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41.
Rolf Wichmann Christian Wandreg Joachim Große-Wiesmann 《Applied microbiology and biotechnology》1990,32(4):373-379
Summary Continuous production ofl-leucine was carried out withCorynebacterium glutamicum, strain ATCC 13032 starting from-ketoisocaproic acid as the precursor, glucose as the carbon source and ammonium sulphate as the nitrogen source, with biotin in a mineral medium. By means of cross-flow microfiltration or centrifugal separation for cell retention in continuous fermentation an increase in cell density was achieved and the product solution was obtained cell-free. The cells were concentrated to over 70 g cell dry mass/1. In experiments of up to 42 days, conversion rates of 85%–99% andl-leucine yields of 85%–93% were achieved. With a substrate residence time of 3.6 h, 114 mmol/1l-leucine was produced with a space-time yield of 97 g/1 per day. A scale-up of the fermentation volume from 4 to 1001 provided comparable results. 相似文献
42.
Induction of cytotoxicity by biological response modifiers (BRMs) is only one aspect of macrophage activation. After the use of BRMs there were other changes in the functional activity of cells and in particular their increased production or secretion of a number of growth factors. Thus, activation of macrophage antitumor activity induced by BCG vaccine was transitory while activation of growth factor production was more stable in time which finally led to increased proliferation of tumor cells. Combined use of cyclophosphamide and BCG vaccine significantly increased not only the toxicity induced by BCG vaccine but also their liberation of the growth factors. Such macrophages lost their ability to control the growth of a small number of the tumor cells cultivated in their presence. Development of ways for directed activation of macrophages aimed at elimination of the tumor cells which survived the chemotherapy should include evaluation of the combined effect of various BRMs and chemotherapeutics on both antitumor and protumor activity i. e. ability to produce the factors stimulating the tumor growth. 相似文献
43.
A methodology is proposed for assessing the ecological value of streams in the catchment of the Moravská Dyje River. It is concluded that by using a wide range of parameters that a more objective assessment is achieved than if only one were used. The landscape of the catchment studied contains excessive amounts of nutrients and, in comparison to its natural state, has become too uniform. 相似文献
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45.
R. Kempken A Preißmann W. Berthold 《Journal of industrial microbiology & biotechnology》1995,14(1):52-57
Summary Animal cells from 80-L and 2000-L fed batch fermentations were removed by a prototype disc stack centrifuge in order to achieve a fast and reliable separation of solids from large quantities of cell culture fluids. The clarification capacity was excellent for animal cells but particles remained in the liquid phase and affected further downstream processing of the cell-free harvest fluid. No significant loss of product was observed. A number of parameters were monitored to optimize process conditions for use with animal cells. 相似文献
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The synthesis of 5-aminolevulinic acid commences with the ligation of glutamate to a specific tRNAGlu by a glutamyl-tRNA synthetase (E.C. 6.1.1.17) (Huang et al., 1984, Science 225, 1482–1484). The synthetase from the yellow pigment mutant C-2A of the unicellular green alga Scenedesmus obliquus was purified by sequential column chromatography on Sephacryl S-300, Blue Sepharose, phosphocellulose P11 and by fast protein liquid chromatography (FPLC) on Mono Q. After denaturing sodium dodecylsulfate (SDS)-gel electrophoresis the purified enzyme preparation revealed a single protein band with a molecular mass of 55 kDa, proving the apparent homogeneity of the glutamyl-tRNA synthetase. A molecular mass of 105 ± 10 kDa was determined for the native protein by chromatography on Sephadex G-150. From these data it can be concluded that the glutamyl-tRNA synthetase from S. obliquus is a homodimer. The purified protein is active within a pH range from 7.0 to 9.0 with a maximum activity at pH 8.0. Kinetics for the binding of glutamate to the tRNA, performed with highly purified enzyme preparations, showed a K
m value of 2.3 M ± 0.3 for glutamate.Abbreviations ALA
5-aminolevulinic acid
- FPLC
fast protein liquid chromatography
- Glu
glutamate
- Hepes
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- SDS
sodium dodecylsulfate
- Tricine
N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]-glycine
This work was supported by a grant of the Deutsche Forschungsgemeinschaft. U.C. Vothknecht is grateful for a Nachwuchs-förderungsstipendium des Landes Hessen. The authors want to thank Ms. B. Böhm, J. Gade and K. Eckhardt for skillful technical assistance. The authors also want to thank Dr. C.G. Kannangara (Carlsberg Institute, Kopenhagen, Denmark) for the donation of tRNA from barley and Dr. D. Jahn (FB Biology/Microbiology, Philipps-University, Marburg, FRG) for the tRNAGlufrom E. coli. 相似文献
49.
Resonance Raman experiments were performed on different green bacteria. With blue excitation, i.e. under Soret resonance or preresonance conditions, resonance Raman contributions were essentially arising from the chlorosome pigments. By comparing these spectra and those of isolated chlorosomes, it is possible to evaluate how the latter retain their native structure during the isolation procedures. The structure of bacteriochlorophyll oligomers in chlorosomes was interspecifically compared, in bacteriochlorophyllc- and bacteriochlorophylle- synthesising bacteria. It appears that interactions assumed by the 9-keto carbonyl group are identical inChlorobium limicola, Chlorobium tepidum, andChlorobium phaeobacteroides. In the latter strain, the 3-formyl carbonyl group of bacteriochlorophylle is kept free from intermolecular interactions. By contrast, resonance Raman spectra unambiguously indicate that the structure of bacteriochlorophyll oligomers is slightly different in chlorosomes fromChloroflexus auranticus, either isolated or in the whole bacteria. 相似文献
50.
Nucleotide sequence information from a partial genomic clone, a cDNA clone, a RACE clone and a PCR fragment was combined to reconstruct the first reported complete gene sequence encoding a large legumin subunit, designated LelB3. The length difference to the well-characterized major legumin subunits is caused by an extended glutamin/glutamic acid-rich region encoded by the C-terminal part of the chain. Amino acid sequence comparisons reveal that gene LelB3 is more closely related to B-type than to A-type legumin genes of Vicia faba. Gene LelB3 is a member of a small gene family as indicated by published (Pich and Schubert, Biol Zbl 112 (1993); 342–350) and limited own data. 相似文献