ANALYTICAL BIOCHEMISTRY
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2018
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IF 2.275
Fanjun Zhu,Guangying Zhao,Wenchao Dou
Herein, a non-enzymatic sandwich-type electrochemical immunoassay was fabricated for quantitative monitoring of Escherichia coli O157:H7 ( E. coli O157:H7). Silica coated Fe 3 O 4 magnetic nanoparticles (Fe 3 O 4 @SiO 2 ) were modified with mouse anti- E. coli O157:H7 monoclonal antibody (Ab 1 ) to act as capture probes to reduce detection time and increase the sensitivity of the immunoassay . The Au@Pt nanoparticles were loaded on neutral red (NR) functionalized graphene to form composite complex rGO-NR-Au@Pt. rGO-NR-Au@Pt has high specific surface area and good biocompatibility. rGO-NR-Au@Pt was used as the carriers of detection antibodies (Ab 2 ). Au@Pt catalyzed the reduction of hydrogen peroxide (H 2 O 2 ) to detection of E. coli O157:H7 with the thionine (TH) as electron mediator to effectually amply the current signal. Under the optimized conditions, a linear relationship between the reduction peak current change (ΔI pc ) and the logarithm of the E. coli O157:H7 concentration is obtained in the range from 4.0 × 10 3 to 4.0 × 10 8 CFU mL −1 and the limit of detection (LOD) is 4.5 × 10 2 CFU mL -1 at a signal-to-noise ratio of 3. The immunoassay exhibits acceptable specificity, reproducibility and stability on the detection of E. coli O157:H7. Furthermore, the immunoassay showed good performance in pork and milk samples. The results suggest that this immunoassay will be promising in the food safety area.
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SENSORS AND ACTUATORS B-CHEMICAL
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2018
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IF 5.667
Jiao Li,Baoxin Li,Mei Liu
Development of effective pathogen detection systems is critical for human health. In this study, Escherichia coli ( E. coli ) O157:H7 as a model microorganism, mannose-modified polyethyleneimine copolymer particles (Man-PEI CPs) were one-step synthesized through nucleophilic addition between primary amine and aldehyde group, and the fluorescent Man-PEI CPs have been successfully applied for selective and sensitive detection of Escherichia coli . The Man-PEI CPs with highly solubility had an average particle diameter of 54.4 nm. The fluorescence quantum yields of Man-PEI CPs was 0.42. The fluorescent Man-PEIs could provide good targeting ability toward E. coli pili due to the selectively binding to the FimH lectin unit of mannose. In order to get good binding efficiency to E. coli , the ratio of polyethyleneimine to mannose during their synthesis was optimized. The fluorescence emission by Man-PEI CPs/ E. coli conjugate is closely related to the content of E. coli . Man-PEI CPs showed selective response towards E. coli and our assay exhibited potential practical applications for E. coli determination in water, beer and human urine. The simple, inexpensive and efficient preparation of Man-PEI CPs showed potential advantages in the detection of bacteria.
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ACS Sustainable Chemistry & Engineering
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2024
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IF 7.1
Meng-Qi Wang,Ming-Xin Sun,Han-Guang Li,Ze-Hua Wu,Jian-Zhong Xu
l-Hypaphorine (l-HYP) is an l-tryptophan-derived alkaloid with significant medicinal value. The objective of this study tried to use Escherichia coli as a chassis cell to produce l-HYP from glucose by fermentation. To do this, the optimized methyltransferases were first mined based on the data of the phylogenetic tree of methyltransferase, indicating that the methyltransferase from Mycobacterium smegmatis with two mutation sites (i.e., EgtDM252 V,E282A and MsE) was designed as the best enzyme for producing l-HYP using l-tryptophan as a substrate. After this, a mutant MsET163G with high catalytic efficiency was constructed by semirational directed evolution focusing on the substrate binding cavity. To achieve the self-supply of l-tryptophan (l-Trp) and S-adenosyl methionine (SAM) in E. coli, the biosynthetic pathway of l-Trp and SAM was reconstructed. As a result, the final strain E. coli HYP-12 could produce 200.5 ± 2.6 mg/L of l-HYP with a glucose conversion efficiency (α) of 2.01% in shake-flask fermentation. This is the first report on producing l-HYP from glucose by microbial fermentation, which provides a real possibility for industrial l-HYP production using environmentally friendly methods rather than extraction from plant and provides a general concept for constructing other nonendogenous products’ high-producing strains.
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Journal of Functional Foods
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2025
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IF 4
Zhaoxi Deng,Yanfei Ma,Kangwei Hou,Jinyan Dai,Yifan Zhong,Yingying Mao,Jinzhi Zhang,Haifeng Wang
Quorum sensing (QS) is an essential pathway for bacterial communication through autoinducers (AIs). The luxS gene involved in QS has been proven to regulate different behavior of Lactobacillus rhamnosus GG (LGG), whereas it is unclear whether the AI-2/LuxS system have beneficial effects the host by regulating LGG. Our aim was to investigate whether luxS mutation affects the ability of LGG to maintain intestinal microbiota homeostasis, intestinal barrier integrity and inflammatory immune responses in mice infected with Escherichia coli ( E. coli ). This study showed that both wild-type (WT) and luxS mutant (ΔluxS) of LGG can alleviate changes in the microbiota caused by E. coli by down-regulating the relative abundance of Parasturtella . Supplementation with WT and ΔluxS increased the CD4 + /CD8 + ratio in spleen, improved goblet cell numbers and enhanced Muc 2 secretion. Moreover, WT and ΔluxS decreases proinflammatory mediator levels by inhibiting MAPK and NF-κB signal transduction.
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MATERIALS LETTERS
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2012
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IF 2.307
Bing Sun,Zhi Qiao,Kun Shang,Hai Fan,Shiyun Ai
In this paper, novel uniformly distributed silver sulfide/bismuth sulfide nanocomposites (Ag 2 S/Bi 2 S 3 NCs) were prepared by using one-step method for the photocatalytic inactivation against Gram-negative bacteria Escherichia coli ( E. coli ) under solar light irradiation. The results showed that Ag 2 S/Bi 2 S 3 NCs simultaneously had uniform platelets and coralloid particles with regular shape and perfect dispersion properties and could render the capability of absorbing a broad solar spectrum. The antibacterial tests demonstrated that higher bactericidal rate was obtained with 1.0 mg/mL of Ag 2 S/Bi 2 S 3 NCs under solar light irradiation during 100 min at 37 °C. It was confirmed by using fluorescence method that hydroxyl radicals generated in the photocatalytic process were the major responsibility for the photoinactivation. This work provides a promising photocatalyst in the bactericidal fields.
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JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY
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2014
·Vol. 90
·期 4
·678-685
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IF 2.494
Xiaolian Jing,Dengpo Huang,Huimei Chen,Tareque Odoom-Wubah,Daohua Sun,Jiale Huang,Qingbiao Li
BACKGROUND The synthesis and application of novel Au nanostructures are of increasing importance in modern nanotechnology. RESULTS Closely packed and chemically difficult-to-synthesize Au nanohorns (AuNHs) were synthesized in the presence of Escherichia coli cells (ECCs) and hexadecyltrimethylammonium chloride (CTAC) by a microorganism-mediated, CTAC-directed (MCD) approach. A proper ECC dosage, ascorbic acid (AA) and CTAC concentrations were essential for the growth of the AuNHs. In the formation mechanism of the AuNHs the ECCs surface acted as a platform for preferential nucleation and initial anisotropic growth of Au nanocrystals. As a result, some of the adjacent nanoparticles over the cell surface connected together via linear fusion to form dendritic nanostructures. Meanwhile, secondary nucleation in the solution gave rise to smaller nanoparticles that were consumed later on via Ostwald ripening during the formation of the AuNHs. Eventually, the two-dimensional film-like nanostructures between adjacent cells easily connected to form well-defined AuNHs with three-dimensional nanostructures. Interestingly, the AuNH/ECC composites can be used directly as sensitive surface-enhanced Raman spectroscopy (SERS) substrates for effective detection of 4-mercaptobenzoic acid (MBA). CONCLUSION The MCD strategy was an effective approach to novel AuNHs and AuNH/microorganism nanocomposites as SERS substrate. © 2014 Society of Chemical Industry
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CHEMICAL ENGINEERING JOURNAL
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2015
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IF 4.321
Can-Hui Deng,Ji-Lai Gong,Guang-Ming Zeng,Yan Jiang,Chang Zhang,Hong-Yu Liu,Shuang-Yan Huan
Graphene–CdS (G–CdS) nanocomposite was prepared successfully via a two-step solvothermal process, with CdS uniformly dispersed on the graphene nanosheets. The photocatalytic disinfection activity of G–CdS was evaluated, and the result shows that G–CdS exhibited higher inactivation efficiency toward the gram-negative bacterium, Escherichia coli , than pure CdS nanoparticles under visible light irradiation. Exposure to 10 mg of pure CdS resulted in a 1.1-log inactivation after 60 min, but resulted in 5.3-log reduction of viable bacteria when exposure to 10 mg G–CdS under the same illumination conditions. In addition, the impacts of humic acid (HA), a kind of natural organic matter (NOM), on its bactericidal properties have also been determined. G–CdS in the presence of HA (10 mg/L) significantly decreased its toxicity, causing less than 0.4-log inactivation after 60 min. Lipid peroxidation, intercellular ROS generation and antioxidant enzyme activities assays indicate that excess oxidative stress induced by G–CdS suppressed the antioxidant defense system, subsequently affected the normal function of lipid, protein and nucleic acid, and thus resulted in cell death. However, the decreased toxicity of G–CdS in the presence of HA may be attributed to that (1) HA presents a barrier to prevent the physical contact between bacteria cells and G–CdS, which was the first step of toxicity mechanisms; (2) HA acts as an antioxidant to react with any ROS and reduce the toxicity.
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ACS Sustainable Chemistry & Engineering
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2024
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IF 7.1
Jiamei Liu,Wenli Xia,Xin Yan,Linguo Zhao,Jianjun Pei
The production of high-value bioproducts using cellobiose and glucose is crucial for cellulose utilization. Cellobiose as a glycosyl precursor for biosynthesizing uridine diphosphate glucose (UDP-glucose) has been used for the glycosylation of flavonoids. Hyperoside is the key pharmacological component in Hypericum monogynum L and has unique pharmacological activities. In this study, a recombinant strain was constructed by introducing glycosyltransferase from Petunia hybrida (PhUGT), UDP-glucose epimerase (GalE), and the cellobiose phosphinylation route to produce hyperoside. By optimizing the fermentation conditions, the maximal hyperoside production reached 3274 mg/L. Subsequently, microcrystalline cellulose was pretreated with organic electrolyte solution (OES) to produce cellobiose and glucose, which was used as the carbon source and glycosyl precursor for hyperoside production. The hydrolysis yield of cellulose was increased from 30.1 to 91.7%, and the yield of cellobiose was increased by 298% with OES pretreatment. The highest yield of hyperoside in the recombinant strain reached 2013.2 mg/L when the optimal cellulose enzymatic solution was used as the glycosyl precursor. Finally, 100 g of cellulose could yield 60.25 g of glucose and 39.5 g of cellobiose, which served as the glycosyl precursor to produce 20.13 g of hyperoside. This study provides a novel method for the production of hyperoside by using enzymatic hydrolysis of microcrystalline cellulose.
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JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
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2009
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IF 2.562
Zhao-Feng Li,Bin Li,Zhi-Guo Liu,Miao Wang,Zheng-Biao Gu,Guo-Cheng Du,Jing Wu,Jian Chen
Overexpression of recombinant genes in Escherichia coli and targeting recombinant proteins to the culture medium are highly desirable for the production of industrial enzymes. However, a major barrier is inadequate secretion of recombinant protein across the two membranes of E. coli cells. In the present study, we have attempted to circumvent this secretion problem of the recombinant α-cyclodextrin glycosyltransferase (α-CGTase) from Paenibacillus macerans strain JFB05-01. It was found that glycine, as a medium supplement, could enhance the extracellular secretion of recombinant α-CGTase in E. coli. In the culture with glycine at the optimal concentration of 150 mM, the α-CGTase activity in the culture medium reached 23.5 U/mL at 40 h of culture, which was 11-fold higher than that of the culture in regular TB medium. A 2.3-fold increase in the maximum extracellular productivity of recombinant α-CGTase was also observed. However, further analysis indicated that glycine supplementation exerted impaired cell growth as demonstrated by reduced cell number and viability, increased cell lysis, and damaged cell morphology, which prevented further improvement in overall enzyme productivity. Significantly, Ca2+ could remedy cell growth inhibition induced by glycine, thereby leading to further increase in the glycine-enhanced extracellular secretion of recombinant α-CGTase. In the culture with 150 mM glycine and 20 mM Ca2+, both extracellular activity and maximum productivity of recombinant enzyme were 1.5-fold higher than those in the culture with glycine alone. To the best of our knowledge, this is the first article about the synergistic promoting effects of glycine and Ca2+ on the extracellular secretion of a recombinant protein in E. coli.
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APPLIED BIOCHEMISTRY AND BIOTECHNOLOGY
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2024
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IF 3.1
Yuan Dongxu,Liu Bingbing,Jiang Lin,Chen Yuhuan,Xu Gang,Lin Jianping,Yang Lirong,Lian Jiazhang,Jiang Yiqi,Ye Lidan,Wu Mianbin
Xylitol is a polyol widely used in food, pharmaceuticals, and light industries. It is currently produced through the chemical catalytic hydrogenation of xylose and generates xylose mother liquor as a substantial byproduct in the procedure of xylose extraction. If xylose mother liquor could also be efficiently bioconverted to xylitol, the greenness and atom economy of xylitol production would be largely improved. However, xylose mother liquor contains a mixture of glucose, xylose, and arabinose, raising the issue of carbon catabolic repression in its utilization by microbial conversion. Targeting this challenge, the transcriptional activator XylR was overexpressed in a previously constructed xylitol-producing E. coli strain CPH. The resulting strain CPHR produced 16.61 g/L of xylitol in shake-flask cultures from the mixture of corn cob hydrolysate and xylose mother liquor (1:1, v/v) with a xylose conversion rate of 90.1%, which were 2.23 and 2.15 times higher than the starting strain, respectively. Furthermore, XylR overexpression upregulated the expression levels of xylE , xylF , xylG , and xylH genes by 2.08–2.72 times in arabinose-containing medium, suggesting the alleviation of transcriptional repression of xylose transport genes by arabinose. This work lays the foundation for xylitol bioproduction from xylose mother liquor.
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FOOD MICROBIOLOGY
·
2024
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IF 4.5
Zhenlong Zhou,Ruoxin Chen,Pengzhen Li,Penghui Fan,Lin Ma,Xinyu Cai,Yuchao Hou,Binbin Li,Jianyu Su
Photodynamic inactivation (PDI), a non-thermal sterilization method, has attracted considerable attention due to its broad-spectrum antimicrobial activity, environmental friendliness and cost-effectiveness. Curcumin (Cur), a food-grade photosensitizer, exhibits photodynamic antimicrobial activity based primarily on its efficiency in intracellular accumulation. However, Cur's low water solubility and the barriers presented by the outer membrane of Gram-negative bacteria challenge its ability to penetrate the cytoplasm. Natural borneol (NB), a monoterpene food flavoring agent, has also been shown to improve the efficiency of drug absorption. In this study, we demonstrated that NB significantly improved the cellular uptake of Cur, thereby enhancing its photodynamic bactericidal activity against Gram-negative Escherichia coli ( E. coli ) ATCC 8739, a potential alternative to enterohemorrhagic E. coli O157:H7. This effect was attributed to NB's ability to disrupt the integrity of the E. coli bacterial membrane, thereby increasing cellular permeability. Transcriptomic analysis further confirmed that NB dysregulated the expression of genes associated with bacterial membrane structure and function in E. coli . Consequently, the increased accumulation of Cur in E. coli led to excessive production of intracellular reactive oxygen species (ROS) upon exposure to 6.5 J/cm 2 blue light (BL). These ROS, analyzed biochemically and transcriptionally, primarily disrupted bacterial membrane structure and function, the antioxidant system, and ultimately caused bacterial death. Remarkably, this combined strategy not only reduced E. coli contamination in the tested orange juice, but also preserved its nutritional quality. In conclusion, this research provides an innovative and effective approach to maintaining food safety.
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ADVANCED ENGINEERING MATERIALS
·
2024
·
IF 3.4
Zihao Song,Longjin Huang,Sheng Cui
In this work, a novel strategy for preparing Ga-doped TiO 2 composite aerogel antibacterial agent through the sol–gel method and supercritical technology is demonstrated. The specific surface area of the samples is as high as 175 m 2 g −1 and exhibits a 3D network structure with a multistage pore distribution. The obtained antibacterial agent combines the phototoxicity of TiO 2 , photo-independent toxicity of Ga 3+ , and structural properties of aerogels, showing a synergistic antibacterial effect. On the one hand, TiO 2 produces reactive oxygen species in the presence of light, thus destroying the structure of bacteria. On the other hand, Ga 3+ competitively replaces Fe 3+ and hinders the metabolic process of bacteria. Moreover, the structural properties of aerogels promote superior antimicrobial performance of antibacterial agents. Their antibacterial properties against Escherichia coli and Staphylococcus aureus bacteria are mainly investigated through the inhibition zone and natural colony counting method. In the results, it is shown that the structure and bactericidal activity of TiO 2 aerogel is effectively optimized with Ga 3+ doping. The maximum zone of inhibition of the composite aerogel against E. coli and S. aureus is 17.5 and 16 mm, and the bactericidal rate is as high as 98.57% and 96.60%, which exhibit outstanding bactericidal performance.
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