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We investigated the effects of coexisting surfactants and high-molecular-weight organic compounds on the reductive dechlorination of trichloroethylene by zerovalent iron powder to determine whether these additives had utility as washing reagents for remediation of soil and groundwater pollution. During the dechlorination reaction, the amount of trichloroethylene decreased, and the formation of cis-1,2-dichloroethylene was observed. The decomposition of trichloroethylene was found to be first-order with respect to the trichloroethylene and zerovalent iron concentrations when the solution contained no additives. The rates of decomposition of trichloroethylene in the presence of the additives were lower than the rate in the absence of the additives: the rate constant was reduced by a factor of 0.7 for the cationic surfactant cetyltrimethylammonium bromide; by a factor of 0.5 for the anionic surfactants sodium n-dodecylbenzenesulfonate, sodium n-dodecylsulfate, and sodium n-dodecanesulfonate and for the high-molecular-weight organic compounds soluble starch, beta-cyclodextrin, and polyethyleneglycol 6000; and by a factor of 0.2 for sodium laurate and the nonionic surfactants Triton X-100, Tween 20, Tween 60, Brij 35, and Brij 58. Comparison of the concentrations of the nonionic surfactants with their critical micellar concentrations indicated that the rate-reducing effect of these additives was due to solubilization of trichloroethylene into the micellar phase. The adsorption of trichloroethylene onto the zerovalent iron surface was also affected by the presence of the additives. Thus, our results indicated that the changes in the decomposition rate of trichloroethylene were determined by several factors.

The chlorinated organic compounds, trichloroacetic acid (TCAA), 2, 2, 2-trichloroethanol (TCAol), dichloroacetic acid (DCAA) and chloral were produced from the biotransformation of trichloroethylene (TCE) by a methane utilizing bacterium Methylocystis sp. strain M. The degradation of TCE by strain M was influenced by pH, with an optimum between 6 and 7. The conversions to TCAA, TCAol and DCAA derived from added TCE were 7.8%, 0.04% and 1.8%, respectively, at pH 7, and varied with pH. The reactions that convert chloral to these metabolites were also influenced by pH. The conversions to TCAA, TCAol and DCAA from added chloral were 77%, 0.6% and 6.0%, respectively, at pH 7. Strain M did not degrade TCAA, TCAol and DCAA, which were shown to be end products of TCE degradation by strain M. The production of DCAA from chloral suggested a new pathway for producing DCAA via chloral, in addition to that via TCEoxide. Thrity-four percent and 66% of DCAA produced from TCE were derived via chloral and TCEoxide, respec...

The optimum electrotransformation conditions were determined for Pseudomonas putida PpY101 with plasmid pSUP104 (9.5 kb) and pSR134 (18.6 kb). Field strength was a very important parameter for electrotransformation efficiency. Optimum efficiencies (1.1 x 10(5) transformants/micrograms DNA) with pSUP104 and pSR134 were obtained at a field strength of 12.5 kV/cm, a time constant of about 4.5 ms (resistance setting of 200 ohms), a supercoiled DNA concentration of 100 ng/ml, and a cell concentration of 10(9)/ml. Because the efficiency obtained is high enough, electrotransformation is useful for the direct cloning of P. putida PpY101. No significant relationship between plasmid size and electrotransformation efficiency was observed. These efficiencies were about 4.5 times higher than those using the MgCl2 method. Under these conditions, electrotransformation efficiencies of relaxed plasmid DNA treated with topoisomerase I and that linearized by EcoRI digestion were high.