Bioprospecção de genes envolvidos na síntese de biossurfactantes a apartir de microbiota de resevatórios de petróleo / Bioprospection of genes involved in the synthesis of biosurfactants from braziliam petroleum reservoirs microbial communities

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

14/07/2010

RESUMO

Bioemulsifiers or biosurfactants are compounds produced by microorganisms which enhance the bioavailability of hydrophobic substances promoting the stabilization of substances with different polarities, like oil-in-water emulsion occurring in petroleum reservoirs. The samples used in this work were collected in the Potiguar Basin (RN, Brazil), and employed as inoculum for aerobic and anaerobic enrichments of the petroleum microbiota. The selected oil sample (GMR 75) was obtained from a reservoir presenting a moderate biodegradation level. After the incubation period of the microbial enrichments, total DNA was extracted and used for the assembly of the metagenomic libraries by using a comercial kit. The evaluation of the potential for emulsifier production by the fosmid clones derived from the metagenomic libraries was performed by means of two screening assays, one based on biological activity and another based on sequence similarity. The functional assay, named “drop collapse”, has a qualitative character and was used for the preliminary screening of 2,880 clones, yielding 2,104 positive results. For the sequence-based assay, clones shown to be positive in the functional assay were evaluated through PCR reactions using primers homologous to conserved regions of genes for biosurfactant synthesis. However, no positive amplification signal was observed with the primers used. Tensitometric assays, using mineral medium and hexadecane as sole carbon and energy source, were performed to confirm the production of the biosurfactants by the clones. Nine clones able to reduce the interfacial tension from 45 mNm to 30 mN/m were selected and subsequently submitted to emulsification assays using petroleum, diesel oil and hexadecane. Results demonstrated the formation of an emulsion, mainly in diesel oil, suggesting the emulsifier power of the biosurfactants over this substance. Colorimetric analyses of the biosurfactants produced by the clones revealed similar proportion of carbohydrates, proteins and uronic acids, not allowing conclusive characterization of their composition.

ASSUNTO(S)

petróleo biossurfactantes metagenômica bioemulsificante substâncias exopélimericas petroleum biosurfactants metagenomics bioemulsifiers exopolymeric substances

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