Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 19 de 19
Filter
Add more filters








Publication year range
1.
Psychol Sport Exerc ; 67: 102436, 2023 07.
Article in English | MEDLINE | ID: mdl-37665889

ABSTRACT

Success as a dancer is closely associated with positive dance judgments by perceivers. Although dancers' physical appearance (attractiveness, style) might affect dance judgments beyond dance-specific attributes (technique, expression), they have largely been unconsidered in previous studies. To contribute to a comprehensive explanation of real-life dance judgments, we applied the lens model, an approach explicitly developed to explain the emergence of social judgments by multiple attributes. Therefore, video-records of 70 solo performances were (1) rated regarding dancers' physical appearance, technique, and expression and (2) judged by 33 perceivers. Results of cross-classified mixed-effects models revealed that attributes of all domains were significantly related to dance judgements. Considered simultaneously, however, only dance-specific attributes contributed to the prediction of dance judgments. Additional moderation analyses underscored the importance of perceivers' expertise in judging dance. We discuss the lens model as suitable framework for a naturalistic approach to the study of aesthetic experiences and sports performances.


Subject(s)
Athletic Performance , Dancing , Lens, Crystalline , Lenses , Unionidae , Animals , Judgment
2.
Urologe A ; 46(9): 1019-26, 2007 Sep.
Article in German | MEDLINE | ID: mdl-17589820

ABSTRACT

BACKGROUND: During laser-induced fragmentation, differences in assessing the intraoperative results can depend on the individual characteristics of the laser system used. METHODS: Laser parameters like pulse energy and repetition rate, the penetration depth in silicon tissue, and the laser beam width on photographic paper were determined for three different clinical laser systems. RESULTS: Pulse energy and repetition rate were subject to variations depending on the laser system employed. Significant differences between the three devices were found for penetration depth in silicon and interaction. CONCLUSIONS: Further investigations to ascertain the ablation threshold and fragmentation rate can be based on these findings. Intraoperative assessment of the lithotripsy results should take technical aspects of the laser equipment, stone consistency, and the surgeon's experience into consideration.


Subject(s)
Kidney Calculi/therapy , Lithotripsy, Laser/instrumentation , Equipment Design , Humans , Technology Assessment, Biomedical
3.
Plant Physiol ; 127(3): 803-16, 2001 Nov.
Article in English | MEDLINE | ID: mdl-11706164

ABSTRACT

We report here the isolation of the Arabidopsis SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE 1 (AtSERK1) gene and we demonstrate its role during establishment of somatic embryogenesis in culture. The AtSERK1 gene is highly expressed during embryogenic cell formation in culture and during early embryogenesis. The AtSERK1 gene is first expressed in planta during megasporogenesis in the nucellus [corrected] of developing ovules, in the functional megaspore, and in all cells of the embryo sac up to fertilization. After fertilization, AtSERK1 expression is seen in all cells of the developing embryo until the heart stage. After this stage, AtSERK1 expression is no longer detectable in the embryo or in any part of the developing seed. Low expression is detected in adult vascular tissue. Ectopic expression of the full-length AtSERK1 cDNA under the control of the cauliflower mosaic virus 35S promoter did not result in any altered plant phenotype. However, seedlings that overexpressed the AtSERK1 mRNA exhibited a 3- to 4-fold increase in efficiency for initiation of somatic embryogenesis. Thus, an increased AtSERK1 level is sufficient to confer embryogenic competence in culture.


Subject(s)
Arabidopsis/genetics , Protein Kinases/genetics , Arabidopsis/embryology , Arabidopsis/enzymology , Arabidopsis Proteins , Caulimovirus , Cloning, Molecular , DNA, Complementary , Fertilization , Gene Expression Regulation, Developmental , Gene Expression Regulation, Plant , Multigene Family , Plants, Genetically Modified , Protein Kinases/metabolism , Seeds/genetics , Seeds/metabolism , Signal Transduction , Zygote/growth & development
4.
Planta ; 213(1): 1-10, 2001 May.
Article in English | MEDLINE | ID: mdl-11523644

ABSTRACT

Genes encoding two novel members of the leucine-rich repeat receptor-like kinase (LRR-RLK) superfamily have been isolated from maize (Zea mays L.). These genes have been named ZmSERK1 and ZmSERK2 since features such as a putative leucine zipper (ZIP) and five leucine rich repeats in the extracellular domain, a proline-rich region (SPP) just upstream of the transmembrane domain and a C-terminal extension (C) after the kinase domain identify them as members of the SERK (somatic embryogenesis receptor-like kinase) family. ZmSERK1 and ZmSERK2 are single-copy genes and show 79% identity among each other in their nucleotide sequences. They share a conserved intron/exon structure with other members of the SERK family. In the maize genome, ZmSERK1 maps to position 76.9 on chromosome arm 10L and ZmSERK2 to position 143.5 on chromosome arm 5L, in regions generally not involved in duplications. ZmSERK1 is preferentially expressed in male and female reproductive tissues with strongest expression in microspores. In contrast, ZmSERK2 expression is relatively uniform in all tissues investigated. Both genes are expressed in embryogenic and non-embryogenic callus cultures.


Subject(s)
Plant Proteins/genetics , Protein Kinases/genetics , Zea mays/genetics , Amino Acid Sequence , Chromosome Mapping , Cloning, Molecular , Consensus Sequence , DNA, Complementary/genetics , Gene Expression Regulation, Plant , Genes, Plant , Leucine-Rich Repeat Proteins , Molecular Sequence Data , Multigene Family , Phylogeny , Plant Proteins/chemistry , Plant Proteins/classification , Protein Kinases/classification , Proteins/chemistry , RNA, Messenger/analysis , RNA, Plant/analysis , Restriction Mapping , Sequence Analysis, DNA , Sequence Homology, Amino Acid , Zea mays/chemistry , Zea mays/enzymology
5.
J Mol Biol ; 309(3): 641-55, 2001 Jun 08.
Article in English | MEDLINE | ID: mdl-11397085

ABSTRACT

The Arabidopsis thaliana somatic embryogenesis receptor kinase 1 (AtSERK1) gene is expressed in developing ovules and early embryos. AtSERK1 is also transiently expressed during somatic embryogenesis. The predicted AtSERK1 protein contains an extracellular domain with a leucine zipper motif followed by five leucine-rich repeats, a proline-rich region, a single transmembrane region and an intracellular kinase domain. The AtSERK1 cDNA was fused to two different variants of green fluorescent protein (GFP), a yellow-emitting GFP (YFP) and a cyan-emitting GFP (CFP), and transiently expressed in both plant protoplasts and insect cells. Using confocal laser scanning microscopy it was determined that the AtSERK1-YFP fusion protein is targeted to plasma membranes in both plant and animal cells. The extracellular leucine-rich repeats, and in particular the N-linked oligosaccharides that are present on them appear to be essential for correct localization of the AtSERK1-YFP protein. The potential for dimerization of the AtSERK1 protein was investigated by measuring the YFP/CFP fluorescence emission ratio using fluorescence spectral imaging microscopy. This ratio will increase due to fluorescence resonance energy transfer if the AtSERK1-CFP and AtSERK1-YFP fusion proteins interact. In 15 % of the cells the YFP/CFP emission ratio for plasma membrane localized AtSERK1 proteins was enhanced. Yeast-protein interaction experiments confirmed the possibility for AtSERK1 homodimerization. Elimination of the extracellular leucine zipper domain reduced the YFP/CFP emission ratio to control levels indicating that without the leucine zipper domain AtSERK1 is monomeric.


Subject(s)
Arabidopsis/cytology , Arabidopsis/enzymology , Mitogen-Activated Protein Kinase Kinases/chemistry , Mitogen-Activated Protein Kinase Kinases/metabolism , Amino Acid Motifs , Animals , Arabidopsis/drug effects , Arabidopsis/metabolism , Cell Line , Cell Membrane/metabolism , Dimerization , Energy Transfer , Fluorescence , Glycosylation , Leucine Zippers , Membrane Proteins/chemistry , Membrane Proteins/metabolism , Plant Proteins/chemistry , Plant Proteins/metabolism , Protein Binding , Protein Structure, Tertiary , Protein Transport , Protoplasts/cytology , Protoplasts/metabolism , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/metabolism , Spectrometry, Fluorescence , Spodoptera , Tunicamycin/pharmacology , Two-Hybrid System Techniques
6.
Biotechnol Bioeng ; 70(4): 391-9, 2000 Nov 20.
Article in English | MEDLINE | ID: mdl-11005921

ABSTRACT

Degradation of phenol and benzoic acid was studied in a fluidized-bed reactor (liquid volume 2.17 L) under nonsterile conditions with special emphasis on maximizing the flow through the reactor and investigating reactor performance at fluctuating feeds. Reactor response to substrate pulses was investigated by applying substrate square-wave inputs at a liquid flow of 1.00 L h(-1). A twofold increase of the phenol and benzoic acid feed concentrations for 2.5 h did not lead to accumulation and breakthrough. The cells were able to survive four to fivefold increases of the feed concentration for 1 h without loss of viability, although the phenol pulse lead to phenol accumulation in the reactor. Reactor performance at constantly fluctuating loads was investigated by varying the feed concentrations using sine wave functions. No accumulation of phenol or benzoic acid was observed. Influence of induction was studied using shift experiments. After 35 days of operation (369 hydrodynamic residence times) with phenol as sole substrate (carbon source) the reactor was able to mineralize benzoic acid without any adaptation or lag phase. The capability of phenol degradation, on the other hand, was lost by most cells after only 3 days operation with benzoic acid as the sole substrate. The experiments underline the importance of induction. In order to maximize the flow through the reactor, the liquid flow was increased stepwise while the feed concentrations were reduced correspondingly, keeping the volumetric conversion rates of phenol (0.24 g L(-1) h(-1)) and benzoic acid (0.17 g L(-1) h(-1)) constant. By this means, liquid flow could be increased up to 13.32 L h(-1), which was more than 20-fold higher than the maximum liquid flow achievable in a chemostat using the same conditions.


Subject(s)
Benzoic Acid/metabolism , Bioreactors , Biotechnology/methods , Burkholderia cepacia/metabolism , Phenol/metabolism , Biotechnology/instrumentation , Carbon Dioxide/metabolism , Oxygen/metabolism
7.
Plant Mol Biol ; 39(3): 551-64, 1999 Feb.
Article in English | MEDLINE | ID: mdl-10092182

ABSTRACT

In order to identify important promoter elements controlling the ammonium-regulated expression of the soybean gene GS15 encoding cytosolic glutamine synthetase, a series of 5' promoter deletions were fused to the GUS reporter gene. To allow the detection of positive and negative regulatory elements, a series of 3' deletions were fused to a -90 CaMV 35S promoter fragment placed upstream of the GUS gene. Both types of construct were introduced into Lotus corniculatus plants and soybean roots via Agrobacterium rhizogenes-mediated transformation. Both spectrophotometric enzymatic analysis and histochemical localization of GUS activity in roots, root nodules and shoots of transgenic plants revealed that a strong constitutive positive element (SCPE) of 400 bp, located in the promoter distal region is indispensable for the ammonium-regulated expression of GS15. Interestingly, this SCPE was able to direct constitutive expression in both a legume and non-legume background to a level similar to that driven by the CaMV 35S full-length promoter. In addition, results showed that separate proximal elements, located in the first 727 bp relative to the transcription start site, are essential for root- and root nodule-specific expression. This proximal region contains an AAAGAT and two TATTTAT consensus sequences characteristic of nodulin or nodule-enhanced gene promoters. A putative silencer region containing the same TATTTAT consensus sequence was identified between the SCPE and the organ-specific elements. The presence of positive, negative and organ-specific elements together with the three TATTTAT consensus sequences within the promoter strongly suggest that these multiple promoter fragments act in a cooperative manner, depending on the spatial conformation of the DNA for trans-acting factor accessibility.


Subject(s)
Genes, Plant/genetics , Glutamate-Ammonia Ligase/genetics , Glycine max/genetics , Quaternary Ammonium Compounds/pharmacology , Regulatory Sequences, Nucleic Acid , Base Sequence , Cytosol/enzymology , DNA, Plant/chemistry , DNA, Plant/genetics , Fabaceae/enzymology , Fabaceae/genetics , Gene Expression/drug effects , Gene Expression Regulation, Enzymologic , Gene Expression Regulation, Plant , Glutamate-Ammonia Ligase/metabolism , Molecular Sequence Data , Plants, Genetically Modified , Plants, Medicinal , Promoter Regions, Genetic , Sequence Alignment , Sequence Analysis, DNA , Sequence Deletion , Glycine max/chemistry , Glycine max/enzymology
8.
Biotechnol Bioeng ; 57(1): 62-70, 1998 Jan 05.
Article in English | MEDLINE | ID: mdl-10099179

ABSTRACT

Plasmid stability of recombinant Pseudomonas sp. B13 FR1 pFRC20P, a strain capable of mineralizing 3- and 4-chlorobenzoate and 4-methylbenzoate, was investigated in continuous culture. The hybrid cosmid pFRC20P enables the strain to mineralize 4-methylbenzoate. Rapid plasmid loss was observed under nonselective conditions using 3-chlorobenzoate as the substrate. Plasmid stability decreased with increasing dilution rate. Despite the growth advantage of the generated plasmid free cells a total depletion of plasmid bearing cells was not observed. After approximately 50 generations the fraction of plasmid bearing cells reached a constant level of 10%, which was stably maintained during the next 25 generations. Cells from this stage were used to inoculate a new culture that resulted in a stable level of 50% plasmid bearing cells. By a temporary substrate change to selective conditions (4-methylbenzoate), this level could be further increased to 70%. Literature models on plasmid stability could not be applied to describe the experimental data. Therefore, a new but unstructured model was developed to describe the experimental results. The model is based on the existence of three subpopulations: a plasmid free one, an original plasmid bearing one with a growth disadvantage compared to plasmid free cells, and a second plasmid bearing subpopulation with increased stability that is generated from the original one and has a growth rate comparable to the plasmid free cells.


Subject(s)
Plasmids/genetics , Pseudomonas/genetics , Benzoates/metabolism , Biodegradation, Environmental , Bioreactors , Biotechnology , Chlorobenzoates/metabolism , Models, Biological , Pseudomonas/metabolism , Recombination, Genetic
9.
Plant J ; 11(6): 1325-31, 1997 Jun.
Article in English | MEDLINE | ID: mdl-9225471

ABSTRACT

Programmed cell death or apoptosis is a process in which unwanted cells are eliminated during growth and development. In mammals, several genes have been identified whose products are necessary to prevent entry into the apoptotic process. We have isolated a clone from an Arabidopsis thaliana cDNA library whose predicted translation product shows highly significant similarity to the mammalian defender against apoptotic death 1 (DAD1) protein. Transformation of the mutant hamster tsBN7 cells, which undergo apoptosis at restrictive temperature, demonstrates that the plant protein is as efficient as human DAD1 in rescuing these hamster cells from apoptosis. In contrast to mammals, Southern hybridisation and genomic data indicate that there are probably two genes in Arabidopsis thaliana. Northern blot analysis shows that AtDAD transcripts are present in all tissues examined, although the abundance of the transcripts is reduced in siliques during the maturation and desiccation phase of the seed. This is the first experimental proof that a homologue of an animal gene involved in apoptosis exists in plants and the first demonstration of complementation of a vertebrate mutant by a plant cDNA. Our results suggest that this process of suppression of apoptosis has been conserved in animals and plants.


Subject(s)
Apoptosis/genetics , Arabidopsis/genetics , DNA, Plant/metabolism , Membrane Proteins/genetics , Amino Acid Sequence , Animals , Apoptosis Regulatory Proteins , Cricetinae , DNA, Complementary/metabolism , Genetic Complementation Test , Humans , Membrane Proteins/metabolism , Molecular Sequence Data , Sequence Analysis, DNA , Suppression, Genetic
10.
Biotechnol Bioeng ; 54(6): 567-76, 1997 Jun 20.
Article in English | MEDLINE | ID: mdl-18636412

ABSTRACT

Multiplicity of steady states of a continuous culture with an inhibitory substrate was used to estimate kinetic parameters under steady-state conditions. A continuous culture of Pseudomonas cepacia G4, using phenol as the sole source of carbon and energy, was overloaded by increasing the dilution rate above the critical dilution rate. The culture was then stabilized in the inhibitory branch by a proportional controller using the carbon dioxide concentration in the reactor exhaust gas as the controlled variable and the dilution rate as the manipulated variable. By variation of the set point, several unstable steady states in the inhibitory branch were investigated and the specific phenol conversion rates calculated. In addition, phenol degradation was investigated under substrate limitation (chemostat operation).The results show that the phenol degradation by P. cepacia can be described by the same set of inhibition parameters under substrate limitation and under high substrate concentrations in the inhibitory branch. Biomass yield and maintenance coefficients were identical. Fitting of the data to various inhibition models resulted in the best fit for the Yano and Koga equation. The well-known Haldane model, which is most often used to describe substrate inhibition by phenol, gave the poorest fit. The described method allows a precise data estimation under steady-state conditions from the maximum of the biological reaction rate up to high substrate concentrations in the inhibitory branch. Inhibition parameter estimation by controlling unstable steady states may thus be useful in avoiding discrepancies between data generated by batch runs and their application to continuous cultures which have been often described in the literature. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 567-576, 1997.

11.
Plant Mol Biol ; 34(1): 119-24, 1997 May.
Article in English | MEDLINE | ID: mdl-9177318

ABSTRACT

An Arabidopsis thaliana cDNA encoding a new RNA-binding protein (RBP37) was cloned from a silique cDNA library. The predicted amino acid sequence corresponds to a RBP containing two RNA recognition motifs (RRM) and a basic domain. An affinity for nucleic acids was confirmed in binding assays using in vitro synthesised AtRBP37 protein. In situ hybridisation experiments on sections of flowers and siliques showed expression only in growing organs: gynoecium, petals, filaments and during early-embryogenesis expression is located in the embryo proper and the suspensor up to late heart stage. Expression is not detected in the embryo during maturation. This results suggests an expression pattern correlated with dividing cells.


Subject(s)
Arabidopsis/growth & development , Arabidopsis/genetics , Gene Expression Regulation, Plant , Genes, Plant , Plant Proteins/genetics , RNA-Binding Proteins/genetics , Amino Acid Sequence , Arabidopsis/cytology , Base Sequence , Cell Division/genetics , Molecular Sequence Data , Plant Proteins/biosynthesis , Plant Proteins/chemistry , RNA-Binding Proteins/biosynthesis , RNA-Binding Proteins/chemistry , Sequence Homology, Amino Acid
12.
Biotechnol Bioeng ; 56(3): 295-303, 1997 Nov 05.
Article in English | MEDLINE | ID: mdl-18636645

ABSTRACT

Quinoline degradation by Comamonas acidovorans was investigated in a three phase fluidized bed reactor at dilution rates below and above the critical value (micro(max) = 0.42 h(-1)). Quinoline was used as the sole source of carbon, nitrogen, and energy. Two attachment carriers, polyurethane foam (Bayvitec) and modified cellulose (Aquacel), and a gel entrapment carrier (polyvinyl alcohol) were studied and compared with regard to their effectiveness to immobilize cells. Attachment and biofilm formation was best at higher dilution rates, regardless of carrier type used. Except for the maximum biomass concentration on the carrier, Y(V) (biomass per volume of solid particles), there was no significant difference in reactor performance between the investigated carriers under stationary conditions. The highest value for Y(V) was found for the gel entrapment carrier (Y(V) = 35 g L(-1)). In a long-term run (66 days), the gel entrapment carrier established a permanent biofilm on the surface of the gel beads after 900 h of cultivation time. Complete quinoline mineralization was achieved at a dilution rate of 2.0 h(-1), which is 4.7 times higher than the critical dilution rate. Identical substrate overloads were applied to the gel entrapment and the cellulose carrier by a step increase of the quinoline feed concentration at a dilution rate of 0.8 h(-1) (D approximately 2micro(max)). The cells survived the overload, but the accumulation of quinoline and quinoline degradation products and the degradation efficiency were different for the two systems during the overload, showing the influence of the carrier type on the dynamic performance and stability of the process.

13.
Biotechnol Bioeng ; 51(5): 528-37, 1996 Sep 05.
Article in English | MEDLINE | ID: mdl-18629816

ABSTRACT

Degradation of 3-chlorobenzoic acid (3CB), 4-chlorobenzoic acid (4CB), and 4-methylbenzoic acid (4MB) as single substrates (carbon sources) and as a substrate mixture were studied in batch and continuous culture using the genetically modified microorganism Pseudomonas sp. B13 FR1 SN45P. The strain was able to mineralize the single compounds as well as the substrate mixture completely. Conversion of the three compounds in the substrate mixture proceeded simultaneously. Maximum specific substrate conversion rates were calculated to be 0.9 g g(-1) h(-1) for 3 CB and 4CB and 1.1 g g(-1) h(-1) for 4MB. Mass balances indicated the transient accumulation of pathway intermediates during batch cultivations. Hence, the rate limiting step in the degradative pathway is not the initial microbial attack of the original substrate or its transport through the cell membrane. Degradation rates on 3CB were comparable to those of the parent strain Pseudomonas sp. B13. The stability of the degradation pathways of strain Pseudomonas sp. B13 FR1 SN45P could be demonstrated in a continuous cultivation over 3.5 months (734 generation times) on 3CB, 4MB, and 4CB, which were used as single carbon sources one after the other.

14.
J Mol Evol ; 42(4): 422-31, 1996 Apr.
Article in English | MEDLINE | ID: mdl-8642611

ABSTRACT

In contrast to prokaryotes, which typically possess one thioredoxin gene per genome, three different thioredoxin types have been described in higher plants. All are encoded by nuclear genes, but thioredoxins m and f are chloroplastic while thioredoxins h have no transit peptide and are probably cytoplasmic. We have cloned and sequenced Arabidopsis thaliana genomic fragments encoding the five previously described thioredoxins h, as well as a sixth gene encoding a new thioredoxin h. In spite of the high divergence of the sequences, five of them possess two introns at positions identical to the previously sequenced tobacco thioredoxin h gene, while a single one has only the first intron. The recently published sequence of Chlamydomonas thioredoxin h shows three introns, two at the same positions as in higher plants. This strongly suggests a common origin for all cytoplasmic thioredoxins of plants and green algae. In addition, we have cloned and sequenced pea DNA genomic fragments encoding thioredoxins m and f. The thioredoxin m sequence shows only one intron between the regions encoding the transit peptide and the mature protein, supporting the prokaryotic origin of this sequence and suggesting that its association with the transit peptide has been facilitated by exon shuffling. In contrast, the thioredoxin f sequence shows two introns, one at the same position as an intron in various plant and animal thioredoxins and the second at the same position as an intron in thioredoxin domains of disulfide isomerases. This strongly supports the hypothesis of a eukaryotic origin for chloroplastic thioredoxin f.


Subject(s)
Biological Evolution , Introns/genetics , Plants/genetics , Thioredoxins/genetics , Amino Acid Sequence , Arabidopsis/classification , Arabidopsis/genetics , Base Sequence , Chloroplast Thioredoxins , Genetic Markers , Genome, Plant , Isomerases/genetics , Molecular Sequence Data , Pisum sativum/classification , Pisum sativum/genetics , Plants/classification , Protein Disulfide-Isomerases , Sequence Homology, Amino Acid
15.
Biotechnol Bioeng ; 47(4): 461-9, 1995 Aug 20.
Article in English | MEDLINE | ID: mdl-18623422

ABSTRACT

A bubble column bioreactor was used as bioscrubber to carry out a feasibility study for the cometabolic degradation of trichloroethylene (TCE). Phenol was used as cosubstrate and inducer. The bioreactor was operated like a conventional chemostat with regard to the cosubstrate and low dilution rates were used to minimize the liquid outflow. TCE degradation measurements were carried out using superficial gas velocities between 0.47and 4.07 cm s(-1) and TCE gas phase loads between 0.07 and 0.40 mg L(-1) Depending on the superficial gas velocity used, degrees of conversion between 30% and 80% were obtained. A simplified reactor model using plug flow for the gas phase, mixed flow for the liquid phase, and pseudo first order reaction kinetics for the conversionof TCE was established. The model is able to give a reasonable approximation of the experimental data. TCE degradation at the used experimental conditions is mainly limited by reaction rate rather than by mass transfer rate. The model can be used to calculate the reactor volume and the biomass concentration for a required conversion. (c) 1995 John Wiley & Sons Inc.

16.
Biotechnol Bioeng ; 46(1): 80-7, 1995 Apr 05.
Article in English | MEDLINE | ID: mdl-18623265

ABSTRACT

Quinolie degradation by Comamonas acidovorans was studied in a continuously operated three-phase airlift reactor. Porous glass beads were applied as support matrix for cell imobilization by colonization. Under steady-state conditions (S approximately 0), cell attachment was poor at low dilution rates but imporved considerably with increasing dilution rate. Conversion of quinoline was investigated below and above the washout for suspended culture (D(crit) = mu(max) = 0.42 h(-1)). With immobilized cells the reactor could be operated at D > mu(max), and complete conversion of quinoline was achieved as long as the specific quinoline feed rate D*S(0)/X did not exceed the maximum specific degradation rate (r(S, max)). The biofilm thickness was about 100 mum, and its efficiency was about 54% compared to suspended organisms. If quinoline overloads were supplied to the reactor, quinoline, as overloads were supplied to the reactor, quinoline, as well as its pathway intermediates, appeared in the reactor and conversion was low. Hence, the immobilized microorganisms remained viable and active. They could survive quinoline overloads. If the quinoline feed rate was reduced agains, complete conversion was reestablished. (c) 1995 John Wiley & Sons, Inc.

17.
Biotechnol Bioeng ; 42(5): 589-95, 1993 Aug 20.
Article in English | MEDLINE | ID: mdl-18613080

ABSTRACT

The microbial degradation of quinoline by Comamonas acidovorans was studied in a laboratory scale stirred tank reactor. In continuous culture experiments using quinoline as a sole source of carbon and nitrogen, it was shown by means of mass balances that quinoline was converted completely to biomass, carbon dioxide, and ammonia. Degradation rates up to 0.7 g/L h were obtained. Measured yield coefficients Y(x/s) for quinoline were about 0.7 g/g, which is in agreement with the theoretical value for complete mineralization. Kinetic constants based on Haldane substrate inhibition were evaluated. The values were micro(max) = 0.48 h(-1), K(i) = 69 mg/L, and K(s) < 1.45 mg/L.

18.
Biotechnol Bioeng ; 35(10): 1042-50, 1990 Apr 25.
Article in English | MEDLINE | ID: mdl-18588250

ABSTRACT

To study the influence of ammonium on an antibiotic cultivation, mass transfer measurements of ammonium through microporous hydrophobic membranes using different stripping methods were carried out and compared. The higher overall mass transfer coefficients for ammonium were obtained with an acid stripping solution compared to water, vacuum, or sweeping air. A hollow fiber module for in situ removal of ammonium during cultivation was designed and operated in an external bypass to a 10-L fermentor. Compared to a control fermentation, the cell dry mass could be increased 2.6 times and the antibiotic concentration 8 times, if the in situ ammonium removal was in operation.

19.
Biotechnol Bioeng ; 29(2): 222-7, 1987 Feb.
Article in English | MEDLINE | ID: mdl-18576379

ABSTRACT

A vortex chamber for continuous adsorption of the antibiotic Myxovirescin A on XAD resins was developed. In this paper the design and use of the vortex chamber in an external bypass of a continuous process is described. Compared with the normal continuous process, the specific production rate of the antibiotic is four to five times higher when the antibiotic is continuously adsorbed. A semicontinuous process could be performed by using two chambers for adsorption and regeneration alternatively.

SELECTION OF CITATIONS
SEARCH DETAIL