title: Rhamnolipid production by a novel thermophilic hydrocarbon-degrading Pseudomonas aeruginosa AP02-1.
abstract: Thermophilic bacterial cultures were isolated from a hot spring environment on hydrocarbon containing mineral salts media. One strain identified as Pseudomonas aeruginosa AP02-1 was tested for the ability to utilize a range of hydrocarbons both n-alkanes and polycyclic aromatic hydrocarbons as sole carbon source. Strain AP02-1 had an optimum growth temperature of 45 degrees C and degraded 99% of crude oil 1% (v/v) and diesel oil 2% (v/v) when added to a basal mineral medium within 7 days of incubation. Surface activity measurements indicated that biosurfactants, mainly glycolipid in nature, were produced during the microbial growth on hydrocarbons as well as on both water-soluble and insoluble substrates. Mass spectrometry analysis showed different types of rhamnolipid production depending on the carbon substrate and culture conditions. Grown on glycerol, P. aeruginosa AP02-1 produced a mixture of ten rhamnolipid homologues, of which Rha-Rha-C10-C10 and Rha-C10-C10 were predominant. Rhamnolipid-containing culture broths reduced the surface tension to approximately 28 mN and gave stable emulsions with a number of hydrocarbons and remained effective after sterilization. Microscopic observations of the emulsions suggested that hydrophobic cells acted as emulsion-stabilizing agents.
authors.affiliation: Department of Agrobiology and Agrochemistry, University of Tuscia, Viterbo, Italy.|Microbial Biotechnology Group, School of Biomedical Sciences, University of Ulster, Coleraine, BT52 ISA, N. Ireland, UK.
authors.forename: Amedea
authors.initials: A
authors.lastname: Perfumo
authors.affiliation: Microbial Biotechnology Group, School of Biomedical Sciences, University of Ulster, Coleraine, BT52 ISA, N. Ireland, UK. im.banat@ulster.ac.uk.
authors.forename: Ibrahim M
authors.initials: IM
authors.lastname: Banat
authors.affiliation: Department of Agrobiology and Agrochemistry, University of Tuscia, Viterbo, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Canganella
authors.affiliation: Microbial Biotechnology Group, School of Biomedical Sciences, University of Ulster, Coleraine, BT52 ISA, N. Ireland, UK.
authors.forename: Roger
authors.initials: R
authors.lastname: Marchant
mesh_terms: D003470:Culture Media / Q000737:chemistry; D004655:Emulsions; D005742:Gasoline; D006017:Glycolipids / Q000096:biosynthesis*; D045482:Hot Springs / Q000382:microbiology; D006838:Hydrocarbons / Q000378:metabolism*; D010578:Petroleum / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D013696:Temperature
chemical_list: D003470:Culture Media; D004655:Emulsions; D005742:Gasoline; D006017:Glycolipids; D006838:Hydrocarbons; D010578:Petroleum; C418382:rhamnolipid