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Aims: To characterize the bioemulsifier produced by a nonfluorescent strain of Pseudomonas putida isolated from a polluted sediment and to determine the influence of pH, temperature, media composition, and carbon and nitrogen source on growth and emulsifying activity. Methods and Results: Different indexes were employed to determine the emulsifying properties of culture supernatants of P. putida ML2 in defined and complex media. Surface tension of cell-free supernatants was measured. Purification and chemical analysis of the emulsifier was performed. Confirmed results indicate that a polysaccharide with hexasaccharide repeating units is responsible for the emulsifying activity in a mineral medium with glucose as sole carbon source. Moreover, an emulsifier is produced when growing on naphthalene. Conclusions: Culture media composition influences the amount and the properties of the emulsifier produced by this P. putida strain. Under nitrogen limiting conditions, a polysaccharide is responsible for the emulsifying activity in defined mineral media. In complex nitrogen rich medium, a different kind of emulsifier is produced. The exopolymer may contribute to hydrocarbons solubilization. Significance and Impact of the Study: This is the first exopolysaccharide with emulsifying properties produced by a Pseudomonas strain reported to the present. Also chemical composition is significantly different from previous reports. This strain has potential use in bioremediation and the purified polysaccharide may be used in food and cosmetic industry. Moreover, the production of the exopolymer may play a role on biofilm formation.

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RESUMO: "Triagem fi toquímica de plantas nativas do rio Uruguai". Prospecção da biodiversidade é a exploração de um ecossistema para se obter informações sobre possíveis utilizações inovadoras em diferentes processos de produção humanos. Exemplos do tipo de informação pretendida são os dados científi cos contidos no material genético dos organismos vivos, os compostos químicos produzidos por eles e suas interações ou no conhecimento das pessoas que já interagiram com eles de várias maneiras. Uma das ferramentas de prospecção da biodiversidade é a procura por informações químicas. Esta informação está contida nos compostos produzidos por muitos seres vivos para comunicar-se, defender-se e trocar informações, e eles são conhecidos como metabólitos secundários. Neste projeto, nós propomos a prospecção botânica, química e biológica da biodiversidade da mata ciliar da Bacia do Rio Uruguay próxima ao riacho Guaviyú. Este ecossistema particular apresenta uma substancial biodiversidade de aproximadamente 200 espécies com um perfi l subtropical incomum.Unitermos: Bioprospeção, triagem fi toquímica.ABSTRACT: "Phytochemical screening of the native forest of Uruguay River". Biodiversity prospecting is the exploration of an ecosystem for information regarding possible innovative uses in different human production processes. Examples of the kind of information sought are the scientifi c data contained in the genetic material of living organisms, the chemical compounds they produce and their interactions or in the knowledge of people that have interacted with them in various ways. One of the tools of biodiversity prospecting is searching for chemical information. This information is contained in the compounds produced by many living beings to communicate, to defend themselves and exchange information, and they are known as secondary metabolites. In this project, we propose the botanical, chemical and biological biodiversity prospecting of the gallery forest of the Uruguay River Basin near the Guaviyú stream. This particular ecosystem presents a substantial biodiversity of approximately 200 species with an unusual subtropical profi le.Keywords: Bioprospection, phytochemical screening. INTRODUCCIÓNLas especies arbóreas que forman parte de las comunidades nativas del Uruguay son alrededor de 170 ascendiendo a unas de 250 si se consideran también las especies arbustivas y caméfi tas sobre un total algo mayor a las 2600 especies de plantas vasculares que crecen en el país. Este es un número considerablemente más alto al de la provincia de Buenos Aires (Argentina) a la que tradicionalmente se asocia en la bibliografía a la fl ora uruguaya, ubicándolas en la misma Provincia fi togeográfi ca (Escudero, 2004). La vegetación leñosa, arbóreo arborescente del Uruguay incluyendo a los palmares, según la carta forestal (Uruguay, 1980) cubre el 3,7% de la superfi cie del territorio nacional, totalizando 667.315 hás. Dichas agrupaciones boscosas ocupan diferentes ambientes que determinan situaciones en la mayoría de los casos perfectamente ...

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