Isolation of biosurfactant producers, optimization and properties of biosurfactant produced by Acinetobacter sp. from petroleum-contaminated soil.

AIMS: 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. METHODS AND 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. SIGNIFICANCE AND IMPACT OF THE STUDY: 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(+) .

Aerosol lead and associated elements in Beijing, China.

The relative importance of local and regional sources of lead and associated elements in fine and coarse aerosol particles of an urban atmosphere was assessed by means of a two-day study, July 20 and 30, 1980 in Beijing, China. Five near-ground locations were selected for aerosol sampling by cascade impactors and elemental analysis by proton induced X-ray emission (PIXE): the imperial palace courtyard, a park, near two streets, and a mid-street traffic island. These sites, ranked in order of increasing traffic intensity and fugitive surface dust, showed that concentrations of major dust constitutents, represented by coarse particle (>2 µm diameter) Si, Al, and Ca, increased correspondingly. Pb, as well as Zn, As, and Cu, were present mainly in fine (<2 µm) particles; their concentrations were unrelated to traffic, indicating they resulted mainly from regional combustion or other sources. However, these elements also were present in coarse particles at concentrations that varied with the major dust elements and were relatively enriched, compared to average earth crust rock material, by factors of more than 100 (Pb), 50 (Zn), and 10 (Cu). Nonurban Beijing shows much smaller coarse aerosol enrichments of Pb, Zn, and Cu, indicating urban contamination of surface dust. Published data from St. Louis, USA show both fine and coarse aerosol Pb and Zn. Compared with Beijing, fine and coarse concentrations in St. Louis are similar for Pb, but lower for Zn, Ca, and Fe. Both Pb and Zn are enriched relative to earth crust composition to a greater degree in St. Louis than Beijing in both fine and coarse particle size ranges. The results suggest that heavy metals from combustion occur in the air as fine particles and, after deposition on the surface, as reentrained coarse particles of fugitive dust. Both many contribute to human exposures of these heavy metals.