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1.
The arabinogalactan protein-binding β-d-glucosyl Yariv reagent (βGlcY) was applied to the various developmental stages of embryogenic carrot (Daucus carota L. cv. Early Nantes) cell-suspension cultures. Roots without shoot structures were produced in cultures grown under embryo-inducing
conditions in medium containing βGlcY. Only low concentrations of βGlcY permitted the subsequent production of embryos in
these cultures. When early stage embryos were transferred to medium containing βGlcY, the roots elongated greatly while the
shoot apices expanded radially. These embryos did not progress to the next developmental stage. Torpedo embryos and plantlets,
however, showed an overall inhibition of growth in the presence of βGlcY. Developmental stage therefore appears to determine
how cultures and embryos respond to βGlcY, root growth being promoted in the early stages, and overall growth reduced in the
late stages.
Received: 1 July 1997 / Accepted: 31 July 1997 相似文献
2.
J. Rabenhorst 《Applied microbiology and biotechnology》1996,46(5-6):470-474
In our screening program for microorganisms that are able to metabolize eugenol, the main component of the essential oil
of the clove tree Syzigium aromaticum (sy. Eugenia cariophyllus), we found a new Pseudomonas sp. that produces several substituted methoxyphenols when eugenol is fed to the culture. A taxonomic characterization of this
new organism has been performed. Examples of the biotransformation products, produced in high amounts, were vanillic acid
with 3.25 g/l within 99 h, ferulic acid with 5.8 g/l within 75 h and coniferyl alcohol with 3.22 g/l within 47.5 h. By changing
the culture conditions the ratio of the different metabolites could be varied. Based on these results a scheme for the degradation
of eugenol by this strain has been established.
Received: 1 April 1996 / Received revision: 24 June 1996 / Accepted: 1 July 1996 相似文献
3.
R. Sachidanandham K. Jenny A. Fiechter K. Jayaraman 《Applied microbiology and biotechnology》1997,47(1):12-17
Bacillus thuringiensis subsp. galleriae, grown in continuous cultures, segregated to spontaneous asporogenic variants replacing the wild-type Spo+ Cry+ strains [Sachidanandham R, Jayaraman K (1993) Appl Microbiol Biotechnol 40:504–507]. Realizing that this was due to specific
but unknown nutritional requirements, we undertook further continuous-culture studies to identify growth requirement(s) by
pulsing various medium components and growth factors. While carbon, nitrogen and pulses of nutrients exhibited a neutral pulse
response, a group of amino acids were shown to improve the stability and volumetric productivity of biomass. The formation
of spores and insecticidal crystal proteins was found to be higher with amino acid supplementation. Comparison of carbon-limited
steady-state continuous cultures under two different conditions of growth brought forth the stabilizing effects of the amino
acid supplementation. Batch experiments carried out with these inputs demonstrated a better carbon utilization, resulting
in a higher biomass as well as enhancement of bioinsecticidal activity.
Received: 14 May 1996 / Received revision: 9 September 1996 / Accepted: 13 September 1996 相似文献
4.
Monoclonal antibodies recognizing two classes of developmentally regulated plant cell surface components – arabinogalactan-proteins
(AGPs) and extensins – have been used to immunolabel cells at the root apices of four species with different characteristics
of pericycle and vascular tissue development. Root apices of pea (Pisum sativum L.), radish (Raphanus sativus L.), carrot (Daucus carota L.) and onion (Allium cepa L.) were immunolabelled with the anti-AGP monoclonal antibodies JIM4 and JIM13 and anti-extensin monoclonal antibodies JIM11,
JIM12, JIM19 and JIM20. All of these antibodies recognized subsets of pericycle cells in at least one, but never all, of these
species. The restricted patterns of epitope occurrence also reflected vascular cell development. The differences in patterns
of antibody recognition in the four species are discussed in relation to the possible roles of these cell surface molecules
in cell differentiation and root patterning events.
Received: 11 March 1997 / Accepted: 20 May 1997 相似文献
5.
Use of immobilized bacteria to treat industrial wastewater containing a chlorinated pyridinol 总被引:1,自引:0,他引:1
Pseudomonas sp. strain M285 immobilized on diatomaceous earth beads was used to remove 3,5,6-trichloro-2-pyridinol (TCP) from industrial
wastewater. Batch studies showed that immobilized Pseudomonas sp. strain M285 mineralized [2,6-14C]TCP rapidly; about 75% of the initial radioactivity was recovered as 14CO2. Transformation of TCP was inhibited by high concentrations of salt, and addition of osmoprotectants (proline and betaine
at 1 mM) did not reduce the adverse effect of salt. TCP-containing wastewater (60–140 mg/l) was passed through columns containing
immobilized Pseudomonas sp. strain M285 at increasing flow rates and increasing TCP concentrations; TCP removal of 80%–100% was achieved. Addition
of nutrients, such as glucose and yeast extract, retarded TCP degradation. Growing cell cultures were found to be better inocula
for immobilization than resting cells.
Received: 5 February 1996 / Received last revision: 12 August 1996 / Accepted: 24 August 1996 相似文献
6.
N. Sriubolmas W. Panbangred S. Sriurairatana V. Meevootisom 《Applied microbiology and biotechnology》1997,47(4):373-378
Various concentrations of isopropyl β-d-thiogalactopyranoside (IPTG) were used to induce production of the enzyme penicillin G acylase by recom binant Escherichia coli harboring plasmid pQEA11. The plasmid pQEA11 carries a wild-type pga gene, which is under the control of the tac promoter and lacI q. At low IPTG concentrations (0.025 – 0.1 mM), enzyme activity increased with increasing IPTG concentrations. At higher IPTG
concentrations (0.2 and 0.5 mM), enzyme activity declined progressively. Examination of induced recombinant E. coli cells by transmission electron microscopy showed the presence of only periplasmic inclusion bodies at low IPTG concentrations
(up to 0.1 mM) and both periplasmic and cytoplasmic inclusion bodies at high IPTG concentrations (0.2 mM and 0.5 mM). Results
from sodium dodecyl sulfate/polyacrylamide gel electrophoresis and immunoblots of whole-cell proteins, membrane proteins and
inclusion body proteins in these cells indicated that cytoplasmic inclusion bodies constituted an accumulation of preproenzyme
(i.e., precursor polypeptide containing a signal peptide) and that periplasmic inclusion bodies constituted an accumulation
of proenzyme (i.e., precursor polypeptide lacking a signal peptide).
Received: 27 March 1996 / Received revision: 2 July 1996 / Accepted: 10 November 1996 相似文献
7.
Poly[(R)-3-hydroxybutyric acid] (PHB) was produced at 37 °C by a recombinant Escherichia coli harboring the Alcaligenes eutrophus biosynthesis phbCAB genes in Luria-Bertani media containing glucose at 10–30 g/l at different pH values and the time-dependent changes in the
molecular mass of PHB were studied. PHB polymers accumulated within cells while glucose was present in the medium. The number-average
molecular mass of PHB decreased with time during the course of PHB accumulation, and the values for PHB were markedly dependent
on the cultivation conditions of the E. coli, ranging from 0.5 MDa to 20 MDa. Under specific conditions (pH 6.0), E. coli produced PHB with an extremely high molecular mass (20 MDa). It has been suggested that a chain-transfer agent is generated
in E. coli cells during the accumulation of PHB.
Received: 18 July 1996 / Received revision: 4 November 1996 / Accepted: 4 November 1996 相似文献
8.
L. Lesage-Meessen M. Haon M. Delattre J.-F. Thibault B. Colonna Ceccaldi M. Asther 《Applied microbiology and biotechnology》1997,47(4):393-397
The effects of adding cellobiose on the transformation of vanillic acid to vanillin by two strains of Pycnoporus cinnabarinus MUCL39532 and MUCL38467 were studied. When maltose was used as the carbon source in the culture medium, very high levels
of methoxyhydroquinone were formed from vanillic acid. When cellobiose was used as the carbon source and/or added to the culture
medium of P. cinnabarinus strains on day 3 just before vanillic acid was added, it channelled the vanillic acid metabolism via the reductive route
leading to vanillin. Adding 3.5 g l−1 cellobiose to 3-day-old maltose cultures of P. cinnabarinus MUCL39532 and 2.5 g l−1 cellobiose to 3-day-old cellobiose cultures of P. cinnabarinus MUCL38467, yielded 510 mg l−1 and 560 mg l−1 vanillin with a molar yield of 50.2 % and 51.7 % respectively. Cellobiose may either have acted as an easily metabolizable
carbon source, required for the reductive pathway to occur, or as an inducer of cellobiose:quinone oxidoreductase, which is
known to inhibit vanillic acid decarboxylation.
Received: 24 July 1996 / Received revision: 29 November 1996 / Accepted: 29 November 1996 相似文献
9.
Reduction of biomass in a bioscrubber for waste gas treatment by limited supply of phosphate and potassium ions 总被引:2,自引:0,他引:2
Elimination of n-butanol from the gas phase was examined with a mixed culture in a compact bioscrubber. The extent of the cell concentration
was limited by the supply of n-butanol, phosphate or potassium, and the growth rate was determined by the dilution rate. With n-butanol as the limiting substrate the cellular yield was 0.53 g dry cell weight/g n-butanol. Phosphate limitation decreased this yield to 0.34 g and potassium limitation to 0.31 g dry cell weight/g n-butanol at a dilution rate of 0.1/h. Under these conditions n-butanol was eliminated from the gas phase by 84%–100%. In the same order of limitations the specific degradation rate ranged
from 0.19 g to 0.32 g n-butanol g dry cell weight−1 h−1. The fraction of n-butanol required to satisfy the needs for maintenance energy increased significantly depending on the limiting nutrient.
Limitation by n-butanol, phosphate or potassium caused a maintenance requirement of 0.07, 0.16 and 0.34 g n-butanol g dry cell weight−1 h−1, thus showing a fivefold increase. This high demand for the carbon source demonstrated the feasibility of operating a bioscrubber
under mineral limitation to reduce biomass formation significantly, and to maintain a high degree of substrate elimination
from the gas phase.
Received: 22 May 1996 / Received revision: 23 July 1996 / Accepted: 5 August 1996 相似文献
10.
Xylitol and riboflavin accumulation in xylose-grown cultures of Pichia guilliermondii 总被引:1,自引:0,他引:1
Seven strains of Pichia guilliermondii (Candida guilliermondii, asexual state) from diverse isolation sources were examined for the production of xylitol and riboflavin in xylose-grown
cultures. Under the conditions tested, all strains produced xylitol from xylose; conversion efficiencies varied, on a strain-specific
basis, from 7% to 36% of the initial substrate. Four of seven strains metabolized xylitol immediately as xylose levels became
depleted. The remaining three strains metabolized xylitol slowly and incompletely. Surprisingly, utilization of xylitol showed
an apparent relationship with riboflavin production. Strains that readily metabolized xylitol produced at least threefold
greater levels of riboflavin than did strains that used xylitol slowly. Moreover, riboflavin accumulation took place during
xylitol consumption. P. guilliermondii strains that produced the highest levels of riboflavin on xylose produced significantly less riboflavin when grown on glucose
or directly on xylitol.
Received: 24 April 1996 / Received revision: 29 July 1996 / Accepted: 24 August 1996 相似文献
11.
P. J. M. Teunissen H. J. Swarts J. A. Field 《Applied microbiology and biotechnology》1997,47(6):695-700
Ligninolytic basidiomycetes were screened for their ability to produce the tetrachlorinated hydroquinone metabolites drosophilin
A (DA, tetrachloro-4-methoxyphenol) and drosophilin A methyl ether (DAME, tetrachloro-1,4-dimethoxybenzene). Five fungal strains
produced these metabolites in detectable amounts, including strains from Bjerkandera and Peniophora, which are genera not previously known for DA or DAME production. Phellinus fastuosus ATCC26.125 had the highest and most reliable production of DA and DAME in peptone medium, respectively 15–60 μM and 4–40 μM.
This fungus was used to study culture conditions that could increase DAME production. A fourfold increase in DAME production
was found after the addition of hydroquinone to growing cultures of P. fastuosus. Therefore, hydroquinone is postulated to be a possible biosynthetic precursor of DAME in the fungus. Antagonising P. fastuosus by adding filter-sterilised culture fluid of a competing fungus, Phlebia radiata, increased DAME production significantly by tenfold. This result suggests that DAME production is elicited by compounds present
in the culture fluid of P. radiata, indicating that DAME has an antibiotic function in P. fastuosus.
Received: 17 September 1996 / Received revision: 7 February 1997 / Accepted: 15 February 1997 相似文献
12.
Microemulsions as a tool for the regioselective lipase-catalysed esterification of aliphatic diols 总被引:1,自引:0,他引:1
The efficiency of Humicola lanuginosa and Candida cylindracea lipases to catalyse the regioselective esterification of butane-1,3-diol with oleic acid has been demonstrated in water-in-oil
microemulsion systems stabilized with sodium (bis-2-ethylhexyl) sulphosuccinate as a surfactant in isooctane. Mono- and diesters
were selectively synthesized with high reaction rates. The product distribution depends on the positional specificity of the
lipases. Water-in-oil microemulsions appear to be an effective and fast system for the regioselective enzymatic esterification
of diols.
Received: 29 April 1996 / Received revision: 29 July 1996 / Accepted: 5 August 1996 相似文献
13.
U. Mukundan V. Bhide G. Singh W. R. Curtis 《Applied microbiology and biotechnology》1998,50(2):241-245
Brief exposure of Beta vulgaris root cultures to acidic medium resulted in release of betalain pigments while the capability for regrowth and continued pigment
accumulation was retained. A 10-min exposure to pH 2 followed by return to standard growth medium (pH 5.5, 1.1 mM PO4) resulted in release of 0.59 mg pigment/g dry weight over the subsequent 24-h period. The released pigment corresponds to
36.8% of the total pigments. Further improvement in culture productivity was achieved through phosphate limitation. Specific
pigment productivity increased fivefold for cultures grown in phosphate-free medium as compared to cultures grown in control
medium (1.1 mM PO4). A maximum total pigment production of 25.2 mg/l was observed at an initial medium phosphate level 0.3 mM. When combined
with phosphate limitation, low pH facilitated the release of 3.03 mg pigment/g dry weight, which corresponds to 50% of the
total pigment. The permeabilized roots were capable of regrowth and continued pigment accumulation. A cytochemical assay for
respiratory activity revealed that the basis of regrowth was lateral root initials that were unaffected during the acidic
pH treatment.
Received: 16 December 1997 / Received revision: 7 May 1998 / Accepted: 16 May 1998 相似文献
14.
I. Krallish H. Jeppsson A. Rapoport B. Hahn-Hägerdal 《Applied microbiology and biotechnology》1997,47(4):447-451
The effects of dehydration/rehydration on two strains of Saccharomyces cerevisiae: S600, a metabolically engineered xylose-utilising strain, and H158, the non-xylose-utilising host strain; and on the naturally
xylose-utilising yeast Pachysolen tannophilus CBS 4044, were compared after glucose and xylose utilisation respectively. The yeast strains differed in their ability to
excrete and accumulate intracellular xylitol. A high intracellular xylitol content before and after dehydration coincided
with a higher viability after a dehydration/rehydration cycle. The intracellular trehalose content increased during dehydration
in all three yeast strains, but this did not correspond to enhanced cell viability after dehydration/rehydration. The results
are discussed in relation to the ability of xylitol and trehalose to structure water.
Received: 9 July 1996 / Received revision: 29 October 1996 / Accepted: 2 November 1996 相似文献
15.
Escherichia coli K-12 transformed with pACYC184 plasmid DNA was exposed to ozone (O3) in aqueous solution. The damage to the membrane, protein, plasmid DNA, and cell survival were investigated. Cell viability
was unaffected by short-term O3 exposure (1–5 min) but membrane permeability was compromised as indicated by protein and nucleic acid leakage and lipid oxidation.
The intracellular components, protein and DNA, remained intact. With longer durations of O3 exposure (up to 30 min) cell viability decreased with a more significant increase in lipid oxidation and protein and nucleic
acid leakage. The proteins leaking out were further oxidized by O3. The total intracellular proteins run on sodium dodecyl sulfate/polyacrylamide gel electrophoresis, and plasmid DNA run on
agarose gel, showed progressive degradation corresponding to the decrease in cell viability. The data indicate that membrane
components are the primary targets of O3 damage with subsequent reactions involving the intracellular components, protein and DNA.
Received: 18 Apirl 1996 / Received revision: 26 July 1996 / Accepted: 5 August 1996 相似文献
16.
K. Sangthongpitag R. J. Penfold S. F. Delaney P. L. Rogers 《Applied microbiology and biotechnology》1997,47(4):379-384
Genes encoding the mosquitocidal binary toxin of Bacillus sphaericus 2362 were introduced into Synechococcus PCC6301, a cyanobacterium that can tolerate a number of potential variations in the mosquito breeding environment, and can
serve as a food source for mosquito larvae. The toxin genes, preceded by a Synechococcus rbcL promoter, were located on a mobilizable Escherichia coli Synechococcus shuttle vector, which was introduced into Synechococcus PCC6301 at frequencies of 10−5–10−7 exconjugants/recipient, depending on the selective conditions used. Recombinant Synechococcus exhibited significant toxicity against 2-day-old and 6-day-old Culex quinquefasciatus larvae, the concentration required to kill 50 % of larvae (LC50) being 2.1 × 105 and 1.3 × 105 cells/ml respectively. Mosquitocidal activity decreased tenfold after 20 generations of non-selective growth.
Received: 23 July 1996 / Received revision: 11 November 1996 / Accepted: 15 November 1996 相似文献
17.
The covalent modification of cell surface proteins with N-hydroxysuccinimide esters of biotin was used to develop a strategy for following the turnover of proteins on the surface
of carrot (Daucus carota L.) protoplasts. A biotinylation/internalisation assay was established which enabled the turnover of cell surface proteins
to be examined by biochemical and immunocytochemical techniques. The detection of biotinylated proteins after sodium dodecyl
sulfate-polyacrylamide gel electrophoresis and Western blotting indicated that a variety of proteins on the surface of the
protoplasts were covalently modified. Immunolocalisation of biotinylated proteins in protoplasts directly after their derivatisation,
demonstrated that the proteins were initially restricted to the cell surface. Incubation of biotinylated protoplasts at 25 °C
for 1 h resulted in the detection of biotin-labelled proteins on the cell surface and intracellularly. A small proportion
of these proteins was associated with coated pits, the Golgi apparatus and vacuolar compartments. Biochemical analysis of
internalised proteins revealed that a polypeptide of approximate Mr 100 000 was internalised by the protoplasts. Immunolabelling of a biotinylated protein of Mr 100 000 by an antibody raised against an isoform of a tobacco plasma-membrane H+-ATPase, strongly suggests that the plasma-membrane H+-ATPase is internalised by carrot protoplasts. The implications of these results are discussed within the context of endocytosis
in plants.
Received: 13 July 1998 / Accepted: 11 November 1998 相似文献
18.
Synthetic genes were designed to encode analogs of the two proteins of Nephila clavipes dragline silk, spidroins 1 and 2. The genes were constructed of tandem repeats of relatively long (more than 300 bp) DNA
sequences assembled from synthetic oligonucleotides, and encoded proteins of high molecular mass (65–163 kDa). Both analogs
were produced efficiently in Escherichia coli. The yield and homogeneity of the products of longer genes were limited by premature termination of synthesis, probably as
a result of processivity errors in protein synthesis. Average termination rates were determined to be 1 in 1100 codons to
1 in 300 codons, depending on the length and synonymous codon choices of the gene. Both analog proteins could be induced to
form stable aqueous solutions without denaturants. Circular dichroism spectra of the purified proteins in dilute solution
resembled spectra of redissolved natural dragline silk in reflecting a largely disordered structure in water and more ordered
structures in mixed solvents with methanol and trifluoroethanol.
Received: 4 March 1996 / Received revision: 29 July 1996 / Accepted: 12 August 1996 相似文献
19.
Effects of oxygen on invertase expression in continuous culture of recombinant Saccharomyces cerevisiae containing the SUC2 gene 总被引:2,自引:0,他引:2
The yeast SUC2 gene, cloned on a multicopy plasmid pRB58, was used to study the effect of oxygen on the invertase expression of the recombinant
Saccharomyces cerevisiae. Glucose repression was not the only factor affecting the invertase expression. The results obtained from the single-stage
continuous cultures under microaerobic conditions showed that invertase expression was also strongly dependent on oxygen availability,
and moving from anaerobic to aerobic conditions led to a five-fold increase in specific invertase activity. However, the cell
yields under anaerobic conditions were quite low compared to those under aerobic conditions. These opposite effects of oxygen
on cell growth and gene expression offer a strategy for maximizing invertase productivity by a two-stage continuous culture.
The first stage was operated at a low level of glucose, around 100 mg/l, under aerobic conditions in order to obtain a high
yield of yeast biomass, and the second stage maintained anaerobic conditions with residual glucose levels of 50 mg/l to derepress
and fully induce invertase expression. The two-stage continuous culture resulted in a 2.5-fold increase in invertase productivity
over that of a single-stage continuous culture.
Received: 28 July 1998 / Received revision: 22 September 1998 / Accepted: 7 November 1998 相似文献
20.
F. Eismann F. Becker P. Kuschk U. Stottmeister 《Applied microbiology and biotechnology》1996,46(5-6):604-609
Biotreatment experiments with solutions of autoxidized phenolic compounds as well as coal-conversion wastewater stored for
30 years and rich in humic matter were performed under nitrate-reducing, sulphate-reducing and methanogenic conditions. The
removal of total organic carbon in fractions of different molecular mass and of monomeric phenolic compounds in the wastewater
was determined. A comparison of biotransformation potentials and rates indicated a relationship between these aspects and
the availability of electron acceptors in the system. The capacities of the microbial consortia increased significantly with
the energy microorganisms could gain from their respective respiration process and can be expressed by the order: aerobic
process – nitrate reduction – sulphate reduction – methanogenesis.
Received: 25 April 1996 / Received revision: 23 July 1996 / Accepted: 5 August 1996. 相似文献