Submitted to: Biotechnology Progress
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/4/2002
Publication Date: 11/3/2002
Citation: KIM, J., RAININA, E.I., MULBRY III, W.W., ENGLER, C.R., WILD, J.R. ENHANCED-RATE BIODEGRADATION OF ORGANOPHOSPHATE NEUROTOXINS BY IMMOBILIZED NON-GROWING BACTERIA. BIOTECHNOLOGY PROGRESS. 2002. Interpretive Summary: Recent progress in the biodegradation of organophosphate insecticides suggests that biological treatment may prove to be the most environmentally and economically feasible strategy for detoxifying these compounds and for cleaning up contaminated soils and water. In this research, scientists compared the biodegradation rates of the insecticide coumaphos by bacterial cells trapped (immobilized) in a synthetic gel to rates by the same cells that were suspended in buffer. Rates of the trapped cells were about twice the rate of the suspended cells. In addition, the immobilized cells retained much of their activity over a four-month period of use and storage. Biodegradation technologies using non-growing immobilized cells should be particularly effective for cases growing organisms are not effective and where long-term storage is important. In addition to using this technology for environmental clean-up, the U.S. Army may use such approaches in making protective foams and decontaminating agents for soldiers and equipment. .
Technical Abstract: Pesticide wastes generated from livestock dipping operations containing the organophosphate (OP) insecticide coumaphos (CP) are well suited for disposal by biodegradation since they are highly concentrated , generally contained, and lack additional toxic components. In this study, a significantly enhanced efficiency of degrading CP in cattle dip waste (CDW) is reported using a dense, non-growing cell population which functions without the addition of nutrients required for growing cell cultures. A recombinant strain of Escherichia coli containing the opd gene for organophosphate hydrolase (OPH) which is capable of active hydrolysis of OP neurotoxins was cultivated in a rich medium containing all essential nutrients. Cells were harvested and utilized in lab scale experiments in the form of either freely suspended cells or cells immobilized within a macro-porous gel matrix, poly(vinyl alcohol) (PVA) cryogel. Significantly higher degradation rates were achieved with either suspended or immobilized OPH+ cells compared to rates with the microbial consortium naturally present in CDW. Of the two non-growing cell systems, the detoxification rate with immobilized cells was approximately twice that of freely suspended cells; and kinetic studies demonstrated that a higher maximum reaction rate was achieved with the immobilized cell system. A comparative study using both the CDW and pure CP substrates with free cells indicated that the CDW contained one or more factors that reduced the bioavailability of CP. The immobilized cells retained their activity over a 4 month period of use and storage, demonstrating both sustained catalytic activity and long-term mechanical stability.