JOURNAL OF ELECTRONIC MATERIALS
·
2019
·Vol. 48
·期 12
·7960-7969
·
IF 1.676
Huang Yanyan,Wu Zunyi,Zhao Guangying,Dou Wenchao
In this study, we used gold nanoparticles (AuNPs) modified screen-printed carbon electrodes (SPCE) with a large area working electrode for the detection of Escherichia coli O157:H7 ( E. coli O157:H7) in a direct method by antigen–antibody specificity binding. We compared four SPCE with different working electrode diameters (2 mm, 2.5 mm, 3 mm and 3.5 mm) to choose the optimum one. After electrodepositing chloroauric acid (HAuCl 4 ) on SPCE, a working electrode diameter of 3.5 mm SPCE show the maximum signal. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electrochemical sensor. With the combination of large area working electrode and the great property of AuNPs, this immunoassay plays an ideal detection range from 1.19 × 10 3 CFU mL −1 to 1.19 × 10 9 CFU mL −1 and the limit of detection is 5.94 × 10 2 CFU mL −1 (equivalent to 3.5 CFU) at a signal-to-noise ratio of 3. The immunoassay showed the acceptable specificity, reproducibility, and stability for detection of E. coli O157:H7. These results indicate that this immunoassay has a promising application in the food safety industry.
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MICROCHIMICA ACTA
·
2019
·Vol. 187
·期 1
·1-10
·
IF 5.479
Zhang Xuzhi,Wang Xiaochun,Yang Qianqian,Jiang Xiaoyu,Li Yang,Zhao Jun,Qu Keming
A method is described to determine viable populations of Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ). The method employs aptamer-magnetic separation combined with resistivity based detection. The bacteria were separated by means of aptamer-functionalized magnetic beads. They were then quantified by measuring their growth kinetics through time-dependent conductivity changes of culture media. The time-course of growth was logged by real-time and contactless measurements that yielded starting concentrations from the duration of lag intervals prior to the log phase of growth. In pure water samples, the linear ranges for measuring E. coli and S. aureus cells are 2.5 × 10 3 –2.5 × 10 8 CFU·mL −1 and 4.1 × 10 3 –4.1 × 10 8 CFU·mL −1 , respectively. In spiked tap water samples, the lower limits of detection are 2.3 × 10 4 CFU·mL −1 and 4.0 × 10 3 CFU·mL −1 for E. coli and S. aureus , with recoveries of 87.0–108.7% and 92.5–105.0%, respectively. The relative standard deviation of these measurements (10.0%) is below that of plate counting method (13.9%). The presence of micro/nanoparticles such as magnetic beads or selenium nanoparticles in the culture media does not interfere, unlike in case of automatted optical density monitoring. The E. coli and S. aureus cells captured on the aptamer-functionalized magnetic beads can be directly tested for their susceptibility to antibiotics. The process of magnetic separation and determination of load burden requires neither bulky, sophisticated equipment nor expensive reagents.
Aptamer-functionalized magnetic beads are used to selectively capture and separate E. coli and S. aureus cells in aqueous samples. They are directly transferred to a multichannel conductometric sensor for the quantification of viable bacteria via automated monitoring of their growth kinetics.
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BIOCHEMICAL ENGINEERING JOURNAL
·
2019
·
IF 3.371
Xiaoqiang Jia,Yun He,Dawei Jiang,Chang Liu,Wenyu Lu
Polycyclic aromatic hydrocarbons (PAHs) like phenanthrene are harmful to human health and are difficult to eliminate from environments. In this study, a phenanthrene degrading strain, Pseudomonas aeruginosa PH1, was isolated from oil-contaminated soil. An engineered co-culture consortium was subsequently constructed comprising two engineered bacterial strains, Escherichia coli HY1 and P. aeruginosa PH2, for use in phenanthrene bioremoval. E. coli HY1 harbored two modules of terminal dioxygenases and an electron transfer chain, while P. aeruginosa PH2 contained a module of catechol 1,2-dioxygenase. Phenanthrene removal rates by the wild-type degrader, P. aeruginosa PH1, were 45%, 43%, and 81%, in mineral salt medium supplemented with 100 mg/L phenanthrene, 100 mg/L phenanthrene and 2% (wt/vol) oil, and 100 mg/L phenanthrene and 2% (vol/vol) n -hexadecane, respectively. In contrast, the engineered co-culture consortium removed 71%, 80%, and 88% of the phenanthrene in the corresponding treatments, thus achieving much higher removal efficiencies. Moreover, gas chromatography-mass spectrometry confirmed that the engineered co-culture consortium first oxidized phenanthrene to 9,10-dihydroxy phenanthrene and 1,2-dihydroxy phenanthrene and then metabolized these intermediates via catechol to carbon dioxide and water. During this process, E. coli HY1 dominated the initial oxidation steps, while P. aeruginosa PH2 was primarily responsible for ring cleavage. These results indicate that the engineered co-culture consortium described here represents a potential alternative and attractive means to remove PAHs from natural environments.
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SENSORS AND ACTUATORS B-CHEMICAL
·
2015
·
IF 4.097
Xue-cheng Sun,Zhen Yang,Chong Lei,Yan Liu,Lei Guo,Yong Zhou
A novel bio-sensing system based on a micro-fluxgate and use of magnetic beads labels was developed for detection of Escherichia coli O157H:H7. The micro fluxgate sensor was fabricated using standard microfabrication processes. Magnetic core of the sensor was made using Fe-based amorphous ribbon core and a 3-D magnetic sensitive element was made of Cu solenoid coils. Response of the micro-fluxgate-based bio-sensing system to superparamagnetic Dynabead was first evaluated with different concentrations of Dynabeads. It was found that a concentration as low as 10 ng/ml could be detected with an external dc magnetic field ranging from 450 μT to 700 μT. Double antibody sandwich assay was employed in preparation of E. coli O157H:H7 samples. Detection of E. coli O157H:H7 antigens at different concentrations were demonstrated. A minimum detectable concentration of 100 CFU/ml was observed for this bio-sensing system. On account of the detection performance and other advantages such as miniaturization, portability and stability, this bio-sensing system is a potential candidate for rapid analysis E. coli O157:H7 and other pathogenic bacteria . It is also of considerable interest for biomedical applications employing known specific binding of target and labels.
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JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
·
2013
·
IF 2.906
Ting Wu,Xixi Zang,Mengying He,Siyi Pan,Xiaoyun Xu
Flavonoids are potential sources of natural preservatives. The inhibitory activities of three polymethoxylated flavones (PMFs), three flavones, and four flavonols against Escherichia coli were determined using the microbroth dilution method. Flavonoid inhibitory activities against DNA gyrase from E. coli were estimated by DNA supercoiling. Kaempferol exhibited the greatest antibacterial activity [minimal inhibitory concentration (MIC) = 25 μg/mL], while nobiletin showed the lowest activity (MIC = 177 μg/mL). A good correlation was found between the pIC50 values and the corresponding pMIC values for the purified DNA gyrase (r = 0.9582). The structure–activity relationship analysis suggests that, for a good inhibitory effect, the hydroxyl group substitution at C-5 in the A ring and C-4′ in the B ring and the methoxyl group substitution at C-3 and C-8 in the A ring are essential. The presence of the hydroxyl group at C-6 in the A ring, C-3′ and C-5′ in the B ring, and C-3 in the C ring and the methoxyl group at C-3′ in the B ring greatly reduced inhibition of bacteria. These findings provide a theoretical basis for the development of high-bioactive and low-toxicity natural preservatives.
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BIOCHEMICAL ENGINEERING JOURNAL
·
2013
·
IF 2.579
Lidan Ye,Hongna Xu,Hongwei Yu
Esterase BioH is a critical enzyme for Biotin synthesis in Escherichia coli , which has been previously found to be active in the acylation of secondary alcohols and amines. Directed evolution towards improved acylation activity requires a high-throughput screening method. The aim of this study is to explore whether the acylation activity of BioH can be improved by directed evolution of its hydrolysis activity. A colorimetric method based on p -nitrophenyl butyrate hydrolysis was adopted in the high-throughput determination of hydrolysis activity. The wild-type BioH showed a hydrolysis activity of 18 U/mg, and the specific activities for α-phenylethanol and α-phenylethylamine acylation were 12.8 U/mg and 3.5 U/mg, respectively. After two rounds of directed evolution, seven mutants with improved hydrolysis activity were obtained, among which, K213E, Q70L/M170T and M197L/K213E also showed improvement in acylation activity. To further improve the acylation activity, site mutations were generated in different combinations at the four hot spots Q70L, M170T, M197L and K213E. Among the resulting mutants, Q70L/M197L/K213E showed the highest activity in α-phenylethylamine acylation with a 120% improvement, while Q70L/K213E had the highest α-phenylethanol acylation activity, which was improved by 70%. The results demonstrated that directed evolution of the hydrolysis activity might be a possible approach to improve the acylation activity of the esterase BioH.
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JOURNAL OF ENZYME INHIBITION AND MEDICINAL CHEMISTRY
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2013
·
IF 1.495
Weiqiang Lu,Junsheng Zhu,Shien Zou,Xi Li,Jin Huang
Human skin fibroblast collagenase also known as Matrix Metalloproteinase-1 (MMP-1) is a key enzyme in remodeling and degradation of extracellular matrix, and the inhibitors of human MMP-1 are effective drug candidates for the treatment of cancer. In this study, we report an improved method for high-level expression of soluble human MMP-1 catalytic domain (cd-MMP-1) in E.coli. The enzymatic activity is found maximum at pH 7.5 and temperature 40°C with a Km value of 13.02 µM. Effects of 17 structure-related flavonoids on MMP-1 activity are evaluated using a fluorescent assay, 6 inhibitors are identified with IC50 < 10 µM. Fisetin is the most active agent with an IC50 value of 1.35 µM and is identified as a mixed type inhibitor. Our improved soluble cd-MMP-1 expression method provides a basis for inhibitors identification and may be beneficial to discover novel anti-cancer agent targeting human MMP-1.
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BIOTECHNOLOGY LETTERS
·
2015
·Vol. 38
·期 1
·81-88
·
IF 1.591
Jiang Jingjie,Bi Huiping,Zhuang Yibin,Liu Shaowei,Liu Tao,Ma Yanhe
Objectives To achieve high production of rosmarinic acid and derivatives in Escherichia coli which are important phenolic acids found in plants, and display diverse biological activities. Results The synthesis of rosmarinic acid was achieved by feeding caffeic acid and constructing an artificial pathway for 3,4-dihydroxyphenyllactic acid. Genes encoding the following enzymes: rosmarinic acid synthase from Coleus blumei , 4-coumarate: CoA ligase from Arabidopsis thaliana , 4-hydroxyphenyllactate 3-hydroxylase from E. coli and d -lactate dehydrogenase from Lactobacillus pentosus , were overexpressed in an l -tyrosine over-producing E. coli strain. The yield of rosmarinic acid reached ~130 mg l −1 in the recombinant strain. In addition, a new intermediate, caffeoyl-phenyllactate (~55 mg l −1 ), was also produced by the engineered E. coli strain. Conclusion This work not only leads to high yield production of rosmarinic acid and analogues, but also sheds new light on the construction of the pathway of rosmarinic acid in E. coli .
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ELECTROPHORESIS
·
2016
·Vol. 37
·期 14
·2106-2111
·
IF 2.482
Wei Wang,Lihong Ma,Ping Lin,Kaixuan Xu
In this work, CE-LIF was employed to investigate the amino acid metabolites produced by Escherichia coli ( E. coli ) in microbial fuel cell (MFC). Two peptides, l -carnosine and l -alanyl-glycine, together with six amino acids, cystine, alanine, lysine, methionine, tyrosine, arginine were separated and detected in advance by a CE-LIF system coupled with a homemade spontaneous injection device. The injection device was devised to alleviate the effect of electrical discrimination for analytes during sample injection. All analytes could be completely separated within 8 min with detection limits of 20–300 nmol/L. Then this method was applied to analyze the substrate solution containing amino acid metabolites produced by E. coli . l -carnosine, l -alanyl-glycine, and cystine were used as the carbon, nitrogen, and sulfur source for the E. coli culture in the MFC to investigate the amino acid metabolites during metabolism. Two MFCs were used to compare the activity of metabolism of the bacteria. In the sample collected at the running time 200 h of MFC, the amino acid methionine was discovered as the metabolite with the concentrations 23.3 μg/L.
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JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
·
2025
·
IF 6.2
Ling Ma,Zhichao Chen,Xu Li,Weiwei Liu,Zichen Yu,Changgeng Li,Yu Gong,Qingyang Xu
Metabolic regulation and fermentation strategies limit the synthesis of tyramine. Here, a de novo synthetic tyramine-producing strain, LAN 25, was constructed. First, tyramine-producing strain was obtained by modifying the key metabolic nodes of tyrosine synthesis and overexpressing the tyrosine decarboxylase gene from Lactobacillus brevis. Then, a two-stage dissolved oxygen (DO)-controlled fermentation process was established in a 5 L fed-batch bioreactor. In the first stage, sufficient DO was supplied to accumulate tyrosine precursors, while in the second stage, limited DO was provided to promote tyramine synthesis. Next, ldhA and adhE were deleted to improve the strain’s robustness. To enhance the redox flux (ATP/ADP ratio) under limited DO conditions, the anaerobic promoter, Pvgb, was used to control the expression of a ppk-based ATP regeneration system in response to DO changes. Additionally, the tyrosine internal transport system was modified. Finally, a titer of 21.33 g/L of tyramine with a yield of 0.092 g/g glucose was obtained.
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CHEMOSPHERE
·
2017
·
IF 4.208
Can-Hui Deng,Ji-Lai Gong,Guang-Ming Zeng,Peng Zhang,Biao Song,Xue-Gang Zhang,Hong-Yu Liu,Shuang-Yan Huan
Nanotechnology has great potential in water purification . However, the limitations such as aggregation and toxicity of nanomaterials have blocked their practical application. In this work, a novel copper nanoparticles-decorated graphene sponge (Cu-GS) was synthesized using a facile hydrothermal method. Cu-GS consisting of three-dimensional (3D) porous graphene network and well-dispersed Cu nanoparticles exhibited high antibacterial efficiency against Esherichia coli when used as a bactericidal filter. The morphological changes determined by scanning electron microscope and fluorescence images measured by flow cytometry confirmed the involvement of membrane damage induced by Cu-GS in their antibacterial process. The oxidative ability of Cu-GS and intercellular reactive oxygen species (ROS) were also determined to elucidate the possible antibacterial mechanism of Cu-GS. Moreover, the concentration of released copper ions from Cu-GS was far below the drinking water standard, and the copper ions also have an effect on the antibacterial activity of Cu-GS. Results suggested that Cu-GS as a novel bactericidal filter possessed a potential application of water disinfection .
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MOLECULES
·
2017
·Vol. 22
·期 3
·432
·
IF 2.861
Rensen Ran,Huan Zeng,Dong Zhao,Ruiyuan Liu,Xia Xu
Microcin C7 (McC), widely distributed in enterobacteria, is a promising antibiotic against antibiotic resistance. Previous studies have demonstrated that the heptapeptide of McC is only responsible for recognizing the inner membrane transporterYejABEFto deliver McC into microbial cells, but lacks the capacity for inhibiting microbial cell growth. In this study, the effect of the heptapeptide (MR) and two analogues,N-formylated heptapeptide (f-MR) andN-aceylated heptapeptide (a-MR), on microbial cell growth were examined. It is surprising to find that MR not only inhibits the activity of intracellular β-galactosidase, respiratory chain dehydrogenases, and 6-phosphogluconate dehydrogenases (6PGDH), but it is also able to inhibitEscherichia coligrowth, and eventually leads to cell death at the lethal concentration of 5.34 mM within 10 min. The modification of MR results in a slight increase in the lethal concentration. Cell membrane integrity at the lethal concentration confirms that MR undergoes the inhibition effect, but not by destroying the cell membrane integrity. The novel property of MR provides a new insight into the Trojan horse strategy of McC and opens a new route for antibiotics design.Keywords:microcin C7;heptapeptide;cell growth;membrane integrity
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