title: Characterization and properties of biosurfactants produced by a newly isolated strain Bacillus methylotrophicus DCS1 and their applications in enhancing solubility of hydrocarbon.
abstract: Six biosurfactant-producing bacteria were isolated from hydrocarbon contaminated soils in Sfax, Tunisia. Isolates were screened for biosurfactant production by different conventional methods including hemolytic activity, surface tension reduction, drop-collapsing and oil displacement tests. All these screening tests show that all the isolates behave differently. Among the isolated bacteria, DCS1 strain was selected for further studies based on its highest activities and it was identified as Bacillus methylotrophicus DCS1. This strain was found to be a potent producer of biosurfactant when cultivated in mineral-salts medium supplemented with diesel oil (2 %, v/v) as a sole carbon source. Physicochemical properties and stability of biosurfactants synthesized by B. methylotrophicus DCS1 were investigated. The produced biosurfactants DCS1, from Landy medium, possess high surface activity that could lower the surface tension of water to a value of 31 from 72 mN m(-1) and have a critical micelle concentration (CMC) of 100 mg L(-1). Compared with SDS and Tween 80, biosurfactants showed excellent emulsification activities against different hydrocarbon substrates and high solubilization efficiency towards diesel oil. Biosurfactants DCS1 showed good stability in a wide range of temperature, pH and salinity. These results suggested that biosurfactants produced by B. methylotrophicus DCS1 could be an alternative to chemically synthesized surfactants for use in bioremediation processes to enhance the solubility of hydrophobic compounds.
authors.affiliation: Laboratoire de Génie Enzymatique et de Microbiologie, Ecole Nationale d'Ingénieurs de Sfax, Université de Sfax, B. P. 1173-3038, Sfax, Tunisia. Nawel.1501@yahoo.com.
authors.forename: Nawel
authors.initials: N
authors.lastname: Jemil
authors.affiliation: Laboratoire de Génie Enzymatique et de Microbiologie, Ecole Nationale d'Ingénieurs de Sfax, Université de Sfax, B. P. 1173-3038, Sfax, Tunisia.
authors.forename: Hanen
authors.initials: H
authors.lastname: Ben Ayed
authors.affiliation: Laboratoire de Génie Enzymatique et de Microbiologie, Ecole Nationale d'Ingénieurs de Sfax, Université de Sfax, B. P. 1173-3038, Sfax, Tunisia.
authors.forename: Noomen
authors.initials: N
authors.lastname: Hmidet
authors.affiliation: Laboratoire de Génie Enzymatique et de Microbiologie, Ecole Nationale d'Ingénieurs de Sfax, Université de Sfax, B. P. 1173-3038, Sfax, Tunisia.
authors.forename: Moncef
authors.initials: M
authors.lastname: Nasri
mesh_terms: D001407:Bacillus / Q000145:classification* / Q000302:isolation & purification* / Q000378:metabolism; D001673:Biodegradation, Environmental; D057166:High-Throughput Screening Assays / Q000379:methods; D006838:Hydrocarbons / Q000737:chemistry*; D008823:Micelles; D010802:Phylogeny; D012988:Soil Microbiology; D012995:Solubility; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry / Q000378:metabolism*; D014416:Tunisia
chemical_list: D006838:Hydrocarbons; D008823:Micelles; D013501:Surface-Active Agents
keywords: Bacillus methylotrophicus DCS1; Biosurfactants; Characterization; Diesel solubilization; Screening