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2.
Pinhas Shlomai Ami Ben-Amotz Pinhas Margalith 《Applied microbiology and biotechnology》1991,34(4):458-462
Summary -Carotene steroisomers, mainly all-trans and to a small extent 9-cis, may be produced by the fungus Phycomyces blakesleeanus under normal fermentation conditions. The amount of the 9-cis--carotene may comprise up to 15% of the total -carotene. Similarly, cis-lycopene or-phytoene stereoisomers may be obtained when the fungus is fermented in the presence of specific -carotene inhibitors such as nicotine or diphenylamine respectively. This is the first report on the occurrence of cis-stereoisomers of carotenes in mycelial fungi. 相似文献
3.
Partial Characterization of K and Ca Uptake Systems in the Halotolerant Alga Dunaliella salina 下载免费PDF全文
The uptake of K+ and Ca2+ in Dunaliella salina is mediated by two distinct carriers: a K+ carrier with a high selectivity against Na+, Li+, and choline+ but not towards Rb+, K+, Cs+, or NH4+, and a Ca2+ carrier with a high selectivity against Mg2+. The latter is specifically blocked by La3+ and by Cd2+. Apparent Km values for K+ and Ca2+ uptake are 2.5 and 0.8 millimolar, respectively, and their maximal calculated fluxes are 22 and 0.8 nanomoles per square meter per second, respectively. Effects of permeable ions and ionophores on K+ and Ca2+ uptake suggest that the driving force for their uptake is the transmembrane electrical potential. Inhibitors of ATP production, typical inhibitors of plasma membrane H+-ATPases and protonionophores inhibit K+ and Ca2+ uptake and accelerate K+ efflux. The results suggest that an H+-ATPase in the cell membrane provides the driving force for K+ and Ca2+ uptake. Efflux measurements from 86Rb+ and 45Ca2+ loaded cells suggest that part of the intracellular K+ and most of the intracellular Ca2+ is nonexchangeable with the extracellular pool. Correlations between phosphate and K+ contents and the effect of phosphate on K+ efflux suggest intracellular associations between K+ and polyphosphates. On the basis of these results, it is suggested that: (a) K+ and Ca2+ uptake in D. salina is driven by the transmembrane electrical potential which is generated by the action of an H+-ATPase of the plasma membrane. (b) Part of the intracellular K+ is associated with polyphosphate bodies, while most of the intracellular Ca2+ is accumulated in intracellular organelles in the algal cells. 相似文献
4.
An assay system was developed in which the effects of inhibitorsof ß-carotene biosynthesis in Dunaliella bardawilcould be tested. Since D. bardawil can be induced to accumulateover 10% of its dry weight as ß-carotene, it is particularlysuitable for such studies. Norflurazon a desaturation inhibitor,caused the accumulation of phytoene, or of phytoene and phytofluene,depending on the concentration employed. J-334, a substituted6-methylpyrimidine which also inhibits desaturation, causedthe accumulation of ß-zeacarotene, -carotene and phytoenein different proportions, depending on the concentration employed.The cyclization inhibitors, nicotine, CPTA and MPTA, severelyaffected the growth and survival of the alga, and their effectscould therefore not be studied directly. However, their actionwas observed indirectly by following the transformation of phytoenein norflurazon-pretreated phytoene-rich algae. Under these conditions,presence of the cyclase inhibitors caused the transformationof phytoene to lycopene, rather than to ß-carotene.The accumulated ß-carotene or the intermediates ß-zeacarotene,lycopene, -carotene, phytofluene and phytoene in D. bardawilwere all composed of two stereoisomers, tentatively assignedas the all-trans stereoisomer (55%) and the 9-cis stereoisomer(45%). This suggests that the isomerization reaction which leadsto the production of the presumed 9-cis isomers occurs earlyin the pathway of carotene biosynthesis, at or before phytoene,with no isomerization during the further transformations leadingto ß-carotene. (Received January 29, 1990; Accepted May 9, 1990) 相似文献
5.
Ami Ben-Amotz 《Journal of phycology》1996,32(2):272-275
Dunaliella bardawil Ben-Amotz & Avron, a β-carotene-accumulating halotolerant alga, was analyzed for the effect of growth temperatures on its pigment content and on the stereoisomeric composition of β-carotene by the use of advanced liquid chromatography and photodiode array detection. Decreasing culture temperature from 30° to 10°C increased the β-carotene content twofold and the ratio of 9-cis to all-trans β-carotene fourfold, with no significant changes in the other cell pigments. The variation of total β-carotene content by temperature was correlated with the integral irradiance received by the algal culture during a cell division cycle, whereas the 9-cis stereoisomer increased over the amount expected by that integration. The massive accumulation of 9-cisβ-carotene within the β-carotene globules is interpreted as indicating that the oily 9-cis stereoisomer protects against the crystallization of all-trans β-carotene at low temperatures. 相似文献
6.
The purpose of this work was to test whether induction of massive -carotene synthesis in the alga Dunaliella bardawil is triggered by oxygen radicals. The following results were obtained: (i) The induction of -carotene synthesis is preceded by a lag period of about 4 h during which the cells swell and photosynthesis is partially inhibited, (ii) Addition of promoters of oxygen radicals or of azide (an inhibitor of catalase and superoxide dismutase) during the induction period, under conditions which are suboptimal for massive -carotene accumulation, greatly enhances -carotene synthesis, photodegradation of chlorophyll and inhibition of photosynthesis, (iii) High irradiance, which induces massive -carotene accumulation, also induces a high catalase activity. It is suggested that photosynthetically produced oxygen radicals are involved in triggering massive -carotene accumulation in D. bardawil. 相似文献
7.
Ami Ben-Amotz 《Journal of applied phycology》1995,7(1):65-68
Attempts to adapt the laboratory experience of bi-phasic growth and carotenogenesis in Dunaliella to large-scale conditions were highly successful. Algae were initially cultivated in stage one for optimizing biomass production
of cells containing a low β-carotene to chlorophyll ratio. The culture was then transferred to stage two, diluted to about
one third and induced for carotenogenesis. The bi-phase cultivation increased β- carotene productivity to 450 mg m-2 d-1 in stage one and to 300 mg m-2 d-1 in stage two, compared to the relatively low productivity of below 200 mg β- carotene m-2 d-1, in the conventional one phase type of cultivation. The results indicate that a selected algal product can be promoted specifically
by growth manipulation of the alga and its environment. 相似文献
8.
A number of chemical compounds are known to affect the biosynthetic pathways of β-carotene. Both site-specific inhibitors as well as general stimulators of carotenogenesis have been described. It has been reported that veratrole enhances β-carotene synthesis when applied to agar cultures of Phycomyces blakesleeanus but we found no significant stimulation of β-carotene production in submerged culture. Moreover, veratrole in high concentrations (> 0.1% w/v), unlike diphenylamine, inhibits the formation of phytoene, resulting in an almost total block of carotenoid biosynthesis. 相似文献
9.
Dunaliella bardawil Ben-Amotz & Avron accumulates high concentrations of β-carotene when grown under high light intensity. The β-carotene is composed mainly of 9-cis and all-trans β-carotene. Accumulation of β-carotene and an increase in the ratio of the 9-cis to the all-trans isomer are strongly dependent on the light intensity under which the algae are cultivated but are independent of light quality within the photosynthetically active radiation range. Cells grown under continuous red (>645 nm) or white light of 500 W·m?2 reach a value of about 32 pg β-carotene·cell?1 and a ratio of 9-cis to all-trans β-carotene of around 2, whereas cells grown under low red or white light intensity of 25 W·m?2 contain about 3 pg·cell?1 and a ratio of isomers of around 0.3. 相似文献
10.
Shiran Shapira Oded Ben-Amotz Osnat Sher Dina Kazanov Jacob Mashiah Sarah Kraus Eyal Gur Nadir Arber 《PloS one》2015,10(10)