Production of biosurfactant by hydrocarbon degrading Rhodococcus ruber and Rhodococcus erythropolis

Abstract

There is world wide concern about the liberation of hydrocarbons in the environment, both from industrial activities and from accidental spills of oil and oil-related compounds. Biosurfactants, which are natural emulsifiers of hydrocarbons, are produced by some bacteria, fungi and yeast. They are polymers, totally or partially extracellular, with an amphipathyc structure, which allows them to form micelles that accumulate at the interface between liquids of different polarities such as water and oil. This process is based upon the ability of biosurfactants to reduce surface tension, blocking the formation of hydrogen bridges and certain hydrophilic and hydrophobic interactions. The ability of biosurfactant production by five strains of Rhodococcus isolated from oil prospecting sites was evaluated. Surface tension measurement and emulsifying index were used to quantify biosurfactant production. The influence of environmental conditions was also investigated pH, temperature, medium composition, and type of carbon source on cell growth and biosurfactant production. Strain AC 239 was shown to be a potential producer, attaining 63% of emulsifying index for a Diesel-water binary system. It could be used, either directly on oil spills in contained environments, or for the biotechnological production of biosurfactant. removal from the environment. These bio-molecules are produced by several strains of bacteria and fungi. Bushnell and Haas (1) were among the first to demonstrate bacterial production of biosurfactants by isolating Corynebacterium simplex and strains of Pseudomonas in a mineral media, containing either kerosene, mineral oil or paraffin. The genus Rhodococcus bacteria with a diverse and efficient metabolism is also able to transform, biodegrade or utilize as carbon source several hydrophobic compounds such as hydrocarbons, chlorinated phenols, steroids, lignin, coal and crude Revista de Microbiologia (1999) 30:231-236

Diesel oil and PCB-degrading psychrotrophic bacteria isolated from Antarctic seawaters (Terra Nova Bay, Ross Sea)

“…Diesel oil is a complex combination of hydrocarbons deriving from the distillation of crude oil and represents an excellent substrate in the study of hydrocarbon biodegradation thanks to its composition (Bicca et al 1999). Diesel oil contains 2000 to 4000 different hydrocarbons (Marchal et al 2003) with a carbon number ranging approximately from C 9 to C 20 , including paraffi n, olefi ns, naphtha and aromatic compounds.…”

Biorremediação de solos contaminados com resíduos oleosos através de bioaumentação e atenuação natural

“…Para a realização do branco foi misturado 2 mL de óleo de milho e 3,5 mL de água destilada. A mistura foi agitada por 1 min e após 24 h de repouso foi realizada leitura da altura da emulsão formada e da altura total da camada de líquido (camada emulsionada + camada não emulsionada) dos tubos, obtendo-se o índice de emulsificação, E24 (BICCA; FLECK; AYUB, 1999 …”

Estudo da produção de biossurfactante em caldo de fermentação

“…11 A bactéria Bacillus pumilus foi inoculada em tubos de ensaio contendo 5 mL de caldo nutriente e incubada por 24 h a 30 o C. Após a incubação, as suspensões de células de cada tubo foram submetidas a leituras de densidade óptica a 650 nm para padronização celular a 0,05 e foram transferidas para frascos Erlenmeyer de 250 mL contendo 45 mL de meio de produção. …”

“…9,11,18,[21][22][23] Neste trabalho foram estudadas outras fontes de carbono, inclusive a sacarose e o caldo de cana, pois estas são matérias-primas abundantes no mercado nacional e de baixo custo.…”