Ulrich Stottmeister

White biotechnology for green chemistry: fermentative 2-oxocarboxylic acids as novel building blocks for subsequent chemical syntheses

Functionalized compounds, which are difficult to produce by classical chemical synthesis, are of special interest as biotechnologically available targets. They represent useful building blocks for subsequent organic syntheses, wherein they can undergo stereoselective or regioselective reactions. “White Biotechnology” (as defined by the European Chemical Industry [http://www.europabio.org/white_biotech.htm], as part of a sustainable “Green Chemistry,”) supports new applications of chemicals produced via biotechnology. Environmental aspects of this interdisciplinary combination include: Use of renewable feedstockOptimization of biotechnological processes by means of: New “high performance” microorganismsOn-line measurement of substrates and products in bioreactorsAlternative product isolation, resulting in higher yields, and lower energy demand In this overview we describe biotechnologically produced pyruvic, 2-oxopentaric and 2-oxohexaric acids as promising new building blocks for synthetic chemistry. In the first part, the microbial formation of 2-oxocarboxylic acids (2-OCAs) in general, and optimization of the fermentation steps required to form pyruvic acid, 2-oxoglutaric acid, and 2-oxo-d-gluconic acid are described, highlighting the fundamental advantages in comparison to chemical syntheses. In the second part, a set of chemical formula schemes demonstrate that 2-OCAs are applicable as building blocks in the chemical synthesis of, e.g., hydrophilic triazines, spiro-connected heterocycles, benzotriazines, and pyranoic amino acids. Finally, some perspectives are discussed.

Free phosphine from the anaerobic biosphere

The possible liberation of highly toxic and mutagenic phosphine from putrefying media raises the question of its significance as a problem of hygiene. Free phosphine was established by gas chromatography as a universal trace component in gas emitted from the anaerobic biosphere. Sources of phosphine include landfills, compost processing, sewage sludge, animal slurry and river sediments. We detected maximum concentrations in the order of 20 ppb(v/v).

Oxygen Release by Roots of Typha latifolia and Juncus effusus in Laboratory Hydroponic Systems

Laboratory-scale investigations using individual T.latifolia and J. effusus plants in hydroponic systems were carried out to evaluate the potentials and differences in the species regarding the release of oxygen into their rhizospheres. Their oxygen release intensities were found to vary between the species and also to depend on the redox state of the rhizosphere. The highest release rates with mean values of 1.1 mg/h plant for T.latifolia and 0.5 mg/h plant for J.effusus were estimated at Eh - - 200 mV for both species. The amounts of oxygen released were sufficient to be of biotechnological relevance for oxidative processes in constructed wetlands. The plants even released oxygen under oxidized rhizospheric conditions and for individual plants, an intensification of the oxygen release was estimated, forming further local release maxima at Eh = 250-400 mV with about 0.2 mg/h plant. The total size of the root system does not significantly affect the intensity of oxygen release; instead, the oxygen release state was governed by the size of the above-ground biomass. The intensification of illumination causes an increase in the oxygen release rates, which is pronounced for T.latifolia but small for J.effusus. Further investigations involving other wetland species and using laboratory-scale, pilot-scale and full-scale wetland systems to evaluate oxygen release are of biotechnological interest.

Phosphine by bio-corrosion of phosphide-rich iron

Phosphine is a toxic agent and part of the phosphorus cycle. A hitherto unknown formation mechanism for phosphine in the environment was investigated. When iron samples containing iron phosphide were incubated in corrosive aquatic media affected by microbial metabolites, phosphine was liberated and measured by gas chromatography. Iron liberates phosphine especially in anoxic aquatic media under the influence of sulfide and an acidic pH. A phosphine-forming mechanism is suggested: Phosphate, an impurity of iron containing minerals, is reduced abioticly to iron phosphide. When iron is exposed to the environment (e.g. as outdoor equipment, scrap, contamination in iron milled food or as iron meteorites) and corrodes, the iron phosphide present in the iron is suspended in the medium and can hydrolyze to phosphine. Phosphine can accumulate to measurable quantities in anoxic microbial media, accelerating corrosion and preserving the phosphine formed from oxidation.

CONSTRUCTED WETLANDS AND THEIR PERFORMANCE FOR TREATMENT OF WATER CONTAMINATED WITH ARSENIC AND HEAVY METALS

This study investigated the removal mechanisms of arsenic and heavy metals in constructed wetland systems. The biotic and abiotic processes in the wetlands and the influences of plants, soil and micro-organisms on arsenic and heavy metal removal were examined. Various small-scale constructed wetlands were set up in order to study and compare the removal efficiency of laboratory-scale wetland models and small-scale field test systems. In the field test systems, acid mine drainage (AMD) was used as an example of acidic wastewater contaminated with heavy metals.

Strategies for Remediation of Former Opencast Mining Areas in Eastern Germany

Lignite was for decades the main source of energy and the primary raw material used by the chemical industry in the now German Federal States of Saxony, Saxony-Anhalt, and Brandenburg. Except during the initial phases of extraction, lignite was exclusively recovered by opencast mining. The close ties between industry and mining led to the establishment of major industrial operations such as petrochemical, organochemical, and electrochemical plants located near the mining centers. In terms of its quality and composition, lignite in eastern Germany can be classified into West and East Elbian formations, corresponding to the Central German and the Lusatian mining districts.

Batch methanogenic fermentation experiments of wastewater from a brown coal low-temperature coke plant

Coke plant effluents with high contents of organic compounds are mainly treated by biological aerobic fermentation after physical pre-treatment. In this study, a brown coal condensate wastewater from a low temperature coking process was fermented under methanogenic conditions in discontinuous experiments. By this fermentation, acetate, propionate, and the main polyphenolic compounds (catechol, resorcinol and hydroquinone) were degraded to a level below the detection limit. The COD was reduced by 72% with a residual concentration of 2.1 g/L. This anaerobic fermented wastewater had a residual BOD5 of 0.66 g/L and 2.2 L CH4 were formed per litre of wastewater. An abiotic pre-treatment for this wastewater with air had a negative effect on the COD reduction and decrease of colour on the methanogenic fermentation due to the autoxidation of polyphenolic compounds to humic-like compounds. This study showed that methanogenic fermentations in the treatment sequence of brown coal coking wastewaters could reduce energy consumption for aeration in further treatment processes and had the potential for a better effluent quality due to a less formation of recalcitrant humic-like compounds.

Distribution of contaminants and the self-purifying potential for aromatic compounds in a carbonization wastewater deposit

The Schwelvollert, a highly colored carbonization wastewater deposit located in Saxony-Anhalt (eastern Germany) was the subject of extensive analytical studies. When sampled in autumn the pyrolysis effluent lake was found to be stratified in three distinct layers, each exhibiting different physicochemical and microbiological characteristics. Although no oxygen was detectable in the whole deposit, aerobic bacteria were shown to predominate among pollutant degraders: in the upper layers about 40–60% degraders of phenolic compounds in heterotrophic microbial communities were found. Neither nitrate-reducers nor sulfate-reducing or methanogenic consortia that degraded benzoate were detectable. However, nitrite-reducing benzoate degraders were found with MPNs ranging from 0.03 to 20/mL. The attempt to identify aerobic isolates from the top layer with the commercially available BIOLOG and API 20NE identification systems revealed their unsuitability for the determination of specific pyrolysis effluent bacteria. Although the aerobic bacteria with specific degradation abilities are not likely to use their abilities under in-situ conditions, they represent a degradation potential which might be useful for aerobic remediation strategies.

Microbial phenol degradation of organic compounds in natural systems: Temperature-inhibition relationships

The combined influence of high phenol concentrations and low temperatures on aerobic and anaerobic phenol degradation kinetics was investigated in microbial enrichment cultures to evaluate temperature-inhibition relationships with respect to the ambient conditions in polluted habitats. The inhibition of microbial phenol degradation by excess substrate was found to be temperature-dependent. Substrate inhibition was intensified when temperatures were lower. This results in an elevated temperature sensitivity of phenol degradation at inhibitory substrate concentrations.The synergistic amplification of substrate inhibition at low temperatures may help to explain the limited self-purification potential of contaminated habitats such as soils, sediments and groundwater aquifers where high pollutant concentrations and low temperatures prevail.

Model experiments on the influence of artificial humic compounds on chemodenitrification

Chemodenitrification is of importance in both soils and the treatment of some types of wastewater. During model experiments,the impact of various conditions, such as pH and especially artificial humic matter and oxygen on this process was studied to build upkinetic models. The chemodenitrification rate decreased due to the ongoingautoxidation/polymerization of hydroquinone to artificial humic matterfrom 11.02 μg (L h)-1 after 7 days autoxidation to 5.38 μg (L h)-1 after 14 days at pH 4 under aerobic conditionsand an initial nitrite concentration of 250 μg L-1. At the same pH,with the same nitrite concentration, and in the presence of Roth humic matter(2 mg L-1) under aerobic conditions, the chemodenitrification rate was0.73 μg (L h)-1, whereas under anaerobic conditions itwas considerably higher (2.88 μg (L h)-1). In anothermodel experiment, it was shown that the amount of nitrite incorporated into the artificial humic matter was less then 1%. Further, it was found that the main reaction product of chemodenitrification is NO.