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1.
Yingda Wang Shijun Qian Guangzhen Meng Shuzheng Zhang 《Applied biochemistry and biotechnology》2001,95(2):93-101
The L-asparaginase (ASN) from Escherichia coli AS1.357 was cloned as a DNA fragment generated using polymerase chain reaction technology and primers derived from conserved
regions of published ASN gene sequences. Recombinant plasmid pASN containing ASN gene and expression vector pBV220 was transformed
in different E. coli host strains. The activity and expression level of ASN in the engineering strains could reach 228 IU/mL of culture fluid
and about 50% of the total soluble cell protein respectively, more than 40-fold the enzyme activity of the wild strain. The
recombinant plasmid in E. coli AS1.357 remained stable after 72h of cultivation and 5h of heat induction without selective pressure. The ASN gene of E. coli AS1.357 was sequenced and had high homology compared to the reported data. 相似文献
2.
M. Walid Qoronfleh 《Applied biochemistry and biotechnology》1999,80(2):107-120
A central problem in aerobic growth of any culture is the maintenance of dissolved oxygen concentration (DOC) above growth-limiting
levels especially in high-cell density fermentations that are usually of the fed-batch type. Fermentor studies have been conducted
to determine the influence of DOC on the production of heterologous proteins in Escherichia coli. The results demonstrated that there is a significant degree of product-to-product variation in the response of heterologous
protein accumulation to DOC. For translational fusions of the human immunodeficiency virus-1 (HIV-1) proteins p24Gag and Env41,
the imposition of a dissolved oxygen (DO) limitation resulted in 100 and 15% increases in the respective product yields. On
the other hand, the imposition of a DO limitation had no effect on the production of a similar translational fusion of the
HIV-1 protein p55Gag, and a large negative effect on the production of an influenza protein (C13). The stimulatory effects
of DOC on p24Gag production were investigated further. The results of my studies suggested that the stimulatory effect observed
at reduced agitation rates on p24Gag accumulation was owing to an oxygen effect and not a shear effect. Furthermore, the results
of my investigations indicated that the effect a DOC had on the production of p24Gag was strongly influenced by the cell density
at which the culture was induced. 相似文献
3.
Madhavan Nampoothiri K Roopesh K Chacko S Pandey A 《Applied biochemistry and biotechnology》2005,120(2):97-108
Escherichia coli NCIM 2569 was evaluated for its potential for amidase production under submerged fermentation. Among the various amide compounds
screened, maximum substrate specificity and enzyme yield (8.1 U/mL) were obtained by using 1% acetamide. Fermentation was
carried out at 30°C in shake-flask culture under optimized process conditions. A maximum of 0.52 U/mL of intracellular amidase
activity was also obtained from cells incubated for 24 h. Studies were also performed to elucidate the optimal conditions
(gel concentration, initial biomass, curing period of beads, and calcium ion concentration in the production medium) for immobilization
of whole cells. By using E. coli cells entrapped in alginate, a maximum of 6.2 U/mL of enzyme activity was obtained after 12 h of incubation under optimized
conditions. Using the immobilized cells, three repeated batches were carried out successfully, and 85% of the initial enzyme
activity was retained in the second and third batches. The study indicated that the immobilized E. coli cells offered certain advantages such as less time for maximum enzyme production, more stability in the enzyme production
rate, and repeated use of the biocatalyst. 相似文献
4.
Xi Li Yi Liu Jun Wu Huigang Liang Songsheng Qu 《Journal of Thermal Analysis and Calorimetry》2002,67(3):589-595
The action of three kinds of the selenomorpholine compounds on a strain ofEscherichia coli was studied by microcalorimetry. Differences in their capacities to affect the metabolism of this bacterium were observed.
The extent and duration of the effect on the metabolism as judged from the rate constant (k) of Escherichia coli (in log phase) varied with the different drugs. The kinetics show that selenomorpholine compounds had an effect on the metabolism
process of Escherichia coli. The k of Escherichia coli in the presence of the drugs increased with the increasing concentrations of the drugs (C) at low concentration; but at high concentration, the rate constant decreased with the increasing concentrations of the drugs.
The experimental results reveal that the sequence of antibiotic activity of selenomorpholines is: N-selenomorpholinemethyl
succinimide and its hydrochloride>N-(α-selenomorpholinebenzyl) succinimide.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
Biosynthesis of polyhydroxyalkanoates (PHAs) consisting of 3-hydroxyalkanoates (3HAs) of 4 to 10 carbon atoms was examined
in metabolically engineered Escherichia coli strains. When the fadA and/or fadB mutant E. coli strains harboring the plasmid containing the Pseudomonas sp. 61-3 phaC2 gene and the Ralstonia eutropha phaAB genes were cultured in Luria-Bertani (LB) medium supplemented with 2 g/L of sodium decanoate, all the recombinant E. coli strains synthesized PHAs consisting of C4, C6, C8, and C10 monomer units. The monomer composition of PHA was dependent on
the E. coli strain used. When the fadA mutant E. coli was employed, PHA containing up to 63 mol% of 3-hydroyhexanoate was produced. In fadB and fadAB mutant E. coli strains, 3-hydroxybutyrate (3HB) was efficiently incorporated into PHA up to 86 mol%. Cultivation of recombinant fadA and/or fadB mutant E. coli strains in LB medium containing 10 g/L of sodium gluconate and 2 g/L of sodium decanoate resulted in the production of PHA
copolymer containing a very high fraction of 3HB up to 95 mol%. Since the material properties of PHA copolymer consisting
of a large fraction of 3HB and a small fraction of medium-chain-length 3HA are similar to those of low-density polyethylene,
recombinant E. coli strains constructed in this study should be useful for the production of PHAs suitable for various commercial applications. 相似文献
6.
Dien Bruce S. Nichols Nancy N. O'Bryan Patricia J. Bothast Rodney J. 《Applied biochemistry and biotechnology》2000,84(1-9):181-196
Two new ethanologenic strains (FBR4 and FBR5) of Escherichia coli were constructed and used to ferment corn fiber hydrolysate. The strains carry the plasmid pLO1297, which contains the genes
from Zymomonas mobilis necessary for efficiently converting pyruvate into ethanol. Both strains selectively maintained the plasmid when grown anaerobically.
Each culture was serially transferred 10 times in anaerobic culture with sugar-limited medium containing xylose, but noselective
antibiotic. An average of 93 and 95% of the FBR4 and FBR5 cells, respectively, maintained pLO1297 in anaerobic culture. The
fermentation performances of the repeatedly transferred cultures were compared with those of cultures freshly revived from
stock in pH-controlled batch fermentations with 10% (w/v) xylose. Fermentation results were similar for all the cultures.
Fermentations were completed within 60 h and ethanol yields were 86–92% of theoretical. Maximal ethanol concentrations were
3.9–4.2% (w/v). The strains were also tested for their ability to ferment corn fiber hydrolysate, which contained 8.5% (w/v)
total sugars (2.0% arabinose, 2.8% glucose, and 3.7% xylose). E. coli FBR5 produced more ethanol than FBR4 from the corn fiber hydrolysate. E. coli FBR5 fermented all but 0.4% (w/v) of the available sugar, whereas strain FBR4 left 1.6% unconsumed. The fermentation with
FBR5 was completed within 55 h and yielded 0.46 g of ethanol/g of available sugar, 90% of the maximum obtainable.
Author to whom all correspondence and reprint requests should be addressed.
Names are necessary to report factually on available data. However, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by USDA im plies no approval of the product to the exclusion of others that may also
be suitable. 相似文献
7.
The inflence of extremely low-frequency (ELF) electromagnetic fields on Escherichia coli cultures in submerse fermentation was studied. The fermentation processes were carried out recycling the culture medium externally
through a stainless steel tube inserted in a magnetic field generator (solenoid). The exposure time and electromagnetic induction
were varied in a range of 1 to 12 h and 0.010 to 0.10 T, respectively, according to a Box-Wilson Central Composite Designs
of face centered with five central points. Growth of E. coli could be altered (stimulated or inhibited) under magnetic fieldinduced effects. E. coli culturesexposed at 0.1 T during 6.5 h exhibited changes in its viability compared to unexposed cells, which was 100 times
higher than the control. The magnetic field generator associated with the cellular suspension recycle is a new way of magnetic
treatment in fermentation processes and could be appropriate to industrial scale up. 相似文献
8.
The cellular response of a heat-shocked controlled chemostat of Escherichia coli JM105 [pSH101] was characterized and compared to that of a similar culture induced by isopropyl-β-d-thiogalactopyranoside (IPTG). The proteases elicited by the IPTG pulse were previously shown to be upregulated by the stringent
stress response and were shown here to be upregulated by heat shock, although to a lesser extent. Owing to the apparent overlap
between these responses, a relaxed mutant (rel
−, devoid of the stringent response; JM109) was examined for its response to both a chemically imposed stringent response and
to IPTG induction in controlled chemostats. There was no significant upregulation of protease activity under either imposed
stress. More important, a nine-fold increase of chloramphenicol acetyltransferase (CAT) activity was found for the IPTG-induced
relaxed mutant culture. Additionally, the responses from heat shock and IPTG induction were examined in batch cultures. The
culture that was simultaneously IPTG-induced and heat-shocked was observed to have the highest CAT activity as well as the
most rapid loss in activity after a maximum. Control experiments indicated that the heat shock did not affect loss of CAT
activity; instead, the loss of activity correlated with the amount of CAT synthesized. Furthermore, an increase in CAT expression
was found during heat shock. Results indicated that heat shock and, alternatively, the use of stringent response-mutant hosts
could both be used to facilitate increased recombinant protein yields in the E. coli expression system. 相似文献
9.
Although the mechanisms of eukaryotic chromosome segregation and cell division have been elucidated to a certain extent, those for bacteria remain largely unknown. Here we present a computational string model for simulating the dynamics of Escherichia coli chromosome segregation. A novel thermal-average force field accounting for stretching, bending, volume exclusion, friction and random fluctuation is introduced. A Langevin equation is used to simulate the chromosome structural changes. The mechanism of chromosome segregation is thereby postulated as a result of free energy-driven structural optimization with replication introduced chromosomal mass increase. Predictions of the model agree well with observations of fluorescence labeled chromosome loci movement in living cells. The results demonstrate the possibility of a mechanism of chromosome segregation that does not involve cytoskeletal guidance or advanced apparatus in an E. coli cell. The model also shows that DNA condensation of locally compacted domains is a requirement for successful chromosome segregation. Simulations also imply that the shape-determining protein MreB may play a role in the segregation via modification of the membrane pressure. 相似文献
10.
Guosheng Liu Zhilin Ran Hailei Wang Yi Liu Ping Shen Yan Lu 《Frontiers of Chemistry in China》2008,3(1):70-75
Biological effect of rare-earth lanthanum nitrate on the growth of Escherichia coli B was studied using the calorimetric method. There were exceptional changes on the growth thermogenic curves for high concentrations
of lanthanum nitrate. For example, the peak high, the total quantity of heat (Q) of cultures and the growth rate constants (k) are evidently increased when compared with normal E. coli B cultures. When the concentration of lanthanum nitrate was at 300 mg/L and 500 mg/L, and Q of the cultures reached 3.89 and 2.54 times of normal cultures, respectively. The survivability of cells and the biomass
of the cultures were measured using biological methods and the results show that the growth and multiplication of cells were
inhibited and that the biomass decreased at high concentration of lanthanum nitrate. These revealed that the inhibiting cells
discharged more quantity of heat than the normal growing cells. We named this phenomenon as “eruption of heat”. It was suggested
that the mechanism for the eruption of heat was that La3+ ion damages the outer cell membrane and increases its permeability and the proton-electron potential energy across the cell
membrane was reduced or couldn’t even be initiated. Energy could not be translated into ATP effectively in the course of oxidative
phosphorylation resulting in heat release. So, the growth of the cells was inhibited due to scarceness of energy ATP.
__________
Translated from Acta Chimica Sinica, 2007, 65(10): 917–922 [译自: 化学学报] 相似文献
11.
An efficient system for the production of (R)-hydroxyalkanoicacids (RHAs) was developed in natural polyhydroxyalkanoate (PHA)-producing bacteria and recombinant Escherichia coli. Acidic alcoholysis of purified PHA and in vivo depolymerization of PHA accumulated in the cells allowed the production of
RHAs. In recombinant E. coli, RHA production was achieved by removing CoA from (R)-3-hydroxyacyl-CoA and by in vivo depolymerization of PHA. When the recombinant E. coli harboring the Ralstonia eutropha PHA biosynthesis genes and the depolymerase gene was cultured in a complex or a chemically defined medium containing glucose,
(R)-3-hydroxybutyric acid (R3HB) was produced as monomers and dimers. R3HB dimers could be efficiently converted to monomers
by mild alkaline heat treatment. A stable recombinant E. coli strain in which the R. eutropha PHA biosynthesis genes were integrated into the chromosome disrupting the pta gene was constructed and examined for the production of R3HB. When the R. eutropha intracellular depolymerase gene was expressed by using a stable plasmid containing the hok/sok locus of plasmid R1, R3HB could be efficiently produced. 相似文献
12.
Takahashi CM Takahashi DF Carvalhal ML Alterthum F 《Applied biochemistry and biotechnology》1999,80(3):193-203
Escherichia coli KO11, in which the genes pdc (pyruvate decarboxylase) and adh (alcohol dehydrogenase) encoding the ethanolpathway from Zymomonas mobili were inserted into the chromosome, has been shown to metabolize all major sugars that are consituents of hemicellulosic hydrolysates
to ethanol, in anaerobic conditions. However, the growth and fermentation performance of this recombinant bacteria may be
affected by acetic acid a potential inhibitor present in hemicellulose hydrolysates in a range of 2.0–15.0 g/L. It was observed
that acetate affected the growth of E. coli KO11, prolonging the lag phase and inducing loss of biomass production and reduction of growth rate. At lower pH levels,
the sensitivity to acetic acid was enhanced owing to the increased concentration of the protonated species. On the other hand,
the recombinant bacteria showed a high tolerance to acetic acid regarding fermentative performance. In Luria broth medium
with glucose or xylose as a single sugar source, it was observed that neither yield nor productivity was affected by the addition
of acetate in a range of 2.0–12.0 g/L, suggesting some uncoupling of the growth vs ethanol production. 相似文献
13.
Functional expression of a β-d-1,4 glucanase-encoding gene (egl1) from a filamentous fungus was achieved in both Escherichia coli and Saccharomyces cerevisiae using a modified version of pRS413. Optimal activity of the E. coli-expressed enzyme was found at incubation temperatures of 60°C, whereas the enzyme activity was optimal at 40°C when expressed
by S. cerevisiae. Enzyme activity at different pH levels was similar for both bacteria and yeast, being highest at 5.0. Yeast expression resulted
in a highly glycosylated protein of approx 60 kDa, compared to bacterial expression, which resulted in a protein of 30 kDa.
The hyperglycosylated protein had reduced enzyme activity, indicating that E. coli is a preferred vehicle for production scale-up. 相似文献
14.
Penna Thereza Christina Vessoni Chiarini Eb Machoshvili Irene Alexeevna Ishii Marina Pessoa Adalberto 《Applied biochemistry and biotechnology》2002,98(1-9):791-802
The recombinant green fluorescent protein (gfp
uv
) was expressed by Escherichia coli DH5-α cells transformed with the plasmid pGFPuv. The gfp
uv
was selectively permeabilized from the cells in buffer solution (25 mM Tris-HCl, pH 8.0), after freezing (−70°C for 15 h), by four freeze (−20°C)/thaw cycles interlaid by sonication. The average
content of released gfp
uv
(experiment 2) was 7.76, 34.58, 39.38, 12.90, and 5.38%, for the initial freezing (−70°C) and the first, second, third and
fourth freeze/thaw cycles, respectively. Superfusion on freezing was observed between −11°C and −14°C, after which it reached
−20°C at 0.83°C/min. 相似文献
15.
The influence of total organic carbon (TOC), pH, and mating temperature on transfer of chromium-resistant plasmid between
Escherichia coli strains in terms of variation in the number of transconjugants formed and variation in transfer frequency was investigated.
In vitro transfer was studied in five chromate-tolerant E. coli strains isolated from tannery effluent using E. coli K12 J62 (Nalr Lac−) as a recipient. Conjugal transfer of different selection markers was observed in three strains. The study was carried out
in sterile wastewater. A gradual decrease was observed both in the number of transconjugants and in transfer frequencies as
the concentration of TOC in the mating medium descended from 10,095 to 1.2 mg of C/L, obtaining the maximum values with a
TOC concentration of 10,095 mg of C/L. The number of transconjugants and the transfer frequency were maximum at 30°C. However,
neither the transfer frequency nor the transconjugant number varied significantly in the range of pHs assayed. The strains
were also found resistant to different heavy metals and antibiotics. Curing of these strains resulted in loss of one or more
resistance markers indicating the plasmid-borne resistance. It is inferred that plasmid transfer by conjugation occurs in
wastewater bodies within a wide range of conditions. 相似文献
16.
Hong Kui Leung Yun Chung Kwok Sui Yi Law Kin Ho Lo Wai Hung Chua Hong Yu Peter Hoi Fu 《Applied biochemistry and biotechnology》2000,84(1-9):381-390
Construction and comparison of recombinant Escherichia coli strains harboring the polyhydroxybutyrate (PHB) operon from Ralstonia entropha using vectors possessing different promotors, as well as the production of PHB from soy waste by the recombinant strain,
are reported. The lac promotor was the most efficient on expression of the phb operon among the three promotors studied: i.e., lac promotor, T7 promotor and the normal σ70 promotor. The pKS/PHB was the most efficient plasmid for phboperon expression among the three plasmids used: i.e., pKS−, pAED4, and pJM9131. It was observed that isopropyl-β-d-thiogalactopyranoside was not required for the induction of the expression of phb operon. The cell dry wt and polyhydroxyalkan cote content by E. coli XL-1 Blue (pKS/PHB) were 3.025 g/L and 27.83%, respectively. 相似文献
17.
Kin-Ho Law Pui-Ling Chan Wai-Sum Lau Yin-Chung Cheng Yun-Chung Leung Wai-Hung Lo Hugh Lawford Hoi-Fu Yu 《Applied biochemistry and biotechnology》2004,114(1-3):361-372
Plastic wastes constitute a worldwide environmental problem, and the demand for biodegradable plastics has become high. One
of the most important characteristics of microbial polyesters is that they are thermoplastic with environmentally degradable
properties. In this study, pUC 19/PHA was cloned and transformed into three different Escherichia coli strains. Among the three strains that were successfully expressed in the production of polyhydroxyalkanoates (PHA), E. coli HMS174 had the highest yield in the production of poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (P[HB-HV]). The cell dry
weight and PHA content of recombinant HMS174 reached as high as 10.27 g/L and 43% (w/w), respectively, in fed-batch fermentor
culture. The copolymer of PHA, P(HB-HV), was found in the cells, and the biopolymers accumulated were identified and analyzed
by gas chromatography, proton nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. We demonstrated
clearly that the E. coli host for PHA production has to be carefully selected to obtain a high yield. The results obtained indicated that a superior
E. coli with high PHA production can be constructed with a desirable ratio of P(HB-HV), which has potential applications in industry
and medicine. 相似文献
18.
L. N. Yang F. Xu L. X. Sun Z. C. Tan H. D. Tan Z. B. Zhao J. G. Liang 《Journal of Thermal Analysis and Calorimetry》2006,85(3):807-810
A microcalorimetric
technique based on the bacterial heat output was applied to evaluate the influence
of antibiotics PIP (Piperacillin Sodium)
and composite preparation of PIP and SBT (Sulbactam
Sodium) on the growth of E. coli
DH5α. The power–time curves of the growth metabolism of E. coli DH5α were studied using a TAM Air Isothermal
Microcalorimeter at 37°C. By analyzing the power–time curves, the
parameters such as growth rate constants (k),
inhibitory ratio (I), the maximum heat
power (P
m) and the
time of the maximum heat power (t
m)
were obtained. The results show that different concentrations of antibiotics
affect the growth metabolism of E. coli
DH5α. The PIP in the concentration range of 0–0.05 μg mL–1
has a stimulatory effect on the E. coli
DH5α growth, while the PIP of higher concentrations (0.05 –0.25
μg mL–1) can inhibit its growth. It seems
that the composite preparation composed of PIP and SBT cannot improve the
inhibitory effect on E. coli DH5α
as compared with the PIP. 相似文献
19.
Dr. Carolina Fontana Prof. Dr. Andrej Weintraub Prof. Dr. Göran Widmalm 《ChemistryOpen》2015,4(1):47-55
Shiga-toxin-producing Escherichia coli (STEC) is an important pathogen associated to food-borne infection in humans; strains of E. coli O181, isolated from human cases of diarrhea, have been classified as belonging to this pathotype. Herein, the structure of the O-antigen polysaccharide (PS) from E. coli O181 has been investigated. The sugar analysis showed quinovosamine (QuiN), glucosamine (GlcN), galactosamine (GalN), and glucose (Glc) as major components. Analysis of the high-resolution mass spectrum of the oligosaccharide (OS), obtained by dephosphorylation of the O-deacetylated PS with aqueous 48 % hydrofluoric acid, revealed a pentasaccharide composed of two QuiNAc, one GlcNAc, one GalNAc, and one Glc residue. The 1H and 13C NMR chemical shift assignments of the OS were carried out using 1 D and 2 D NMR experiments, and the OS was sequenced using a combination of tandem mass spectrometry (MS/MS) data and NMR 13C NMR glycosylation shifts. The structure of the native PS was determined using NMR spectroscopy, and it consists of branched pentasaccharide repeating units joined by phosphodiester linkages: →4)[α-l-QuipNAc-(1→3)]-α-d-GalpNAc6Ac-(1→6)-α-d-Glcp-(1→P-4)-α-l-QuipNAc-(1→3)-β-d-GlcpNAc-(1→; the O-acetyl groups represent 0.4 equivalents per repeating unit. Both the OS and PSs exhibit rare conformational behavior since two of the five anomeric proton resonances could only be observed at an elevated temperature. 相似文献
20.
Capillary electrophoresis approaches have been utilized for the study of bacteria under specific experimental conditions.
The main objective within our research work was to study electrophoretic behaviors of Pseudomonas aeruginosa by means of capillary electrophoresis with UV and fluorescence detection. Edwardsiella tarda and Enteropathogenic escherichia coli were also included in the study. The results showed that proper pretreatment (vortexing or sonication) for each bacterial
sample before injection was necessary to disperse the clusters of cells, which is helpful to observe the single peaks and
better peak shape of bacteria during electrophoresis. Apart from this, it was found that ionic strength of buffer affected
mobilities of Pseudomonas aeruginosa as a result of increasing of buffer concentration from 25 mM to 150 mM. Moreover, sharp and single peaks were still observed
without significant increase of noise in the concentration range. Eventually, mixtures of bacteria were well separated under
optimized separation conditions with UV and fluorescence detection. In the mean time, comparison of concentration sensitivities
for Pseudomonas aeruginosa by UV and fluorescence detection was made. Blue light emitting diode induced fluorescence detection was found to be more
sensitive (8.5-fold higher) than UV detection with home-made fluorescence detection system. Generally, proposed CE methods for the analysis of bacteria could be potentially valuable for the monitoring of bacteria contamination in real life. 相似文献