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In Situ Biosurfactant Production at a Petroleum Refinery

A. J. Hudak and D. P. Cassidy
Western Michigan Univ., Kalamazoo, MI

The subsurface at the former Crystal Refinery in Carson City, Michigan has been impacted with petroleum products for several decades. Since many genera of microorganisms produce biosurfactants during growth on petroleum compounds, a study was conducted in the smear zone at the former Crystal Refinery to determine whether biosurfactants were produced in situ by the prevailing microorganisms in impacted areas. Microorganisms were identified in cultures obtained from soil samples using fatty acid methyl ester (FAME) analysis. Surface tension was measured in filtered ground water samples from wells from hydrocarbon impacted areas and from control wells. Groundwater samples were concentrated in a rotary evaporator. Rhamnolipid surfactant concentrations were measured in derivitized samples using HPLC.

Results showed that the most populous species in hydrocarbon impacted areas was Pseudomonas aeruginosa, which is known to produce rhamnolipid surfactants. Surface tension measurements in groundwater samples from impacted wells decreased from above 65 dynes/cm to roughly 30 dynes/cm as groundwater was increasing concentrated in the rotary evaporator, indicating that surfactants were present. In contrast, groundwater samples from control wells showed no such decrease in surface tension. HPLC analysis showed that monorhamnolipids and dirhamnolipids were present in measurable amounts in the impacted wells, but were absent in the control wells. These results document in situ biosurfactant production from indigenous microorganisms.

AAPG Search and Discovery Article #90900©2001 AAPG Eastern Section Meeting, Kalamazoo, Michigan