Oramas Suttinun, Peter B. Lederman, and Ekawan Luepromchai

pp. 131 - 142

Abstract

Trichloroethylene (TCE), a chlorinated solvent, is a major water pollutant originating from spillage
and inappropriate disposal of dry cleaning agents, degreasing solvents, and paint strippers. Due to its widespread contamination and potential health threat, remediation technology to clean-up TCE is necessary. Aerobic
biodegradation of TCE is reported to occur via cometabolism, by which TCE degrading bacteria utilize other
compounds such as toluene, phenol, and methane as growth substrate and enzyme inducer. Although toluene
is reported to be the most effective inducer, it is regulated as a hazardous material and should not be applied
to the environment. The objectives of this study were to identify an alternative enzyme inducer as well as to
apply the induced bacteria for degradation of TCE in contaminated soil. We investigated the effect of terpenes,
the main components in volatile essential oils of plants, on induction of TCE degradation in Rhodococcus
gordoniae P3, a local Gram (+) bacterium. Selected terpenes including cumene, limonene, carvone and pinene
at various concentrations were used in the study. Results from liquid culture showed that 25 mg l^-1 cumeneinduced R. gordoniae P3 cells resulted in 75% degradation of 10 ppm TCE within 24 hrs. Soil microcosms
were later employed to investigate the ability of cumene to enhance TCE biodegradation in the environment. There were two bioremediation treatments studied, including bioaugmentation, the inoculation of cumeneinduced R. gordoniae P3, and biostimulation, the addition of cumene to induce soil indigenous microorganisms to degrade TCE. Bioaugmentation and biostimulation were shown to accelerate TCE reduction
significantly more than control treatment at the beginning of study. The results suggest that cumene-induced
R. gordoniae P3 and cumene can achieve rapid TCE biodegradation.