title: Simultaneous hydrocarbon biodegradation and biosurfactant production by oilfield-selected bacteria.
abstract: OBJECTIVE
  To study the bacterial diversity associated with hydrocarbon biodegradation potentiality and biosurfactant production of Tunisian oilfields bacteria.
  
  
  RESULTS
  Eight Tunisian hydrocarbonoclastic oilfields bacteria have been isolated and selected for further characterization studies. Phylogenetic analysis revealed that three thermophilic strains belonged to the genera Geobacillus, Bacillus and Brevibacillus, and that five mesophilic strains belonged to the genera Pseudomonas, Lysinibacillus, Achromobacter and Halomonas. The bacterial strains were cultivated on crude oil as sole carbon and energy sources, in the presence of different NaCl concentrations (1, 5 and 10%, w/v), and at 37 or 55°C. The hydrocarbon biodegradation potential of each strain was quantified by GC-MS. Strain C450R, phylogenetically related to the species Pseudomonas aeruginosa, showed the maximum crude oil degradation potentiality. During the growth of strain C450R on crude oil (2%, v/v), the emulsifying activity (E24) and glycoside content increased and reached values of 77 and 1.33 g l(-1), respectively. In addition, the surface tension (ST) decreased from 68 to 35.1 mN m(-1), suggesting the production of a rhamnolipid biosurfactant. Crude biosurfactant had been partially purified and characterized. It showed interest stability against temperature and salinity increasing and important emulsifying activity against oils and hydrocarbons.
  
  
  CONCLUSIONS
  The results of this study showed the presence of diverse aerobic bacteria in Tunisian oilfields including mesophilic, thermophilic and halotolerant strains with interesting aliphatic hydrocarbon degradation potentiality, mainly for the most biosurfactant produced strains.
  
  
  CONCLUSIONS
  It may be suggested that the bacterial isolates are suitable candidates for practical field application for effective in situ bioremediation of hydrocarbon-contaminated sites.
authors.affiliation: Laboratoire des Bioprocédés Environnementaux, Pôle d'Excellence Régional AUF (PER-LBPE), Centre de Biotechnologie de Sfax, Université de Sfax, Sfax, Tunisie.
authors.forename: S
authors.initials: S
authors.lastname: Mnif
authors.forename: M
authors.initials: M
authors.lastname: Chamkha
authors.forename: M
authors.initials: M
authors.lastname: Labat
authors.forename: S
authors.initials: S
authors.lastname: Sayadi
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D001673:Biodegradation, Environmental; D003470:Culture Media / Q000737:chemistry; D045703:Emulsifying Agents / Q000378:metabolism; D006017:Glycolipids; D006838:Hydrocarbons / Q000378:metabolism*; D061329:Oil and Gas Fields / Q000382:microbiology*; D010578:Petroleum / Q000378:metabolism*; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013500:Surface Tension; D014416:Tunisia
chemical_list: D003470:Culture Media; D045703:Emulsifying Agents; D006017:Glycolipids; D006838:Hydrocarbons; D010578:Petroleum; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; C418382:rhamnolipid