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11.
Optimum growth conditions for the fermentation of non-concentrated whey permeate by Kluyveromyces fragilis NRRL 665 have been defined. Use of 3.75 g yeast extract l?1, a growth temperature of 38°C and a pH of 4.0 allowed a maximum productivity of 5.23 g ethanol l?1 h?1 in continuous culture with a yield 91% of theoretical. Complete batch fermentation of permeate with 100 g lactose l?1 was possible with a maximum specific growth rate of 0.276 h?1 without any change in ethanol yield. Fermentation of concentrated permeate resulted, however, in a general decrease of specific substrate consumption rate, demonstrated by the inability to completely convert an initial 90 or 150 g lactose l?1 in continuous culture, even at dilution rates as low as 0.05 and 0.08 h?1, respectively. The decrease could be related to substrate inhibition, to an increase in osmotic pressure caused by lactose and salts, and to ethanol inhibition of both alcohol and biomass yield. The decrease in specific productivity could be counterbalanced by use of high cell density cultures, obtained by cell recycle of K. fragilis. Fermentation of a non-concentrated permeáte at a dilution rate of 1 h?1 resulted in a productivity of 22 g l?1 h?1 at 22 g ethanol l?1. Cell recycle using flocculating Kluyveromyces lactis NCYC 571 was also tested. With this strain a productivity of 9.3 g l?1 h?1 at 45 g product l?1 was attained at a dilution rate of 0.2 h?1, with an initial lactose concentration of 95 g l?1. 相似文献
12.
1. The separation of the alpha-components of codfish-skin and calf-skin collagen from the higher-molecular-weight components was accomplished by gel filtration with Bio-Gel P-300 resin in 5m-lithium chloride and at pH7.4. 2. From this fraction three distinct alpha-components, corresponding to the alpha1-, alpha2- and alpha3- chains of collagen, were isolated by free-flow electrophoresis in 6m-urea at 4 degrees . At the temperatures and pH values used there was no detectable degradation of the alpha-chains. 相似文献
13.
Jérôme Etienne Guy Gerbaud Patrice Courvalin Jean Fleurette 《FEMS microbiology letters》1989,61(1-2):133-138
Staphylococcus epidermidis strain BM2641, isolated from a patient, was resistant to penicillin G, methicillin, aminoglycosides, chloramphenicol, macrolide, lincosamide and streptogramin B-type (MLS) antibiotics, and to high levels of fosmycin. Resistance to forsfomycin and/or to MLS was lost at low frequencies either spontaneously or after curing with novobiocin. The plasmid DNA from BM2641 and its cured derivatives was purified, analyzed by agarose gel electrophoresis and transferred to a nitrocellulose sheet. Comparative analysis of the resistance phenotypes with the plasmid content of the strains indicated that fosfomycin and MLS resistance were encoded by plasmids pIP1842 (2.5 kb) and pIP1843 (2.6 kb), respectively. Southern hybridization with a probe specific for gene fosA of Serratia marcescens showed that the fosfomycin resistance determinant in Staphylococcus is not homologous to that of Gram-negative bacteria. 相似文献
14.
Stefan Evers Barbara Casadewall Murielle Charles Sylvie Dutka-Malen Marc Galimand Patrice Courvalin 《Journal of molecular evolution》1996,42(6):706-712
Thed-alanine:d-alanine-ligase-related enzymes can have three preferential substrate specificities. Usually, these enzymes synthesized-alanyl-d-alanine. In vancomycin-resistant Gram-positive bacteria, structurally related enzymes synthesized-alanyl-d-lactate or Dalanyl-d-serine. The sequence of internal fragments of eight structurald-alanine:d-alanine ligase genes from enterococci has been determined. Alignment of the deduced amino acid sequences with those of other
related enzymes from Gram-negative and Gram-positive bacteria revealed the presence of four distinct sequence patterns in
the putative substrate-binding sites, each correlating with specificity to a particular substrate (d-alanine:d-lactate ligases exhibited two patterns). Phylogenetic analysis showed different clusters. The enterococcal subtree was largely
superimposable on that derived from 16S rRNA sequences. In lactic acid bacteria, structural divergence due to differences
in substrate specificity was observed. Glycopeptide resistance proteins VanA and VanB, the VanC-type ligases, and Dd1A and
DdlB from enteric bacteria andHaemophilus influenzae constituted separate clusters.
Correspondence to: P. Courvalin 相似文献
15.
Hanne Gahéry-Ségard Evelyne Jouvin-Marche Adrien Six Carine Gris-Liebe Marie Malissen Bernard Malissen Pierre-André Cazenave Patrice N. Marche 《Immunogenetics》1996,44(4):298-305
The number of mouse Tcra-V gene segments varies from one individual to another and is estimated to be about 100. Southern blot analysis revealed that
most of the Tcra-V are organized in clusters composed of copies of Tcra-V belonging to different subfamilies. We analyzed in detail a Tcra-V subfamily and looked for new Tcra-V in order to improve the knowledge of the mouse Tcra locus organization. A series of genomic clones derived from the B10.A mouse strain enclosing these clusters was used to determined
the structure of all the Tcra-V2. We were able to identify ten Tcra-V2. This study showed that the Tcra-V2 can be organized into three structural subgroups. The distribution of the genes along the Tcra locus, plus their structural organization, indicates that successive duplications occurred during the processes of expansion
and contraction of the Tcra-V gene subfamilies. Several Tcra-V2 are also identical, indicating recent duplications. The most divergent Tcra-V2 differ by 7.4% nucleotides, leading to 5.2% differences in amino acid contents.
Received: 8 August 1995 / Revised: 24 April 1996 相似文献
16.
The techniques of 27Al- and 31P-nuclear magnetic resonance (NMR) spectroscopy were used to investigate the interactions of aluminium with intracellular ligands within the mycelium of the ectomycorrhizal basidiomycete Laccaria bicolor (Maire) Orton (S238). The vegetative mycelium was grown on medium containing 0.5 mM AlCl3 for 0.5 to 3 d. The 27Al-NMR spectra showed that aluminium was rapidly taken up and accumulated into polyphosphate complexes in the vacuole. Comparison with Al-polyphosphate complexes obtained in vitro on model systems indicated that Al forms at least three mixed-solvation complexes with Pi and polyphosphates, that there is more than one complex present under any set of conditions, and that the equilibrium between these complexes shifts dramatically with Al concentration in the medium. The high phosphate concentrations in the growth medium favoured the accumulation of the Al-polyphosphate complexes. When mycelium containing Al-polyphosphate complexes was transferred to Al-free nutrient solution for 9 d, the Alpolyphosphate complexes were not remobilized. The sequestration of Al in the polyphosphate complexes could therefore make a significant contribution to the protection of mycorrhizal plants against aluminium toxicity.Abbreviations NMR
nuclear magnetic resonance
- PolyP
polyphosphate(s)
- PP1
terminal phosphate of PolyP
- PP3
middle phosphate of PolyP
We thank Prof. Daniel Canet (Laboratoire de Méthodologie RMN, University of Nancy I, Vandceuvre-lès-Nancy, France) for his constant encouragement and Christine Delaruelle for skilled technical assistance in growing the fungal cultures. This work was supported by a research grant from the Commission of the European Communities (STEP-CT90-0059, Role of Ectomycorrhiza in Stress Tolerance of Forest Trees) to F.M. and a travel grant from the Institut National de la Recherche Agronomique to I.K.; R.C. is a recipient of a Postdoctoral Fellowship from the Natural Sciences and Engineering Research Council of Canada. 相似文献
17.
Patrice Daniel Erwin de Waele Jean-Noël Hallet 《Applied microbiology and biotechnology》1993,38(5):638-641
Genomic DNA of several strains oof oenological lactic bacteria belonging to the species Lactobacillus plantarum, Leuconostoc oenos and Pediococcus pentosaceus was digested by the rare-cutting endonucleases ApaI and SmaI. The restriction products were separated by transverse alternating field electrophoresis (TAFE). The size of the genome of L. oenos estimated by adding the molecular size of the ApaI fragments was on average 1320 kb. A strong polymorphism was observed between the strains, which could be easily differentiated except for two industrial strains of L. oenos. A simple modification of the TAFE apparatus is proposed to improve the separation of the DNA fragments.
Correspondence to: J.-N. Hallet 相似文献
18.
Joelle Vilamitjana-Amedee Reine Bareille Francois Rouais Arnold I. Caplan Marie-Francoise Harmand 《In vitro cellular & developmental biology. Animal》1993,29(9):699-707
Summary This study reports the selection and characterization of osteogenic precursors from human bone marrow which were isolated
by two “clonings” and successive subculturing. These cell lines express alkaline phosphatase activity. Gel electrophoresis
of [3H]-proline labeled cultures showed that the cloned cells produce only type I collagen. They synthetize osteocalcin and osteonectin.
They respond to 1,25 dihydroxy vitamin D3 by increasing osteocalcin synthesis and secretion, and to parathyroid hormone by increasing cyclic AMP synthesis. After the
third subculture in the absence of β-glycerophosphate, these cell lines formed lots of clusters which exhibit high alkaline
phosphatase activity and positive von Kossa staining. X-ray energy spectrum shows that these cells are surrounded by “budding”
structures containing calcium and phosphorus with a ratio Ca:P identical to those of pure hydroxyapatite. This process was
associated with45Ca uptake into the cells. All these data support the selection of osteogenic cells which may be of considerable clinical importance. 相似文献
19.
Induction of phagocytic behaviour in human epithelial cells by Escherichia coli cytotoxic necrotizing factor type1 总被引:7,自引:0,他引:7
Loredana Falzano Carla Fiorentini Gianfranco Donelli Eric Michel Christine Kocks Pascale Cossart Lucien Cabanié Eric Oswald Patrice Boquet 《Molecular microbiology》1993,9(6):1247-1254
Cytotoxic necrotizing factor type 1 (CNF1) from strains of pathogenic Escherichia coli induces in human epithelial HEp-2 cells, a profound reorganization of the actin cytoskeleton into prominent stress fibres and membrane ruffles. We report here that this process is associated with induction of phagocytic-like activity. CNF1-treated cells acquired the ability to ingest latex beads as well as non-invasive bacteria such as Listeria innocua, which were taken as a model system. Uptake of bacteria was similar to pathogen-induced phagocytosis, since L. innocua transformed with DNA coding for the pore-forming toxin listeriolysln O behaved, with respect to intracellular growth, like the invasive, pathogenic species L. monocytogenes. Our results raise the possibility that, in vivo, pathogenic CNF1 -producing E. coli may invade epithelia by this novel induced phagocytic-like mechanism. 相似文献
20.
Bruno Mhul Michle Aubery Hans-Georg Mannherz Patrice Codogno 《Journal of cellular biochemistry》1993,52(3):266-274
The myoblast cell surface activity of ecto-5′-nucleotidase was stimulated by a laminin substrate, whereas fibronectin and gelatin did not increase the AMPase activity of ecto-5′-nucleotidase. This increase was related to a higher expression of ecto-5′-nucleotidase on the surface of cells seeded on a laminin substrate, but without the mobilization of an intracellular pool of enzyme. Furthermore, laminin and its fragments E′1 and E8 modified the AMPase activity of the ecto-5′-nucleotidase purified from chicken striated muscle and reconstituted in liposomes. Over the range of concentrations used, intact laminin and its fragment E8, consisting of the distal half of the long arm, stimulated the AMPase activity of ecto-5′-nucleotidase. By contrast, the large fragment derived from the short arms, designated E′1, inhibited the AMPase activity. Furthermore, the monoclonal anti-ecto-5′-nucleotidase antibody, CG37, abolished the stimulatory effect of fragment E8 on the AMPase activity of ecto-5′-nucleotidase but did not reverse the inhibitory effect of fragment E′1. In conclusion, laminin stimulates the AMPase activity of ecto-5′-nucleotidase by two mechanisms: inducing the expression of ecto-5′-nucleotidase to the cell surface and direct modulation of the enzymatic activity. 相似文献