RESUMO
Background: The aim of the present study was to propose a low-cost method for the production of a biosurfactant by the yeast Candida sphaerica and assess its toxicity and phytotoxicity. The medium was formulated with distilled water supplemented with residue from a soy oil refinery (5%) and corn steep liquor (2.5%) as substrates. These two products were the sources of carbon and nitrogen as well as mineral elements to encourage the growth of the microorganism and production of a biosurfactant. Results: The isolated biosurfactant yield was 6.364 g/l. The biosurfactant exhibited an excellent ability to reduce surface tension (26 mN/m) and demonstrated no toxicity against seeds of Brassica oleracea, Chicoria intybus and Solanum gilo or the micro crustacean Artemia salina employed as a bioindicator. The biosurfactant exhibited no antimicrobial activity against the fungi and bacteria tested. Conclusions: The promising results obtained in this study indicate the feasibility of producing biosurfactants from powerful non-toxic organic residues and their application in the bioremediation of contaminated soil and water.
Assuntos
Tensoativos/toxicidade , Candida/metabolismo , Tensoativos/isolamento & purificação , Cinética , Reatores Biológicos , Meios de Cultura , Resíduos IndustriaisRESUMO
The production of a new biosurfactant by Candida glabrata UCP1002 was studied to evaluate the influence of the concentration of the cotton seed oil, glucose and yeast extract. The dynamics of the growth and surfactant production were showed for all the cultivation conditions studied. The best emulsification of the n-hexadecane, quantified by the emulsifying index was observed in the medium containing 7.5 percent cotton seed oil, 5 percent glucose and 0.3 percent yeast extract. The isolated biosurfactant showed a CMC of 2.5 percent and the surface tension at that point showed to be 31mN/m. The potential application of the biosurfactant in oil recovery from the sand, in acid and alkaline environments and over exposure to high salinity and different temperatures was demonstrated by the percentage of oil removal and by the stability of the surface tension, respectively.
A produção de um novo biossurfactante por Candida glabrata UCP1002 foi inicialmente investigada com a finalidade de avaliar a influência da concentração dos substratos óleo de algodão, glicose e extrato de levedura. As cinéticas de crescimento e de produção do surfactante foram demonstradas para todas as condições de cultivo testadas. A melhor emulsificação do nhexadecano, quantificada através do índice de emulsificação foi observada na condição de cultivo contendo 7,5 por cento de óleo de algodão, 5 por cento de glicose e 0,3 por cento de extrato de levedura. O biossurfactante produzido apresentou uma concentração micelar crítica de 2,5 por cento, sendo a tensão superficial nesse ponto de 31mN/m. O potencial de aplicação do biossurfactante na recuperação de óleo de areia contaminada, em condições ácidas e alcalinas, bem como sob exposição a altas salinidades e diferentes temperaturas, foram demonstrados com base no percentual de remoção do óleo e na estabilidade da tensão superficial, respectivamente.
RESUMO
Evaluation of both tenso-active and emulsifying activities indicated that a biosurfactant was produced by the newly isolated and promising strain Candida glabrata isolated from mangrove sediments. The extracellular water-soluble emulsifying agent was isolated and identified as a heteropolymer. The maximum of bioemulsifier production was observed when the strain was grown on soluble and insoluble substrates cotton seed oil plus glucose, reaching values of 10.0 g/l after 144 hrs at 200 rpm. The cell-free culture broth containing the examined agent lowered the surface tension of the medium to 31 mN/m. Stable and compact emulsions with emulsifying activity of 75 percent of cotton seed oil were detected. The emulsification capacity remained practically unaltered within a wide pH (2-12), temperature (4-80°C) ranges and under NaCl concentrations up to 10 percent.