Effect of culture conditions on fatty acids composition of a biosurfactant produced by Candida ingens and changes of surface tension of culture media.

This work investigated the effect of culture medium composition on a biosurfactant production and their total fatty acids content, as well as the surface tension of media, and biomass production by Candida ingens. A factorial experimental design was used to evaluate the combined effect of C/P, C/N(inorganic), C/Fe, C/Mg ratios and yeast extract concentration. The highest biosurfactant production was reached when high C/Fe and high C/P ratio variables were combined; biosurfactant concentration increased by a 3.42 fold. The variable with the highest effect on net decrease surface tension (DeltaST) and fatty acids percentage of C. ingens biosurfactant was yeast extract. The average of DeltaST (25 mN/m) and fatty acids percentage (34.7%) values were enhanced at high yeast extract concentration of 1g/l. The main conclusion of this study was that the culture composition affected the biosurfactant production by C. ingens. It was also observed that the surface tension and total fatty acids of the biosurfactant were modified as the media composition changed.

Role of phenanthrene in rhamnolipid production by P. putida in different media.

The role of phenanthrene in rhamnolipid production by P. putida in eight media with different culture conditions was investigated. Cultures using Fe2SO4.7H2O, KH2PO4, NH4Cl, yeast extract, glucose, and corn oil, with and without 200 mg l(-1) of phenanthrene, were evaluated under shaking for rhamnolipid production through a 2(7-4) fractional factorial experimental design. The biosurfactant production, decrease in the surface tension of the broth and the total cell growth in media without phenanthrene were affected significantly (p < 0.001) by yeast extract, glucose, corn oil and NH4Cl, and in media with phenanthrene by glucose and yeast extract. The non polar fraction of the biosurfactant in all media was composed of linoleic (C18:2), arachidic (C20:0) and behenic (C22:0) fatty acids. The medium with phenanthrene (200 mg l(-1)), Fe2SO4.7H2O (5 x 10(-4) g l(-1)), KH2PO4 (0.2 g l(-1)), glucose (50 g l(-1)), yeast extract (1 g l(-1)), corn oil (2% vol), and NH4Cl (1 g l(-1)), shaken at 150 rpm at 37 degrees C, and pH 7.0, presented the highest biosurfactant production. For this medium the surface tension decreased by 35.9 mN m(-1) in relation to the initial value, and only this medium showed an emulsion capacity of 20%. The polar fraction (Rhamnose) in media 1, 3, 7 and 8 with phenanthrene was c.a 100%, in contrast to those without phenanthrene where this fraction was undetectable.

Effect of combined nutrients on biosurfactant produced by Pseudomonas putida.

This work investigated biosurfactant production by Pseudomonas putida in combined C/P, C/Ninorganic, C/Fe, C/Mg nutrient ratios and peptone concentration. Analysis of the 2(5-1) fractional factorial experimental design showed that only the C/Fe ratio had a significant (p<0.02) effect on biosurfactant production. The highest amount of biosurfactant was obtained at low C/Fe ratios, but net surface tension did not show significant differences. In addition, low amounts of peptone and the C/P-C/Mg nutrient ratios interaction significantly (p < 0.05) enhanced the biomass produced by P. putida. Analysis of biosurfactant by gas chromatography (GC) showed that the hydrophilic fraction was composed by rhamnose and the hydrophobic fraction, mainly by palmitic (C16), stearic (C18:0), oleic (C18:1) and linoleic (C18:2) fatty acids.

Isolation and characterization of bacteria degrading polychlorinated biphenyls from transformer oil.

Polychlorinated biphenyls from transformer oil were degraded in liquid culture under aerobic conditions using a mixed bacterial culture isolated from a transformer oil sample with a high content of polychlorinated biphenyls and other hydrocarbons. Four strains were identified, three of them corresponded to genus Bacillus, the other one to Erwinia. Bacteria in the transformer oil could remove as much as 65% of polychlorinated biphenyls (88% W/V in the transformer oil). Additional data showed that the two isolated strains of B. lentus were able to grow on transformer oil and degrade polychlorinated biphenyls by 80 and 83%. Our results provide evidence that microorganisms occurring in transformer oil have the potential to degrade polychlorinated biphenyls.

[Microbial sources of pigments]. / Fuentes microbianas de pigmentos.

Pigments from natural sources has been obtained since long time ago, and their interest has increased due to the toxicity problems caused by those of synthetic origin. In this way the pigments from microbial sources are a good alternative. Some of more important natural pigments, are the carotenoids, flavonoids (anthocyanins) and some tetrapirroles (chloropyls, phycobilliproteins). Another group less important are the betalains and quinones. The carotenoids are molecules formed by isoprenoids units and the most important used as colorant are the alpha and beta carotene which are precursors of vitamin A, and some xantophylls as astaxanthin. The pigment more used in the industry is the beta-carotene which is obtained from some microalgae and cyanobacteria. The astaxanthin another important carotenoid is a red pigment of great commercial value, and it is used in the pharmaceutical feed and acuaculture industries. This pigments is mainly obtained from Phaffia rhodozyma and Haematococcus pluvialis and other organisms. The phycobilliproteins obtained from cyanobacteria and some group of algae, have recently been increased on the food industries. In the last years it has been used as fluorescent marker in biochemical assays. Our research group have carried out studies about the factors that improve the production of these pigments obtained from different microbial species as well as the methods for their extraction and application.