-1) for 12. SIGNIFICANCE AND IMPACT OF THE STUDY: Only scattered data on the antifungal activity of phytosphingolipids have been reported in the literature. This is the first time that a series of analogues of this kind are tested and compared to discern their structural requirements for antifungal activity.

Abstract: Biocompatible cationic surfactants from the amino acid lysine (hydrochloride salts of N(varepsilon)-lauroyl lysine methyl ester, N(varepsilon)-myristoyl lysine methyl ester and N(varepsilon)-palmitoyl lysine methyl ester) have been prepared in high yields by lysine acylation in varepsilon position with three natural saturated fatty acids. The micellization process of these surfactants has been studied using the PGSE-NMR technique. The compounds were tested as antimicrobial agents against Gram-positive and Gram-negative bacteria. The surfactants show moderate antimicrobial activity against the Gram-positive bacteria but Gram-negative bacteria are resistant to these surfactants in the concentration range tested. The haemolytic activity is considerably lower than those reported for other cationic N(alpha)-acyl amino acid analogues. The acute toxicity against Daphnia magna and biodegradability was studied. The toxicity is clearly lower than that reported for conventional cationic surfactants from quaternary ammonium and the three surfactants from lysine can be classified as ready biodegradable surfactants.

Abstract: Pseudomonas aeruginosa 42A2 produces a polyunsaturated polyhydroxyalkanoates (PHA-L) when grown on linseed oil as a substrate. Its high unsaturation content (36.5%) provides highly reactive PHA-L, generating a cross-linked biopolymer after ultraviolet (UV) irradiation. Both PHAs (PHA-L and uvPHA-L) were characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy, gel permeation chromatography, gas chromatography-mass spectrometry and differential scanning calorimetry-thermogravimetric analysis. The structural analysis of the new polymer revealed a dramatic decrease in unsaturated monomer content (8.5%), due to the complete disappearance of the polyunsaturated monomers (C(12:2), C(14:2), and C(14:3)). The cross-linking reaction was also confirmed by atomic force microscopy (AFM) and transmission electron microscopy. AFM showed morphological changes in bacteria cells with and without PHA granules. The microscope techniques provided us with micrographs of the native and cross-linked polymers, showing the formation of a reticular structure as the consequence of the cross-linking reaction.

Abstract: Aqueous two-phase systems often face mass transfer limitations due to very poor miscibility of the fluids, and to enhance the homogeneity (or emulsification) in the reaction volume, high energy inputs are required which result in high shear forces in the culture medium. For the purposes of emulsification, microporous systems have advantages over other conventional methods due to mild operating conditions and narrow droplet-size distribution. In this study, emulsification within the culture volume was achieved by feeding the oily substrate (dispersed phase) into the aqueous medium (dispersion phase) via ceramic membranes integrated in the bioreactor. The method was investigated for bioprocesses aimed at producing rhamnolipids and polyhydroxyalkanoates (PHA). Better homogenization of the mixed volume and hence improved consumption of oily substrate was successful. Surfactants are produced by various bacterial cultures, especially Pseudomonas aeruginosa species, when oil is present as the only carbon source. Are surfactants produced only as a result of bacteria feeding on the oily substrate, or as a requirement to feed on the oily substrate, owing to their surface-active characteristics? This paper also intends to draw some conclusions in this respect.

Abstract: The interaction of a dirhamnolipid biosurfactant secreted by Pseudomonas aeruginosa with bovine serum albumin was studied by means of various physical techniques. Binding of the biosurfactant to bovine serum albumin was first characterized by isothermal titration calorimetry, showing that one or two molecules of dirhamnolipid, in the monomer state, bound to one molecule of the protein with high affinity. These results were confirmed by surface tension measurements in the absence and presence of bovine serum albumin. As seen by differential scanning calorimetry, dirhamnolipid shifted the temperature of the thermal unfolding of bovine serum albumin toward higher values, thus increasing the stability of the protein on heating. The impact of dirhamnolipid on the structure of the native protein was low, since most of the secondary structure remained unaffected upon interaction with the biosurfactant, as shown by FTIR spectroscopy. However, 2D correlation infrared spectroscopy indicated that the sequence of temperature-induced structural changes in native bovine serum albumin was modified by the presence of the biosurfactant. The consequences of these results in relation to possible applications of these dirhamnolipid biosurfactants for protein studies are discussed.

Abstract: Trehalose lipids are an important group of glycolipid biosurfasctants mainly produced by rhodococci. Beside their known industrial applications, there is an increasing interest in the use of these biosurfactants as therapeutic agents. We have purified a trehalose lipid from Rhodococcus sp. and made a detailed study of the effect of the glycolipid on the thermotropic and structural properties of phosphatidylethanolamine membranes of different chain length and saturation, using differential scanning calorimetry, small and wide angle X-ray diffraction and infrared spectroscopy. It has been found that trehalose lipid affects the gel to liquid crystalline phase transition of phosphatidylethanolamines, broadening and shifting the transition to lower temperatures. Trehalose lipid does not modify the macroscopic bilayer organization of saturated phosphatidylethanolamines and presents good miscibility both in the gel and the liquid crystalline phases. Infrared experiments evidenced an increase of the hydrocarbon chain conformational disorder and an important dehydrating effect of the interfacial region of the saturated phosphatidylethanolamines. Trehalose lipid, when incorporated into dielaidoylphosphatidylethanolamine, greatly promotes the formation of the inverted hexagonal HII phase. These results support the idea that trehalose lipid incorporates into the phosphatidylethanolamine bilayers and produces structural perturbations which might affect the function of the membrane.

Abstract: Trehalose lipids are biosurfactants produced by rhodococci that, in addition to their well known potential industrial and environmental uses, are gaining interest in their use as therapeutic agents. The study of the interaction of biosurfactants with membranes is important in order to understand the molecular mechanism of their biological actions. In this work we look into the interactions of a bacterial trehalose lipid produced by Rhodococcus sp. with dimyristoylphosphatidylserine membranes by using differential scanning calorimetry, X-ray diffraction and infrared spectroscopy. Differential scanning calorimetry and X-ray diffraction show that trehalose lipid broadens and shifts the phospholipid gel to liquid-crystalline phase transition to lower temperatures, does not modify the macroscopic bilayer organization and presents good miscibility both in the gel and the liquid-crystalline phases. Infrared experiments show that trehalose lipid increases the fluidity of the phosphatidylserine acyl chains, changed the local environment of the polar head group, and decreased the hydration of the interfacial region of the bilayer. Trehalose lipid was also able to affect the thermotropic transition of dimyristoylphosphatidyserine in the presence of calcium. These results support the idea that trehalose lipid incorporates into the phosphatidylserine bilayers and produces structural perturbations which might affect the function of the membrane.

Abstract: The process of micelle formation, along with the formation of higher order aggregates, is described for a dirhamnolipid extracellular biosurfactant secreted by Pseudomonas aeruginosa. As determined by surface tension measurements, at pH 7.4 the CMC of dirhamnolipid is 0.110 mM, whereas at pH 4.0 it falls to 0.010 mM, indicating that the negatively charged diRL has a much higher CMC value than the neutral species. Centrifugation and dynamic light scattering measurements show formation of larger aggregates at concentrations above the CMC. These aggregates have been shown by electron microscopy to be mainly multilamellar vesicles of heterogeneous size. X-ray scattering gave a value of 32 A for the interlamellar repeat distance of these vesicles. Taking into account the experimental data, a molecular modelling of the dirhamnolipid moiety has been carried out, which details the size of the hydrophilic and hydrophobic portions, and suggests the possible intermolecular interactions responsible for the stabilisation of dirhamnolipid aggregates. The relevance of this aggregation behaviour is discussed with respect to the molecular basis of its activities.

Abstract: The study of the interaction of biosurfactants with biological membranes is of great interest in order to gain insight into the molecular mechanisms of their biological actions. In this work we report on the interaction of a bacterial trehalose lipid produced by Rhodococcus sp. with phosphatidylcholine membranes. Differential scanning calorimetry measurements show a good miscibility of the glycolipid in the gel state and immiscibility in the fluid state, suggesting domain formation. These domains have been visualized and characterized, for the first time, by scanning force microscopy. Incorporation of trehalose lipid into phosphatidylcholine membranes produces a small shift of the antisymmetric stretching band toward higher wavenumbers, as shown by FTIR, which indicates a weak increase in fluidity. The C=O stretching band shows that incorporation of trehalose lipid increases the proportion of the dehydrated component in mixtures with the three phospholipids at temperatures below and above the gel to liquid-crystalline phase transition. This dehydration effect is also supported by data on the phospholipid P=O stretching bands. Small-angle X-ray diffraction measurements show that in the samples containing trehalose lipid the interlamellar repeat distance is larger than in those of pure phospholipids. These results are discussed within the frame of trehalose lipid domain formation, trehalose lipid/phospholipid interactions and its relevance to membrane-related biological actions.

Abstract: Rhamnolipids are bacterial biosurfactants produced by Pseudomonas spp. These compounds have been shown to present several interesting biological activities, restricting the growth of Bacillus subtilis and showing zoosporicidal activity on zoosporic phytopathogens. It has been suggested that the interaction with the membrane could ultimately be responsible for these actions. Therefore, it is of great interest to gain insight into the molecular mechanism of the interaction of purified rhamnolipids with the various phospholipid components of biological membranes. In this work, the critical micelle concentration (cmc) of a purified dirhamnolipid produced by Pseudomonas aeruginosa has been determined both by isothermal titration calorimetry and surface tension measurements. The partition coefficients from water to membranes of different compositions, as well as the corresponding thermodynamic parameters, have been determined by isothermal titration calorimetry measurements. The results indicate that dirhamnolipid membrane partitioning is an entropically driven process. The presence of cholesterol in the membrane decreases the partition of dirhamnolipid. On the other hand, phosphatidylethanolamine stimulates dirhamnolipid binding, whereas lysophosphatidylcholine opposes binding, suggesting that the biosurfactant behaves as an inverted-cone-shaped molecule. The values obtained for the cmc and the partition constant are considered in relation to the surfactant potency of dirhamnolipids.

Abstract: Rhamnolipids are bacterial biosurfactants produced by Pseudomonas spp. These compounds have been shown to present several interesting biological activities, restricting the growth of Bacillus subtilis and showing zoosporicidal activity on zoosporic phytopathogens. It has been suggested that the interaction with the membrane could be the ultimate responsible for these actions. Therefore, it is of great interest to get insight into the molecular mechanism of the interaction of purified rhamnolipids with the various phospholipid components of biological membranes. In this paper we report on the phase behaviour of mixtures of dielaidoylphosphatidylethanolamine (DEPE) with a purified dirhamnolipid (DiRL) fraction from Pseudomonas aeruginosa, as studied by a number of physical techniques such as differential scanning calorimetry, FTIR, small angle X-ray (SAX) diffraction and dynamic light scattering. Our data indicate that the presence of DiRL counteracts the tendency of DEPE to form vesicular aggregates of large size, forming vesicles of smaller diameter which most probably have a lower lamellarity index. The partial phase diagram obtained from calorimetric data shows a complex behaviour with a solid-phase immiscibility. X-ray diffraction shows that DiRL has a bilayer stabilizing effect, impeding formation of the inverted hexagonal-HII phase of DEPE. The presented data are discussed focussing into how DiRL/DEPE interactions could help to explain the membrane perturbing activities of this biosurfactant.

Abstract: OBJECTIVES: The aim of this study is to gain insight into the mechanism of the antimicrobial action of a novel arginine-based surfactant, bis(N(alpha)-caproyl-L-arginine)-1,3-propanediamine dihydrochloride [C(3)(CA)(2)]. METHODS: To this end, we compared its effects against Staphylococcus aureus and Escherichia coli with those caused by the commercial and widely known antiseptic, chlorhexidine dihydrochloride (CHX). RESULTS: Both disrupted the cell membrane of the target bacteria to cause potassium leakage and morphological damage. The effect of C(3)(CA)(2) on E. coli was concentration dependent, causing loss of membrane potential and membrane integrity leading to cell death, whereas CHX did not have these effects on E. coli. The effect of C(3)(CA)(2) on S. aureus was the formation of mesomes and cytoplasmic clear zones, but the loss of membrane potential and membrane integrity was slightly lower than that with CHX. CONCLUSIONS: We propose that C(3)(CA)(2) acts preferentially against Gram-negative bacteria through strong initial binding to the surface lipopolysaccharides and subsequently partitioning into the cell membrane to cause membrane damage, followed by cell death.

Abstract: Rhamnolipids are biosurfactants produced by Pseudomonas aeruginosa which are well known for their potential industrial and environmental uses. Rhamnolipids have gained considerable interest in recent years due to their potential use in cosmetics and pharmaceutics. They also show broad biological activities and have potential applications as therapeutic agents. The amphiphilic nature of rhamnolipids points to the membrane as their hypothetical site of action. We have purified dirhamnolipid and studied its interaction with phosphatidylcholine membranes, using differential scanning calorimetry, X-ray diffraction and infrared spectroscopy. It has been found that dirhamnolipid greatly affects the gel to liquid crystalline phase transition of phosphatidylcholines, broadening and shifting the transition to lower temperatures. Dirhamnolipid increases the interlamellar repeat distance of phosphatidylcholines and reduces the long-range order of the multilamellar systems. The phospholipid hydrocarbon chain conformational disorder is increased and the packing of the phospholipid molecules is perturbed in the presence of dirhamnolipid. The above evidence supports the idea that dirhamnolipid intercalates into the phosphatidylcholine bilayers and produces structural perturbations which might affect the function of the membrane.

Abstract: Novel bis(N(alpha)-phenylacetyl-L-arginine)-alpha,omega-alkanediamide dihydrochloride (bis(PhAcArg)) derivatives with antimicrobial activity were designed and synthesised by a chemoenzymatic strategy. The new structures consist of two N(alpha)-phenylacetyl-L-arginine moieties connected by an alkanediamine spacer chain of 6, 8, 10, 12, and 14 methylene units through amide bonds. The key step in the chemoenzymatic strategy is the double aminolysis of the N(alpha)-phenylacetyl-L-arginine methyl ester by the corresponding alpha,omega-alkanediamine catalyzed by papain in ethanolic media. The compounds synthesised were tested as antimicrobials against 15 bacterial and 8 fungal species. The antimicrobial activity and selectivity depend strongly on the spacer chain length. The bis(PhAcArg) derivative with the spacer chain of 12 methylene groups gave the lowest MIC values against Gram-positive bacteria, whereas that with 14 methylene units was the best against Gram-negative bacteria. Interestingly, these novel compounds showed enhanced antibacterial activity relative to the lead compound, bis(N(alpha)-caproyl-L-arginine)-1,3-propanediamide dihydrochloride (C(3)(CA)(2)), and moderate antifungal activity. Moreover, tests of haemolytic activity toward human erythrocytes revealed that haemolysis increases with spacer chain length. Importantly, the compounds were classified as not irritating to eyes, with the exception of the compound with the spacer chain of 14 methylene groups, which was a slight eye irritant.

Abstract: 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.

Abstract: The isolation of a new lipoxygenase-like (LOX-like) enzyme from Pseudomonas 42A2 and its characterization is described. The enzyme, located in the periplasm of the cell, which contained 0.55 mol of Fe2+ per mol of protein, is monomeric and has a molecular mass of 45 kDa. In the presence of oxygen, the enzyme converts oleic acid into (E)-10-hydroperoxy-8-octadecenoic acid (HPOD), which decomposes to the corresponding (E)-10-hydroxy-8-octadecenoic acid (HOD). The absolute configuration of this acid was determined as S on the basis of exciton-coupled CD data, and specific rotation and NMR analysis of the corresponding p -bromobenzoate derivative. The reaction in vivo leads to the dihydroxy derivative (E)-7,10-dihydroxy-8-octadecenoic acid (DHOD), so that the three hydroxy-fatty acids can be isolated from the culture medium. The activity of the enzyme was optimal between 25 and 30 degrees C and 44% of its activity still remained at 55 degrees C. Its optimal pH is 8.5-9; and the presence of magnesium ions increased LOX activity by 1.5. The activity of the LOX is highest in unsaturated fatty acids containing double bonds in position 9 (oleic, linoleic and linolenic acids), linoleic acid being preferred (100% activity) over linolenic (60.4%) and oleic acids (46%). However, kinetic studies showed that the affinity of the enzyme is similar for the three substrates.

Abstract: AIMS: Here we study the effect of monohydrochloride of L-arginine, N(alpha)-lauroyl ethylester (LAE), a cationic preservative derived from lauric acid and arginine, on the cell envelopes of Salmonella typhimurium and Staphylococcus aureus at sub-lethal concentration such as their respective minimal inhibitory concentrations, 32 and 8 microg ml(-1), respectively. METHODS AND RESULTS: Bacterial populations were studied by using transmission electron and fluorescence microscopy (TEM and FM), flow cytometry (FC) and ion-flux across the cellular membrane. Cell integrity was altered mainly in the outer membrane of S. typhimurium, but there was no significant change in the cytoplasm. However, in Staph. aureus, clear zones, abnormal septation and mesosome-like structures were observed in the cytoplasm. Bacterial populations were double-stained with propidium iodide (PI) and SYTO-13 for FC analysis. In S. typhimurium the proportion of damaged cells after 24 h was 97% and in Staph. aureus 56.3%. LAE induced transmembrane ion flux, the increase of potassium leakage after 30 min of contact was 7.7 and 3.34 microg ml(-1) for Staph. aureus and S. typhimurium, respectively. Membrane disruption was detected by measuring the proton flow across the membrane. CONCLUSIONS: Disturbance in membrane potential and structural changes was caused by LAE, although cells were not disrupted. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first time the cellular effects of LAE on bacterial cells were studied.

Abstract: Pseudomonas aeruginosa LBI isolated from petroleum-contaminated soil produced rhamnolipids (RL(LBI)) when cultivated on soapstock as the sole carbon source. HPLC-MS analysis of the purified culture supernatant identified 6 RL homologues (%): R(2) C(10) C(10) 28.9; R(2) C(10) C(12:1) 23.0; R(1) C(10) C(10) 23.4; R(2) C(10) C(12) 11.3; R(2) C(10) C(12) 7.9; R(2) C(10) C(12) 5.5. To assess the potential antimicrobial activity of the new rhamnolipid product, RL(LBI), its physicochemical properties were studied. RL(LBI) had a surface tension of 24 mN m(-1) and an interfacial tension of 1.31 mN m(-1); the cmc was 120 mg l(-1). RL(LBI) produced stable emulsions with hydrocarbons and vegetable oils. This product showed good antimicrobial behaviour against bacteria: MIC for Bacillus subtilis, Staphylococcus aureus and Proteus vulgaris was 8 mg l(-1), for Streptococcus faecalis 4 mg l(-1), and for Pseudomonas aeruginosa 32 mg l(-1). RL(LBI) was active against phytopathogenic fungal species, MIC values of 32 mg l(-1) being found against Penicillium, Alternaria, Gliocadium virens and Chaetonium globosum. Due to its physicochemical properties and antimicrobial behaviour, RL(LBI) could be used in bioremediation treatment and in the food, cosmetic and pharmaceutical industries.

Abstract: Pseudomonas aeruginosa 47T2, grown in submerged culture with waste frying oil as a carbon source, produced a mixture of rhamnolipids with surface activity. Up to 11 rhamnolipid homologs (Rha-Rha-C(8)-C(10); Rha-C(10)-C(8)/Rha-C(8)-C(10);Rha-Rha-C(8)-C(12:1); Rha-Rha-C(10)-C(10); Rha-Rha-C(10)-C(12:1); Rha-C(10)-C(10); Rha-Rha-C(10)-C(12)/Rha-Rha-C(12)-C(10); Rha-C(10)-C(12:1)/Rha-C(12:1)-C(10); Rha-Rha-C(12:1)-C(12); Rha-Rha-C(10)-C(14:1); Rha-C(10)-C(12)/Rha-C(12)-C(10)) were isolated from cultures of P. aeruginosa 47T2 from waste frying oil and identified by HPLC-MS analysis. This article deals with the production, isolation, and chemical characterization of the rhamnolipid mixture RL(47T2). The physicochemical and biological properties of RL(47T2) as a new product were also studied. Its surface tension decreased to 32.8 mN/m; and the interfacial tension against kerosene to 1 mN/m. The critical micellar concentration for RL(47T2) was 108.8 mg/mL. The product showed excellent antimicrobial properties. Antimicrobial activity was evaluated according to the minimum inhibitory concentration (MIC), the lowest concentration of an antimicrobial agent that inhibits development of visible microbial growth. Low MIC values were found for bacteria Serratia marcescens (4 microg/mL), Enterobacter aerogenes (8 microg/mL), Klebsiella pneumoniae (0.5 microg/mL), Staphylococcus aureus and Staphylococcus epidermidis (32 microg/mL), Bacillus subtilis (16 microg/mL), and phytopathogenic fungal species: Chaetonium globosum (64 microg/mL), Penicillium funiculosum (16 microg/mL), Gliocadium virens (32 microg/mL) and Fusarium solani (75 microg/mL).

Abstract: Biological properties of novel gemini (double-chain/double-head) cationic surfactants, Nalpha,Nomega-bis(Nalpha-acylarginine)alpha,omega-alkylendiamides, so-called bis(Args), are reported. The effect of both the alkyl (10 and 12 carbon atoms) and the spacer chain (from 2-10 methylene groups) of bis(Args) on their antimicrobial activity, acute toxicity on Daphnia magna and Photobacterium phosphoreum, and aerobic biodegradability is studied. These surfactants constitute a novel class of chemicals of low toxicity with excellent surface properties and considerable antimicrobial activity. The aquatic toxicity of these compounds is lower than that of the conventional Monoquats. As regards the biodegradation test, the molecules with a spacer chain < or =6 methylene groups can be considered as ready biodegradable. The increase of hydrophobicity in the bis(Args) is a negative structural parameter for their environmental behavior.

Abstract: The accumulation of cytoplasmic polyhydroxyalkanoates (PHAs) and the heterogeneity ofbacterial populations were analysed by flow cytometry and SYTO-13 and Nile red staining in rhamnolipid-producing Pseudomonas aeruginosa cultures grown in waste frying oil as carbon source. A combination of SYTO-13 and Nile red fluorescence with cytometric forward and side scatter values may allow increases in the final production of polyhydroxyalkanoates (PHA) by two basic mechanisms: (i) rapid assessment of polyhydroxyalkanoate content and (ii) definition of flow cytometric cell sorting protocols to select high polyhydroxyalkanoate (PHA)-producing strains. We report a rapid (less than 30 min) flow cytometric assessment of PHAs in Pseudomonas aeruginosa 47T2 following Nile red staining: (i) to estimate cellular PHAs content; (ii) to study heterogeneity of the batch cultures producing PHAs and (iii) to establish the basis for sorting sub-populations with a high capacity to accumulate PHAs.

Abstract: 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.

Abstract: Biotransformation of oleic acid with Pseudomonas sp. 42A2 has been found to produce(E)-10-hydroxy-8-octadecenoic acid (2a), (E)-10-hydroperoxy-8-octadecenoic acid (3a), and (E)-7,10-dihydroxy-8-octadecenoic acid (4a). Structures of the metabolites were fully characterized by infrared and 1H and 13C NMR spectra of the acids, by fast atom bombardment (FAB) and electron impact (EI) and chemical ionization (CI) mass spectrometry of the corresponding methyl esters. This is the first time that the two former compounds of trans stereochemistry have been described to have originated from a Pseudomonas sp. cell culture. Time course of products accumulation showed that biotransformation started with bacterial growth, the amount of products 2a (5.58 g/l) and 4a (2.63 g/l) being optimum after 24 h of incubation while hydroperoxide 3a (1.15 g/l) reached its maximum after 16 h of the biotransformation process. Experiments conducted to ascertain whether the conversion enzyme(s) was cell-bound or extracellular, showed that the enzyme(s) is cell bound, located in the periplasmic space and has lipoxygenase activity.

Abstract: In this paper, the antibacterial activity against Bacillus pumilus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa of the wool fabrics treated with new antimicrobial bis-quaternary surfactants, DABK and DABB, is studied. The activity was established on the basis of the agar diffusion and protective antibacterial test results and on the basis of scanning electron microscopy (SEM) observation. The results were compared with the HTAB, a monoquaternary surfactant of conventional use. The results from the agar diffusion and protective antibacterial tests do not enable us to confirm whether these compounds are potentially useful antimicrobial agents for the protection of textiles. However, SEM observations show clearly the efficacy of these compounds to protect the wool fabrics against the micro-organisms. SEM has been a useful technique for the assessment of antibacterial activity in textiles.