Grantee Research Project Results
Final Report: The Effect of In Situ Biosurfactant Production on Hydrocarbon Biodegradation
EPA Grant Number: R826161Title: The Effect of In Situ Biosurfactant Production on Hydrocarbon Biodegradation
Investigators: Strevett, Keith A. , Sabatini, David A. , Everett, Jess , Tanner, R.
Institution: University of Oklahoma
EPA Project Officer: Aja, Hayley
Project Period: March 10, 1998 through March 9, 2001 (Extended to September 9, 2001)
Project Amount: $323,072
RFA: Exploratory Research - Environmental Engineering (1997) RFA Text | Recipients Lists
Research Category: Land and Waste Management , Safer Chemicals
Objective:
The objective of this research project was to investigate the effect of biosurfactants on the bioremediation of chemical matrices. Specifically, the impact (or enhancement) of biosurfactants on the bioavailability of hydrocarbons, assessment of microbial membrane characteristics as altered by biosurfactants that may have an impact on the bioavailability of hydrocarbons, and the impact of biosurfactants on microbial migration (the ability of a microorganism to transport with a contaminated plume) were studied.Summary/Accomplishments (Outputs/Outcomes):
This study was designed to find ways to predict the effect of in situ biosurfactant production on the degradation of various hydrocarbons under anaerobic conditions. However, the resulting data clearly highlight the complex nature of the relationship between microbes, biosurfactants, hydrocarbons, and soil/sediment matrixes. It is apparent that the current subject literature contains enough data to create an atmosphere of confusion but not enough data to answer the resulting questions regarding the issue of biosurfactants and their effect on hydrocarbon degradation. Regardless, the results found in this study must be examined in context of the available literature.Similar results were observed for both surfactants studies germane to the
impact of surface
tension and enhanced solubility of the contaminants. As an
example, the surface tension of dichlorobenzene (DCB) decreased from 66.8?1.2
dynes/cm (average of all initial conditions and negative control, which remained
within the average value plus/minus one standard deviation) to 42.9?1.8
dynes/cm. This demonstrates the activity of the wild type to produce
biosurfactant while degrading the compound. Furthermore, it was observed for
naphthalene that the cultures growing on naphthalene did not reduce the initial
concentration of the compound to the same percent removal as in the toluene and
DCB experiment, and the wild type did apparently produce a biosurfactant as
indicated by the reduction of liquid surface tension. The final surface tension
for the naphthalene experiment set was 47.8?3.2 dynes/cm. However, these
reductions did not directly translate to enhanced bioavailability as observed by
percent contaminant removal.
For all experimental sets that contained a NAPL, the resulting concentration
was higher than the
toxicity limit of the bacteria. Although some acclimation
has resulted in partial degradation of the toluene, naphthalene, and DCB (when
introduced as a NAPL), the acclimation process resulted in the wild-type IGB83
and loss of their surfactant production potential. Essentially, this acclimation
period was performed by sequential subculture transfers. As stated in the
literature and verified herein, subculturing of IGB83 results in lose of
surfactant production. Thus, no results can be reported for RL impact on
experiments containing a NAPL test compound.
Regarding those bacteria isolated as biosurfactant producers, identifications found that the majority were Pseudomonas and Bacillus species (Bacillus cereus, Bacillus mycoides, Bacillus sphaericus, Bacillus thuringiensis, Burkholderia vietnamiensis, Pseudomonas aureofaciens, and Pseudomonas fluorescens). This was not unexpected, because these are common soil organisms, and all species identified have literature support for their ability to produce a biosurfactant. Results from the FAME analysis were similar to the results of the Biolog analysis. Future work in the area of biosurfactants can include obtaining additional evidence of biosurfactant producers indigenous to various soils, such as surface tension data and molecular comparisons to known biosurfactant genes. Novel biosurfactants can be tested for their ability to increase degradation of currently unaffected soil contaminants. Additionally, more research is needed in the area of gram positive biosurfactant producers and anaerobic biosurfactant producers. With more data available, concerns regarding applying knowledge about gram negative or aerobic biosurfactant producers to gram positive or anaerobic cultures will be addressed. Furthermore, the issue of biosurfactants themselves being degraded preferentially to the target hydrocarbon(s) of interest should be addressed.
This study does bring to the forefront one of these novel variables for consideration?the presence and activity of indigenous biosurfactant producers. The role of biological variables is often overlooked in most studies. The role of biosurfactant producers in uncontaminated soil is extremely important because this may be an untapped source of potentially useful microorganisms. Novel biosurfactants may have additional benefits, such as being more resistant to degradation than many of the current biosurfactants. This would increase the likelihood that the biosurfactant will be in the environment long enough to function in hydrocarbon degradation while still retaining its ability to not become a contaminant itself.
Journal Articles:
No journal articles submitted with this report: View all 3 publications for this projectSupplemental Keywords:
applied biosurfactant technology, microbial surface thermodynamics, biodegradation kinetics, environment restoration, toluene, naphthalene, hexadecane, JP-4, rhamnolipid, lipopeptide., Scientific Discipline, Toxics, Waste, Ecosystem Protection/Environmental Exposure & Risk, Bioavailability, Bioremediation, Ecology and Ecosystems, 33/50, Environmental Engineering, aerobic degradation, bioremediation model, Toluene, biodegradation, chemical transport, biokinetic model, contaminant release, biosurfactant specifity, surface thermodynamicsProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.