Isolation of biosurfactant‐producing bacteria, product characterization, and evaluation

Abstract

A gram-positive, nonfermentative, rod-shaped bacterium designated ST-5, identified as Rhodococcus, was isolated from Kuwait soil. Grown on hydrocarbon, such as kerosene and n-paraffin, the bacterium produced surface-active compounds (biosurfactants). Neasurements of surface tension, critical micelle dilution and emulsifying activity indicated that the biosurfactant is produced as a primary metabolite. The ST-5 culture surface-active component is mainly giycolipid in nature. Whole-culture broth dropped surface tension to values below 27 mN/m and was stable during exposure to high salinity (10% NaCI), elevated temperatures (120°C for 15 min) and a wide range of pH values. The culture broth was effective in recovering up to 86% of the residual oil from oil-saturated sand packs, indicating potential value in enhanced oil-recovery processes.

Isolation and characterization of hydrocarbon-degrading and biosurfactant-producing yeast strains obtained from a polluted lagoon water

“…was produced as a primary metabolite accompanying a cellular biomass formation. Similar results were obtained by Abu-Ruwaida et al (1991) and Ilori et al Microbiol Biotechnol (2008) 24:2539-25452543. It was found that the best biosurfactant-producing and diesel-degrading between the two strains was Candida albicans with an E 24 of 64.2% and specific growth rate constant of 0.48 day -1 (Table 2, Fig.…”

Enhancement of stability of biosurfactant produced by Candida lipolytica using industrial residue as substrate

“…These results indicate that the biosurfactant produced has high-emulsification specificity toward motor oil and hexadecane. Similar results were obtained by Abu-Ruwaida et al (1991) for a bacterium identified as Rhodococcus cultivated on hydrocarbon. These findings suggest that the emulsifier's activity depends on its affinity for hydrocarbon substrates, which involves a direct interaction with the hydrocarbon itself rather than an effect on the surface tension of the medium.…”

Effect of pH and salinity on the emulsifying capacity and naphthalene solubility of a biosurfactant produced by Pseudomonas fluorescens

“…1), in agreement with the available literature [34]. This could be caused by a better stability of fatty acids-surfactant micelles in presence of NaOH and the precipitation of secondary metabolites at higher pH values.…”