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71.
José Edmundo Nava Saucedo Jean-Noël Barbotin Daniel Thomas 《Applied microbiology and biotechnology》1989,30(3):226-233
Summary The continuous production of gibberellic acid with immobilized mycelia of Gibberella fujikuroi was maintained over a hundred days in a tubular fixed-bed reactor. Free mycelium at the beginning of the storage phase was harvested from G. fujikuroi shake-flask culture and was immobilized by ionotropic gelation in calcium alginate beads.The continuous recycle production system consisted of a fixed-bed reactor, a container in which the culture medium was heated, stirred and aerated, and valves for sample withdrawal or reactant addition during the first 1320 h (55 days). A two-phase continuous extractor was then added for the last 960 hours (40 days). Free and immobilized mycelium shake-flask cultures with the same strain used in the continuous culture system were also realized to compare growth, maintenance and production parameters. The results show about the same gibberellic acid productivity in both free and immobilized mycelium shakeflask cultures: 0.384 and 0.408 mgGA3·gBiomass-1 ·day-1, respectively, whereas in the continuous system the gibberellic acid production is about twice as large for a similar biomass: 0.768 mgGA3·gBiomass-1·day-1. Several factors affecting the overall productivity of the immobilized systems were found to be: the quality and the quantity of mycelia in the biocatalyst beads and the immobilization conditions. 相似文献
72.
73.
It is generally accepted that during fast growth of Escherichia coli, the time (D) between the end of a round of DNA replication and cell division is constant. This concept is not consistent with the fact that average cell mass of a culture is an exponential function of the growth rate, if it is also accepted that average cell mass per origin of DNA replication (Mi) changes with growth rate and negative exponential cell age distribution is taken into account. Data obtained from cell composition analysis of E. coli OV-2 have shown that not only (Mi) but also D varied with growth rate at generation times () between 54 and 30 min. E. coli OV-2 is a thymine auxotroph in which the replication time (C) can be lengthened, without inducing changes in , by growth with limiting amounts of thymine. This property has been used to study the relationship between cell size and division from cell composition measurements during growth with different amounts of thymine. When C increased, average cell mass at the end of a round of DNA replication also increased while D decreased, but only the time lapse (d) between the end of a replication round and cell constriction initiation appeared to be affected because the constriction period remained fairly constant. We propose that the rate at which cells proceed to constriction initiation from the end of replication is regulated by cell mass at this event, big cells having shorter d times than small cells.Abbreviations OD450 and OD630
Optical density at a given wavelength in nm
Dedicated to Dr. John Ingraham to honor him for his many contributions to Science 相似文献
74.
The in situ localization of Ca2+ in stage I sporangiophores of the fungus Phycomyces blakesleeanus was achieved with the potassium pyroantimonate technique. Precipitates of calcium-antimonate were present in mitochondria, vacuoles, endoplasmic reticulum and adjacent cytoplasm, Golgi-like bodies, and nuclei but not cell walls. Material treated with the calcium chelator EGTA lacked these precipitates. The preferential localization of Ca2+ in mitochondria, endoplasmic reticulum and vacuoles suggests that these organelles modulate the level of this cation in sporangiophores of P. blakesleeanus.Abbreviations EGTA
ethyleneglycol-bis-(-aminoethyl ether) N,N, tetraacetic acid 相似文献
75.
Nucleotide sequence of 10 kilobases of rat tyrosine aminotransferase gene 5'' flanking region. 总被引:5,自引:3,他引:2
J Oddos T Grange K D Carr B Matthews J Roux H Richard-Foy R Pictet 《Nucleic acids research》1989,17(21):8877-8878
76.
D R Tocher J Carr J R Sargent 《Comparative biochemistry and physiology. B, Comparative biochemistry》1989,94(2):367-374
1. The incorporation and metabolism of (n-3) and (n-6) polyunsaturated fatty acids (PUFA) supplemented to growing cultures were studied in rainbow trout (RTG-2) and turbot (TF) cell lines. 2. A fatty acid concentration of 20 microM considerably altered the fatty acid composition of the cells without affecting lipid class composition or the appearance of cytoplasmic lipid droplets. 3. Both cell lines exhibited considerable delta 6 desaturase activities. 4. Whereas delta 5 desaturase activity was expressed in RTG-2 cells, delta 4 desaturase activity was absent and, conversely, delta 4 desaturase activity was expressed in TF cells, but there was an apparent deficiency in the C18 to C20 elongase multi-enzyme complex. 5. The delta 6 desaturase activity in both cell lines showed little preference between 18:2(n-6) and 18:3(n-3) but the delta 5 desaturase activity of RTG-2 cells and the delta 4 desaturase activity of TF cells showed a preference for (n-3)PUFA. 6. Two fish oil concentrates were assessed for their ability to generate fatty acid compositions in the cell lines more closely resembling those of intact fish tissues. 相似文献
77.
1. A Clark-type electrode that responds to nitric oxide has been used to show that cytoplasmic membrane vesicles of Paracoccus denitrificans have a nitric-oxide reductase activity. Nitrous oxide is the reaction product. NADH, succinate or isoascorbate plus 2,3,5,6-tetramethyl-1,4-phenylene diamine can act as reductants. The NADH-dependent activity is resistant to freezing of the vesicles and thus the NADH:nitric-oxide oxidoreductase activity of stored frozen vesicles provides a method for calibrating the electrode by titration of dissolved nitric oxide with NADH. The periplasmic nitrite reductase and nitrous-oxide reductase enzymes are absent from the vesicles which indicates that nitric-oxide reductase is a discrete enzyme associated with the denitrification process. This conclusion was supported by the finding that nitric-oxide reductase activity was absent from both membranes prepared from aerobically grown P. denitrificans and bovine heart submitochondrial particles. 2. The NADH: nitric-oxide oxidoreductase activity was inhibited by concentrations of antimycin or myxothiazol that were just sufficient to inhibit the cytochrome bc1 complex of the ubiquinol--cytochrome-c oxidoreductase. The activity was deduced to be proton translocating by the observations of: (a) up to 3.5-fold stimulation upon addition of an uncoupler; and (b) ATP synthesis with a P:2e ratio of 0.75. 3. Nitrite reductase of cytochrome cd1 type was highly purified from P. denitrificans in a new, high-yield, rapid two- or three-step procedure. This enzyme catalysed stoichiometric synthesis of nitric oxide. This observation, taken together with the finding that the maximum rate of NADH:nitric-oxide oxidoreductase activity catalysed by the vesicles was comparable with that of NADH:nitrate-oxidoreductase, is consistent with a role for nitric-oxide reductase in the physiological conversion of nitrate or nitrite to dinitrogen gas. 4. Intact cells of P. denitrificans also reduced nitric oxide in an antimycin- or myxothiazol-sensitive manner. However, nitric oxide was not detected by the electrode during the reduction of nitrate. Nitric-oxide synthesis from nitrate could be detected with cells in the presence of very low concentrations of Triton X-100 which selectively inhibits nitric-oxide reductase activity. 5. Nitric oxide was detected as an intermediate in denitrification by including haemoglobin with an anaerobic suspension of cells that was reducing nitrate. The characteristic spectrum of the nitric oxide derivative of haemoglobin was observed.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
78.
Nora Goosen Harold P. A. Horsman René G. M. Huinen Arjan de Groot Pieter van de Putte 《Antonie van Leeuwenhoek》1989,56(1):85-91
From a gene bank of theAcinetobacter calcoaceticus genome a plasmid was isolated that complements four different classes of PQQ- mutants. Subclones of this plasmid revealed that the four corresponding PQQ genes are located on a fragment of 5 kilobases. The nucleotide sequence of this 5 kb fragment was determined and by means of Tn5 insertion mutants the reading frames of the PQQ genes could be identified. Three of the PQQ genes code for proteins of Mr 29700 (gene I), Mr 10800 (gene II) and Mr 43600 (gene III) respectively. In the DNA region where gene IV was mapped however the largest possible reading frame encodes for a polypeptide of only 24 amino acids. A possible role for this small polypeptide will be discussed. Finally we show that expression of the four PQQ genes inAcinetobacter lwoffi andEscherichia coli lead to the synthesis of the coenzyme in these organisms. 相似文献
79.
80.
Cecilia Gotor Eloísa Pajuelo Luís C. Romero Antonio J. Márquez José M. Vega 《Archives of microbiology》1990,153(3):230-234
Polyclonal antiserum specific for ferredoxin-nitrite reductase (EC 1.7.7.1) from the green alga Chlamydomonas reinhardii recognized the nitrite reductase from other green algae, but did not cross-react with the corresponding enzyme from different cyanobacteria or higher plant leaves. An analogous situation was also found for ferredoxin-glutamate synthase (EC 1.4.7.1), using its specific antiserum. Besides, the antibodies raised against C. reinhardii ferredoxin-glutamate synthase were able to inactivate the ferredoxin-dependent activity of nitrite reductase from green algae.These results suggest that there exist similar domains in ferredoxin-nitrite reductases and ferredoxin-glutamate synthases from green algae. In addition, both types of enzymes share common antigenic determinants, probably located at the ferredoxin-binding domain. In spite of their physicochemical resemblances, no apparent antigenic correlation exists between the corresponding enzymes from green algae and those from higher plant leaves or cyanobacteria.Abbreviations Fd
ferredoxin
- GOGAT
glutamate synthase
- MV+
reduced methyl viologen (radical cation)
- NiR
nitrite reductase
- PMSF
phenylmethylsulphonyl fluoride
- SDS
sodium dodecyl sulfate 相似文献