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  • 1
    Electronic Resource
    Electronic Resource
    New Routes to Plant Secondary Products (1987)
    [s.l.] : Nature Publishing Company
    Nature biotechnology 5 (1987), S. 800-804 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] For some years, there has been great interest in the exploitation of plant cell cultures to produce fine chemicals. With a few exceptions, progress in commercialization has been slow, largely due to the low and/or unstable productivity of many undifferentiated cultures. Recent developments leading ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt0887-800
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  • 2
    Electronic Resource
    Electronic Resource
    Metabolic flux in glucose/citrate co-fermentation by lactic acid bacteria as measured by isotopic ratio analysis (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 182 (2000), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The flux of carbon into lactic acid, diacetyl and acetoin during the co-metabolism of glucose and citrate by Lactococcus lactis subsp. lactis biovar. diacetylactis has been determined using natural abundance isotopic ratio analysis. During fermentation in the conditions used (glucose, 27.8 mM; citric acid, 13.9 mM; initial pH 6.2–6.4, anaerobic) it is shown that approximately 65% of the carbon source used for the aroma compounds is derived from the carbohydrate. Equally, citrate contributes approximately 30% of the carbon recovered in lactic acid. Thus, there is no evidence for a metabolic separation of the catabolism of these two carbon sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2000.tb08896.x
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  • 3
    Electronic Resource
    Electronic Resource
    The stimulation of anthraquinone production by Cinchona ledgeriana cultures with polymeric adsorbents (1986)
    Springer
    Applied microbiology and biotechnology 24 (1986), S. 35-41 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Anthraquinones produced by suspension cultures of Cinchona ledgeriana are released into the medium, which becomes saturated with products late in the growth cycle. When a high affinity polymeric adsorbent, such as the macro-reticular Amberlite XAD-7, is added to the culture the concentration of anthraquinone in the medium is maintained at a low level and production may be stimulated 15-fold, yielding up to 20 mg/1/day. More than 90% of the product is released from the cells. For maximal yields it is shown that both the amount of adsorbent used and the time after sub-culture at which it is added to the system are critical. The value of such a method for product recovery from immobilised cells is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266282
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  • 4
    Electronic Resource
    Electronic Resource
    Purification and properties of putrescine N-methyltransferase from transformed roots of Datura stramonium L. (1994)
    Springer
    Planta 193 (1994), S. 9-15 
    Details
    ISSN: 1432-2048
    Keywords: Datura ; Cadaverine ; Putrescine-N-methyltransferase ; Root culture (Agrobacterium-transformed) ; Tropane alkaloid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Putrescine-N-methyltransferase (PMT; EC 2.1.1.53), the first enzyme in the biosynthetic pathway leading from putrescine to tropane and pyrrolidine alkaloids, has been purified about 700-fold from root cultures of Datura stramonium established following genetic transformation with Agrabacterium rhizogenes. The native enzyme had a molecular weight estimated by gel-permeation chromatography on Superose-6 of 40 kDa; sodium dodecyl sulphate-polyacrylamide gel electrophoresis of the peak fractions from Superose-6 chromatography revealed a band of 36 kDa molecular weight. Kinetic studies of the purified enzyme gave K m values for putrescine and S-adenosyl-l-methionine of 0.31 mM and 0.10 mM, respectively, and K i values for S-adenosyl-l-homocysteine and N-methylputrescine of 0.01 mM and 0.15 mM, respectively. The enzyme was active with some derivatives and analogous of putrescine, including 1,4-diamino-2-hydroxybutane and 1,4-diamino-trans-but-2-ene. Little activity was observed with 1,4-diamino-cis-but-2-ene and none with 1,3-diaminopropane or 1,5-diaminopentane (cadaverine), indicating a requirement for substrate activity of two amino groups in a trans conformation, separated by four carbon atoms. A large number of monoamines were inhibitors of the enzyme. Though not a substrate, cadaverine was a competitive inhibitor of the enzyme, with a K i of 0.04 mM; the significance of this in relation to the biosynthesis of cadaverine-derived alkaloids is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191600
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  • 5
    Electronic Resource
    Electronic Resource
    In vivo nuclear-magnetic-resonance analysis of polyamine and alkaloid metabolism in transformed root cultures of Datura stramonium L.: evidence for the involvement of putrescine in phytohormone-induced de-differentiation (1998)
    Springer
    Planta 205 (1998), S. 205-213 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Alkaloid biosynthesis (15N-NMR) ; Datura ; Phytohormone ; Polyamine ; Putrescine ; Root culture (transformed) ; Tropane alkaloid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The utilisation and accumulation of 15N-labeled metabolites by a 15N-labeled transformed root culture of Daturastramonium L. was investigated by in vivo 15N-nuclear-magnetic-resonance (NMR) spectroscopy. After resuspension in spent growth medium, the pools of [15N]glutamate and [15N]glutamine were rapidly depleted and there was an increase in the 15N-NMR signals from conjugated putrescines and hyoscyamine. The signal from the conjugated putrescines passed through a maximum 2 d after the roots were resuspended, and it was concluded that putrescine could be stored as putrescine conjugates prior to its utilisation in other pathways. The transient accumulation of 15N-label in the hydroxy-cinnamoylputrescines was reduced when the de-differentiation of the root cultures into a suspension culture was initiated by exposure to a medium containing α-napthaleneacetic acid and kinetin. This led to the hypothesis that phytohormone-induced de-differentiation of the root cultures required the presence of free polyamines, and this was tested using two potent inhibitors of putrescine biosynthesis, dl-α-difluoromethylarginine and dl-α-difluoromethylornithine. In-vivo 15N-NMR spectra of roots grown in 15N-enriched medium supplemented with these inhibitors showed that the 15N-labelling of the conjugated polyamines and hyoscyamine was markedly reduced. dl-α-difluoromethylarginine also prevented the phytohormone induced de-differentiation of the root cultures, and this effect could be reversed by the supply of exogenous putrescine. Thus the supply of putrescine appears to play a crucial role in mediating the phytohormone induced de-differentiation of the root culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050313
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  • 6
    Electronic Resource
    Electronic Resource
    Abiotic factors elicit sesquiterpenoid phytoalexin production but not alkaloid production in transformed root cultures of Datura stramonium (1991)
    Springer
    Plant cell reports 10 (1991), S. 111-114 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The treatment of root cultures of Datura stramonium with copper and cadmium salts at external concentrations of approximately 1mM has been found to induce the rapid accumulation of high levels of sesquiterpenoid defensive compounds, notably lubimin and 3-hydroxylubimin. These compounds were undetectable in unelicited cultures. No net change was seen in the alkaloid content of the system following treatment with Cu2+ or Cd2+, the tropane alkaloid titre apparently being insensitive to elicitation. However, a considerable rapid and, in some instances, reversible release of alkaloid was observed. This resulted in the appearance of up to 50–75% of the total alkaloid in the medium after 40–60 h. Subsequently, in cultures treated with Cu2+ ions, though not in cultures treated with Cd2+ ions, this alkaloid was re-absorbed. These observations show how, in a single system, different groups of secondary products can show distinct differences in their responses to potential elicitors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232039
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  • 7
    Electronic Resource
    Electronic Resource
    Toxicity of quinoline alkaloids to cultured Cinchona ledgeriana cells (1987)
    Springer
    Plant cell reports 6 (1987), S. 118-121 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The toxicity of Cinchona alkaloids to cell cultures of C. ledgeriana has been studied in relation to alkaloid uptake and possibilities for selecting high-yielding cell lines. The most toxic, quinine, was completely toxic at 5.5 mM. Both quinine and quinidine were more toxic than their unmethoxylated precursors, cinchonidine and cinchonine. The permanently-charged metho-chlorides of quinine and cinchonidine were less toxic than the parent alkaloids, despite showing similar accumulation ratios in 5-day uptake experiments at sub-toxic concentrations (ca 1.7mM). The toxicity of the natural quinoline alkaloids appears to be a non-specific effect which may be caused by intracellular alkalinisation following uptake of the uncharged bases. The use of precursors of quinine and quinidine as toxic agents for the selection of cell lines with enhanced quinine and quinidine production is ruled out by the lower toxicity of these precursors and by the correlation of an apparently non-specific toxicity with uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276667
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  • 8
    Electronic Resource
    Electronic Resource
    Apparent free space and cell volume estimation: A non-destructive method for assessing the growth and membrane integrity/viability of immobilised plant cells (1984)
    Springer
    Plant cell reports 3 (1984), S. 161-164 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pre-existing methods for measuring cell or organelle volume based on the selective permeability of biological membranes have been modified to make them suitable for determining the intracellular volume of immoblised cells. When a freely permeable substance (e.g. tritiated water) and an impermeable substance (14C labelled mannitol is often suitable) are mixed with an immobilised cell culture, the two substances are diluted to different degrees. The extent of the difference allows the total intracellular volume of intact cells to be calculated. This volume is shown to be a useful parameter for assessing cell growth. The application of the method to follow membrane integrity and cell viability is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00270214
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  • 9
    Electronic Resource
    Electronic Resource
    Permeabilization of Cinchona ledgeriana cells by dimethylsulphoxide. effects on alkaloid release and long-term membrane integrity (1984)
    Springer
    Plant cell reports 3 (1984), S. 262-265 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dimethyl sulphoxide (DMSO) has been used to permeabilize cells of Cinchona ledgeriana in suspension culture and promote the release of intracellular alkaloids. 5–6% v/v is required before any release is seen, and greater than 20% DMSO is required for full release. Even at these high levels of DMSO release is slow, taking in excess of seven hours to reach completion. Conditions which produce significant release of alkaloids have a deleterious effect on cells. Many of the membranes permeabilized did not recover their ability to selectively exclude compounds such as mannitol when the DMSO was removed. It is concluded that DMSO is not a suitable material for inducing alkaloid release in any biotechnological exploitation of alkaloid production by C. ledgeriana.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00269308
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  • 10
    Electronic Resource
    Electronic Resource
    Enzymes of N-methylputrescine biosynthesis in relation to hyoscyamine formation in transformed root cultures of Datura stramonium and Atropa belladonna (1990)
    Springer
    Planta 182 (1990), S. 136-141 
    Details
    ISSN: 1432-2048
    Keywords: Atropa ; Datura ; Hyoscyamine ; N-Methyl-putrescine ; Tropane alkaloids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The activities of enzymes related to the biosynthesis of N-methylputrescine, a precursor of the alkaloid hyoscyamine, have been measured in root cultures of Datura stramonium L. and Atropa belladonna L. transformed with Agrobacterium rhizogenes. Ornithine δ-Nmethyltransferase and δ-N-methylornithine decafboxylase were undetectable, indicating that δ-N-methylornithine is an unlikely intermediate in the formation of N-methylputrescine. The activity of putrescine-N-methyltransferase (EC 2.1.1.53) was comparable to, or greater than, that of arginine decarboxylase (EC 4.1.1.19) or ornithine decarboxylase (EC 4.1.1.17). Radiolabel from dl-[5-14C]ornithine, l-[U-14C]arginine, [U-14C]agmaine and [1,4-14C]putrescine was incorporated into hyosyamine by Datura cultures. Hyoscyamine production by Datura cultures was substantially inhibited by the arginine-decarboxylase inhibitor, dl-α-difluoromethylarginine, but not by the corresponding ornithine-decarboxylase inhibitor, dl-α-difluoromethylornithine. Together with the demonstration that label was incorporated from [U-14C]agmatine, this indicates clearly that arginine is metabolised to hyoscyamine at least in part via decarboxylation to agmatine, even though a high activity of arginase (EC 3.5.3.1) was measurable under optimal conditions. The effect of unlabelled putrescine in diminishing the incorporation into hyoscyamine of label from dl-[ 5-14C] ornithine and l-[U-14C] arginine does not lend support to the theory that ornithine is metabolised via a bound, asymmetric putrescine intermediate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239995
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