共查询到20条相似文献,搜索用时 15 毫秒
1.
Kacena MA Merrell GA Manfredi B Smith EE Klaus DM Todd P 《Applied microbiology and biotechnology》1999,51(2):229-234
Previous investigations have reported that bacterial suspension cultures grow to higher stationary concentrations in space
flight than on Earth; however, none of these investigations included extensive ground controls under varied inertial conditions.
This study includes extensive controls and cell-growth data taken at several times during lag phase, log phase, and stationary
phase of Escherichia coli and Bacillus subtilis. The Marquardt-Levenberg, least-squares fitting algorithm was used to calculate kinetic growth parameters from the logistic
bacterial growth equations for space-flight and control growth curves. Space-flight cultures grew to higher stationary-phase
concentrations and had shorter lag-phase durations. Also, evidence was found for increased exponential growth rate in space.
Received: 27 February 1998 / Received revision: 21 August 1998 / Accepted: 3 September 1998 相似文献
2.
The effect of some culture variables in the production of β-galactosidase from Escherichia coli in Bacillus subtilis was evaluated. The lacZ gene was expressed in B. subtilis using the regulatory region of the subtilisin gene aprE. The host contained also the hpr2 and degU32 mutations, which are known to overexpress the aprE gene. We found that, when this overproducing B. subtilis strain was grown in mineral medium supplemented with glucose (MMG), β-galactosidase production was partially growth-associated,
as 40%–60% of the maximum enzyme activity was produced before the onset of the stationary phase. In contrast, when a complex
medium was used, β-galactosidase was produced only at low levels during vegetative growth, whereas it accumulated to high
levels during early stationary phase. Compared with the results obtained in complex media, a 20% increase in specific β-galactosidase
activity in MMG supplemented with 11.6 g/l glucose was obtained. On the 1-l fermenter scale, a threefold increase in volumetric
β-galactosidase activity was obtained when the glucose concentration was varied from 11 g/l to 26 g/l. In addition, glucose
feeding during the stationary phase resulted in a twofold increase in volumetric enzyme activity as cellular lysis was prevented.
Finally, we showed that oxygen uptake and carbon dioxide evolution rates can be used for on-line determination of the onset
of stationary phase, glucose depletion and biomass concentration.
Received: 18 April 1996 / Received revision: 27 August 1996 / Accepted: 6 September 1996 相似文献
3.
K. S. Lam S. W. Mamber E. J. Pack S. Forenza P. B. Fernandes D. M. Klaus 《Applied microbiology and biotechnology》1998,49(5):579-583
The effect of space flight on the production of the antibiotic monorden on two types of agar media, T8 and PG, by Humicola fuscoatra WC5157 was examined on board the US Space Shuttle mission STS-77 in May 1996. Paired space-flight and ground control samples
were prepared using identical hardware, protocol, media, and inoculum. Inoculation occurred simultaneously for both groups
2.5 h after launch. The flight and ground samples were allowed to grow for the entire 10-day mission in a dark, thermally
controlled (22 °C) environment. Post-flight HPLC analysis of the flight and ground sample extracts indicated that the production
of monorden by H. fuscoatra WC5157 in the flight samples was higher than in the ground samples in both agar media. In the T8 medium, the production of
monorden in the flight and ground samples was 11.6 ± 3.5 μg and 8.9 ± 1.1 μg respectively (30% increase). In the PG medium,
the production of monorden in the flight and ground samples was 23.8 ± 3.3 μg and 8.2 ± 2.2 μg respectively (190% increase).
The production of monorden in the flight and ground control samples was confirmed by HPLC-MS analysis.
Received: 30 September 1997 / Received revision: 23 December 1997 / Accepted: 2 January 1998 相似文献
4.
The present work was devoted to the study of the biosorption capacities of various microbial species (Bacillus subtilis, Pseudomonas aeruginosa, Ralstonia metallidurans CH34 previously Alcaligenes eutrophus CH34, Mycobacterium smegmatis, Saccharomyces cerevisiae) for ions of the lanthanide gadolinium (Gd3+). The uptake by sand of this element was also measured. Saturation curves and Scatchard models were established for all biosorbants
used in this work. The results enabled us to determine the binding affinities and the maximum capacities for biosorption of
Gd3+, which ranged from 350 μmol g−1 for B. subtilis to 5.1 μmol g−1 for S. cerevisiae. This study demonstrated the usefulness of optimisation of experimental conditions in biosorption investigations. Experimental
results showed that biosorption could be influenced by the growth stage and by the composition of the growth medium of microbial
cells. Finally, particular attention was given to the transfer of gadolinium ions from a loaded sand to a bacterial suspension.
Received: 8 November 1999 / Received revision: 3 February 2000 / Accepted: 4 February 2000 相似文献
5.
S. Ramachandra Rao R. Sarada G. A. Ravishankar 《Applied microbiology and biotechnology》1996,46(5-6):619-621
Elicitors of both fungal and bacterial origin that is, polysaccharides, proteins and fatty acids, are widely used for enhancement
of secondary metabolites in plant cell cultures. In the present study, phycocyanin – a natural blue pigment that is the major
light-harvesting biliprotein in the blue-green alga Spirulina platensis– was used as an elicitor to enhance the accumulation of capsaicin and anthocyanin in Capsicum frutescens and Daucus carota cell cultures respectively. Phycocyanin at 0.3, 0.6 and 1.2 mg% in capsicum cell cultures elicited a more than two-fold increase
in capsaicin content with maximum productivity of 192 μg/g fresh weight. Similarly in Daucus carota cell cultures a two-fold increase in anthocyanin content was obtained at 0.3 mg% with a maximum productivity of 24.8 mg%
on a dry-weight basis. In both the systems, phycocyanin showed an early elicitation of secondary metabolites.
Received: 15 December 1995 / Received last revision: 15 July 1996 / Accepted: 18 July 1996 相似文献
6.
Nucleotide sequence and biochemical analysis of d-β-hydroxybutyrate dehydrogenase (EC 1.1.1.30), isolated from Rhodobacter sp., indicate functional oligomers composed of subunits of 257 amino acids with a calculated M
r of 26,800 and a pI of 5.90. Compared to mammalian short-chain alcohol dehydrogenases, the bacterial enzyme lacks a C-terminal
lipid anchor domain and was found to be highly active upon expression in Escherichia coli even without lipid supplement. The recombinant enzyme could be highly enriched using a single chromatography step and was
shown to be stable over a broad range of pH and temperature.
Received: 1 April 1999 / Received last revision: 11 June 1999 / Accepted: 11 June 1999 相似文献
7.
Parshikov IA Freeman JP Williams AJ Moody JD Sutherland JB 《Applied microbiology and biotechnology》1999,52(4):553-557
Cultures of the fungi Aspergillus niger, Cunninghamella verticillata, and Penicillium simplicissimum, grown in a sucrose/peptone medium, transformed N-acetylphenothiazine to N-acetylphenothiazine sulfoxide (from 13% to 28% of the total) and phenothiazine sulfoxide (from 5% to 27%). Phenothiazin-3-one
(4%) and phenothiazine N-glucoside (4%) were also produced by C. verticillata. The probable intermediate, phenothiazine, was detected only in cultures of P. simplicissimum (6%).
Received: 15 January 1999 / Received revision: 7 May 1999 / Accepted: 21 May 1999 相似文献
8.
U. Horn W. Strittmatter A. Krebber U. Knüpfer M. Kujau R. Wenderoth K. Müller S. Matzku A. Plückthun D. Riesenberg 《Applied microbiology and biotechnology》1996,46(5-6):524-532
Functional bivalent miniantibodies, directed against the epidermal growth factor receptor, accumulated to more than 3 gl−1 in high-cell-density cultures of Escherichia coli RV308(pHKK) on a pilot scale. The miniantibodies consist of scFv fragments with a C-termi-nal hinge followed by a helix-turn-helix
motif, which homodimerizes in vivo. The improved expression vector pHKK is characterized by the hok/sok suicide system, improving plasmid maintenance, and the inducible lac p/o promoter system with the very strong T7g10 Shine-Dalgarno sequence. The expression unit is flanked by terminators. The prototrophic
RV308 cells were cultivated in glucose mineral salt medium and reached a cell density of 145 g dry biomass l−1 after 33 h. After induction, growth continued almost unchanged for a further 4 h with concomitant miniantibody formation.
In the fed-batch phase, the concentration of glucose was kept almost constant at the physiological level of approximately
1.5 g l−1, using on-line flow injection analysis for control. Surprisingly, E. coli RV308(pHKK) did not accumulate significant amounts of the metabolic by-product acetate under these unlimited aerobic growth
conditions.
Received: 26 February 1996 / Received revision: 1 August 1996 / Accepted: 12 August 1996 相似文献
9.
A two-phase organic/aqueous reactor configuration was developed for use in the biodegradation of benzene, toluene and p-xylene, and tested with toluene. An immiscible organic phase was systematically selected on the basis of predicted and experimentally
determined properties, such as high boiling points, low solubilities in the aqueous phase, good phase stability, biocompatibility,
and good predicted partition coefficients for benzene, toluene and p-xylene. An industrial grade of oleyl alcohol was ultimately selected for use in the two-phase partitioning bioreactor. In
order to examine the behavior of the system, a single-component fermentation of toluene was conducted with Pseudomonas sp. ATCC 55595. A 0.5-l sample of Adol 85 NF was loaded with 10.4 g toluene, which partitioned into the cell containing 1 l
aqueous medium at a concentration of approximately 50 mg/l. In consuming the toluene to completion, the organisms were able
to achieve a volumetric degradation rate of 0.115 g l−1 h−1. This system is self-regulating with respect to toluene delivery to the aqueous phase, and requires only feedback control
of temperature and pH.
Received: 16 November 1998 / Received revision: 28 March 1999 / Accepted: 9 April 1999 相似文献
10.
Although acetate formation and tolerance are important criteria for various aspects of biotechnological process development,
available studies on acetate tolerance in different species are disparate. We evaluate the response of eight bacterial strains,
including two variants of Escherichia coli, two variants of Staphylococcus capitis, and one each of Acetobacter aceti, Gluconobacter suboxydans, Lactobacillus acetotolerans, and L. bulgaricus, to acetate challenges under identical conditions. Our findings were: (1) wild-type organisms of species that are considered
tolerant of acetate perform only slightly better than E. coli in unadapted shaker cultures; (2) the ability to tolerate acetate is strongly dependent on the carbon source, and is, especially
for E. coli, much greater on glycerol than on glucose; (3) respiration is not as important to acetate tolerance in E. coli and S. capitis as has been reported for the acetic acid bacteria; (4) S. capitis was the least affected by acetate under all conditions and grew at up to 44 g/l acetate without any preconditioning; and
(5) qualitative high-throughput screening of growth characteristics can be achieved with relatively inexpensive multiwell
plate readers.
Received: 29 October 1999 / Received revision: 13 January 2000 / Accepted: 14 January 2000 相似文献
11.
A. E. Cazemier J. C. Verdoes H. J. M. Op den Camp J. H. P. Hackstein A. J. J. van Ooyen 《Applied microbiology and biotechnology》1999,52(2):232-239
A gene library of Cellulomonas pachnodae was constructed in Escherichia coli and was screened for endoglucanase activity. Five endoglucanase-positive clones were isolated that carried identical DNA
fragments. The gene, designated cel6A, encoding an endoglucanase enzyme, belongs to the glycosyl hydrolase family 6 (cellulase family B). The recombinant Cel6A
had a molecular mass of 53 kDa, a pH optimum of 5.5, and a temperature optimum of 50–55 °C. The recombinant endoglucanase
Cel6A bound to crystalline cellulose and beech litter. Based on amino acid sequence similarity, a clear cellulose-binding
domain was not distinguished. However, the regions in the Cel6A amino acid sequence at the positions 262–319 and 448–473,
which did not show similarity to any of the known family-6 glycosyl hydrolases, may be involved in substrate binding.
Received: 14 January 1999 / Received revision: 29 March 1999 / Accepted: 6 April 1999 相似文献
12.
J. M. Obón J. R. Maiquez M. Cánovas H.-P. Kleber J. L. Iborra 《Applied microbiology and biotechnology》1999,51(6):760-764
The use of a biological procedure for l-carnitine production as an alternative to chemical methods must be accompanied by an efficient and highly productive reaction
system. Continuous l-carnitine production from crotonobetaine was studied in a cell-recycle reactor with Escherichia coli O44 K74 as biocatalyst. This bioreactor, running under the optimum medium composition (25 mM fumarate, 5 g/l peptone), was
able to reach a high cell density (26 g dry weight/l) and therefore to obtain high productivity values (6.2 g l-carnitine l−1 h−1). This process showed its feasibility for industrial l-carnitine production. In addition, resting cells maintained in continuous operation, with crotonobetaine as the only medium
component, kept their biocatalytic capacity for 4 days, but the biotransformation capacity decreased progressively when this
particular method of cultivation was used.
Received: 10 December 1998 / Received revision: 19 February 1999 / Accepted: 20 February 1999 相似文献
13.
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
14.
K. Hofvendahl E. W. J. van Niel B. Hahn-Hägerdal 《Applied microbiology and biotechnology》1999,51(5):669-672
Lactococcus lactis ssp. lactis ATCC 19435 is known to produce mixed acids when grown on maltose. A change in fermentation conditions only, elevated temperatures
(up to 37 °C) and reduced pH values (down to 5.0) resulted in a shift towards homolactic product formation. This was accompanied
by decreased growth rate and cell yield. The results are discussed in terms of redox balance and maintenance, and the regulation
of lactate dehydrogenase and pyruvate formate-lyase.
Received: 14 December 1998 / Received revision: 12 January 1999 / Accepted: 22 January 1999 相似文献
15.
The gene dak1 encoding a dihydroxyacetone kinase (DHAK) isoenzyme I, one of two isoenzymes in the Schizosaccharomyces pombe IFO 0354 strain, was cloned and sequenced. The dak1 gene comprises 1743 bp and encodes a protein of 62 245 Da. The deduced amino acid sequence showed a similarity to a putative
DHAK of Saccharomyces cerevisiae and DHAK of Citrobacter freundii. The dak1 gene was expressed at a high level in Escherichia coli, and the recombinant enzyme was purified to homogeneity and characterized. The acetone powder of recombinant E. coli cells was used to produce dihydroxyacetone phosphate.
Received: 25 August 1998 / Received revision: 22 September 1998 / Accepted: 11 October 1998 相似文献
16.
Liu JQ Odani M Yasuoka T Dairi T Itoh N Kataoka M Shimizu S Yamada H 《Applied microbiology and biotechnology》2000,54(1):44-51
The dtaAX gene encoding a pyridoxal 5′-phosphate (pyridoxal-P)-dependent low-specificity d-threonine aldolase was cloned from the chromosomal DNA of Alcaligenes xylosoxidans IFO 12669. It contains an open reading frame consisting of 1,134 nucleotides corresponding to 377 amino acid residues. The
predicted amino acid sequence displayed 54% identity with that of d-threonine aldolase from gram-positive bacteria Arthrobacter sp. DK-38, but showed no significant similarity with those of other known pyridoxal-P enzymes. This gram-negative bacterial enzyme was highly overproduced in recombinant Escherichia coli cells, and the specific activity of the enzyme in the cell extract was as high as 18 U/mg (purified enzyme 38.6 U/mg), which
was 6,000 times higher than that from the wild-type Alcaligenes cell extract. The recombinant enzyme was thus feasibly purified to homogeneity by ammonium sulfate fractionation and DEAE-Toyopearl chromatography
steps. The recombinant low-specificity d-threonine aldolase was shown to be an efficient biocatalyst for resolution of l-β-3,4-methylenedioxyphenylserine, an intermediate for production of a therapeutic drug for Parkinson's disease.
Received: 9 September 1999 / Received revision: 1 November 1999 / Accepted: 12 November 1999 相似文献
17.
Growth of Streptomyces hygroscopicus under conditions of simulated microgravity in a rotating-wall bioreactor resulted in a pellet form of growth, lowered dry
cell weight, and inhibition of rapamycin production. With the addition of Teflon beads to the bioreactor, growth became much
less pelleted, dry cell weight increased but rapamycin production was still markedly inhibited. Growth under simulated microgravity
favored extracellular production of rapamycin, in contrast to a greater percentage of cell-bound rapamycin observed under
normal gravity conditions.
Received: 20 September 1999 / Received revision: 18 November 1999 / Accepted: 19 November 1999 相似文献
18.
Axenic aerobic biofilms inhibit corrosion of SAE 1018 steel through oxygen depletion 总被引:1,自引:0,他引:1
A. Jayaraman E. T. Cheng J. C. Earthman T. K. Wood 《Applied microbiology and biotechnology》1997,48(1):11-17
Corrosion inhibition of SAE 1018 steel by pure-culture biofilms of Pseudomonas fragi and Escheri-chia coli DH5α has been evaluated in complex Luria-Bertani medium, seawater-mimicking medium, and modified Baar's medium at 30 °C.
In batch cultures, both bacteria inhibited corrosion three to six fold compared to sterile controls, and the corrosion was
comparable to that observed in anaerobic sterile media. To corroborate this result, a continuous reactor and electrochemical
impedance spectroscopy were used to show that both P. fragi K and E. coli DH5α decreased the corrosion rate by 4- to 40-fold as compared to sterile controls; this matched the decrease in corrosion
found with sterile medium in the absence of oxygen and with E. coli DH5α grown anaerobically. In addition, the requirement for live respiring cells was demonstrated by the increase in the corrosion
rate that was observed upon killing the P. fragi K biofilm in continuous cultures, and it was shown that fermentation products do not cause an increase in corrosion. Hence,
pure-culture biofilms inhibit corrosion of SAE 1018 steel by depleting oxygen at the metal surface.
Received: 16 December 1996 / Received revision: 18 March 1997 / Accepted: 27 March 1997 相似文献
19.
A. Arai S. Masuda A. Matsuyama S. Murakami M. Nakajima 《Applied microbiology and biotechnology》1998,49(3):272-276
The gene for the thermostable pyruvate kinase of Microbispora thermodiastatica IFO 14046, a moderate thermophilic actinomycete, was cloned in Escherichia coli. This gene consists of an open reading frame of 1422 nucleotides and encodes a protein of 474 amino acids with molecular
mass of 50 805 Da. The open reading frame was confirmed as the pyruvate kinase gene by comparison with the N-terminal amino
acid sequence of the purified pyruvate kinase from M. thermodiastatica.
Received: 19 May 1997 / Received last revision: 22 September 1997 / Accepted: 14 October 1997 相似文献
20.
The production of feruloyl esterase activity by Bacillus spp. and lactobacilli can be detected in an agar-plate assay. The assay involves the substitution of the main carbon source
in specific agar with ethyl ferulate. A number of Bacillus spp., predominantly B. subtilis strains, were found to exhibit feruloyl esterase activity by this method. Of the examined lactobacilli, Lb. fermentum (NCFB 1751) showed the highest level of ferulic acid esterase activity. The enzyme was released from harvested cells by sonication
and showed pH and temperature optima of 6.5 and 30 °C respectively.
Received: 2 February 1998 / Received revision: 20 April 1998 / Accepted: 27 April 1998 相似文献