title: Emulsifier of Arthrobacter RAG-1: isolation and emulsifying properties.
abstract: The oil-degrading Arthrobacter sp. RAG-1 produced an extracellular nondialyzable emulsifying agent when grown on hexadecane, ethanol, or acetate medium. The emulsifier was prepared by two procedures: (i) heptane extraction of the cell-free culture medium and (ii) precipitation with ammonium sulfate. A convenient assay was developed for measurement of emulsifier concentrations between 3 and 75 micrograms/ml. The rate of emulsion fromation was proportional to both hydrocarbon and emulsifier concentrations. Above pH 6, activity was dependent upon divalent cations; half-maximum activity was obtained in the presence of 1.5 mM Mg2+. With a ratio of gas oil to emulsifier of 50, stable emulsions were formed with average droplet sizes of less than 1 micron. Emulsifier production was parallel to growth on either hydrocarbon or nonhydrocarbon substrates during the exponential phase; however, production continued after growth ceased.
mesh_terms: D001173:Arthrobacter / Q000378:metabolism*; D004655:Emulsions; D006017:Glycolipids / Q000378:metabolism; D006838:Hydrocarbons / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008070:Lipopolysaccharides / Q000096:biosynthesis* / Q000302:isolation & purification; D010578:Petroleum; D012623:Seawater; D013501:Surface-Active Agents / Q000096:biosynthesis* / Q000302:isolation & purification; D014871:Water Microbiology
chemical_list: D004655:Emulsions; D006017:Glycolipids; D006838:Hydrocarbons; D008070:Lipopolysaccharides; D010578:Petroleum; D013501:Surface-Active Agents