Degradation pathways of trichloroethylene and 1,1,1-trichloroethane by Mycobacterium sp. TA27

We analyzed the kinetics and metabolic pathways of trichloroethylene and 1,1,1-trichloroethane degradation by the ethane-utilizing Mycobacterium sp. TA27. The apparent Vmax and Km of trichloroethylene were 9.8 nmol min(-1) mg of cells(-1) and 61.9 microM, respectively. The apparent Vmax and Km of 1,1,1-trichloroethane were 0.11 nmol min(-1) mg of cells(-1) and 3.1 microM, respectively. 2,2,2-trichloroethanol, trichloroacetic acid, chloral, and dichloroacetic acid were detected as metabolites of trichloroethylene. 2,2,2-trichloroethanol, trichloroacetic acid, and dichloroacetic acid were also detected as metabolites of 1,1,1-trichloroethane. The amounts of 2,2,2-trichloroethanol, trichloroacetic acid, chloral, and dichloroacetic acid derived from the degradation of 3.60 micromol trichloroethylene were 0.16 micromol (4.4%), 0.11 micromol (3.1%), 0.02 micromol (0.6%), and 0.02 micromol (0.6%), respectively. The amounts of 2,2,2-trichloroethanol, trichloroacetic acid and dichloroacetic acid derived from the degradation of 1.73 micromol 1,1,1-trichloroethane were 1.48 micromol (85.5%), 0.22 micromol (12.7%), and 0.02 micromol (1.2%), respectively. More than 90% of theoretical total chloride was released in trichloroethylene degradation. Chloral and 2,2,2-trichloroethanol were transformed into each other, and were finally converted to trichloroacetic acid, and dichloroacetic acid. Trichloroacetic acid and dichloroacetic acid were not degraded by strain TA27.     

Degradation of chlorinated and brominated hydrocarbons by Methylomicrobium album BG8

The degradation kinetics of ten halogenated hydrocarbons by Methylomicrobium album BG8 expressing particulate methane monooxygenase (pMMO) and the inhibitory effects of these compounds on microbial growth and whole-cell pMMO activity were measured. When M. album BG8 was grown with methane, growth was completely inhibited by dichloromethane (DCM), bromoform (BF), chloroform (CF), vinyl chloride (VC), 1,1-dichloroethylene (1,1-DCE), and cis-dichloroethylene (cis-DCE). Trichloroethylene (TCE) partially inhibited growth on methane, while dibromomethane (DBM), trans-dichloroethylene (trans-DCE), and 1,1,1-trichloroethane (1,1,1-TCA) had no effect. If the cells were grown with methanol, DCM, BF, CF, and 1,1-DCE completely inhibited growth, while VC, trans-DCE, TCE, and 1,1,1-TCA partially inhibited growth. Both DBM and cis-DCE had no effect on growth with methanol. Whole-cell pMMO activity was also affected by these compounds, with all but 1,1,1-TCA, DCM, and DBM reducing activity by more than 25%. DCM, DBM, VC, trans-DCE, cis-DCE, 1,1-DCE, and TCE were degraded and followed Michaelis-Menten kinetics. CF, BF, and 1,1,1-TCA were not measurably degraded. These results suggested that the products of DCM, TCE, VC, and 1,1-DCE inactivated multiple enzymatic processes, while trans-DCE oxidation products were also toxic but to a lesser extent. cis-DCE toxicity, however, appeared to be localized to pMMO. Finally, DBM and 1,1,1-TCA were not inhibitory, and CF and BF were themselves toxic to M. album BG8. Based on these results, the compounds could be separated into four general categories, namely (1) biodegradable with minimal inactivation, (2) biodegradable with substantial inactivation, (3) not biodegradable with minimal inactivation, and (4) not biodegradable but substantial inactivation of cell activity. Received: 17 June 1999 / Accepted: 3 September 1999     

Kinetic and inhibition studies for the aerobic cometabolism of 1,1,1-trichloroethane, 1,1-dichloroethylene,and 1,1-dichloroethane by a butane-grown mixed culture

Batch kinetic and inhibition studies were performed for the aerobic cometabolism of 1,1,1-trichloroethane (1,1,1-TCA), 1,1-dichloroethylene (1,1-DCE), and 1,1-dichloroethane (1,1-DCA) by a butane-grown mixed culture. These chlorinated aliphatic hydrocarbons (CAHs) are often found together as cocontaminants in groundwater. The maximum degradation rates (k(max)) and half-saturation coefficients (K(s)) were determined in single compound kinetic tests. The highest k(max) was obtained for butane (2.6 micromol/mg TSS/h) followed by 1,1-DCE (1.3 micromol/mg TSS/h), 1,1-DCA (0.49 micromol/mg TSS/h), and 1,1,1-TCA (0.19 micromol/mg TSS/h), while the order of K(s) from the highest to lowest was 1,1-DCA (19 microM), butane (19 microM), 1,1,1-TCA (12 microM) and 1,1-DCE (1.5 microM). The inhibition types were determined using direct linear plots, while inhibition coefficients (K(ic) and K(iu)) were estimated by nonlinear least squares regression (NLSR) fits to the kinetic model of the identified inhibition type. Two different inhibition types were observed among the compounds. Competitive inhibition among CAHs was indicated from direct linear plots, and the CAHs also competitively inhibited butane utilization. 1,1-DCE was a stronger inhibitor than the other CAHs. Mixed inhibition of 1,1,1-TCA, 1,1-DCA, and 1,1-DCE transformations by butane was observed. Thus, both competitive and mixed inhibitions are important in cometabolism of CAHs by this butane culture. For competitive inhibition between CAHs, the ratio of the K(s) values was a reasonable indicator of competitive inhibition observed. Butane was a strong inhibitor of CAH transformation, having a much lower inhibition coefficient than the K(s) value of butane, while the CAHs were weak inhibitors of butane utilization. Model simulations of reactor systems where both the growth substrate and the CAHs are present indicate that reactor performance is significantly affected by inhibition type and inhibition coefficients. Thus, determining inhibition type and measuring inhibition coefficients is important in designing CAH treatment systems.     

A 1,1,1-Trichloroethane-Degrading Anaerobic Mixed Microbial Culture Enhances Biotransformation of Mixtures of Chlorinated Ethenes and Ethanes

1,1,1-Trichloroethane (1,1,1-TCA) is a common groundwater pollutant as a result of improper disposal and accidental spills. It is often found as a cocontaminant with trichloroethene (TCE) and inhibits some TCE-degrading microorganisms. 1,1,1-TCA removal is therefore required for effective bioremediation of sites contaminated with mixed chlorinated organics. This study characterized MS, a 1,1,1-TCA-degrading, anaerobic, mixed microbial culture derived from a 1,1,1-TCA-contaminated site in the northeastern United States. MS reductively dechlorinated 1,1,1-TCA to 1,1-dichloroethane (1,1-DCA) and then to monochloroethane (CA) but not further. Cloning of bacterial 16S rRNA genes revealed among other organisms the presence of a Dehalobacter sp. and a Desulfovibrio sp., which are both phylogenetically related to known dehalorespiring strains. Monitoring of these populations with species-specific quantitative PCR during degradation of 1,1,1-TCA and 1,1-DCA showed that Dehalobacter proliferated during dechlorination. Dehalobacter growth was dechlorination dependent, whereas Desulfovibrio growth was dechlorination independent. Experiments were also performed to test whether MS could enhance TCE degradation in the presence of inhibiting levels of 1,1,1-TCA. Dechlorination of cis-dichloroethene (cDCE) and vinyl chloride (VC) in KB-1, a chloroethene-degrading culture used for bioaugmentation, was inhibited with 1,1,1-TCA present. When KB-1 and MS were coinoculated, degradation of cDCE and VC to ethene proceeded as soon as the 1,1,1-TCA was dechlorinated to 1,1-DCA by MS. This demonstrated the potential application of the MS and KB-1 cultures for cobioaugmentation of sites cocontaminated with 1,1,1-TCA and TCE.     

A simple and rapid microwave-assisted hematoxylin and eosin staining method using 1,1,1 trichloroethane as a dewaxing and a clearing agent

The use and practicability of microwave-assisted staining procedures in routine histopathology has been well established for more than 17 years. In the study reported here, we aimed to examine an alternative approach that would shorten the duration of dewaxing and clearing steps of hematoxylin and eosin (H & E) staining of paraffin sections by using a microwave oven. Although xylene is one of the most popular dewaxing and clearing agents, its flammability restricts its use in a microwave oven; thus we preferred 1,1,1 trichloroethane, which is not flammable, as the dewaxing and clearing agent in the present study. In Group I and Group II (control groups), intestine was processed with xylene and 1,1,1 trichloroethane, respectively. The sections were then stained with H & E according to the conventional staining protocol at room temperature and subdivided into two groups according to the duration of dewaxing and clearing in xylene. In Groups III and IV (experimental groups) similar tissues were processed with xylene and 1,1,1 trichloroethane, respectively; however, sections from these groups were divided into four subgroups to study the period required for dewaxing and clearing in 1,1,1 trichloroethane, then stained with H & E in the microwave oven at 360 W for 30 sec. Our conventional H & E staining procedure, which includes dewaxing, staining and clearing of sections, requires approximately 90 min, while our method using 1,1,1 trichloroethane and microwave heating required only 2 min. Our alternative method for H & E staining not only reduced the procedure time significantly, but also yielded staining quality equal or superior to those stained the conventional way. Our results suggest that 1,1,1 trichloroethane can be used effectively and safely as a dewaxing and clearing agent for H & E staining in a microwave oven.     

A 1,1,1-trichloroethane-degrading anaerobic mixed microbial culture enhances biotransformation of mixtures of chlorinated ethenes and ethanes

1,1,1-trichloroethane (1,1,1-TCA) is a common groundwater pollutant as a result of improper disposal and accidental spills. It is often found as a cocontaminant with trichloroethene (TCE) and inhibits some TCE-degrading microorganisms. 1,1,1-TCA removal is therefore required for effective bioremediation of sites contaminated with mixed chlorinated organics. This study characterized MS, a 1,1,1-TCA-degrading, anaerobic, mixed microbial culture derived from a 1,1,1-TCA-contaminated site in the northeastern United States. MS reductively dechlorinated 1,1,1-TCA to 1,1-dichloroethane (1,1-DCA) and then to monochloroethane (CA) but not further. Cloning of bacterial 16S rRNA genes revealed among other organisms the presence of a Dehalobacter sp. and a Desulfovibrio sp., which are both phylogenetically related to known dehalorespiring strains. Monitoring of these populations with species-specific quantitative PCR during degradation of 1,1,1-TCA and 1,1-DCA showed that Dehalobacter proliferated during dechlorination. Dehalobacter growth was dechlorination dependent, whereas Desulfovibrio growth was dechlorination independent. Experiments were also performed to test whether MS could enhance TCE degradation in the presence of inhibiting levels of 1,1,1-TCA. Dechlorination of cis-dichloroethene (cDCE) and vinyl chloride (VC) in KB-1, a chloroethene-degrading culture used for bioaugmentation, was inhibited with 1,1,1-TCA present. When KB-1 and MS were coinoculated, degradation of cDCE and VC to ethene proceeded as soon as the 1,1,1-TCA was dechlorinated to 1,1-DCA by MS. This demonstrated the potential application of the MS and KB-1 cultures for cobioaugmentation of sites cocontaminated with 1,1,1-TCA and TCE.     

A simple and rapid microwave-assisted hematoxylin and eosin staining method using 1,1,1 trichloroethane as a dewaxing and a clearing agent

The use and practicability of microwave-assisted staining procedures in routine histopathology has been well established for more than 17 years. In the study reported here, we aimed to examine an alternative approach that would shorten the duration of dewaxing and clearing steps of hematoxylin and eosin (H & E) staining of paraffin sections by using a microwave oven. Although xylene is one of the most popular dewaxing and clearing agents, its flammability restricts its use in a microwave oven; thus we preferred 1,1,1 trichloroethane, which is not flammable, as the dewaxing and clearing agent in the present study. In Group I and Group II (control groups), intestine was processed with xylene and 1,1,1 trichloroethane, respectively. The sections were then stained with H & E according to the conventional staining protocol at room temperature and subdivided into two groups according to the duration of dewaxing and clearing in xylene. In Groups III and IV (experimental groups) similar tissues were processed with xylene and 1,1,1 trichloroethane, respectively; however, sections from these groups were divided into four subgroups to study the period required for dewaxing and clearing in 1,1,1 trichloroethane, then stained with H & E in the microwave oven at 360 W for 30 sec. Our conventional H & E staining procedure, which includes dewaxing, staining and clearing of sections, requires approximately 90 min, while our method using 1,1,1 trichloroethane and microwave heating required only 2 min. Our alternative method for H & E staining not only reduced the procedure time significantly, but also yielded staining quality equal or superior to those stained the conventional way. Our results suggest that 1,1,1 trichloroethane can be used effectively and safely as a dewaxing and clearing agent for H & E staining in a microwave oven.     

Pollutant degradation by a Methylocystis strain SB2 grown on ethanol: bioremediation via facultative methanotrophy

A facultative methanotroph, Methylocystis strain SB2, was examined for its ability to degrade chlorinated hydrocarbons when grown on methane or ethanol. Strain SB2 grown on methane degraded vinyl chloride (VC), trans-dichloroethylene (t-DCE), trichloroethylene (TCE), 1,1,1-trichloroethane (1,1,1-TCA), and chloroform (CF), but not dichloromethane (DCM). Growth on methane was reduced in the presence of any chlorinated hydrocarbon. Strain SB2 grown on ethanol degraded VC, t-DCE, and TCE, and 1,1,1-TCA, but not DCM or CF. With the exception of 1,1,1-TCA, the growth of strain SB2 on ethanol was not affected by any individual chlorinated hydrocarbon. No degradation of any chlorinated hydrocarbon was observed when acetylene was added to ethanol-grown cultures, indicating that this degradation was due to particulate methane monooxygenase (pMMO) activity. When mixtures of chlorinated alkanes or alkenes were added to cultures growing on methane or ethanol, chlorinated alkene degradation occurred, but chlorinated alkanes were not, and growth was reduced on both methane and ethanol. Collectively, these data indicate that competitive inhibition of pMMO activity limits methanotrophic growth and pollutant degradation. Facultative methanotrophy may thus be useful to extend the utility of methanotrophs for bioremediation as the use of alternative growth substrates allows for pMMO activity to be focused on pollutant degradation.     

A simple and rapid microwave-assisted hematoxylin and eosin staining method using 1,1,1 trichloroethane as a dewaxing and a clearing agent.

The use and practicability of microwave-assisted staining procedures in routine histopathology has been well established for more than 17 years. In the study reported here, we aimed to examine an alternative approach that would shorten the duration of dewaxing and clearing steps of hematoxylin and eosin (H & E) staining of paraffin sections by using a microwave oven. Although xylene is one of the most popular dewaxing and clearing agents, its flammability restricts its use in a microwave oven; thus we preferred 1,1,1 trichloroethane, which is not flammable, as the dewaxing and clearing agent in the present study. In Group I and Group II (control groups), intestine was processed with xylene and 1,1,1 trichloroethane, respectively. The sections were then stained with H & E according to the conventional staining protocol at room temperature and subdivided into two groups according to the duration of dewaxing and clearing in xylene. In Groups III and IV (experimental groups) similar tissues were processed with xylene and 1,1,1 trichloroethane, respectively; however, sections from these groups were divided into four subgroups to study the period required for dewaxing and clearing in 1,1,1 trichloroethane, then stained with H & E in the microwave oven at 360 W for 30 sec. Our conventional H & E staining procedure, which includes dewaxing, staining and clearing of sections, requires approximately 90 min, while our method using 1,1,1 trichloroethane and microwave heating required only 2 min. Our alternative method for H & E staining not only reduced the procedure time significantly, but also yielded staining quality equal or superior to those stained the conventional way. Our results suggest that 1,1,1 trichloroethane can be used effectively and safely as a dewaxing and clearing agent for H & E staining in a microwave oven.     

Toxicity of 1,1,1-Trichloroethane and Trichloroethene on a Mixed Culture of Methane-Oxidizing Bacteria

The influence of trichloroethene (TCE; 0 to 65 mg/liter) and 1,1,1-trichloroethane (1,1,1-TCA; 0 to 103 mg/liter) on methane consumption of a mixed culture of methane-oxidizing bacteria was studied in laboratory batch experiments. Increasing concentrations of TCE or 1,1,1-TCA resulted in decreasing methane consumption. Methane consumption was totally inhibited at a concentration of 13 mg of TCE per liter, while methane consumption was still observed at the upper studied concentration of 103 mg of 1,1,1-TCA per liter. The inhibition of methane consumption by TCE depended on the initial concentration of methane. A model accounting for competitive inhibition between methane and TCE or 1,1,1-TCA was used to simulate methane consumption at various concentrations of TCE or 1,1,1-TCA. The simulations indicated that competitive inhibition may be the mechanism causing the inhibitory effect of TCE on methane consumption, while this does not seem to be the case for 1,1,1-TCA.     

Bacterial and fungal cometabolism of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) and its breakdown products.

Resting cells of bacteria grown in the presence of diphenylmethane oxidized substituted analogs such as 4-hydroxydiphenylmethane, bis(4-hydroxyphenyl)methane, bis(4-chlorophenyl)methane (DDM), benzhydrol, and 4,4'-dichlorobenzhydrol. Resting cells of bacteria grown with benzhydrol as the sole carbon source oxidized substituted benzhydrols such as 4-chlorobenzhydrol, 4,4'-dichlorobenzhydrol, and other metabolites of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT), such as DDM and bis(4-chlorophenyl)acetic acid. Bacteria and fungi converted 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane to 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane, DDM, 4,4'-dichlorobenzhydrol, and 4,4'-dichlorobenzophenone. Aspergillus conicus converted 55% of bis(4-chlorophenyl)acetic acid to unidentified or unextractable water-soluble products. Aspergillus niger and Penicillium brefeldianum converted 12.4 and 24.6%, respectively, of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane to water-soluble and unidentified products. 4-Chlorophenylacetic acid, a product of ring cleavage, was formed from DDM by a false smut fungus of rice. A. niger converted 4,4'-dichlorobenzophenone to 4-chlorobenzophenone and a methylated 4-chlorobenzophenone.     

Bacterial and fungal cometabolism of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) and its breakdown products

Resting cells of bacteria grown in the presence of diphenylmethane oxidized substituted analogs such as 4-hydroxydiphenylmethane, bis(4-hydroxyphenyl)methane, bis(4-chlorophenyl)methane (DDM), benzhydrol, and 4,4'-dichlorobenzhydrol. Resting cells of bacteria grown with benzhydrol as the sole carbon source oxidized substituted benzhydrols such as 4-chlorobenzhydrol, 4,4'-dichlorobenzhydrol, and other metabolites of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT), such as DDM and bis(4-chlorophenyl)acetic acid. Bacteria and fungi converted 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane to 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane, DDM, 4,4'-dichlorobenzhydrol, and 4,4'-dichlorobenzophenone. Aspergillus conicus converted 55% of bis(4-chlorophenyl)acetic acid to unidentified or unextractable water-soluble products. Aspergillus niger and Penicillium brefeldianum converted 12.4 and 24.6%, respectively, of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane to water-soluble and unidentified products. 4-Chlorophenylacetic acid, a product of ring cleavage, was formed from DDM by a false smut fungus of rice. A. niger converted 4,4'-dichlorobenzophenone to 4-chlorobenzophenone and a methylated 4-chlorobenzophenone.     

Inactivation of bovine plasma amine oxidase by 1,1,1–trihalo–3–aminopropanes

In this paper, we report the inactivation of copper containing bovine plasma amine oxidase (BPAO) by a series of saturated alkylamines containing halogen atoms at γ-position, which are 1,1,1-trihalo-3-aminopropane, 1,1,1-trifluoro-2-hydroxy-3-aminopropane, 1,1,1-trichloro-2-hydroxy-3-aminopropane, and 1,1,1-trichloro-2-(2-phenethyloxy)-3-aminopropane. The trihalo-2-hydroxypropylamine analogs exhibited a time-dependent inactivation behavior of BPAO, with 1,1,1-trifluoro-2-hydroxy-3-aminopropane as the most efficient inactivator. The incorporation of a OH group at β-position increased inactivation efficiency by 10-fold within the trifluoro analogs, and the incorporation of a phenethyloxy group at β-position exhibited a higher efficiency by 3-fold within the trichloro analogs based on I₇₅ values. All four compounds were found to be irreversible inactivators for BPAO.     

A combined method for determining inhibition type, kinetic parameters, and inhibition coefficients for aerobic cometabolism of 1,1,1-trichloroethane by a butane-grown mixed culture.

A combined method for determining inhibition type, kinetic parameters, and inhibition coefficients is developed and presented. The method was validated by applying it to data obtained from batch kinetics of the aerobic cometabolism of 1,1,1-trichloroethane (1,1,1-TCA) by a butane-grown mixed culture. The maximum degradation rates (k(max)) and half-saturation coefficients (K(s)) were independently determined in single compound tests, and compared with those obtained from inhibition tests. The inhibition type was determined using direct linear plots at various substrate and inhibitor concentrations. Kinetic parameters (k(max) and K(s)) and inhibition coefficients (K(ic) and K(iu)) were determined by nonlinear least squares regression (NLSR) fits of the inhibition model determined from the direct linear plots. Initial guesses of the kinetic parameters for NLSR were determined from linearized inhibition equations that were derived from the correlations between apparent maximum degradation rates (k(app)(max)) and/or the apparent half-saturation coefficient (K(app)(s)) and the k(max), K(s), and inhibitor concentration (I(L)) for each inhibition equation. Two different inhibition types were indicated from the direct linear plots: competitive inhibition of 1,1,1-TCA on butane degradation, and mixed inhibition of 1,1,1-TCA transformation by butane. Good agreement was achieved between independently measured k(max) and K(s) values and those obtained from both NLSR and the linearized inhibition equations. The initial guesses of all the kinetic parameters determined from linear plots were in the range of the values estimated from NLSR analysis. Overall the results show that use of the direct linear plot method to identify the inhibition type, coupled with initial guesses from linearized plots for NLSR analysis, results in an accurate method for determining inhibition types and coefficients. Detailed studies with pure cultures and purified enzymes are needed to further demonstrate the utility of this method.     

Urinary excretion of mercapturates as a biological indicator of exposure to electrophilic agents

The urinary excretion of mercapturates was followed photometrically in individuals exposed to styrene, a mixture of aromatic hydrocarbons, butadiene, vinyl chloride, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, 1,1,1-trifluoro-2-bromo-2-chloroethane (Halothane), ethylene oxide, epichlorhydrin, bis(chloromethyl)-ether, N-methylacrylamide, dimethylformamide, nitrosamines or cis-platinum and in groups of controls, smokers and nonsmokers, males and females, the residents of city P, industrial town V.M. and mountain village S. The increase in the urinary excretion of mercapturates was found in individuals exposed to styrene, aromatic hydrocarbons, dimethylformamide, 1,1,1-trichloroethane, and in smokers. In groups of controls, the lowest mercapturate concentrations were detected in the urine samples of nonsmokers from the mountain village S. where the degree of air pollution due to motor vehicle emissions was lowest at the time of investigation.     

Complete transformation of 1,1,1-trichloroethane to chloroethane by a methanogenic mixed population

A methanogenic mixed population in a packed-bed reactor completely transformed 1,1,1-trichloroethane (10 μM) to chloroethane by a cometabolic process. Chloroethane was not further transformed. Acetate and methanol served as electron donors. Complete transformation of 1,1,1-trichloroethane to chloroethane only occurred when sufficient electron donor was fed into the reactor. Otherwise, besides chloroethane, 1,1-dichloroethane was also found as a product. The products of 1,1,1-trichloroethane transformation also depended on the type of electron donor present. With acetate, the degree of dechlorination was higher, i.e. more 1,1,1-trichloroethane was transformed to chloroethane than with methanol. In an enrichment culture obtained from the reactor contents, 1,1,1-trichloroethane was only transformed to 1,1-dichloroethane and was not further metabolized. Methanol, acetate, formate, ethanol, 2-propanol, trimethylamine and H₂, but not dimethylamine and methylamine, served as electron donors for 1,1,1-trichloroethane transformation by this enrichment culture. Both nitrate and nitrite inhibited 1,1,1-trichloroethane transformation; while nitrate completely inhibited 1,1,1-trichloroethane dechlorination, some conversion did occur in the presence of nitrite. The product(s) of this conversion remain unknown, since no chlorinated hydrocarbons were detected. Received: 19 June 1998 / Received revision: 14 September 1998 / Accepted: 17 September 1998     

Bioaugmentation of butane-utilizing microorganisms to promote cometabolism of 1,1,1-trichloroethane in groundwater microcosms

The transformation of 1,1,1-trichloroethane (1,1,1-TCA) in ioaugmented and non-augmented microcosms was evaluated. The microcosms contained roundwater and aquifer materials from a test site at Moffett Field, Sunnyvale, CA. The initial inoculum for bioaugmentation was a butane-utilizing enrichment from the subsurface of the Hanford DOE site. The non-augmented microcosm required 80 days of incubation before butane-utilization was observed while the augmented microcosms required 3 days. Initially the augmented microcosms were effective in transforming 1,1,1-TCA, but their transformation ability decreased after prolonged incubation. The non-augmented microcosms initially showed limited 1,1,1-TCA transformation but improved with time. After 440 days, both the non-augmented and augmented microcosms had similar transformation yields (0.04 mg 1,1,1-TCA/mg butane) and had similar microbial composition (DNA fingerprints). Subsequent microcosms, when bioaugmented with a Hanford enrichment that was repeatedly grown in 100% mineral media, did not effectively grow or transform 1,1,1-TCA under groundwater nutrient conditions. Microcosm tests to study the effect of mineral media on transformation ability were performed with the Hanford enrichment. Microcosms with 50% mineral media in groundwater most effectively utilized butane and transformed 1,1,1-TCA, while microcosms with groundwater only and microcosms with 5% mineral media in groundwater lost their 1,1,1-TCA transformation ability. DNA fingerprinting indicated shifts in the microbial composition with the different mineral media combinations. Successful bioaugmentation was achieved by enriching butane-utilizers from Moffett Field microcosms that were effective in groundwater with no mineral media added. The results suggest that successful in-situ bioaugmentation might be achieved through the addition of enriched cultures that perform well under subsurface nutrient conditions.     

Aerobic Cometabolism of Chloroform and 1,1,1-Trichloroethane by Butane-Grown Microorganisms

Aerobic cometabolism of chloroform (CF) and 1,1,1-trichloroethane (1,1,1-TCA) was observed by subsurface microorganisms grown on butane. Studies performed in batch incubated microcosms were screened for CF transformation potential using the following cometabolic substrates: ammonia, methane, propane, butane, propene, octane, isoprene, and phenol. CF transformation was observed in microcosms fed ammonia, methane, propane, and butane. The butane microcosms achieved the most effective transformation. The transformation of CF and 1,1,1-TCA was strongly correlated with butane utilization and oxygen consumption. CF transformation ceased in the absence of butane or when oxygen was depleted to low concentrations in the microcosms. No transformation of carbon tetrachloride was observed. With successive additions of CF and butane to the microcosms, complete transformation of CF was achieved at solution concentrations as high as 1 mg/L. High CF concentrations appeared to inhibit butane utilization. Maximum transformation yield (T_y) of 0.01 mg CF trans-formed/mg of butane consumed, were achieved. The results indicate that a monooxygenase enzyme required for butane utilization is likely responsible for the transformation of CF. Chloride measurements demonstrated that CF was completely dechlorinated. Approximately 70% of the chloride in the transformed 1,1,1 -TCA was released into solution, indicating incomplete dechlorination of 1,1,1-TCA. The results indicate that butane is a promising cometabolic substrate for the transformation of chlorinated methanes, chlorinated ethanes, and potentially chlorinated ethenes.     

Characterization of two carbonyl reductases from Ogataea polymorpha NBRC 0799

Applied Microbiology and Biotechnology - The enzyme responsible for the enantioselective production of (S)-1,1,1-trifluoro-2-propanol ((S)-TFP) from 1,1,1-trifluoroacetone (TFA) has been identified...     

Effect of phenobarbital and 3-methylcholanthrene pretreatment on the hepatotoxicity of 1,1,1-trichloroethane and 1,1,2-trichloroethane

Pretreatment of rats with phenobarbital potentiated the hepatotoxicity of both 1,1,1- and 1,1,2-trichloroethane given by inhalation. The toxicity of the 1,1,2-isomer was increased to a greater extent than that of the 1,1,1-isomer. 3-Methylcholanthrene pretreatment did not result in increased hepatotoxicity.