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Biodegradation of Hazardous Compounds Using Immobilized Microorganisms

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  057005,  2005 ASAE Annual Meeting . (doi: 10.13031/2013.19651) @2005
Authors:   Jiyeon Ha, Adriana Z. Diaz, James R. Wild, Cady R. Engler
Keywords:   Organophosphates, Coumaphos, Chlorferon, DETP, Biodegradation, Immobilization

Coumaphos, an organophosphate insecticide, is hydrolyzed to chlorferon and diethyl thiophosphate (DETP). In this research, two different consortia of microorganisms responsible for degrading either chlorferon or DETP were enriched from cattle dip solution. Both consortia of organisms were mostly rod type gram-negative bacteria. The enriched cultures were used as inocula to grow biomass for degradation studies. At concentrations greater than 50 mg/l, chlorferon inhibited DETP degrading organisms. From experiments using freely suspended cells, the optimum biomass concentration for chlorferon degradation was found to be 80 g/L, and pH 7.5 was selected as the optimum operating pH. Chlorferon degradation followed substrate inhibition kinetics. Parameters were estimated as Vm,C = 0.062 mg/g-biomassh, Km,C = 20.634 mg/L, and KSi,C = 117.628 mg/L. For DETP degradation, the optimum biomass concentration was found to be 60 g/L and the operating reaction pH was in the range of 7.5 to 8. The DETP degradation reaction followed Monod kinetics with kinetic parameters estimated to be Vm,D = 1.523 mg/g-biomassh and Km,D = 609.791mg/L. Chlorferon or DETP degrading organisms were separately immobilized in Ca-alginate beads. The optimum bead loading rate in a reactor was found to be 20% for chlorferon degradation and 30% for DETP degradation. The chlorferon degradation rate was significantly enhanced with immobilized cells. Both specific reaction rate and volumetric reaction rate were five times higher than that with freely suspended cells. This was attributed to the protection of cells from inhibitory ingredients in UCD solution by immobilization.

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