| Summary: | Biosurfactants, a wide group of compounds produced by different microorganisms, generally have less toxicity and are more biodegradable than synthetic surfactants. Biosurfactant-producing bacteria can be found in contaminated environments, such as soils receiving pesticide applications constantly, or in pesticides treatment systems where microorganisms are adapted to biodegrading pesticides. Five pesticide-tolerant bacteria previously isolated from a pesticide biopurification system were evaluated as biosurfactant-producers. <i>Pseudomonas rhodesiae</i> C4, <i>Rhodococcus jialingiae</i> C8 and <i>Pseudomonas marginalis</i> C9 strains were positive in qualitative tests. Biosurfactant production by these strains using Bushnell-Haas medium with olive oil at 2% (<i>w</i>/<i>v</i>) was evaluated as emulsification index, oil displacement, droplet collapse test and surface tension. After 144 h, these strains showed a similar emulsification index of >55%. The two <i>Pseudomonas</i> (C4 and C9) strains showed lower superficial tension compared with <i>Rhodococcus</i> strain (C8)—34.47, 37.44 and 47.55 mN/m for strains C4, C9 and C8, respectively. The chemical characterization of the biosurfactants revealed the presence of glycolipids in <i>P. rhodesiae</i> (C4) and glycopeptides in <i>P. marginalis</i> (C9). The degradation of chlorpyrifos increased from 39.2% to 51.6% when biosurfactants produced by <i>P.</i><i>rhodesiae</i> (C4) were added (10%) with respect to the control. Therefore, biopurification systems are a relevant source of biosurfactant-producing bacteria with environmental biotechnology applications.
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