FOOD RESEARCH INTERNATIONAL
·
2024
·
IF 7
Jie Xiao,Hongchao Zhang
Frequent outbreaks caused by foodborne pathogens pose long-term risks to consumer health. To proactively reduce the load of pathogenic bacteria during food processing, a novel light-based antibacterial approach was developed by sequential application of 365 nm and 420 nm light-emitting diodes (LEDs). Results demonstrated that after treatment with 365 nm (480 J/cm 2 ) followed by 420 nm (307.2 J/cm 2 ), the reduction of Listeria monocytogenes reached 4.05 ± 0.31 log CFU/mL, significantly higher (an additional 1.8 log CFU/mL, P < 0.05) than cumulative reductions achieved by each 365 nm (2.25 ± 0.92 log CFU/mL) and 420 nm (0.02 ± 0.15 log CFU/mL) treatments. Further analysis revealed that the enhancement in bacterial reduction achieved through the sequential treatment with 365 nm and 420 nm was primarily driven by the exposure time to 365 nm. The inactivation mechanisms were investigated, considering possible photothermal, physical, and oxidative effects. Findings showed that the antibacterial effect of sequential treatment was mainly ascribed to intracellular oxidation generated by reactive oxidative species (ROS), namely hydrogen peroxide and superoxide anion. The antibacterial mechanism of two LEDs may result from the sensitization of bacterial cells to excessive ROS, as evidenced by fluorescent intensity measurements and chemical scavenger assays. This research provides new insight for improving the efficacy of UVA and blue light treatment to control food contamination by Listeria .
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ENZYME AND MICROBIAL TECHNOLOGY
·
2019
·
IF 3.553
Liuyan Gu,Haibo Yuan,Xueqin Lv,Guangsheng Li,Rigang Cong,Jianghua Li,Guocheng Du,Long Liu
5-Methylpyrazine-2-carboxylic acid (MPCA) is an important pharmaceutical intermediate and is used in the production of hypoglycemic agents and lipid-lowering drugs. This work aimed to develop a whole-cell biocatalytic process for the efficient synthesis of MPCA from 2, 5-dimethylpyrazine (DMP). Firstly, a whole-cell biocatalyst Escherichia coli strain was constructed by plasmid-based expression of xylene monooxygenase (XMO), benzyl alcohol dehydrogenase (BADH), and benzaldehyde dehydrogenase (BZDH) from Pseudomonas putida ATCC 33015, resulting in MPCA titer of 5.0 g/L. Then, the reaction conditions were optimized and the MPCA titer was further increased to 9.1 g/L. Next, the Ribosome Binding Site (RBS) Calculator v2.0 was used to predict and compare the translation initiation rates of the RBS sequences preceding xylM and xylA genes, encoding the two subunits of XMO. By optimizing the RBS sequences preceding xylA , the MPCA titer was increased to 10.2 g/L and the yield of MPCA on DMP reached 0.665 mol/mol. Finally, to achieve plasmid-free production of MPCA, we integrated the genes encoding for XMO, BADH and BZDH in the genome by using CRISPR/Cas9 and further fine-tuned the copy number ratios of xylM and xylA in the genome, improving the MPCA titer to 15.6 g/L and the yield of MPCA on DMP to 1.0 mol/mol. This work developed a high-yield and plasmid-free biocatalysis process for the environmentally friendly production of MPCA with 100% substrate conversion, and paved the way for the commercial production of MPCA in the future.
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JOURNAL OF BIOTECHNOLOGY
·
2015
·
IF 2.871
Xiaolin Pei,Qiuyan Wang,Lijun Meng,Jing Li,Zhengfen Yang,Xiaopu Yin,Lirong Yang,Shaoyun Chen,Jianping Wu
Nitrile hydratase (NHase) is an important industrial enzyme that biosynthesizes high-value amides. However, most of NHases expressed in Escherichia coli easily aggregate to inactive inclusion bodies unless the induction temperature is reduced to approximately 20 °C. The NHase from Aurantimonas manganoxydans has been functionally expressed in E. coli , and exhibits considerable potential for the production of nicotinamide in industrial application. In this study, the effects of chaperones including GroEL/ES, Dnak/J-GrpE and trigger factor on the expression of the recombinant Co-type NHase were investigated. The results indicate that three chaperones can significantly promote the active expression of the recombinant NHase at 30 °C. The total NHase activities reached to 263 and 155 U/ml in shake flasks when the NHase was co-expressed with GroEL/ES and DnaK/J-GrpE, which were 52- and 31-fold higher than the observed activities without chaperones, respectively. This increase is possibly due to the soluble expression of the recombinant NHase assisted by molecular chaperones. Furthermore, GroEL/ES and DnaK/J-GrpE were determined to promote the maturation of the Co-type NHase in E. coli under the absence of the parental activator gene. These knowledge regarding the chaperones effect on the NHase expression are useful for understanding the biosynthesis of Co-type NHase.
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PROCESS BIOCHEMISTRY
·
2024
·
IF 3.7
Chuang Li,Xian Zhang,Yuqing Wang,Qingtao Liu,Zhou Wang,Rui Huang,Zhenglian Xue
To enrich ‘epoxide hydrolase (EH) tool cabinet’ for preparing enantiopure epoxides and 1,2-diols, a novel microbial EH, Sf EH2, was identified from Streptomyces fradiae SF-2. Bioinformatics analysis indicated that Sf EH2 has typical structural characteristics of α/β-hydrolase fold superfamily. Its coding gene, sfeh 2, was then codon-optimized and amplified. A recombinant (re) Sf EH2-expressing E. coli BL21(DE3) strain ( E. coli / sfeh 2) was constructed through DNA manipulations. Substrate spectrum assay including fifteen common racemic ( rac -) epoxides by E. coli / sfeh 2 showed that re Sf EH2 displayed the highest and best complementary regioselectivities (regioselectivity coefficients, α R = 89.7% and β S = 91.4%) towards rac - 14a , as well as the highest enantioselectivity (enantiomeric ratio, E = 15.3) in S -type towards rac - 15a . Molecular docking simulation revealed that Sf EH2 preferentially attacked C α of ( R )- 14a and C β of ( S )- 14a geometrically. In kinetic parameter analysis, the K m R (5.74 mM) of purified re Sf EH2 for ( R )- 15a was 1.76-fold lower than K m S (10.09 mM) for ( S )- 15a . At last, using 50 mg dry cell weight/mL E. coli / sfeh 2, the scale-up enantioconvergent hydrolysis of 100 mM rac - 14a at 30 °C for 6.0 h afforded ( S )- 14b with 80.9% ee p and 90.1% yield, while the kinetic resolution of 150 mM rac - 15a retained ( S )- 15a with >99.0% ee s and 42.2% yield.
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MICROCHEMICAL JOURNAL
·
2025
·
IF 5.1
Duoduo Zhang,Xinyu Zhang,Mingshuang Liang,Xiuxiu Li,Nan Wang,Heping Xiao,Dawei Cao,Xiubo Zhao
Escherichia coli ( E. coli ) is one of the most prevalent foodborne pathogens, releasing toxic substances and causing infectious and life-threatening diseases. Thus, the rapid and sensitive detection of E. coli is essential for safeguarding human health. Herein, a ratiometric colorimetric sensor was constructed for detecting E. coli , utilizing the coordination between zirconium (Zr)-tetraphenylporphyrin tetrasulfonic acid (TPPS) hydrate metal–organic frameworks (Zr-TMs) and copper ions (Cu 2+ ). E. coli can capture and convert external Cu 2+ into Cu + through its distinctive metabolic activities. This capability further enhances the coordination interaction between the porphyrin ligands in Zr-TMs and the metal ions. As a result, the ultraviolet–visible (UV–vis) absorption spectral properties of Zr-TMs changed, exhibiting an enhanced absorption peak at 413 nm (A 413 ) and a weakened peak at 434 nm (A 434 ). By monitoring the increase in ratio of A 413 to A 434 , this sensor achieved rapid and sensitive detection of E. coli at concentrations ranging from 10 2 to 10 7 CFU/mL within 63 min, with a detection limit of 19 CFU/mL. The color of the solution gradually changed from green to colorless. This proposed ratiometric method utilized the opposite changes in the two UV–vis absorption peak signals (A 413 and A 434 ) generated by the Zr-TMs probes, improving detection accuracy and achieving visual analysis. Additionally, this method accurately identified E. coli in milk samples, demonstrating substantial potential for detecting pathogenic bacteria in food.
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BIOCHEMICAL ENGINEERING JOURNAL
·
2020
·
IF 3.475
Xiaoyang Ou,Fei Peng,Xiaoling Wu,Pei Xu,Minhua Zong,Wenyong Lou
A robust Escherichia coli ( E. coli ) strain, with a dual protection system to fight against microbial contamination and T7 phage infection, is used as a chassis to overexpress various proteins in auxotrophic MOPS medium. Among them, a robust EH (epoxide hydrolase)-producing E. coli was used as a biocatalyst to enantioselectively resolve racemic glycidyl o -methylphenyl ether ( rac - o -GMPE) for preparing ( R )- o -GMPE with 6416.7 U/g wet cells. The optimal temperature, pH and biocatalyst dosage were 25 °C, 7.0 and 0.2 mg/mL in aqueous buffer, respectively. The maximal yield (23.0 %) and ee (99.2 %) were achieved within 12 min in 20 mM rac - o -GMPE. Additionally, 98.0 % ee and 38.7 % yield were observed by cell-supplemental strategy with substrate concentration of 100 mM. Furthermore, to alleviate substrate inhibition and product toxicity toward the cells, a biphasic system (aqueous buffer: butyl acetate = 0.5:1) was developed to catalyze 3 M rac - o -GMPE with the initial reaction rate of 549.7 mmol/L/h, 91.7 % ee , 17.1 % yield and 3.66 g/L/h space-time yield.
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JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
·
2026
·Vol. 74
·期 31
·24501-24512
·
IF 6.7
Xie Sikui,He Yu-Cai
Lignocellulosic biomass, which consists primarily of
cellulose,
hemicellulose, and lignin, is a promising renewable feedstock for
producing high-value biobased amines. In this study, an integrated
chemobiocatalytic strategy was developed to synthesize furfurylamine
from corncob using a newly formulated deep eutectic solvent, [Bet][FA][LA],
that provides both catalytic and solubilizing functions. Under optimized
conditions, corncob was efficiently converted into furfural, which
was subsequently aminated by recombinant Escherichia coli BM-AlaDH coexpressing an ω-transaminase
and alanine dehydrogenase. The whole-cell catalyst enabled in situ
regeneration of L -alanine, thereby reducing amine-donor
requirements and improving biocatalytic efficiency. Integration of
[Bet][FA][LA]-mediated chemocatalysis with whole-cell biocatalysis
converted corncob into furfurylamine in [Bet][FA][LA]. The biocatalytic
amination system could convert biomass-derived 5-hydroxymethylfurfural
(320 mM) and vanillin (20 mM) into the corresponding amines in yields
of 95.4% and 91.0%, respectively. This work establishes a sustainable
route for converting lignocellulose-derived aldehydes into value-added
biobased amines and advances the comprehensive valorization of lignocellulosic
biomass.
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INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY
·
2026
·
IF 5.2
Jinming Dai,Chenghui Zhang,Mei Bai,Tariq Aziz,Nada K. Alharbi,Fatma Alshehri,Ashwag Shami,Fahad Saad Alhodieb,Saleh A. Alsanie,Mansour Alblaji,Haiying Cui
The quorum sensing (QS) system is a critical drug target that regulates the toxins production and biofilms formation in pathogens. This study elucidates the mechanism by which the plant polyphenol gallic acid (GA) acts as a QS inhibitor targeting the LuxS/AI-2 system in Escherichia coli O157: H7, and evaluates its potential for antibiofilm applications. Results show that GA broadly interferes with the transcription of genes in the AI-2 synthesis pathway and inhibits AI-2 production. Molecular docking combined with in vitro enzymatic inhibition assays identified LuxS as a key target of GA. Thermodynamically favored, GA binds to LuxS via hydrogen bonds and van der Waals interactions, forming a stable ground-state complex that alters the enzyme's secondary structure and inhibits its activity. Further mechanistic analysis indicates that GA induces conformational changes in the protein, reduces active site volume, and restricts key catalytic residues, thereby blocking substrate access. Under simulated meat broth conditions, GA significantly enhances the biofilm-inhibitory effect of conventional disinfectants even at subinhibitory concentrations on food-contact surfaces. These findings provide theoretical support for the potential utilization of GA as a QS-targeted antibiofilm adjuvant in the food industry.
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BIORESOURCE TECHNOLOGY
·
2018
·
IF 5.807
Junhua Di,Cuiluan Ma,Jianghao Qian,Xiaolong Liao,Bo Peng,Yucai He
In this study, chemo-enzymatic synthesis of furfuralcohol from biomass-derived xylose was successfully demonstrated by a sequential acid-catalyzed dehydration under microwave and whole-cells reduction. After dry dewaxed chestnut shells (CNS, 75 g/L) was acid-hydrolyzed with dilute oxalic acid (0.5 wt%) at 140 °C for 40 min, the obtained CNS-derived xylose (17.9 g/L xylose) could be converted to furfural at 78.8% yield with solid acid SO 4 2− /SnO 2 -Attapulgite (2.0 wt% catalyst loading) in the dibutyl phthalate-water (1:1, v:v) under microwave (600 W) at 180 °C for 10 min. In the dibutyl phthalate-water (1:1, v/v) media at 30 °C and pH 6.5, the furfural liquor (47.0 mM furfural) was biologically converted to furfuralcohol by recombinant Escherichia coli CCZU-Y10 whole-cells harboring an NADH-dependent reductase (PgCR) without extra addition of NAD + and glucose, and furfural was completely converted to furfuralcohol after 2.5 h. Clearly, this one-pot synthesis strategy can be effectively used for furfuralcohol production.
研究领域:
生物资源技术
·
生物催化
·
绿色化学
·
生物质转化
·
可再生能源
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Microbiology Spectrum
·
2022
·
IF 9.043
Zhaoxi Deng,Kangwei Hou,Teresa G. Valencak,Xin M. Luo,Jianxin Liu,Haifeng Wang
The LuxS enzyme plays a key role in both quorum sensing (QS) and the regulation of bacterial growth. It catalyzes the production of autoinducer-2 (AI-2) signaling molecule, which is a component of the methyl cycle and methionine metabolism. This study aimed at investigating the differences between the Lactobacillus rhamnosus GG (LGG) wild-type strain (WT) and its luxS mutant (ΔluxS) during biofilm formation and when resisting to inflammation caused by Enterotoxigenic Escherichia coli (ETEC) in germ-free zebrafish. Our results suggest that in the absence of luxS when LGG was knocked out, biofilm formation, extracellular polysaccharide secretion and adhesion were all compromised. Addition of synthetic AI-2 indeed rescued, at least partially, the deficiencies observed in the mutant strain. The colonizing and immunomodulatory function in WT versus ΔluxS mutants were further studied in a germ-free zebrafish model. The concentration of AI-2 signaling molecules decreased sharply in zebrafish infected with the ΔluxS. At the same time, compared with the ΔluxS, the wild-type strain could colonize the germ-free zebrafish more effectively. Our transcriptome results suggest that genes involved in immunity, signal transduction, and cell adhesion were downregulated in zebrafish infected with ΔluxS and WT. In the WT, the immune system of germ-free zebrafish was activated more effectively through the MAPK and NF-κB pathway, and its ability to fight the infection against ETEC was increased. Together, our results demonstrate that the AI-2/LuxS system plays an important role in biofilm formation to improve LGG and alleviate inflammation caused by ETEC in germ-free zebrafish.IMPORTANCE Lactobacillus rhamnosus GG is a widely used probiotic to improve host intestinal health, promote growth, reduce diarrhea, and modulate immunity. In recent years, the bacterial quorum sensing system has attracted much attention; however, there has not been much research on the effect of the LuxS/AI-2 quorum sensing system of Lactobacillus on bacteriostasis, microbial ecology balance, and immune regulation in intestine. In this study, we used germ-free zebrafish as an animal model to compare the differences between wild-type and luxS mutant strains. We showed how AI-2/LuxS QS affects the release of AI-2 and how QS regulates the colonization, EPS synthesis and biofilm formation of LGG. This study provides an idea for the targeted regulation of animal intestinal health with probiotics by controlling bacteria quorum sensing system.
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Animals
·
2025
·Vol. 15
·期 24
·3564
·
IF 2.7
Kaiwei Yang,Xi Wu,Bingcun Ma,Jianguo Cheng,Zengting Li,Yin Wang,Zexiao Yang,Xueping Yao,Yan Luo
Simple SummaryEscherichia coli(E. coli) is an opportunistic pathogen and an important reservoir of antibiotic resistance genes. Thetet(X4) gene mediates tigecycline resistance by encoding a flavin-dependent monooxygenase. However, the mechanism by which this gene influences bacterial antibiotic resistance through regulating the expression of other genes is complex and not yet fully understood. In this study,E. coli tet(X4) deletion and complemented strains were constructed to explore the effects of this gene on bacterial growth and antibiotic resistance. We measured the minimum inhibitory concentrations (MICs) of 24 antibiotics and the degradation capability for tetracycline/tigecycline in the wild type, deletion, and complemented strains, and conducted a 4-week starvation stress experiment (with/without subinhibitory concentrations of tigecycline) to analyze growth curves, survival rates, and changes in MICs. Transcriptome sequencing identified 531 differentially expressed genes, which are associated with ABC transporter activity, drug metabolism, and two-component systems. These findings provide reliable insights into the mechanism by which thetet(X4) gene affectsE. coliantibiotic resistance and offer a reference for the prevention and control of tigecycline-resistantE. coliinfections.Escherichia coli(E. coli) is a ubiquitous opportunistic pathogen in nature and serves as an important reservoir for antibiotic resistance genes. Thetet(X4) gene is a key determinant mediating tigecycline resistance. Although its core resistance mechanism, encoding a flavin-dependent monooxygenase, has been elucidated, the broader impact of thetet(X4) gene on the secondary regulatory networks ofE. coliremains not fully understood. In recent years, multiple studies have indicated that thetet(X4) gene participates in pathways contributing to resistance to other antibiotics by regulating the expression of various genes. In this study,E. coli tet(X4) gene deletion and complementation strains were constructed to investigate the mechanisms by which thetet(X4) gene influences the growth characteristics and antibiotic resistance ofE. coli. The minimum inhibitory concentrations (MICs) of 24 different antibiotics, as well as the degradation capacities of tetracycline and tigecycline, were determined for the wild-type, deletion, and complementation strains. In addition, a four-week starvation stress experiment was performed under both the presence and absence of sub-inhibitory concentrations of tigecycline, during which the bacterial growth curves, survival rates, and MIC variations were analyzed. Transcriptomic sequencing of the wild-type, deletion, and complementation strains identified 531 differentially expressed genes associated with ABC transporter activity, drug metabolism, and bacterial two-component systems. These findings provide reliable evidence for elucidating the mechanism by which thetet(X4) gene affectsE. coliresistance, offering valuable insights into the prevention and control of tigecycline-resistantE. coliinfections.
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Microorganisms
·
2026
·Vol. 14
·期 5
·1007
·
IF 4.7
Ri-Han Jiang,Zi-Kui Liu,Bing Han,Dan-Ni Liao,Ji-Yun Li,Yong Wu
This study investigated the epidemiology, antimicrobial resistance, and transmission risks of β-lactamase, cefotaxime-hydrolyzing, Munich (blaCTX-M)-positiveEscherichia coli(CTX-M-EC) in large-scale pig farms in Jiangxi Province (China). In total, 278 samples (manure, wastewater, drinking water, and flies) were collected. CTX-M-EC strains were isolated and analyzed using antimicrobial susceptibility testing, resistance gene profiling, multilocus sequence typing, and genetic environment analysis with gene transfer assessed by transduction experiments. Twenty-seven CTX-M-EC strains (9.71%) were isolated, all exhibiting multi-drug resistance with 100% resistance to cefotaxime, ciprofloxacin, and tetracycline, and >90% resistance to ceftazidime, florfenicol, and trimethoprim-sulfamethoxazole. FourblaCTX-Msubtypes were identified.blaCTX-M-55was the predominant subtype (70.37%) and was distributed across diverse sequence types and serotypes. Each strain harbored multiple antibiotic resistance genes, plasmids, and virulence genes. Mobile elements such as ISEcp1and IS26were detected surrounding theblaCTX-Mgene, and 96.29% of strains successfully transferred theblaCTX-Mgene via transduction. Clones highly homologous to pig manure strains were detected in flies and sewage, suggesting that this resistance gene can spread between animals, the environment, and vectors. These findings highlight the high transmission risk ofblaCTX-Mand underscore the need for rational antibiotic use, waste management, and vector control within a One Health framework.
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