title: Isolation of biosurfactant producers, optimization and properties of biosurfactant produced by Acinetobacter sp. from petroleum-contaminated soil.
abstract: OBJECTIVE
  To screen and identify biosurfactant producers from petroleum-contaminated soil; to use response surface methodology (RSM) for medium optimization to enhance biosurfactant production; and to study the properties of the newly obtained biosurfactant towards pH, temperature and salinity.
  
  
  RESULTS
  We successfully isolated three biosurfactant producers from petroleum-contaminated soil and identified them through 16S rRNA sequence analysis, which exhibit the highest similarities to Acinetobacter beijerinckii (100%), Kocuria marina (99%) and Kineococcus marinus (99%), respectively. A quadratic response model was constructed through RSM designs, leading to a 57·5% increase of the growth-associated biosurfactant production by Acinetobacter sp. YC-X 2 with an optimized medium: beef extract 3·12 g l(-1) ; peptone 20·87 g l(-1) ; NaCl 1·04 g l(-1); and n-hexadecane 1·86 g l(-1). Biosurfactant produced by Acinetobacter sp. YC-X 2 retained its properties during exposure to a wide range of pH values (5-11), high temperatures (up to 121°C) and high salinities [up to 18% (w/v) Na(+) and Ca(2+) ], which was more sensitive to Ca(2+) than Na(+).
  
  
  CONCLUSIONS
  Two novel biosurfactant producers were isolated from petroleum-contaminated soil. Biosurfactant from Acinetobacter sp. YC-X 2 has good properties to a wide range of pH, high temperature and high salinity, and its production was optimized successfully through RSM.
  
  
  CONCLUSIONS
  The fact, an increasing demand of high-quality surfactants and the lack of cost-competitive bioprocesses of biosurfactants for commercial utilization, motivates researchers to develop cost-effective strategies for biosurfactant production through isolating new biosurfactant producers with special surface-active properties and optimizing their cultural conditions. Two novel biosurfactant producers in this study will widen our knowledge about this kind of micro-organism. This work is the first application of RSM designs for cultural optimization of biosurfactant produced by Acinetobacter genus and the first report that biosurfactant may be more sensitive to Ca(2+) than Na(+) .
authors.affiliation: Department of Pharmaceutical and Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, China.
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: P T
authors.initials: PT
authors.lastname: Huang
authors.forename: K Y
authors.initials: KY
authors.lastname: Zhang
authors.forename: F R
authors.initials: FR
authors.lastname: Ding
mesh_terms: D000150:Acinetobacter / Q000302:isolation & purification* / Q000378:metabolism; D001673:Biodegradation, Environmental; D006863:Hydrogen-Ion Concentration; D010578:Petroleum / Q000378:metabolism*; D054712:Salinity; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature
chemical_list: D010578:Petroleum; D012987:Soil; D012989:Soil Pollutants; D013501:Surface-Active Agents