细胞培养生产人参寡糖素降低成本的途径

在人参（Ｐａｎａｘｇｉｎｓｅｎｇ）细胞悬浮培养中,以无离子水代替重蒸馏水,细胞生长速率和寡糖素产率分别降低２．３％和２．９％。用白糖代替蔗糖,细胞生长速率和寡糖素产生率分别降低１．７４％和１．２３％。综合上述两方面结果,以无离子水和白糖分别替代原培养基中的重蒸馏水和蔗糖组成替代培养基,用替代培养基培养人参培养细胞,其生长速率可达０．５０９ｇＤＷ／Ｌ．ｄ．寡糖素产率可达１．４４３ｇ／Ｌ,和原培养基相     

Fate of elemental sulfur in an intertidal sediment

Abstract: Sediment from a tidal flat at Wedderwarden, near the mouth of the Weser estuary, northern Germany, was amended with elemental sulfur, and concentrations of metabolic end products were monitored. The production of both sulfate and sulfide was consistent with disproportionation as the most important fate of the added elemental sulfur. A population of bacteria conducting active elemental sulfur disproportionation was also enriched from the sediment. In the enrichments, containing both elemental sulfur and Fe oxides as a sulfide 'scrub', sulfide and sulfate were produced in a ratio of     , somewhat lower than the predicted ratio of     . The mismatch between predicted and observed production ratios is explained by the channelling of electrons into autotrophic or mixotrophic CO₂ fixation rather than sulfide formation. The production of organic carbon, in the correct amount to explain the observed sulfide to sulfate production ratio, was verified by organic carbon analysis. Finally, rates of sulfate reduction were identical in the elemental sulfur amended sediment, and in control sediment with no added sulfur. Hence, the heterotrophic bacterial community was completely unaffected by an active metabolism conducting elemental sulfur disproportionation.     

Sulfonates: novel electron acceptors in anaerobic respiration

The enrichment and isolation in pure culture of a bacterium, identified as a strain of Desulfovibrio, able to release and reduce the sulfur of isethionate (2-hydroxyethanesulfonate) and other sulfonates to support anaerobic respiratory growth, is described. The sulfonate moiety was the source of sulfur that served as the terminal electron acceptor, while the carbon skeleton of isethionate functioned as an accessory electron donor for the reduction of sulfite. Cysteate (alanine-3-sulfonate) and sulfoacetaldehyde (acetaldehyde-2-sulfonate) could also be used for anaerobic respiration, but many other sulfonates could not. A survey of known sulfate-reducing bacteria revealed that some, but not all, strains tested could utilize the sulfur of some sulfonates as terminal electron acceptor. Isethionate-grown cells of Desulfovibrio strain IC1 reduced sulfonate-sulfur in preference to that of sulfate; however, sulfate-grown cells reduced sulfate-sulfur in preference to that of sulfonate. Received: 2 May 1996 / Accepted: 8 June 1996     

The influence of substratum age on patterns of protozoan assemblages in freshwater Aufwuchs — a case study

The sulfate reduction rate was measured for almost four years in the profundal sediments of Lake Kizaki, a mesotrophic lake in central Japan. The rate was generally highest in the surface layer and decreased with depth. Seasonally, sulfate reduction tended to be high in spring and summer, and then to decrease until the end of stratification (December) in spite of a constant in situ temperature of around 6 °C, although fluctuations were found in every year. The rate also fluctuated greatly according to year. The maximum rate of sulfate reduction was 0.33 mmol m⁻² d⁻¹ in May, 1990, and the minimum was 0.004 mmol m⁻² d⁻¹ in March, 1993. These relatively low rates, compared with those reported for freshwater sediments, seem to be due to low concentrations of sulfate in the sediments (5–23 μmol l⁻¹ in the surface layer). The rate was highly correlated with the concentration of sulfate in the sediments. The addition of sulfate stimulated sulfate reduction in all sediment samples tested, but adding lactate did not. Therefore, sulfate reduction should be limited mainly by the supply of sulfate. Measurements of sulfate reduction rates at different concentrations of added sulfate revealed a low concentration of half-saturation constant as low as 12 μmol l⁻¹.     

Dietary Fat Is Shunted Away from Oxidation,Toward Storage in Obese Zucker Rats

BESSESEN, DANIEL H, CONNIE L RUPP AND ROBERT H ECKEL. Dietary fat is shunted away from oxidation, toward storage in obese zucker rats. Obes Res. 1995;3:179–189. Previous measurements of lipoprotein lipase (LPL) activity in adipose tissue (ATLPL) of lean and obese Zucker rats have consistently documented increased activity in obese rats relative to lean. Since LPL is considered to be rate limiting for the delivery of triglyceride fatty acids (TGFA) to muscle and adipose tissue, these data have been used to suggest that the metabolic partitioning of TGFA favors storage over oxidation in obese rats. To document the partitioning of TGFA directly, the fate of ¹⁴C labeled oleic acid (42nmols) was fed to lean, obese, and obese Zucker rats fed a hypocaloric diet designed to chronically reduce weight 25% below that of obese controls (reduced-obese). The amount of ¹⁴C recovered in CO₂ over 6 hours following ingestion was significantly less in obese rats compared to lean (0.45 ± 0.06 vs. 0.88 ± 0.09nmols, p=.0004) and less still in the reduced obese group (0.34 ± 0.06nmols p=.00003). Six hours after ingestion, the quantity of label found in adipose tissue was significantly greater in the obese rats compared to lean (14.51 ± 1.92 vs. 1.38 ± 0.29nmols p<.00001), but was intermediate in the reduced-obese group (9.23 ± 0.98nmols p=.0003). At 2.2 hours there was significantly more label in skeletal muscle of lean rats compared to either obese or reduced-obese (2.33 ± 0.24; 1.35 ± 0.04nmols p=.01; 1.41 ± 0.27nm p=.02). However, at 6 hours these differences between groups were no longer present. These findings Indicate that dietary fat is shunted away from oxidation toward storage in obese Zucker rats. Additionally it appears that there may be a relative block in the oxidation of TGFA that is taken up by skeletal muscle in obese rats. Finally the relative normalization of this partitioning defect in reduced-obese rats is at variance with what was suggested by previous measurements of tissue specific levels of LPL, and suggests an enhanced recirculation of fatty acids from adipose tissue to muscle in reduced-obese rats. This could occur through increased delivery of non-esterified fatty acids (NEFA) to muscle as a result of an increase in net lipolysis.     

Photosynthetic activity and population dynamics of Amoebobacter purpureus in a meromictic saline lake

Abstract A dense population of the purple sulfur bacterium Amoebobacter purpureus in the chemocline of meromictic Mahoney Lake (British Columbia, Canada) underwent consistent changes in biomass over a two year study period. The integrated amount of bacteriochlorophyll reached maxima in August and declined markedly during early fall. Bacteriochlorophyll was only weakly correlated with the light intensity and water temperature in the chemocline. In the summer, bacterial photosynthesis was limited by sulfide availability. During this period the intracellular sulfur concentration of A. purpureus cells decreased. A minimum concentration was measured at the top of the bacterial layer in August, when specific photosynthetic rates of A. purpureus indicated that only 14% of the cells were photosynthetically active. With the exception of a time period between August and September, the specific growth rates calculated from CO₂ fixation rates of A. purpureus were similar to growth rates calculated from actual biomass changes in the bacterial layer. Between August and September 86% of the A. purpureus biomass disappeared from the chemocline and were deposited on the littoral sediment of Mahoney Lake or degraded within the mixolimnion. This rise of cells to the lake surface was not mediated by an increase in the specific gas vesicle content which remained constant between April and November. The upwelling phenomenon was related to the low sulfur content of A. purpureus cells and a low resistance of surface water layers against vertical mixing by wind.     

Consequences of a tidal reduction for the salt-marsh vegetation in the Oosterschelde estuary (The Netherlands)

A storm-surge barrier was constructed in the mouth of the Oosterschelde, a euhaline mesotidal estuary in the SW Netherlands (mean tidal range 3.6 m). As a consequence, the tidal range and the Mean High Water in the estuary have been reduced to about 88% of their original values.During the final construction stage of this barrier (1986–87) both were reduced to a maximum of 65% for more than 18 months. During this period, large-scale die-back of the vegetation occurred in vast areas on the salt marshes; locally, a complete die-back of the vegetation took place. Glycophytes and disturbance indicating species appeared on a large scale and grew abundantly. After the new tidal regime had been established, the vegetation recovered. The species characteristic of disturbance, are gradually being replaced by perennial salt marsh species. In addition, most species are shifting into zones of lower elevation, which correspond (in 1990/1991) more or less with the original flooding frequencies. Moreover, in many basins the levee-species Halimione portulacoides and Elymus pycnanthus are far more prominent than before, probably as a result of the strong ripening of the soil that has occurred in these basins during the extra tidal reduction. In 1991, four years after the establishment of the new tidal regime, the salt marsh vegetation had still not been stabilized.     

The consequences of a drastic fish stock reduction in the large and shallow Lake Wolderwijd,The Netherlands. Can we understand what happened?

In 1990 an experiment started in the large and shallow lake Wolderwijd (2700 ha, mean depth 1.5 m) to improve the water quality. About 75% of the fish stock was removed (425 000 kg fish). The fish was mainly composed of bream and roach. In May 600000 young pikes (3–4 cm) were introduced.In May 1991 the water became very clear (Secchi depth 1.8 m) during a spring bloom of large Daphnia. Then the grazing by zooplankton was eight times higher than the primary production of algae and the total suspended matter concentration became very low. Compared to the situation before the fish reduction, the grazing had increased only slightly, while the primary production had decreased significantly in early spring. The fish stock reduction might have contributed to the reduction in primary production by a reduced internal nutrient load. The clear water period lasted six weeks. Daphnia disappeared in July due to food limitation, the algal biomass increased and the Secchi depth became 50 cm. Daphnia did not recover during summer, due to predation that was not caused by 0 + fish but by the mysid shrimp Neomysis integer. Neomysis could develop abundantly, because of the reduced biomass of the predator perch. The production of young fish had been low because of the cold spring weather. The cold weather was probably also responsible for the slow increase in density of macrophytes. After 1991, perch probably can control Neomysis. Due to lack of spawning places and shelter for 0 + pike, pike was probably not able to control the production of 0 + fish. In a lake of this scale, it will not be easy to get more than 50% coverage of macrophytes, which seems necessary to keep the algal biomass low by nutrient competition. Therefore, we expect also in the future a decrease in transparency in the summer. Locally, especially near Characeae, the water might stay clear.     

Competition between electron acceptors in photosynthesis: Regulation of the malate valve during CO2 fixation and nitrite reduction

For maximal rates of CO₂ assimilation in isolated intact spinach chloroplasts the generation of the adequate NADPH/ATP ratio is achieved either by cyclic electron flow around photosystem I or by linear electron transport to oxaloacetate, nitrite or oxygen (Mehler-reaction). The interrelationships between these poising mechanisms turn out to be strictly hierarchical. In the presence of antimycin A, an inhibitor of ferredoxin-dependent cyclic electron transport, the reduction of both, oxaloacetate and nitrite, but not that of oxygen restores CO₂ fixation. When oxaloacetate and nitrite are added at low concentrations simultaneously during steady-state CO₂ fixation, the reduction of nitrite is clearly preferred over the reduction of oxaloacetate, but CO₂ fixation is not influenced. Nitrite reduction is not decreased upon addition of oxaloacetate, but vice versa. This is due to the regulation of NADP-malate dehydrogenase activation by electron pressure via the ferredoxin/thioredoxin system on the one hand, and by the NADPH/(NADP+NADPH) ratio (anabolic reduction charge, ARC) on the other hand. Thus the closing of the malate valve prevents drainage of reducing equivalents from the chloroplast (1) when a low ARC indicates a high demand for NADPH in the stroma and (2) when nitrite reduction reduces the electron pressure at ferredoxin. The malate valve is opened when cyclic electron transport is inhibited by antimycin A. Under these conditions the rate of malate formation is higher than in the absence of the inhibitor even in the presence of oxaloacetate, thus indicating that the regulation of the malate valve functions at various redox states of the acceptor side of Photosystem I.Abbreviations ARC anabolic reduction charge (NADPH/(NADP+NADPH)) - Chl chlorophyll - DTT dithiothreitol; Fd-ferredoxin - NADP-MDH NADP-malate dehydrogenase - OAA oxaloacetate - PS photosystem - qN non-photochemical quenching - qP photochemical quenching - _E quantum efficiency of PS II Dedicated to Prof. Dr. Hans Walter Heldt on the occasion of his 60th birthday.