Sebastian Lippemeier
University of Kiel
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Featured researches published by Sebastian Lippemeier.
Sensors | 2007
Kai Marxen; Klaus Heinrich Vanselow; Sebastian Lippemeier; Ralf Hintze; Andreas Ruser; Ulf-Peter Hansen
The demonstrated modified spectrophotometric method makes use of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and its specific absorbance properties. The absorbance decreases when the radical is reduced by antioxidants. In contrast to other investigations, the absorbance was measured at a wavelength of 550 nm. This wavelength enabled the measurements of the stable free DPPH radical without interference from microalgal pigments. This approach was applied to methanolic microalgae extracts for two different DPPH concentrations. The changes in absorbance measured vs. the concentration of the methanolic extract resulted in curves with a linear decrease ending in a saturation region. Linear regression analysis of the linear part of DPPH reduction versus extract concentration enabled the determination of the microalgaes methanolic extracts antioxidative potentials which was independent to the employed DPPH concentrations. The resulting slopes showed significant differences (6 - 34 μmol DPPH g−1 extract concentration) between the single different species of microalgae (Anabaena sp., Isochrysis galbana, Phaeodactylum tricornutum, Porphyridium purpureum, Synechocystis sp. PCC6803) in their ability to reduce the DPPH radical. The independency of the signal on the DPPH concentration is a valuable advantage over the determination of the EC50 value.
European Journal of Phycology | 2001
Sebastian Lippemeier; Ralf Hintze; Klaus Heinrich Vanselow; Peter Hartig; Franciscus Colijn
Turbidostat cultures of Dunaliella salina (Chlorophyceae) and Thalassiosira weissflogii (Bacillariophyceae) were grown at fluctuating concentrations of nitrate, phosphate and silicate. In-line measurements of PAM fluorescence were used to monitor the effects of fluctuating nutrient supply on the photochemical efficiency of photosystem II reaction centres of light-adapted cells (ΔF/F′m). Besides the maximal photochemical efficiency of photosystem II reaction centres of dark-adapted cells (F v/F m), chlorophyll a, particulate organic carbon, nitrogen and phosphorus, and the cell number were measured frequently during the experiments. Following nutrient-replete growth, the cells were supplied with medium from which either nitrate, phosphate or silicate was omitted. When significant effects of nutrient starvation were indicated by the fluorescence parameters, a pulse of the deficient nutrient was added to the cultures. Our experimental set-up for in-line fluorescence measurements provided sensitive and reprod...
Journal of Phycology | 2003
Sebastian Lippemeier; Dion Matthew Frederick Frampton; Susan I. Blackburn; Stephanie Geier; Andrew P. Negri
The effects of phosphorus (P) limitation on growth, toxicity, and variable chl fluorescence of Alexandrium minutum were examined in batch culture experiments. Cell division was greatly impaired in P‐limited cultures, but P spiking of these cultures after 9 days stimulated high levels of cell division equivalent to P‐replete cultures. The cellular concentration of paralytic shellfish toxins was consistent over the growth cycle of control cultures from lag phase into logarithmic growth phase, with toxins repeatedly lost to daughter cells during division. The low level of cell division in P‐limited cultures resulted in a 10‐fold increase of cellular toxin compared with controls, but this dropped upon P spiking due to increased rates of cell division. The history of phosphorus supply had an important effect on toxin concentration, with the P‐limited and the P‐spiked cultures showing values 2‐fold higher than the P‐replete cultures. Toxin profiles of the A. minutum strain used in these experiments were dominated by the N1‐hydroxy toxins, gonyautoxins (GTX) GTX1 and GTX4, which were approximately 40 times more abundant than their analogues, GTX2 and GTX3, in P‐limited cultures. The dominance of the N1‐hydroxy toxins increased significantly in control cultures as they advanced through logarithmic growth. In‐line measurements of the variable chl fluorescence of light‐adapted cells indicated consistent photochemical efficiency under P‐replete conditions. P limitation induced a drop in fluorescence‐based photochemical efficiency that was reversible by P spiking. There was an inverse linear relationship between in‐line fluorescence and cell toxin quota (r = −0.88). Monitoring fluorescence in‐line may be valuable in managing efficient biotechnological production of toxins.
Journal of Applied Phycology | 2005
Kai Marxen; Klaus Heinrich Vanselow; Sebastian Lippemeier; Ralf Hintze; Andreas Ruser; Ulf-Peter Hansen
A bioreactor system was developed for the cultivation of the microalgae Synechocystis sp. PCC6803 under controlled physiological conditions. The determination of the actual physiological state of the microalgae was provided by inline recording of chlorophyll fluorescence parameters. A feed-back loop was employed to keep the microalgae in a defined physiological state. For the construction of this feed-back loop, the temporal behaviour of the system was investigated using changes in light conditions (as caused by modulated UVB radiation) as input signal and chlorophyll fluorescence as output signal. The reproducibility of the responses was high. Kinetic analysis based on curve fitting revealed two time constants in the UVB-induced responses. The knowledge of these time constants was utilised for the development of an efficient feed-back loop which allows the cultivation of the microalgae in a defined physiological state. This new process strategy (called physiostat) was successfully tested. The performance in a culture of growing microalgae is shown.
Journal of Applied Phycology | 2010
Kai Marxen; Klaus Heinrich Vanselow; Ralf Hintze; Sebastian Lippemeier; Andreas Ruser; Britta Egge; Franciscus Colijn; Ulf-Peter Hansen
Two different modes of UV-B irradiation of the cyanobacterium Synechocystis sp. PCC 6803 are compared: turbidostatic control and additional physiostatic control. Under turbidostatic control, the cells were exposed to different constant UV-B irradiances, whereas under physiostatic control, an electronic control loop modulated UV-B irradiance in such a way that photosynthetic efficiency ϕPSII was kept constant at a fixed set point. The UV-B-induced stimulation of the synthesis of pigments, α-tocopherol, and the antioxidative potential of methanolic soluble components of Synechocystis showed significant differences depending on the mode of irradiation, even though the overall doses were equal. For example, compared to the initial values, the concentrations of myxoxanthophyll and zeaxanthin increased to 226–244% and 453% upon constant UV-B irradiation in turbidostatic processes, whereas maxima of 600% and 740% were reached in turbidostatic process with additional physiostatic control. The α-tocopherol concentration increased under constant UV-B irradiances, up to a maximum of 150%. Under physiological control, however, maximum increases of 390% over the initial values were measured. Furthermore, a reaction scheme is given explaining the higher yield under physiostatic control.
Marine Ecology Progress Series | 1998
Peter Hartig; Kirsten Wolfstein; Sebastian Lippemeier; Franciscus Colijn
Journal of Plankton Research | 1999
Sebastian Lippemeier; Peter Hartig; Franciscus Colijn
Archive | 2006
Wolf-Dieter Juelich; Ulrike Lindequist; Sabine Witt; Joern Kasbohm; Gerold Lukowski; Kristian Wende; Hans-Peter Welzel; Winfrid Ruehle; Frank Szrama; Martina Wurster; Sebastian Lippemeier; Joachim Schomburg; Christian Schultz; Peter Hartig; Ralf Hintze
Archive | 2006
Wolf-Dieter Juelich; Ulrike Lindequist; Sabine Witt; Joern Kasbohm; Gerold Lukowski; Kristian Wende; Hans-Peter Welzel; Winfrid Ruehle; Frank Szrama; Martina Wurster; Sebastian Lippemeier; Joachim Schomburg; Christian Schultz; Peter Hartig; Ralf Hintze
Archive | 2005
Peter Hartig; Ralf Hintze; Wolf-Dieter Priv.-Doz. Dr. Jülich; Ulrike Lindequist; Sebastian Lippemeier; Winfried Dipl.-Ing. Rühle; Joachim Schomburg; Christian Schultz; Frank Szrama; Hans-Peter Welzel; Martina Wurster