JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
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2021
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IF 5.279
Chen Yang,Jiajia You,Mengkai Hu,Ganfeng Yi,Rongzhen Zhang,Meijuan Xu,Minglong Shao,Taowei Yang,Xian Zhang,ZhiMing Rao
2,5-Dimethylpyrazine (2,5-DMP) is an important pharmaceutical intermediate and an important essence. Conventional chemical synthesis methods are often accompanied by toxic substances as by-products, and the biosynthesis efficiency of 2,5-DMP is insufficient for industrial applications. In this study, the tdh and soaao genes were overexpressed to enhance enzymatic and nonenzymatic reactions in metabolic pathways, and kbl was knocked out to block competitive branching carbon flow metabolic pathways. Finally, a genetically engineered Escherichia coli strain with the highest carbon recovery rate (30.18%) and the highest yield reported to date was successfully constructed, and 9.21 g·L–1 threonine was able to produce 1682 mg·L–1 2,5-DMP after 24 h. At the same time, an expression regulation strategy and whole-cell biocatalysis helped to eliminate the damage to cells caused by 2,5-DMP, aminoacetone, and reactive oxygen species generated by aminoacetone oxidase from S. oligofermentans, and the negative effect of 2-amino-3-ketobutyrate CoA ligase on the yield of 2,5-DMP in E. coli was also demonstrated.
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SENSORS AND ACTUATORS B-CHEMICAL
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2020
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IF 7.1
Xiaoyan Zhang,Tingting Wu,Yuemeng Yang,Yongqiang Wen,Shutao Wang,Li-Ping Xu
Superwettable microchips exhibit excellent ability to anchor microdroplets and great potential in ultratrace sample detection. Herein, we present a superwettable electrochemical biosensor based on a dual-DNA walker strategy (dual-DW biosensor) for the attomolar detection of food-borne microorganisms ssDNA in microdroplets. In the presence of the target E. coli O157: H7 ssDNA, the blocked walking probe is activated as the first-step DNA walker. With the aid of the Nt.BsmAI nicking endonuclease, the partial sequence of the basal probe was released, thus achieving the first-step signal amplification. Then the hairpin probe 1(H1) was opened by the released basal probe and followed by the autonomous strand displacement of the ferrocene (Fc) labeled hairpin probe 2 (H2) and movement of the basal probe. Under optimized conditions, the dual-DNA walker strategy finally renders the dual-DW biosensor an ultrahigh sensitivity of 30 aM toward E. coli O157: H7 ssDNA and a broad detection linear range. The dual-DW biosensor also enables successful analysis of trace amount of E. coli O157: H7 ssDNA in real food samples. The superwettable electrochemical biosensor based on a dual-DNA walker strategy is expected to be a versatile tool for ultratrace DNA detection and be promising in food analysis.
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METABOLIC ENGINEERING
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2020
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IF 7.263
Xi Deng,Liuqing Chen,Mohan Hei,Tiangang Liu,Yan Feng,Guang-Yu Yang
Medium-chain fatty acids (C6–C10) have attracted much attention recently for their unique properties compared to their long-chain counterparts, including low melting points and relatively higher carbon conversion yield. Thioesterase enzymes , which can catalyze the hydrolysis of acyl-ACP (acyl carrier protein) to release free fatty acids (FAs), regulate both overall FA yields and acyl chain length distributions in bacterial and yeast fermentation cultures. These enzymes typically prefer longer chain substrates. Herein, seeking to increase bacterial production of MCFAs, we conducted structure-guided mutational screening of multiple residues in the substrate-binding pocket of the E. coli thioesterase enzyme ‘TesA. Confirming our hypothesis that enhancing substrate selectivity for medium-chain acyl substrates would promote overall MCFA production, we found that replacement of residues lining the bottom of the pocket with more hydrophobic residues strongly promoted the C8 substrate selectivity of ‘TesA. Specifically, two rounds of saturation mutagenesis led to the identification of the ‘TesA RD−2 variant that exhibited a 133-fold increase in selectivity for the C8-ACP substrate as compared to C16-ACP substrate. Moreover, the recombinant expression of this variant in an E. coli strain with a blocked β -oxidation pathway led to a 1030% increase in the in vivo octanoic acid (C8) production titer. When this strain was fermented in a 5-L fed-batch bioreactor , it produced 2.7 g/L of free C8 (45%, molar fraction) and 7.9 g/L of total free FAs, which is the highest-to-date free C8 titer to date reported using the E. coli type II fatty acid synthetic pathway. Thus, reshaping the substrate binding pocket of a bacterial thioesterase enzyme by manipulating the hydrophobicity of multiple residues altered the substrate selectivity and therefore fatty acid product distributions in cells. Our study demonstrates the relevance of this strategy for increasing titers of industrially attractive MCFAs as fermentation products.
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RSC Advances
·
2024
·Vol. 14
·期 21
·15106-15111
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IF 3.9
Weiyun Guo,Chaoyun Wu,Guanghui Li,Yonghui Wang,Shenghua He,Jihong Huang,Xueli Gao,Xiaoyue Yue
Glutathione (GSH) as an antioxidant greatly attenuates the reactive oxygen species (ROS) treatment strategy based on peroxidase-activity nanozymes. Therefore, nanozymes with multiple properties that generate ROS and further GSH-depletion functions would be of great benefit to improve antimicrobial efficacy. Herein, focusing on the green, safe and abundant functional prospects of metal–phenolic networks (MPNs) and the strong prospect of biomedical applications, we have synthesized copper tannic acid (CuTA) nanozymes with dual functional properties similar to peroxidase-like activity and GSH depletion. CuTA can catalyze the decomposition of H2O2 to hydroxyl radicals (˙OH). In addition, CuTA nanozymes can efficiently deplete available GSH, thus enhancing ROS-mediated antimicrobial therapy. The antibacterial results show that CuTA has an excellent antibacterial effect against E. coli.
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WATER RESEARCH
·
2024
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IF 11.4
Zi-Bo Jing,Wen-Long Wang,Yu-Jia Nong,Lu Peng,Zi-Chen Yang,Bei Ye,Min-Yong Lee,Qian-Yuan Wu
Low-pressure mercury lamps emitting at 254 nm (UV254) are used widely for disinfection. However, subsequent exposure to visible light results in photoreactivation of treated bacteria. This study employed a krypton chloride excimer lamp emitting at 222 nm (UV222) to inactivate E. coli . UV222 and UV254 treatment had similar E. coli -inactivation kinetics. Upon subsequent irradiation with visible light, E. coli inactivated by UV254 was reactivated from 2.71-log to 4.75-log, whereas E. coli inactivated by UV222 showed negligible photoreactivation. UV222 treatment irreversibly broke DNA strands in the bacterium, whereas UV254 treatment primarily formed nucleobase dimers. Additionally, UV222 treatment caused cell membrane damage, resulting in wizened, pitted cells and permeability changes. The damage to the cell membrane was mainly due to the photolysis of proteins and lipids by UV222. Furthermore, the photolysis of proteins by UV222 destroyed enzymes, which blocked photoreactivation and dark repair. The multiple damages can be further evidenced by 4.0–61.1 times higher quantum yield in the photolysis of nucleobases and amino acids for UV222 than UV254. This study demonstrates that UV222 treatment damages multiple sites in bacteria, leading to their inactivation. Employing UV222 treatment as an alternative to UV254 could be viable for inhibiting microorganism photoreactivation in water and wastewater.
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Journal of Water Process Engineering
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2020
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IF 3.465
Wanhe Qi,Songming Zhu,Abubakar Shitu,Zhangying Ye,Dezhao Liu
Under Minamata Convention restrictions, mercury-free UV source was in need for ultraviolet disinfection in recirculating aquaculture systems (RAS). Ultraviolet emitting diodes (UV-LEDs) seemed a potential mercury-free UV source and had gained increasing attention in water disinfection. In this study, a mercury-free UVA-LED and low concentration peroxymonosulfate (PMS) combination was proposed for E. coli (CGMCC 1.3373) inactivation and real RAS wastewater disinfection. Results showed that UVA-LED and low concentration PMS combination enhanced E. coli inactivation over UVA-LED alone. A synergistic effect on E. coli inactivation with synergy factor of 58.7 % was found when combining UVA-LED irradiation with 1 mg/L PMS. Kinetic rate constant increased by up to 139 % by UVA-LED and 1 mg/L PMS combination, which implied the required UV fluence to 2-log E. coli inactivation was saved up to 42 %. Also, UVA-LED and 1 mg/L PMS combination showed disinfection potential for real RAS wastewater treatment. Mechanism study revealed that the Cl − , · OH and SO 4 ·- played important roles and · OH was dominant radical in saline solution by UVA-LED/PMS process compared to that in phosphate buffered solution(PBS). The E. coli inactivation was caused by UVA-LED irradiation and reactive species generated in UVA-LED/PMS system. Our study provided a potential strategy to introduce the mercury-free UV-LED into RAS and a better understanding of UVA-LED/PMS disinfection process.
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INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY
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2022
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IF 5.911
Haiying Cui,Xiaojing Yang,Changzhu Li,Yong Ye,Xiaochen Chen,Lin Lin
Escherichia coli O157:H7 ( E. coli O157) is still one of the main pathogenic strains causing food poisoning. Here in, we established a strategy that can simultaneously remove free E. coli O157 and the biofilms it forms. Composite nanofiber (fP-NF) films were synthesized successfully by co-encapsulating E. coli O157 phages which isolated from domestic sewage and D -phenylalanine (D-Phe) into sodium alginate (SA)/polyethylene oxide (PEO) nanofibers by electrospinning. And dehydrated trehalose was added as a phage protectant. When SA:PEO is 3:9, the spinning solution has the optimum conductivity and viscosity, the average diameter of the obtained fP-NFs is 421.87 nm, and the mechanical strength and transparency of the fP-NF film are the best. The thermal stability of the fP-NF film was good, and the phage activity in the fiber was well preserved. The remaining population of phages in fP-NF membranes was still close to 10 6 PFU/mL after one week of placement, and the cumulative release efficiencies of phages at both room temperature (25 °C) and refrigerated storage temperature (4 °C) were above 70%. The antibacterial experiment showed that compared with the control group, the addition of D-Phe slightly enhanced the antibacterial activity of the nanofiber films against free E. coli O157, and the bactericidal rate within 8 h was 99.74%. On the other hand, D-Phe significantly enhanced the inhibitory activity of the nanofiber films against E. coli O157 biofilms, with the inhibition rate exceeding 99.99% within 72 h. The application results further confirmed that the addition of D-Phe could significantly enhance the inhibitory activity of nanofiber films on E. coli O157 proliferation and biofilm formation during short-term storage of beef and fruits and vegetables. It provides an important strategy and reference for the development of new active food packaging materials .
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Frontiers of Materials Science
·
2025
·Vol. 19
·期 3
·1-11
·
IF 2.3
Sheng Yang,Qing Danni,Zhang Peng,Sun Yixin,Zhang Rong
Tetra-aminophenyl porphyrin (TAPP)-grafted Zn–Ag–In–S quantum dots (ZAIS QDs)/poly(maleic anhydride- alt -1-octadecene) (PMAO) nanoparticles were synthesized and their photoluminescence properties as well as photodynamic properties were studied. ZAIS QDs showed the brightest photoluminescence and highest quantum yield at an optimized Zn feeding molar ratio of 20%. Those TAPP-grafted nanoparticles (i.e., ZAIS/PMAO- g -TAPP) were able to produce 1 O 2 in aqueous solution under light irradiation as indicated by the 1 O 2 indicator, 9,10-anthracenediyl-bis(methylene) dimalonic acid (ADMA). ZAIS/PMAO- g -TAPP nanoparticles also demonstrate good biocompatibility and low dark toxicity even at a concentration as high as 2.8 mg·mL −1 , whith can be applied as both a fluorescence probe and a photodynamic therapy (PDT) agent. The PDT treatment showed that the viability of melanoma A2058 cells was less than 10% after treatment with the 420 nm light irradiation for 15 min at a photosensitizer concentration of 1.7 mg·mL −1 . During the PDT treatment with Escherichia coli , the survival rate of the bacteria decreased by −95% after light irradiation at the same concentration. Such dual-functional ZAIS/PMAO- g -TAPP nanoparticles researched in this study demonstrate promising potential for fluorescence labeling as well as effective PDT treatment against cancer cells and bacteria.
研究领域:
纳米技术
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光动力治疗
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材料科学
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生物医学工程
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微生物学
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肿瘤学
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BIOSENSORS & BIOELECTRONICS
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2020
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IF 10.257
Ziqi Zhou,Yangzi Zhang,Mingzhang Guo,Kunlun Huang,Wentao Xu
A relatively-simple and high-efficient fluorescent magnetic biosensor based on DNAzyme was established for the detection of E. coli O157:H7. In order to solve the problem of weak signal and low sensitivity in the detection of foodborne pathogenic bacteria , we ingeniously designed a fluorescent sensor based on triple signal amplification of magnetic beads, DNAzyme and photoluminescence . In the detection process, the E. coli -specific RNA-cleaving DNAzyme can specifically identify the target protein in crude intracellular mixture (CIM), which caused its conformation changes and induced rolling circle amplification (RCA) to the generation and luminescence of copper nanoclusters (CuNCs). This cascade amplification design can capture weak signals in the sample. The biosensor also indicated a good linear range from 10 CFU mL −1 to 1000 CFU mL −1 and obtained a limit of detection (LOD) of 1.57 CFU mL −1 , which showed a relatively high sensitivity compared with other studies. Furthermore, the biosensor displayed high-efficient detection capability in 1.5 h and good reproducibility (relative standard deviations < 2%). It has been proved that this sensor is feasible to the detection of E. coli O157:H7 in drinking water and apple juice. Moreover, we found that the final detection product can effectively wrap the magnetic beads and can be driven by the magnetic field. And this unexpected discovery will provide ideas for the development of biosensing robots.
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SENSORS AND ACTUATORS B-CHEMICAL
·
2024
·
IF 8
Mengyuan Chen,Chong Wang,Jing Tan,Jin Wang,Chen Wang
Nanofluidic membranes hold great prospects in sensitive and rapid detection of bioanalysts, while remaining lacking robust and general approaches for specificity. In this work, we introduce a cell membrane-inspired nanofluidic membrane with excellent ion current rectification properties as a simple and robust platform for label-free and ultrasensitive biosensing. The asymmetric nanofluidic membrane is prepared by coupling a two-dimensional covalent organic framework (COF) membrane to an anodic aluminum oxide (AAO) nanochannel via hydrogen bonding. The prepared COF/AAO membrane presents selective ion transport due to the asymmetric structure and anion selectivity of COF. With the large surface area and abundant functional modification sites of COF, further grafting of the recognition unit can be easily achieved to mimic the recognition process of receptors and ligands on cell membranes. As a proof of concept, the application in bacterial detection is demonstrated by covalently bonded Concanavalin A as recognition units. The highly amplified ionic current based on ion current rectification properties of the COF/AAO membrane allows sensitive and selective bioanalysis. Specifically, the proposed asymmetric nanofluidic membrane presents a linear detection range from 10 to 10 6 CFU/mL with an ultralow detection limit of 7 CFU/mL for E. coli . This work reveals the great potential of COF/AAO hybrid nanofluidic membrane as a sensor for rapid and precise bioanalysis.
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COLLOIDS AND SURFACES B-BIOINTERFACES
·
2024
·
IF 5.4
Lin Wang,Yu Pang,Meihua Xin,Mingchun Li,Lulu Shi,Yangfan Mao
Chitosan exhibits good biocompatibility and some antibacterial activity , making it a popular choice in biomedicine, personal care products, and food packaging. Despite its advantages, the limited antibacterial effectiveness of chitosan hinders its widespread use. Introducing a six-membered heterocyclic structure through chemical modification can significantly enhance its antimicrobial properties and broaden its potential applications. In order to explore the effect of six-membered heterocyclic structure on the antibacterial and antibiofilm activities of chitosan. In this study, seven chitosan derivatives containing six-membered heterocyclics were prepared. They were characterized using Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis . Cell viability assay showed that they were non-toxic. The antibacterial and antibiofilm activities against Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ) were evaluated. Our research findings demonstrate that increasing the hydrophobicity , alkalinity and charge density of the substitute groups improved the antibacterial and antibiofilm activities of chitosan. This study also offers valuable insights into the quantitative structure-activity relationships of chitosan derivatives in terms of antibacterial and antibiofilm activities.
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JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
·
2024
·
IF 5.7
Chenlu Zhu,Renjiao Han,Bixuan Gu,Caiyun Wang,Han Liu,Xiaomei Lyu,Jian He,Ruijin Yang
The limited expression of cellobiose 2-epimerase poses a significant constraint on the industrial enzymatic production of lactulose. Extensive modifications to the expression cassette offer a means to enhance the yield of recombinant proteins. In this study, an integrated strategy, combining individual and collaborative approaches, is proposed to fine-tune each stage of the CsCE overexpression program. This strategy involves the multidimensional integration of standardized genetic elements at various levels, including transcription, translation, folding, and three-dimensional structure. The volumetric activity of the final recombinant strain was markedly increased by 12-fold compared to the wild-type strain, reaching 2260.62 U/L. The protein expression in the newly developed high-yield recombinant strain exhibited a significant enhancement, with a higher proportion of soluble protein compared to that of inclusion bodies. Our findings offer insights into the multifaceted synergistic regulation of protein expression processes, holding promising implications for the production of heterologous recombinant proteins.
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