Annual cycle of nitrogen removal by a pilot-scale subsurface horizontal flow in a constructed wetland under moderate climate.

The annual course of nitrogen removal in a stable operating subsurface horizontal flow constructed wetland (SSF) in a moderate climate was evaluated using a large pool of data from 4 years of operation. In spring and autumn removal efficiencies were found to depend on the nitrogen load in a linear mode. The efficiencies in winter and summer differed extremely (mean removal rates of 0.15/0.7 g m(-2) d(-1) (11%/53%) in January/August) and were independent of the nitrogen load (0.7-1.7 g m(-2) d(-1)) in principle. Oscillations of the removal rates in spring, forming several maxima, suggest seasonal specific effects caused by the dynamics of the plant-physiology finally determining the nitrification efficiency, i.e. via O(2)-supply. Nitrification is limited by temperature during all seasons and surprisingly in midsummer additionally restricted by other seasonal aspects forming a clear-cut relative nitrification minimum (mean rate of 0.43 g m(-2) d(-1) (32%)) in July. The importance and the effect of the plants' gas exchange and oxygen input into the rhizosphere are discussed. Denitrification was nearly complete in midsummer and was clearly restricted at seasonal temperatures below 15 degrees C.

Functional and structural successions in arbitrary samples of heterotrophic bacteria during aerobic treatments of lignite-carbonization wastewater in in situ enclosures.

In situ mesocosm experiments were performed in Lake Schwelvollert (located in the district of Weissenfels, Saxony-Anhalt, Germany), an anaerobic lignite-carbonization effluent lake containing phenolic compounds and their autoxidation products (anthropogenic humic matter). In the aeration enclosure, the anaerobic Schwelvollert wastewater was aerated and in the flocculation enclosure, it was flocculated to precipitate the oxygen-trapping anthropogenic humic matter to enhance the input of oxygen by diffusion. To gain an insight into the metabolic state of the aerobic heterotrophic microbiota during the treatments, arbitrary samples of bacterial isolates were taken from a general agar medium and tested for their abilities to cleave predominant phenolic contaminants by a procedure called the isolate sample assay. In this way, successions of degradation potentials were observed in both mesocosms, with degradation abilities for meta- and para-alkylated phenols appearing before degradation abilities for ortho-substituted phenols as a common phenomenon. To examine the structure of samples, the respective isolates were characterized using the Biolog GN MicroPlate system, the random amplified polymorphic DNA nucleic acid (RAPD) fingerprinting technique, and amplified ribosomal DNA restriction analysis (ARDRA). Although similar functional patterns occurred in both mesocosms, the compositions and diversities of the respective bacterial communities varied significantly, even at different depths from the same enclosure, with members of the Pseudomonas RNA group I being predominant.

[Utilization of paraffins and other noncarbohydrate carbon sources for microbial citric acid synthesis]. / Nutzung von Paraffinen und anderen Nichtkohlenhydrat-Kohlenstoffquellen zur mikrobiellen Citronensäuresynthese.

This article reviews the developments achieved in citrate and isocitrate accumulation with non-carbohydrate substrates by microorganisms presented as well in academic publications as in patients. The efficiency of citrate and isocitrate overproducing microorganisms and of mutants obtained thereof with respect to different carbon sources (n-alkanes, triglycerides, organic acids, etc.) is discussed. The influence of environmental conditions (media, pH etc.) and biochemical mechanisms which lead to metabolic overflow are emphasized. The kinetics of fermentation processes are described, calculations concerning carbon balances are involved. The production of by-products and the conversion of isocitrate to citrate is considered. The production of citric acid by yeasts which utilize different carbon sources may be economically feasible and an accession to the practized molasse-Aspergillus-process.

[Kinetics of citric acid production in Candida lipolytica]. / Zur Kinetik der Citronensäurebildung bei Candida lipolytica.

The kinetics of citrate and isocitrate accumulation by Candida lipolytica has been studied, with special emphasis of the carbon sources glucose and n-alkanes and the shifts from one carbon source to the other. The accumulation of the citric acids starts with the beginning of ideophase. Trophophase and ideophase behaviour is in parts different. Ideophase behaviour may be influenced by exogenic factors during growth. From the course of the curves for the citric acids two phases can be distinguished: The specific production rate of the first phase is higher than in the second phase (pi1 approximately 0.19 h-1; pi2 approximately 0.14 h-1). The influence of the carbon source on the course of the curves and the numeric value for the specific production rate is negligible. Alcane grown cells accumulate citric acids from added glucose and left-over n-alcanes simultaneously. When both substrates are added from the beginning only glucose is taken up for growth, for citric acid production both substances are utilized simultaneously. Glucose grown cells do not utilize alcanes for production of citric acids. Citric acids are accumulated only as long as glucose is available. Alcane uptake starts after addition of a nitrogen source.