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D Schlosser

Publications and source records attributed to D Schlosser.

At least 19 recordsLinked to original sources
PubMed2006

Microbial degradation of nonylphenol and other alkylphenols--our evolving view.

Because the endocrine disrupting effects of nonylphenol (NP) and octylphenol became evident, the degradation of long-chain alkylphenols (AP) by microorganisms was intensively studied. Most NP-degrading bacteria belong to the sphingomonads and closely related genera, while NP metabolism is not restricted to defined fungal taxa. Growth on NP and its mineralization was demonstrated for bacterial isolates, whereas ultimate degradation by fungi still remains unclear. While both bacterial and fungal degradation of short-chain AP, such as cresols, and the bacterial degradation of long-chain branched AP involves aromatic ring hydroxylation, alkyl chain oxidation and the formation of phenolic polymers seem to be preferential elimination pathways of long-chain branched AP in fungi, whereby both intracellular and extracellular oxidative enzymes may be involved. The degradation of NP by sphingomonads does not proceed via the common degradation mechanisms reported for short-chain AP, rather, via an unusual ipso-substitution mechanism. This fact underlies the peculiarity of long-chain AP such as NP isomers, which possess highly branched alkyl groups mostly containing a quaternary alpha-carbon. In addition to physicochemical parameters influencing degradation rates, this structural characteristic confers to branched isomers of NP a biodegradability different to that of the widely used linear isomer of NP. Potential biotechnological applications for the removal of AP from contaminated media and the difficulties of analysis and application inherent to the hydrophobic NP, in particular, are also discussed. The combination of bacteria and fungi, attacking NP at both the phenolic and alkylic moiety, represents a promising perspective.

Bacteria↗
PubMed2006

Separation of technical 4-nonylphenols and their biodegradation products by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry.

Comprehensive two-dimensional gas chromatography (GC x GC) coupled to time-of-flight mass spectrometry (TOF-MS) was applied to improve the separation of 4-nonylphenol isomers and their biodegradation products. The structurally similar nonylphenol isomers were separated by combining a 30 m long semi-polar column and a short polar capillary. Both were coupled via a custom-made liquid nitrogen cryogenic modulator. The advanced GC resolution of coeluting isomers, additionally supported by fast scanning TOF-MS, provided clearer, non-interfered mass spectra of individual isomers. Thus, identification of components is facilitated as shown for isomeric 4-nonylphenols and metabolites of their biodegradation by Clavariopsis aquatica, an aquatic fungus. GC x GC-TOF-MS analysis enabled the separation of about 40 alkylphenol isomers included in technical 4-nonylphenol. During biodegradation the variety of emerging compounds increased with longer reaction time. The comprehensive analysis indicated a broad spectrum of hydroxylated, carboxylated nonylphenolisomers and additionally, chlorinated aromatic compounds produced and released from the fungal culture.

Biodegradation, Environmental↗
PubMed2003

Degradation of 2-fluorophenol by the brown-rot fungus Gloeophyllum striatum: evidence for the involvement of extracellular Fenton chemistry.

Iron-containing liquid cultures of the brown-rot basidiomycete Gloeophyllum striatum degraded 2-fluorophenol. Two simultaneously appearing degradation products, 3-fluorocatechol and catechol, were identified by gas chromatography and mass spectrometry (GC-MS). Concomitantly, fluoride was produced at approximately 50% of the amount that theoretically could be achieved upon complete dehalogenation. Defluorination was strongly inhibited in the presence of either the hydroxyl radical scavenger mannitol or superoxide dismutase, as well as in the absence of iron. The addition of the natural iron chelator oxalate caused a clear but less extensive inhibition, whereas supplementation with the artificial iron chelator nitrilotriacetic acid increased fluoride production. Extracellular 2-fluorophenol degradation was evidenced by defluorination, observed upon addition of 2-fluorophenol to cell-free culture supernatants derived from iron-containing fungal cultures. Ultrafiltered culture supernatants oxidized methanol to formaldehyde, known as a product of the reaction of methanol with hydroxyl radical. In addition, G. striatum was found to produce metabolites extractable with ethyl acetate that are capable of reducing Fe3+. GC-MS analysis of such extracts revealed the presence of several compounds. The mass spectrum of a prominent peak matched those previously reported for 2,5-dimethoxyhydroquinone and 4,5-dimethoxycatechol, fungal metabolites implicated to drive hydroxyl radical production in Gloeophyllum. Taken together, these findings further support an extracellular Fenton-type mechanism operative during halophenol degradation by G. striatum.

Biodegradation, Environmental↗
PubMed2000

Hydroxylated metabolites of 2,4-dichlorophenol imply a fenton-type reaction in Gloeophyllum striatum.

While degrading 2,4-dichlorophenol, two strains of Gloeophyllum striatum, a basidiomycetous fungus causing brown rot decay of wood, simultaneously produced 4-chlorocatechol and 3,5-dichlorocatechol. These metabolites were identified by comparing high-performance liquid chromatography retention times and mass spectral data with those of chemically synthesized standards. Under similar conditions, 3-hydroxyphthalic hydrazide was generated from phthalic hydrazide, a reaction assumed to indicate hydroxyl radical formation. Accordingly, during chemical degradation of 2,4-dichlorophenol by Fenton's reagent, identical metabolites were formed. Both activities, the conversion of 2,4-[U-(14)C]dichlorophenol into (14)CO(2) and the generation of 3-hydroxyphthalic hydrazide, were strongly inhibited by the hydroxyl radical scavenger mannitol and in the absence of iron. These results provide new evidence in favor of a Fenton-type degradation mechanism operative in Gloeophyllum.

Basidiomycota↗
PubMed1999

Degradation of 2,4-dichlorophenol and pentachlorophenol by two brown rot fungi.

Wheat straw cultures of the brown rot fungi Gloeophyllum striatum and G. trabeum degraded 2,4-dichlorophenol and pentachorophenol. Up to 54% and 27% 14CO2, respectively, were liberated from uniformly 14C-labeled substrates within 6 weeks. Under identical conditions Trametes versicolor, a typical white rot species employed as reference, evolved up to 42% and 43% 14CO2 and expressed high activities of laccase, manganese peroxidase, and manganese-independent peroxidase. No such activity could be detected in straw or liquid cultures of Gloeophyllum. Moreover, G. striatum degraded both chlorophenols most efficiently under non-cometabolic conditions, i.e. on a defined mineral medium lacking sources of carbon, nitrogen and phosphate.

Basidiomycota↗
PubMed1999

Novel enzymatic oxidation of Mn2+ to Mn3+ catalyzed by a fungal laccase.

Fungal laccases are extracellular multinuclear copper-containing oxidases that have been proposed to be involved in ligninolysis and degradation of xenobiotics. Here, we show that an electrophoretically homogenous laccase preparation from the white rot fungus Trametes versicolor oxidized Mn2+ to Mn3+ in the presence of Na-pyrophosphate, with a Km value of 186 microM and a Vmax value of 0.11 micromol/min/mg protein at the optimal pH (5.0) and a Na-pyrophosphate concentration of 100 mM. The oxidation of Mn2+ involved concomitant reduction of the laccase type 1 copper site as usual for laccase reactions, thus providing the first evidence that laccase may directly utilize Mn2+ as a substrate.

Diphosphates↗
PubMed1998

Degradation of 2-chlorophenol and formation of 2-chloro-1,4-benzoquinone by mycelia and cell-free crude culture liquids of Trametes versicolor in relation to extracellular laccase activity.

The white-rot fungus Trametes versicolor was used to study the influence of extracellular laccase activity on the degradation of 2-chlorophenol (2-CP) and the formation of metabolites under conditions, characterized by the absence of other phenol-oxidizing enzymes. 2-CP enhanced the production of extracellular laccase by fungal mycelia. The formation of the metabolite 2-chloro-1,4-benzoquinone (2-CIBQ) was found to be correlated with extracellular laccase activity. In cell-free crude culture liquids laccase was responsible for the oxidation of 2-CP. In contrast to this, the disappearance of 2-CP caused by the entire organism did not correlate with extracellular laccase activity. The primary oxidative step during the degradation of this compound can thus only partially be attributed to extracellular laccase; indicating the involvement of cell-bound processes.

Basidiomycota↗
PubMed1997

Involvement of cytochrome P-450 in the 15alpha-hydroxylation of 13-ethyl-gon-4-ene-3,17-dione by Penicillium raistrickii.

The 15alpha-hydroxylation of 13-ethyl-gon-4-ene-3,17-dione (GD) with different subcellular fractions of Penicillium raistrickii i 477 was investigated. Cytochrome P-450 was shown to be involved in this reaction. The steroid transformation was inhibited by carbon monoxide, metyrapone, p-CMB, iodoacetamide, N-methylmaleimide and several metal ions. The 15alpha-hydroxylase was observed to be dependent on nicotinamide-adenine dinucleotide phosphate (NADPH) replaceable by NaIO4, and the activity was enhanced by a NADPH-regenerating system, indicating the involvement of the NADPH-cytochrome c (P-450) reductase. This was further confirmed by the inhibition of the hydroxylase activity in the presence of cytochrome c. No effect was observed in the presence of azide and antimycin A. Solubilized microsomes gave an absorption maximum at 453 nm in carbon monoxide difference spectrum, and showed a Type-I GD-binding spectrum typically for cytochrome P-450 interaction with substrate. First results about the inducibility of the enzymes involved in the 15alpha-hydroxylation of GD are shown.

Carbon Monoxide↗
PubMed1997

A prospective evaluation of the diagnostic work-up before laparoscopic cholecystectomy.

BACKGROUND AND STUDY AIMS: A prerequisite for successful laparoscopic cholecystectomy is the exclusion of potential risks such as cholangiolithiasis or anatomical malformations. As there is no general agreement regarding the appropriate preoperative diagnostic work-up, a comparative study of different diagnostic methods was carried out. PATIENTS AND METHODS: In 180 consecutive patients admitted to a community hospital for cholecystectomy due to symptomatic cholecystolithiasis, a prospective comparison was carried out of the diagnostic accuracy of patient history, physical examination, laboratory tests, upper gastrointestinal endoscopy, intravenous cholangiography, ultrasonography, and endoscopic retrograde cholangiopancreatography (ERCP). RESULTS: Measurement of the diameter of the common bile duct was found to be a reliable method as a single noninvasive parameter for diagnosing cholangiolithiasis (sensitivity 100%, specificity 93%), with good predictive power (positive predictive value 0.7, negative predictive value 1.0). The best accuracy achieved noninvasively and without sonography was with a combination of positive patient history and gamma-glutamyl transferase findings (sensitivity 58%, specificity 84%, positive predictive value 0.37, negative predictive value 0.93). ERCP detected additional cholangiolithiasis in 19 of 139 patients (13.7%) and anatomical malformations in three patients. In all 19 patients, the bile ducts were cleared of stones endoscopically within 24 hours, prior to laparoscopic cholecystectomy. Among the 163 patients primarily assigned to laparoscopic cholecystectomy, the protocol diagnostic work-up, including ERCP, allocated three patients (1.8%) to open surgery. Conversion from laparoscopic cholecystectomy to open cholecystectomy occurred in a further two of 158 patients (1.3%). CONCLUSIONS: These results show that routine ultrasonography prior to laparoscopic cholecystectomy can be recommended in order to determine the diameter of the common bile duct. In patients with a ductal diameter of more than 6 mm, ERCP should be performed. Laparoscopic cholecystectomy can be carried out within 24 hours after ERCP and papillotomy.

Adolescent↗
PubMed1995

Phenol and cresol metabolism in Bacillus pumilus isolated from contaminated groundwater.

From an aquifier contaminated with phenolic compounds seven bacterial strains able to grow on phenol and several mono- and disubstituted alkylphenols as sole source of carbon and energy were isolated. Five isolates belong to the genus Pseudomonas, two to the genus Bacillus. The isolate most active in utilization of the applied xenobiotics was identified as Bacillus pumilus and used for the investigation of the degradation pathways in liquid cultures. Cells of this strain precultured on phenol were able to utilize para-cresol as sole carbon source via the oxidation of the methylsubstituent and intradiol ring cleavage of the resulting protocatechuic acid, whereas an intradiol ring fission of the intermediate 4-methylcatechol led to 4-methylmuconolactone as dead end-product. Cells precultured on meta- and ortho-cresol were able to utilize the respective compounds as sole carbon sources via 3-methylcatechol, which induced the following extradiol ring fission pathway. Cells precultured on phenol were able to cooxidize meta- as well as ortho-cresol to 3-methylcatechol, which was cleaved via an intradiol ring fission, finally leading to the dead end-product 2-methylmuconolactone.

Bacillus↗
PubMed1994

Bioremediation of contaminated groundwater.

Contaminated groundwater from industrial areas in former East Germany was biologically treated using lab-scale solid-state reactors. The ability of bacterial strains of the autochroneous microflora to utilize representative pollutants was tested.

Benzene Derivatives↗
PubMed1993

Investigations of the oxygen supply in Ca-alginate beads and microcapsules loaded with Penicillium raistrickii using a microelectrode.

The oxygen supply of free, Ca-alginate entrapped and microencapsulated mycelia of Penicillium raistrickii i 477 capable of 15 alpha-hydroxylation of 13-ethyl-gon-4-en-3,17-dione was investigated. Using an oxygen microelectrode distinct gradients of oxygen within the Ca-alginate beads as well as the microcapsules were detected. Slope and width of the gradients were investigated in dependence on the kind of immobilization, the culture age and the cell density on or in the carrier as well as the different forms of the oxygen supply in the medium. So it could be shown that large parts of immobilizates, approximately 96% of the diameter of both types, were oxygen-free. In comparison with free mycelia, the lower oxygen supply of the immobilized mycelia led to a metabolic shift to fermentative catabolism.

Alginates↗
PubMed1993

Steroid hydroxylation with free and immobilized cells of Penicillium raistrickii in the presence of beta-cyclodextrin.

Free and Ca-alginate-immobilized cells of Penicillium raistrickii i 477 were used for 15 alpha-hydroxylation of 13-ethyl-gon-4-en-3,17-dione. The product formation of both free and immobilized cells was increased in the presence of beta-cyclodextrin, in comparison with reactions carried out in the presence of methanol. Application of beta-cyclodextrin led to increasing solubility of the steroid substrate. The fungus was able to utilize beta-cyclodextrin as a carbon source.

Alginates↗
PubMed1991

Application of immobilized cells for biotransformations of steroids.

A survey is given of possible solutions and open-ended questions in the biotransformation of steroids (without side chain degradation of sterols) by using immobilized cells. The data of literature between 1975 and 1990 and results of preliminary experiments from the microbial, biochemical, biophysical, physiological, as well as the biotechnological point of view are summarized and discussed.

Bacteria↗
PubMed1989

[Primary non-Hodgkin's lymphoma of the stomach].

Between 1980 and 1987 a total of 17 patients were operated upon in curative intention of the Non-Hodgkin-Lymphoma of the stomach at our surgical department. Ten of these patients were within Ann-Arbor-Stage I, four within stage II/1 and the other three within stage II/2. In six cases we found low-malignant and in the other 11 cases high-malignant tumors. One patient died postoperatively after a myocardial infarction, one female died four months postoperatively in spite of chemotherapy of the disease. 15 patients (94%) are still alive today without any new symptoms of the disease, within a median average observation time of 40.6 months.

Adult↗
PubMed1989

Assessing memory deterioration with the Wechsler Memory Scale, the National Adult Reading Test, and the Schonell Graded Word Reading Test.

The National Adult Reading Test (NART), the Schonell Graded Word Reading Test (SGWRT), and the Wechsler Memory Scale, Form I (WMS) were administered to 65 healthy subjects aged 65 to 89 years. Regression equations were derived which allowed total raw score on the WMS to be predicted from the subject's age and from the number of errors on the NART alone or on the NART and SGWRT combined. The distribution of discrepancies between obtained and predicted WMS scores for each equation did not depart significantly from normality and the percentage of subjects at each discrepancy score is provided. The standard error of prediction for each equation is slightly less than that for predicting WAIS IQ from the NART. Sixteen patients with clinical diagnoses of senile dementia of the Alzheimer type obtained discrepancies as large or larger than the most discrepant 2% of normal subjects. These results suggest that this procedure may provide a brief but effective assessment of cognitive deterioration in the elderly and may be capable of assessing dementia earlier than the NART/WAIS combination.

Aged↗