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101.
Collet C Girbal L Péringer P Schwitzguébel JP Soucaille P 《Archives of microbiology》2006,185(5):331-339
The objective of the present study was to characterize the metabolism of Clostridium thermolacticum, a thermophilic anaerobic bacterium, growing continuously on lactose (10 g l−1) and to determine the enzymes involved in the pathways leading to the formation of the fermentation products. Biomass and metabolites concentration were measured at steady-state for different dilution rates, from 0.013 to 0.19 h−1. Acetate, ethanol, hydrogen and carbon dioxide were produced at all dilution rates, whereas lactate was detected only for dilution rates below 0.06 h−1. The presence of several key enzymes involved in lactose metabolism, including beta-galactosidase, glyceraldehyde-3-phosphate dehydrogenase, pyruvate:ferredoxin oxidoreductase, acetate kinase, ethanol dehydrogenase and lactate dehydrogenase, was demonstrated. Finally, the intracellular level of NADH, NAD+, ATP and ADP was also measured for different dilution rates. The production of ethanol and lactate appeared to be linked with the re-oxidation of NADH produced during glycolysis, whereas hydrogen produced should come from reduced ferredoxin generated during pyruvate decarboxylation. To produce more hydrogen or more acetate from lactose, it thus appears that an efficient H2 removal system should be used, based on a physical (membrane) or a biological approach, respectively, by cultivating C. thermolacticum with efficient H2 scavenging and acetate producing microorganisms. 相似文献
102.
Purification and characterization of hydrosoluble components from the sap of Chinese lacquer tree Rhus vernicifera 总被引:3,自引:0,他引:3
Yun-Yang W Yu-Min D Fang-Xing Y Ying X Rong-Zhi C Kennedy JF 《International journal of biological macromolecules》2006,38(3-5):232-240
Continuous gradient elution chromatography (CGEC) was employed to purify and separate enzymes and polysaccharides from the sap of Rhus vernicifera Chinese lacquer tree. There are three different molecules with laccase enzyme activity. Two are enzymes of each other (L1, and L2), whereas the third (RL) is an entirely separate entity. Two polysaccharides (GP1 and GP2) were also found. The Rhus laccase (RL), and isoenzymes L1 and L2, have peak molecular masses of 109,100, 120,000, 103,000 respectively; each has four copper atoms per molecule, and the pI values were 8.2, 8.6, and 9.1, respectively. The structure of the laccases was studied by Fourier-transform infrared (FT-IR) and Matrix-assisted laser desorption/ionization time-of flight (MALDI-TOF) mass spectrometry. The typical amide I (1646 cm−1) and amide II (1545 cm−1) bands were observed. The results from MALDI-TOF were similar to those from CGEC, but the molecular mass from the MALDI-TOF was significantly different from that obtained from sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). 相似文献
103.
Cooperation in the prisoner's dilemma (PD) played on various networks has been explained by so-called network reciprocity. Most of the previous studies presumed that players can offer either cooperation (C) or defection (D). This discrete strategy seems unrealistic in the real world, since actual provisions might not be discrete, but rather continuous. This paper studies the differences between continuous and discrete strategies in two aspects under the condition that the payoff function of the former is a linear interpolation of the payoff matrix of the latter. The first part of this paper proves theoretically that for two-player games, continuous and discrete strategies have different equilibria and game dynamics in a well-mixed but finite population. The second part, conducting a series of numerical experiments, reveals that such differences become considerably large in the case of PD games on networks. Furthermore, it shows, using the Wilcoxon sign-rank test, that continuous and discrete strategy games are statistically significantly different in terms of equilibria. Intensive discussion by comparing these two kinds of games elucidates that describing a strategy as a real number blunts D strategy invasion to C clusters on a network in the early stage of evolution. Thus, network reciprocity is enhanced by the continuous strategy. 相似文献
104.
Mobile phone exposure‐related effects on the human electroencephalogram (EEG) have been shown during both waking and sleep states, albeit with slight differences in the frequency affected. This discrepancy, combined with studies that failed to find effects, has led many to conclude that no consistent effects exist. We hypothesised that these differences might partly be due to individual variability in response, and that mobile phone emissions may in fact have large but differential effects on human brain activity. Twenty volunteers from our previous study underwent an adaptation night followed by two experimental nights in which they were randomly exposed to two conditions (Active and Sham), followed by a full‐night sleep episode. The EEG spectral power was increased in the sleep spindle frequency range in the first 30 min of non‐rapid eye movement (non‐REM) sleep following Active exposure. This increase was more prominent in the participants that showed an increase in the original study. These results confirm previous findings of mobile phone‐like emissions affecting the EEG during non‐REM sleep. Importantly, this low‐level effect was also shown to be sensitive to individual variability. Furthermore, this indicates that previous negative results are not strong evidence for a lack of an effect and, given the far‐reaching implications of mobile phone research, we may need to rethink the interpretation of results and the manner in which research is conducted in this field. Bioelectromagnetics 33:86–93, 2012. © 2011 Wiley Periodicals, Inc. 相似文献
105.
A 62-year-old man without structural heart disease underwent electrophysiological testing for ventricular tachycardia (VT). Hemodynamically unstable VT was induced after isoproterenol (ISP) provocation. Electroanatomical mapping using a multipolar catheter identified the earliest activation originating from the posterior papillary muscle (PPM) where prepotentials preceding the local ventricular electrogram were observed. Irrigated radiofrequency current guided by the shadow of a multipolar catheter eliminated the VT. This case suggested that multipolar catheters may be helpful for identifying tachycardia origins arising from the PPM. 相似文献
106.
107.
Aglaia Antoniou Georgios Kotoulas Antonios Magoulas Paulo Célio Alves 《European Journal of Wildlife Research》2008,54(4):581-587
Information on reproductive biology of the European hare (Lepus europaeus) in different environmental and landscape conditions comprises part of fundamental knowledge regarding species’ adaptive
responses as well as many aspects of its biology. Most of the studies conducted on European hare reproduction are confined
to midlatitude and northern populations, whereas no data exist on the indigenous southern populations. Here, we present information
on reproductive characteristics of European hares inhabiting Mediterranean ecosystems on the island of Crete, Greece for two
successive hunting seasons. Although the annual reproductive cycle of the species is well known, with an autumn sexual inactivity,
the duration of this period is subjected to fluctuations in different years and for different areas. According to our data,
hare populations of Crete present an autumn–early winter reproductive activity with high proportions of pregnant females observed
in all the months of the study. Furthermore, the estimated mean litter size (1.54 SE ± 0.07) while signed to the lowest values
ever observed for European hares is similar to values obtained in continuous breeding species of the same genus, Lepus granatensis, Lepus corsicanus, Lepus (capensis) mediterraneus, and Lepus capensis also inhabiting warm climates. In conclusion, our results suggest that Cretan European hare populations exhibit a reproductively
active period during autumn–early winter where proportions of pregnant females and litter size give a strong indication of
a continuous reproduction throughout the year. 相似文献
108.
A continuous parallel shaken bioreactor system, combining the advantages of shaken bioreactors with the advantages of continuous
fermentation, was specifically manufactured from quartz glass and provides a geometric accuracy of <1 mm. Two different model
systems (facultative anaerobic bacterium C. glutamicum, and Crabtree-negative yeast P. stipitis), whose growth behaviour and metabolite formation are affected by dilution rate and oxygen availability, were studied. The
transition from non-oxygen to limited conditions as function of the dilution rate could precisely be predicted applying the
approach described by Maier et al. (Biochem Eng J 17:155–167, 2004). In addition, the Crabtree-positive yeast S. cerevisiae was simultaneously studied in the continuous parallel shaken bioreactor system and in a conventional 1-L bioreactor, for
comparison. Essentially the same results were obtained in both types of bioreactors. However, many more reading points were
obtained with the parallel shaken bioreactor system in the same time at much lower consumption of culture media. 相似文献
109.
The dynamics of a continuous stirred‐tank bioreactor for cheese pre‐fermentation is analyzed using elementary concepts of bifurcation theory and continuation techniques. The bioreactor model, which was previously developed and validated, explicitly incorporates the effect of uncontrolled pH levels. The stability analysis of the model is carried out for two cases: In the first case, the bioreactor is equipped with a seed tank, while the second case involves no additional seed tank. The static analysis allows useful analytical results for the study of steady state multiplicity of the model to be derived. The results of this paper provide practical guidelines on the selection of operating parameters that can eliminate difficult operating regions and that can consequently improve the operability of the bioreactor. 相似文献
110.
Natalia Nikolova Kiril Tenekedjiev Krasimir Kolev 《Central European Journal of Biology》2008,3(4):345-350
Progress curve analysis is a convenient tool for the characterization of enzyme action: a single reaction mixture provides
multiple experimental measured points for continuously varying amounts of substrates and products with exactly the same enzyme
and modulator concentrations. The determination of kinetic parameters from the progress curves, however, requires complex
mathematical evaluation of the time-course data. Some freely available programs (e.g. FITSIM, DYNAFIT) are widely applied
to fit kinetic parameters to user-defined enzymatic mechanisms, but users often overlook the stringent requirements of the
analytic procedures for appropriate design of the input experiments. Flaws in the experimental setup result in unreliable
parameters with consequent misinterpretation of the biological phenomenon under study. The present commentary suggests some
helpful mathematical tools to improve the analytic procedure in order to diagnose major errors in concept and design of kinetic
experiments. 相似文献