A. Manresa

Chemical structure, surface properties and biological activities of the biosurfactant produced by Pseudomonas aeruginosa LBI from soapstock

Pseudomonas aeruginosa LBI isolated from petroleum-contaminated soil produced rhamnolipids (RLLBI) when cultivated on soapstock as the sole carbon source. HPLC–MS analysis of the purified culture supernatant identified 6 RL homologues (%): R2 C10 C10 28.9; R2 C10 C12:1 23.0; R1 C10 C10 23.4; R2 C10 C12 11.3; R2 C10 C12 7.9; R2 C10 C12 5.5. To assess the potential antimicrobial activity of the new rhamnolipid product, RLLBI, its physicochemical properties were studied. RLLBI 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. RLLBI 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. RLLBI 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, RLLBI could be used in bioremediation treatment and in the food, cosmetic and pharmaceutical industries.

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.

Cellular effects of monohydrochloride of l‐arginine, Nα‐lauroyl ethylester (LAE) on exposure to Salmonella typhimurium and Staphylococcus aureus

Aims:  Here we study the effect of monohydrochloride of l‐arginine, Nα‐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 μg ml−1, respectively.

Isolation of lipase-secreting bacteria by deploying used frying oil as selective substrate

Abstract It is well known that microorganisms are able to grow and transform vegetable oils due to the excretion of lipase, which renders the lipid substrates available to cells. The purpose of the present study was to screen for lipase production from used olive and sunflower frying oils. From the 47 strains of bacteria and yeast screened, the genera Pseudomonas , Bacillus , Candida , Rhodococcus , and Staphylococcus grew on the waste oils and produced lipolytic activity. The highest producers were Pseudomonas sp 3AT (2748 U/L) and Pseudomonas aeruginosa ATCC 111 (1703.8 U/L).

Investigation of functional and morphological changes in Pseudomonas aeruginosa and Staphylococcus aureus cells induced by Origanum compactum essential oil

Aims:  Evaluation of the cellular effects of Origanum compactum essential oil on Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213.

Functional and ultrastructural changes in Pseudomonas aeruginosa and Staphylococcus aureus cells induced by Cinnamomum verum essential oil

Aims:  To study cellular damage induced by Cinnamomum verum essential oil in Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213.

Reclassification of Geobacillus pallidus (Scholz et al. 1988) Banat et al. 2004 as Aeribacillus pallidus gen. nov., comb. nov.

Although Anoxybacillus and Geobacillus, two genera of thermophilic bacteria close to the genus Bacillus, have only been described recently, the number of species in these genera has increased rapidly. Four thermophilic, lipolytic strains (DR01, DR02, DR03 and DR04) isolated from a hot spring in Veracruz (Mexico), which could not be identified phenotypically, were subjected to 16S rRNA gene sequence analysis. Three strains were identified as belonging to the genus Anoxybacillus, but strain DR03 was identified as Geobacillus pallidus. This result led us to perform a phylogenetic analysis of the genera Anoxybacillus and Geobacillus based on 16S rRNA gene sequences from all the type strains of these genera. Phylogenetic trees showed three major clusters, Anoxybacillus-Geobacillus tepidamans, Geobacillus sensu stricto and Geobacillus pallidus, while the 16S rRNA gene sequences of G. pallidus (DR03 and the type strain) showed low similarity to sequences of Anoxybacillus (92.5-95.1 %) and Geobacillus (92.8-94.5 %) species, as well as to Bacillus subtilis (92.2-92.4 %). In addition, G. pallidus could be differentiated from Anoxybacillus and Geobacillus on the basis of DNA G+C content and fatty acid and polar lipid profiles. From these results, it is proposed that Geobacillus pallidus should be classified in a novel genus, for which we propose the name Aeribacillus, as Aeribacillus pallidus gen. nov., comb. nov. The type strain of Aeribacillus pallidus is H12(T) (=ATCC 51176(T) =DSM 3670(T) =LMG 19006(T)).

Nutritional requirements of a biosurfactant producing strain Rhodococcus sp 51T7

SummaryRhodococcus sp 51T7 produced a trehalose 2,3,4,2′ tetraester with surface active properties. When grown on hydrocarbon, cells were highly segmented and accumulated lipid granules in the cytoplasm. Production and glycolipid composition was affected by the nature of the carbon source. Optimal concentrations of sodium nitrate, potassium phosphate and iron were: 2.5, 1.5 and 0.01 g/L respectively. Surfactant production is growth-associated. Production was increased from 0.5 g/L to 3 g/L of glycolipid.

Synthesis, surface active properties and antimicrobial activity of new bis quaternary ammonium compounds

New dimeric surfactants 1 and 2 containing two saturated hydrocarbon chains and two quaternary ammonium salts linked through an alkene spacer chain with amide and disulfide bonds have been prepared from a betaine type amphoteric surfactant. They show a high effectiveness of adsorption in comparison with their single chain homologues. Surfactants 1 and 2 are very water soluble compounds with extraordinary micelle-forming properties. Both are very active against a wide range of microorganisms including gram negative bacteria.

Structure and interaction with phospholipids of a prokaryotic lipoxygenase from Pseudomonas aeruginosa

Lipoxygenases (LOXs), which are essential in eukaryotes, have no confirmed function in prokaryotes that are devoid of polyunsaturated fatty acids. The structure of a secretable LOX from Pseudomonas aeruginosa (Pa_LOX), the first available from a prokaryote, presents significant differences with respect to eukaryotic LOXs, including a cluster of helices acting as a lid to the active center. The mobility of the lid and the structural variability of the N‐terminal region of Pa_LOX was confirmed by comparing 2 crystal forms. The binding pocket contains a phosphatidylethanolamine phospholipid with branches of 18 (sn‐1) and 14/16 (sn‐2) carbon atoms in length. Carbon atoms from the sn‐1 chain approach the catalytic iron in a manner that sheds light on how the enzymatic reaction might proceed. The findings in these studies suggest that Pa_LOX has the capacity to extract and modify unsaturated phospholipids from eukaryotic membranes, allowing this LOX to play a role in the interaction of P. aeruginosa with host cells.—Garreta, A., Val‐Moraes, S. P., García‐Fernández, Q., Montserrat Busquets, C. J., Oliver, A., Ortiz, A., Gaffney, B. J., Fita, I., Manresa, A., Carpena, X., Structure and interaction with phospholipids of a prokaryotic lipoxygenase from Pseudomonas aeruginosa. FASEB J. 27, 4811‐4821 (2013). www.fasebj.org