Isolation of a methanogenic bacterium, Methanosarcina sp. strain FR, for its ability to degrade high concentration of perchloroethylene.

Tetrachloroethylene (PCE) is a toxic compound essentially used as a degreasing and dry-cleaning solvent. A methanogenic and sulfate-reducing consortium that dechlorinates and mineralizes high concentrations of PCE was derived from anaerobically digested sludge obtained from a waste water treatment plant (Bourg-en-Bresse, France). A methanogenic bacterium, strain FR, was isolated from this acclimated consortium. On the basis of morphological and physiological characteristics, strain FR was classified in the genus of Methanosarcina. Phylogeny analysis with the 16S rRNA gene sequence revealed that strain FR is highly related to Methanosarcina mazei and Methanosarcina frisia (99.6 and 99.5% identity, respectively). High concentrations (50-87 microM) of PCE were completely dechlorinated by strain FR cultures at the rate of 76 nM-mg protein(-1).day(-1). PCE dechlorination produced a nonidentified compound. The tracer experiments with [13C]PCE revealed that the product was nonchlorinated. Dechlorination of PCE to trichloroethylene was still active in the presence of boiled cell extract of the strain FR. However, no further dechlorination was observed. This result suggests that a cofactor rather than an enzymatic system is responsible for the first dechlorination of PCE. Dechlorination-active fractions purified from cell extracts on a XAD-4 column revealed the presence of F(420), F(430), and cobamides cofactors. This is the first report of the isolation of a methanogenic bacterium with the ability to dechlorinate high concentrations of PCE to a nonchlorinated product.

Specific determination of cyanide in blood by headspace gas chromatography.

An improved method has been developed for the quantitative determination of cyanide in human blood by headspace gas chromatography with electron-capture detection. In this novel method, cyanide was detected after conversion of hydrogen cyanide into cyanogen chloride by a reaction with chloramine T. The advantage of this new procedure lies in the fact that hydrogen cyanide formation and chlorination are carried out in a single step and in the same reaction medium. This method is simple, rapid, and specific for cyanide and does not suffer from any interference by cyanate and thiocyanate. The detection limit is 5 micrograms/L. The detection response is linear from 5 to 1000 micrograms/L, and the within-run coefficient of variation in this range is 8% or less. This method is particularly useful for routine diagnostic analysis of biological samples in case of acute cyanide poisoning.

Capillary gas chromatographic determination with electron capture detector of beta-propiolactone in biological materials.

A method has been developed for the determination of beta-propiolactone by derivatizing it to the volatile N-hexyl-3-heptafluorobutanoyloxypropanamide, which can be separated and identified by a capillary CP-Sil 8 column, and detected by an electron capture detector (ECD). First, beta-propiolactone is reacted with N-hexylamine to yield N-hexyl-3-hydroxypropanamide. The fluorobutanoyl ester derivative is next prepared by using heptafluorobutyric acid anhydride in the presence of trimethylamine. The method is very sensitive, simple, and specific, and can be used to detect and quantitate residual beta-propiolactone in lyophilized biological materials. The limit of detection is 0.2 ppm beta-propiolactone in a 50 mg sample; however, because of variability at low levels, the limit of quantitation is 1 ppm. Detector response was linear for 2-500 mg beta-propiolactone. Recoveries were 98% or greater from lyophilized vaccines spiked at the 2-20 ppm level. No side products or interference peaks were observed in the derivatization reaction.

Human ochratoxicosis in France.

The prevalence of human ochratoxicosis in France is being determined using serum and plasma collected from apparently healthy people. The analytical method is based on the partition coefficient of ochratoxin A in aqueous and organic solvents, according to pH. High-performance liquid chromatography and spectrofluorimetry are used for detection and quantification (limit of detection, greater than 0.2 ng/ml). The presence of ochrotoxin A is confirmed by the action of carboxypeptidase to yield ochratoxin alpha or by derivatization of ochratoxin A with boron trifluoride. The significance of the interim values obtained and the number of positive samples is discussed. A comparison with the distribution of known values in Germany and Scandinavia could be helpful in risk assessment with a view to prevention.