title: Production and characterization of microbial biosurfactants for potential use in oil-spill remediation.
abstract: Two biosurfactants, surfactin and fatty acyl-glutamate, were produced from genetically-modified strains of Bacillus subtilis on 2% glucose and mineral salts media in shake-flasks and bioreactors. Biosurfactant synthesis ceased when the main carbohydrate source was completely depleted. Surfactin titers were ∼30-fold higher than fatty acyl-glutamate in the same medium. When bacteria were grown in large aerated bioreactors, biosurfactants mostly partitioned to the foam fraction, which was recovered. Dispersion effectiveness of surfactin and fatty acyl-glutamate was evaluated by measuring the critical micelle concentration (CMC) and dispersant-to-oil ratio (DOR). The CMC values for surfactin and fatty acyl-glutamate in double deionized distilled water were 0.015 and 0.10 g/L, respectively. However, CMC values were higher, 0.02 and 0.4 g/L for surfactin and fatty acyl-glutamate, respectively, in 12 parts per thousand Instant Ocean®[corrected].sea salt, which has been partly attributed to saline-induced conformational changes in the solvated ionic species of the biosurfactants. The DORs for surfactin and fatty acyl-glutamate were 1:96 and 1:12, respectively, in water. In Instant Ocean® solutions containing 12 ppt sea salt, these decreased to 1:30 and 1:4, respectively, suggesting reduction in oil dispersing efficiency of both surfactants in saline. Surfactant toxicities were assessed using the Gulf killifish, Fundulus grandis, which is common in estuarine habitats of the Gulf of Mexico. Surfactin was 10-fold more toxic than fatty acyl-glutamate. A commercial surfactant, sodium laurel sulfate, had intermediate toxicity. Raising the salinity from 5 to 25 ppt increased the toxicity of all three surfactants; however, the increase was the lowest for fatty acyl-glutamate.
authors.affiliation: Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: Marti
authors.affiliation: Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, USA; Center for Crops Utilization Research, Iowa State University, Ames, IA 50011, USA.
authors.forename: W J
authors.initials: WJ
authors.lastname: Colonna
authors.affiliation: Earth and Environmental Engineering, Columbia University, New York, NY 10091, USA.
authors.forename: P
authors.initials: P
authors.lastname: Patra
authors.affiliation: School of Renewable Natural Resources, LSU AgCenter, Baton Rouge, LA 70803, USA.
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Aquaculture Research Station, LSU AgCenter, Baton Rouge, LA 70803, USA.
authors.forename: C
authors.initials: C
authors.lastname: Green
authors.affiliation: Modular Genetics, Inc., Cambridge, MA 02139, USA.
authors.forename: G
authors.initials: G
authors.lastname: Reznik
authors.affiliation: Modular Genetics, Inc., Cambridge, MA 02139, USA.
authors.forename: M
authors.initials: M
authors.lastname: Pynn
authors.affiliation: Modular Genetics, Inc., Cambridge, MA 02139, USA.
authors.forename: K
authors.initials: K
authors.lastname: Jarrell
authors.affiliation: School of Renewable Natural Resources, LSU AgCenter, Baton Rouge, LA 70803, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Nyman
authors.affiliation: Earth and Environmental Engineering, Columbia University, New York, NY 10091, USA.
authors.forename: P
authors.initials: P
authors.lastname: Somasundaran
authors.affiliation: Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, USA.
authors.forename: C E
authors.initials: CE
authors.lastname: Glatz
authors.affiliation: Food Science and Human Nutrition Department, Iowa State University, Ames, IA 50011, USA. Electronic address: lamsal@iastate.edu.
authors.forename: B P
authors.initials: BP
authors.lastname: Lamsal
mesh_terms: D000818:Animals; D001412:Bacillus subtilis / Q000378:metabolism; D001673:Biodegradation, Environmental; D019149:Bioreactors; D005285:Fermentation; D023781:Fundulidae / Q000254:growth & development; D005971:Glutamates / Q000096:biosynthesis / Q000302:isolation & purification* / Q000494:pharmacology / Q000633:toxicity; D007814:Larva / Q000187:drug effects; D055666:Lipopeptides / Q000096:biosynthesis / Q000302:isolation & purification* / Q000494:pharmacology / Q000633:toxicity; D008823:Micelles; D010456:Peptides, Cyclic / Q000096:biosynthesis / Q000302:isolation & purification* / Q000494:pharmacology / Q000633:toxicity; D059392:Petroleum Pollution; D054712:Salinity; D013500:Surface Tension; D013501:Surface-Active Agents / Q000302:isolation & purification* / Q000378:metabolism / Q000494:pharmacology / Q000633:toxicity; D014874:Water Pollutants, Chemical
chemical_list: D005971:Glutamates; D055666:Lipopeptides; D008823:Micelles; D010456:Peptides, Cyclic; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; C009365:surfactin peptide
keywords: Fish toxicity; Lipopeptides; Microbial biosurfactants; Oil spill remediation