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1.
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
2.
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
3.
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
4.
The inclusion of vanadocene dichloride (VDC) and 1,1′-dimethyl vanadocene dichloride (MeVDC) into cyclodextrines (α-CD, β-CD
and γ-CD) was studied by EPR spectroscopy. It was found that VDC and MeVDC with β-CD and γ-CD form true inclusion compounds,
but with α-CD, VDC and MeVDC gave only fine dispersion mixtures. The inclusion was validated by anisotropic EPR spectra of
solid samples. In addition, the antimicrobial was validated by anisotropic EPR spectra of solid samples. In addition, the
antimicrobial behavior (against E. coli) of each of the complexes was determined. It was established that not only did VDC and MeVDC cause elongation of E. coli, but also the new vanadocene inclusion complexes were effective in this regard. 相似文献
5.
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
6.
Kaijun Xiang Yan Qiao Chi Bun Ching Chang Ming Li 《Electrochemistry communications》2009,11(8):1593-1595
Faster electron transfer between bacteria and electrodes in microbial fuel cells can significantly improve the power density of MFCs for practical applications. A recombinant Escherichia coli (E. coli) strain overexpressing glycerol dehydrogenase (GldA) was engineered as the MFC biocatalyst instead of the natural bacteria. Efficient mediators were produced in the fuel cell with this engineered E. coli resulting in lower polarization and much higher power density than with natural E. coli and E. coli with electro-evolved mediators. For the first time, we demonstrate that engineering E. coli by introduction of appropriate oxidoreductase via gene manipulation can greatly improve the rate of electron transfer. This work provides an efficient and economic approach to biologically engineering bacteria for improving MFC performance. 相似文献
7.
Jorge Casas-Sanchez M. Asuncion Alsina Mathias K. Herrlein Concepció Mestres 《Colloid and polymer science》2007,285(12):1351-1360
Oleuropein, a secoiridoid glycoside extracted from the olive tree, Olea europaea L., has been described as showing antibacterial properties. However, the exact mechanism of these antimicrobial properties
is not yet well understood. In the present study, we have studied the interaction of oleuropein with phosphatidylglycerol
(PG) as a model membrane for Staphylococcus aureus (S. aureus) (Gram-positive bacteria) and phosphatidylethanolamine and Escherichia coli (E. coli) lipid extract as a model membrane for E. coli (Gram-negative bacteria). The study has been carried out using monolayers as model membranes and using kinetics at constant
area and compression isotherms with Brewster angle microscopy (BAM) observations. The results show that oleuropein interacts
in higher extent with PG monolayers, which is related with its stronger antibacterial effect against Gram-positive bacteria.
The effects on the membrane are probably produced at the cell surface because oleuropein did not form stable mixed monolayers
with the lipids assayed at the air/water interface. 相似文献
8.
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
9.
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
10.
11.
Krisztián Bogár 《Central European Journal of Chemistry》2005,3(1):63-71
(R, R)-(−)-N, N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminocobalt(II) was encapsulated into MCM-22 using the zeolite synthesis method. The
encapsulated catalyst proved to be active in the oxidation of α-methylstyrene with NaOCl with higher specific activity than
the homogeneous catalyst. At the same time, this encapsulated catalyst was completely inactive in the hydrolytic kinetic resolution
of racemic styrene oxide. This observation is in a good correlation with the assumption of the cooperative bimetallic mechanism
proposed by Annis and Jacobsen. 相似文献
12.
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
13.
Natarajan Raman Chinnathangavel Thangaraja Samuelraj Johnsonraja 《Central European Journal of Chemistry》2005,3(3):537-555
A novel tetradentate N2O2 type Schiff base, synthesized from 1-phenyl-2,3-dimethyl-4-aminopyrazol-5-one(4-aminoantipyrine) and 3-salicylidene-acetylacetone,
forms stable complexes with transition metal ions such as Cu
II
, Ni
II
, Co
II
and Zn
II
in ethanol. Microanalytical data, magnetic susceptibility, IR, UV-Vis.,1H-NMR, ESR and Mass spectral techniques were used to confirm the structures. Electronic absorption spectra of the complexes
suggest a square-planar geometry around the central metal ion. These complexes show higher conductance values, supporting
their electrolytic nature. The monomeric nature of the complexes was confirmed from their magnetic susceptibility values.
Cyclic voltammogram of the copper(II) and nickel(II) complexes in DMSO solution at 300 K were recorded and the results are
discussed. The X-band ESR spectra of the copper complex were recorded and the molecular orbital coefficient values were calculated
from the spectra. The in vitro antimicrobial activities of the investigated compounds were tested against bacteria such as Klebsiella pneumoniae, Staphylococcus aureus, Bacillus subtilis and Escherichia coli and fungi like Aspergillus niger and Rhizoctonia bataicola. Most of the metal chelates show higher antimicrobial activity for the above microorganisms than that of the free ligand. 相似文献
14.
Rupesh KR Padma KR Saravanan P Jayachandran S 《Applied biochemistry and biotechnology》2007,141(2-3):161-174
Background: Seeds ofLathyrus sativus, a legume plant, contain 3-oxalyl and 2,3-dioxalyl DAP (O-DAP), neurotoxins which when consumed causes Neurolathyrism or
Osteolathyrism, in humans, affecting nervous system and bone formation respectively. Some microorganisms viz virulent and
non-virulentSalmonella typhimurium, Salmonella typhi and Pseudomonad have been shown to detoxifyL-α,β-diaminopropionate (DAP), the immediate precursor of O-DAP.
Result: The gene coding for diaminopropionate ammonia lyase (DAPAL) which detoxifies DAP was cloned from nonvirulentS. typhimurium PU011 intoEscherichia coli DH5α and the nucleotides sequenced (1212 bp). Whereas the specific enzyme activity of DAPAL obtained from recombinantE. coli PU018 was 0.346 U/mg, the specific activity of the enzyme from nonvirulentS. typhimurium PU011 was 0.351 U/mg. The DAPAL corresponding to 43 kDa protein was found both in nonvirulentS. typhimurium PU011 andE. coli PU018. The Km value was found to be 0.740 mM and 0.680 mM forS. typhimurium PU011 and 0.741 mM and 0.683 mM forE. coli PU018 when grown in minimal medium (MM+DAP) andL. sativus seed extracts respectively, indicating that both of them were capable of utilizing the neurotoxins present inL. sativus seeds. The biomass, enzyme production and the effect of pH and temperature on DAPAL enzyme activity from both non-virulentS. typhimurium PU011 andE. coli PU018 were found to be similar.
Conclusion: The recombinantE. coli PU018 as well as non-virulentS. typhimurium PU011 are as good as pathogenicS. typhimurium in detoxifying DAP, the immediate precursor of O-DAP present inL. sativus seeds. 相似文献
15.
以手性化合物L-青霉胺、D-青霉胺、L-半胱氨酸为单一修饰剂或组合成双修饰剂,合成不同修饰剂修饰的CdSe纳米晶。对最佳合成条件如配料比,反应pH值,回流温度,回流时间进行了优化,对CdSe纳米晶发光强度及稳定性进行了系统研究。结果发现双修饰剂修饰的纳米晶比单修饰剂修饰的纳米晶荧光强度高,稳定性好;双修饰剂中第二修饰剂的空间位阻小的修饰效果好;不同手性修饰剂之间能以稳定方式结合的修饰效果好。研究了CdSe纳米晶对生物大分子的识别,仅发现核酸对CdSe纳米晶有明显的作用,用CdSe纳米晶作为荧光探针对大肠杆菌进行标记。 相似文献
16.
K. W. Lo H. Chua H. Lawford W. H. Lo Peter H. F. Yu 《Applied biochemistry and biotechnology》2005,122(1-3):575-580
The effects of saturated and unsaturated fatty acids (lauric acid, palmitic acid, steric acid, oleic acid, linoleic acid,
soybean oil) on Sphaerotilus natans, 0B17 (Pseudomonas sp.), and recombinant Escherichia coli DH5(/pUC19/CAB were studied. Oleic acid enhances Poly-3-hydroxybutyrate (PHB) production in these three bacterial strains, suggesting that
the single double bond of the acid activates the polyhydroxylkanoate accumulation enzymatic reaction. Under the effect of
lauric acid and linoleic acid, the growth of S. natans and 0B17 were totally inhibited. However, the enhanced PHB accumulation in recombinant E. coli was observed. 相似文献
17.
Ripp S Jegier P Johnson CM Brigati JR Sayler GS 《Analytical and bioanalytical chemistry》2008,391(2):507-514
Escherichia coli O157:H7 remains a continuous public health threat, appearing in meats, water, fruit juices, milk, cheese, and vegetables,
where its ingestion at concentrations of perhaps as low as 10 to 100 organisms can result in potent toxin exposure and severe
damage to the lining of the intestine. Abdominal pain and diarrhea develop, which in the very young or elderly can progress
towards hemolytic uremic syndrome and kidney failure. To assist in the detection of E. coli O157:H7, a recombinant bacteriophage reporter was developed that uses quorum sensing (luxI/luxR) signaling and luxCDABE-based bioluminescent bioreporter sensing to specifically and autonomously respond to O157:H7 serotype E. coli. The bacteriophage reporter, derived from phage PP01, was tested in artificially contaminated foodstuffs including apple
juice, tap water, ground beef, and spinach leaf rinsates. In apple juice, detection of E. coli O157:H7 at original inoculums of 1 CFU mL−1 occurred within approximately 16 h after a 6-h pre-incubation, detection of 1 CFU mL−1 in tap water occurred within approximately 6.5 h after a 6-h pre-incubation, and detection in spinach leaf rinsates using
a real-time Xenogen IVIS imaging system resulted in detection of 1 CFU mL−1 within approximately 4 h after a 2-h pre-incubation. Detection in ground beef was not successful, however, presumably due
to the natural occurrence of quorum sensing autoinducer (N-3-(oxohexanoyl)-l-homoserine lactone; OHHL), which generated false-positive bioreporter signals in the ground beef samples. 相似文献
18.
M. Hnaiein W.M. Hassen A. Abdelghani C. Fournier-Wirth J. Coste F. Bessueille D. Leonard N. Jaffrezic-Renault 《Electrochemistry communications》2008,10(8):1152-1154
We report a new approach for immunoassays based on magnetite nanoparticles for Escherichia coli (E. coli) detection using conductometric measurements. Biotinylated antibodies, anti-E. coli, were immobilized on streptavidin modified magnetite nanoparticles by biotin–streptavidin interaction. A layer of functionalized nanoparticles were directly immobilized on the conductometric electrode using glutaraldehyde cross-linking.The specific test with E. coli cells and the non specific test using Staphylococcus epidermidis (S. epidermidis) were investigated by conductometric measurements. Results show a good response as a function of antigen additions. The detection of 1 CFU/ml of E. coli induces a conductivity variation of 35 μS. The negative test shows good selectivity using the conductometric immunosensor. Conductometric measurements allow to detect 500 CFU/l. 相似文献
19.
Dujuan Li Yangyang Feng Ling Zhou Zunzhong Ye Jianping Wang Yibin Ying Chuanmin Ruan Ronghui Wang Yanbin Li 《Analytica chimica acta》2011,(1):9450
A label-free capacitive immunosensor based on quartz crystal Au electrode was developed for rapid and sensitive detection of Escherichia coli O157:H7. The immunosensor was fabricated by immobilizing affinity-purified anti-E. coli O157:H7 antibodies onto self-assembled monolayers (SAMs) of 3-mercaptopropionic acid (MPA) on the surface of a quartz crystal Au electrode. Bacteria suspended in solution became attached to the immobilized antibodies when the immunosensor was tested in liquid samples. The change in capacitance caused by the bacteria was directly measured by an electrochemical detector. An equivalent circuit was introduced to simulate the capacitive immunosensor. The immunosensor was evaluated for E. coli O157:H7 detection in pure culture and inoculated food samples. The experimental results indicated that the capacitance change was linearly correlated with the cell concentration of E. coli O157:H7. The immunosensor was able to discriminate between cellular concentrations of 102–105 cfu mL−1 and has applications in detecting pathogens in food samples. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were also employed to characterize the stepwise assembly of the immunosensor. 相似文献
20.
Amperometric determination of live <Emphasis Type="Italic">Escherichia coli</Emphasis> using antibody-coated paramagnetic beads 总被引:2,自引:0,他引:2
Boyaci IH Aguilar ZP Hossain M Halsall HB Seliskar CJ Heineman WR 《Analytical and bioanalytical chemistry》2005,382(5):1234-1241
Detecting and enumerating fecal coliforms, especially Escherichia coli, as indicators of fecal contamination, are essential for the quality control of supplied and recreational waters. We have developed a sensitive, inexpensive, and small-volume amperometric detection method for E. coli -galactosidase by bead-based immunoassay. The technique uses biotin-labeled capture antibodies (Ab) immobilized on paramagnetic microbeads that have been functionalized with streptavidin (bead–Ab). The bead–Ab conjugate captures E. coli from solution. The captured E. coli is incubated in Luria Bertani (LB) broth medium with the added inducer isopropyl -D-thiogalactopyranoside (IPTG). The induced -galactosidase converts p-aminophenyl -D-galactopyranoside (PAPG) into p-aminophenol (PAP), which is measured by amperometry using a gold rotating disc electrode. A good linear correlation (R2=0.989) was obtained between log cfu mL–1 E. coli and the time necessary to product a specific concentration of PAP. Amperometric detection enabled determination of 2×106 cfu mL–1 E. coli within a 30 min incubation period, and the total analysis time was less than 1 h. It was also possible to determine as few as 20 cfu mL–1 E. coli under optimized conditions within 6–7 h. This process may be easily adapted as an automated portable bioanalytical device for the rapid detection of live E. coli. 相似文献