Using Biosurfactant Production to Enhance the Applicability and Performance of Bioslurry Systems for Site Remediation

Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Dr. Daniel P. Cassidy

Second Advisor

Dr. Dave Barnes

Third Advisor

Dr. Duane Hampton

Fourth Advisor

Dr. Anna Jelaso


Bioslurry systems are effective remediation tools that can be used in the treatment of contaminated soils, sediments, and sludges. It is known that biosurfactant-producing species are present in many contaminated soils, and that, under certain conditions, they can produce biosurfactants to enhance rates of contaminant degradation. However, little is known about the conditions necessary for the production and accumulation of biosurfactants by indigenous soil microorganisms during contaminant biodegradation. The purpose of this research was to investigate the conditions that stimulate biosurfactant production in bioslurry reactors.

A literature review and initial experiments indicated that changing conditions in slurry reactors trigger biosurfactant production. To test this hypothesis, two types of reactors were maintained. Soil slurry-sequencing batch reactors (SS-SBR) were operated to provide controlled, non-steady state conditions, and continuous-flow reactors (CSTR) were maintained to provide continuous (i.e., quasi steady state) conditions. Two different contaminated soils were tested, one contaminated with diesel fuel (DF) and another contaminated with polycyclic aromatic hydrocarbon (PAH). In both cases, the SS-SBR encouraged the growth of biosurfactant producing species relative to CSTR operation, which resulted in growth-associated biosurfactant production in the SS-SBR (between 4 and 70 times the critical micelle concentration, or CMC). No biosurfactant production was observed in the CSTR for either contaminated soil. Additional research on the DF-contaminated soil showed that increasing volumetric loadings from 5 to 50% in the SS-SBR enhanced the growth of biosurfactant-producing microorganisms, biosurfactant production, DF degradation, and increased foaming. Sequencing batch bioslurry studies were done on a soil contaminated with lubricating oil (LO) and polychlorinated biphenyls (PCBs) to investigate nutrient-limited biosurfactant production. Limiting nitrogen after a short growth phase stimulated the production of rhamnolipids by Pseudomonas aeruginosa to levels nearly 20 times the CMC. The rhamnolipids produced were able to wash nearly 99% of the PCBs and LO from the contaminated soil. This research shows that biosurfactant production can be manipulated in bioslurry reactors, and provides insights into how in situ biosurfactant production may be achieved.

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