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The iron and nitrogen co-doped porous carbon supported Au nanoparticle catalysts (Au/FeNPC) are synthesized via a facile pyrolysis method. The morphology, crystal structure, surface composition, and chemical state of the Au/FeNPC catalysts are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalytic performances of the Au/FeNPC for BH4− oxidation reaction (BOR) are investigated by cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP), and linear voltammetric sweep (LSV). Among the as-prepared Au/FeNPC catalysts, Au/FeNPC-40 catalyst possesses the highest catalytic activity for BOR, and the BOR peak current density on the Au/FeNPC-40 electrode is up to 45.4 mA cm−2 with the high transferred electron number of 7.0.

Biological antagonists are a series of microbes that can control pathogens to reduce the incidence of disease or reduce symptoms. Herein, four varieties of citrus fruit were selected to perform an amplicon sequencing on their epiphytic microbiota to get a systematic understanding of them. Co-occurrence network, Venn, and LefSe analysis were performed to filter to 24 genera which represent the universality, specificity, and correlation among samples. Functional analysis hinted that the genes related to chitinase, which most of these 24 bacteria carry, might lead to a disease-suppressive phenotype. 115 strains of epiphytic bacteria were isolated, and the bacterial synthetic community was constructed by 8 strains. The in vivo test results indicated they were able to reduce pathogen development for a longer time than separate inoculation. Collectively, this study showed the disease control potential provided by native epiphytic bacteria of fruit and give a new strategy to sustainable agriculture.

The aim of this work was to study the capability and mechanism of enhancing the yield of pulcherriminic acid (PA) produced by Metschnikowia citriensis FL01 with the help of tryptophan for the control of postharvest diseases on citrus caused by Penicillium italicum, Geotrichum citri-aurantii and Penicillium digitatum. The adding of 10 mmol/L tryptophan to the growth medium resulted in the widest pulcherrimin pigment zone produced by M. citriensis FL01. The adding of tryptophan to the growth medium upregulated A3136 and A3022 gene expression (responsible for leucyl-tRNA biosynthesis from leucine), downregulated A1350 gene expression (responsible for the biosynthesis of leucine to branched-chain fatty acids), and decreased the content of intracellular leucine in M. citriensis FL01, speculating that the addition of tryptophan in the growth medium induced leucine conversion toward leucyl-tRNA in M. citriensis FL01. Moreover, the adding of tryptophan to the growth medium upregulated PULs (responsible PA biosynthesis) and Snf2 (transcriptional regulator) gene expression and promoted intracellular, extracellular or total PA production by M. citriensis FL01 in liquid medium. In addition, the addition of tryptophan in the growth medium showed no effect on the growth of M. citriensis FL01 itself in liquid medium, while the population dynamics in citrus fruit wounds of M. citriensis FL01 with the addition of tryptophan in the growth medium were increased compared with those of M. citriensis FL01. What's more, M. citriensis FL01 with the addition of tryptophan in the growth medium completely inhibited the growth of pathogens in vitro. The disease incidences and lesion diameters of blue mold, sour rot and green mold on citrus fruit were lower in group which treated with M. citriensis FL01 containing tryptophan in the growth medium than that treated with M. citriensis FL01 alone. Overall, the postharvest biocontrol of citrus with M. citriensis FL01 containing 10 mmol/L tryptophan in the growth medium is a promising approach to protect these fruits from blue mold, sour rot and green mold.

Pectobacterium carotovorum is a Gram-negative plant-specific pathogen that causes severe rot of postharvest vegetables. Given the safety consideration of pesticides, we developed a peptide approach...

This study aimed to investigate the effect of Pichia galeiformis on disease resistance and elucidate the changes in phenylpropane biosynthesis treated by P. galeiformis in postharvest citrus. The results showed that P. galeiformis reduced the disease incidence and lesion diameters without direct contact with the pathogen Penicillium digitatum. Transcriptome analysis revealed that phenylpropanoid biosynthesis was triggered by P. galeiformis. Genes encoding phenylpropanoid biosynthesis were upregulated, including phenylalanine ammonia-lyase (PAL), 4-coumaroyl-CoA ligase (4CL), cinnamate-4-hydroxylase (C4H), peroxidase (POD), cinnamyl alcohol dehydrogenase (CAD), O-methyltransferase, and hydroxyl cinnamoyl transferase. Moreover, P. galeiformis increased the activity of PAL, 4CL, C4H, POD, polyphenol oxidase, and CAD in citrus pericarp. In addition, P. galeiformis treated citrus displayed higher levels of total phenolic compounds, flavonoid, and lignin and higher amounts of ferulic and sinapic acid. In conclusion, these results suggested that P. galeiformis could induce resistance through modulating the pathway of phenylpropanoid biosynthesis in postharvest citrus.

Carbon-supported Au-doped N-C-coated CoFe alloy nanocomposite electrocatalysts (Au/CoFe@CN/C) are prepared and applied to BH4− electrooxidation. The physical and electrochemical properties of the catalysts are characterized and tested by X-ray diffraction, transmission electron microscopy, cyclic voltammetry, chronamperometry, chronopotentiometry, and rotating disk electrode voltammetry. The results show that Au(50)/CoFe@CN(50)/C has excellent catalytic performance for BH4− electrooxidation, high charge transfer number up to 6.4, and low precious metal content, making it a promising anode electrocatalyst of direct borohydride fuel cell.

An N-doped carbon-coated Co2P-supported Au nanocomposite (Au/Co2P@NC/C) was synthesized via a facile pyrolysis procedure. The morphology and crystal structure of the Au/Co2P@NC/C catalyst were tested by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and the electrocatalytic performances of Au/Co2P@NC/C for borohydride oxidation reaction (BOR) were evaluated by cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP), linear sweep voltammetry (LSV), and rotating disc electrode (RDE) voltammetry. Among the as-prepared Au/Co2P@NC/C catalysts, Au(50)Co2P@NC(50)/C exhibited the highest electrocatalytic activity for BOR. The BOR current density at −0.1 V on the Au(50)Co2P@NC(50)/C electrode was 48.4 mA cm−2, which is much higher than that on the Au/C electrode (24.8 mA cm−2).

Graphdiyne (GDY), a novel two-dimensional (2D) carbon material with sp- and sp2-hybridized carbon atoms, has earned a lot of attention in recent years. Owing to its low reduction potential and highly conjugated electronic structure, it can be used as a reducing agent and stabilizer for the electroless deposition of highly dispersed Au nanoparticles. In this paper, we observe that exfoliated GDY (eGDY), the exfoliation of bulk GDY into single- or few-layered GDY in aqueous solution, can be used as an excellent substrate for the electroless deposition of very small Au nanoparticles to form a Au/eGDY nanocomposite that exhibits higher catalytic performance for the reduction of 4-nitrophenol. The higher catalytic performance is considered to arise from the high specific surface area of eGDY and the electroless deposition of active metal catalysts with eGDY as the support. Our results inspired the present investigation into the use of eGDY for the development of highly efficient catalysts.

ZIF-derived Co, N co-doped porous carbon-supported Au nanoparticles (Au/CoNPC) are synthesized via a novel facile pyrolysis method. The morphology, crystal structure, surface composition and chemical state of the Au/CoNPC composite catalysts are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalytic properties of Au/CoNPC for the borohydride oxidation reaction (BOR) are investigated by cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP), linear sweep voltammetry (LSV), and rotating disc electrode (RDE) voltammetry. Among the as-prepared catalysts, the Au/CoNPC-40 catalyst shows the highest catalytic activity for the BOR. The BOR peak current density on the Au/CoNPC-40 electrode is up to 48.4 mA cm−2 and the transferred electron number is up to 7.5.

In this paper, carbon-supported nickel hydroxide-doped platinum (Pt/Ni(OH)2/C) nanocatalysts are synthesized by a two-step method, and the morphology and structure of Pt/Ni(OH)2/C are studied by transmission electron microscope and X-ray diffraction analysis. The electrocatalytic performance of the Pt/Ni(OH)2/C for borohydride oxidation reaction (BOR) is studied by using cyclic voltammetry, chronoamperometry, chronopotentiometry, and rotating disc electrode voltammetry. The Pt/Ni(OH)2/C catalysts show much better catalytic performance than Pt/C, and Pt(50)/Ni(OH)2(50)/C exhibits the best catalytic performance among all as-prepared Pt/Ni(OH)2/C catalysts. Moreover, the electron transfer number (n) related to BOR is evaluated, and n of 3.5 is achieved on Pt(50)/Ni(OH)2(50)/C electrode.

In this work, by capping a macrolactam ring at the C-terminus of a de novo-designed peptide, namely zp80, we have constructed a small peptide library via the solid phase peptide synthesis for screening. Eight peptides bearing different aspartic acid-rich macrolactam rings but the same linear (IIRR)

Carbon-supported Au modified N-doped carbon-coated FeMn alloy nanoparticle composites (Au/FeMn@CN/C) are prepared and used as electrocatalysts for BH4− electrooxidation. The surface morphology of the Au/FeMn@CN/C is observed using a transmission electron microscope and their composition is analyzed by X-ray diffraction. The results show that the prepared Au/FeMn@CN/C is a three-layer core–shell structure and the FeMn@CN nanosphere is coated with Au nanoparticles. The electrochemical performance of the prepared Au/FeMn@CN/C is studied by electrochemical tests, and the results show that Au(50)/FeMn@CN(50)/C shows the most excellent performance for direct BH4− electrooxidation which has more negative overpotential and an electrooxidation current density of up to 46.46 mA cm−2 with an electron-transfer number of 5.3.

Carbon supported Pd–Sn (Pd–Sn/C) nanoparticle electrocatalysts are prepared via a facile and environmentally friendly method and successfully applied in BH4− electrooxidation. Transmission electron microscopy results and X-ray diffraction results show that Pd–Sn nanocatalysts with a particle size of about 4 nm are uniformly distributed on the surface of a carbon black support without obvious agglomeration. Electrochemical results show that the catalytic activity of the Pd–Sn/C catalysts for BH4− electrooxidation is significantly higher than that of Pd/C. In particular, the Pd50Sn50/C catalyst has the highest electrocatalytic activity for BH4− electrooxidation among the four as-prepared catalysts. In addition, the BH4− electrooxidation reaction electron transfer number (n) of 3.9 was evaluated on the Pd50Sn50/C electrode.

A nitrogen-doped carbon-supported Au-modified NiFe alloy nanoparticle composite catalyst (Au/NiFe/N–C) has been prepared by a simple method and used as an electrocatalyst for the BH4− oxidation reaction (BOR). The physical and electrochemical properties of the as-prepared Au/NiFe/N–C catalyst have been tested by transmission electron microscopy, X-ray diffraction, cyclic voltammetry, chronoamperometry, chronopotentiometry, and rotating disk electrode voltammetry. The results showed that the catalytic activity of Au/NiFe/N–C for BOR was much higher than that of a carbon-supported Au nanocatalyst (Au/C); in particular, the Au(50)NiFe(50)/N–C catalyst demonstrated much higher catalytic activity with 2-fold higher peak current density than Au/C for BOR.

Background:Antimicrobial resistance is found in all microorganisms and has become one of the biggest threats to global health. New antimicrobials with different action mechanisms are effective weapons to fight against antibiotic-resistance.Objective:This review aims to find potential drugs which can be further developed into clinic practice and provide clues for developing more effective antimicrobials.Methods:DNA replication universally exists in all living organisms and is a complicated process in which multiple enzymes are involved in. Enzymes in bacterial DNA replication of initiation and elongation phases bring abundant targets for antimicrobial development as they are conserved and indispensable. In this review, enzyme inhibitors of DNA helicase, DNA primase, topoisomerases, DNA polymerase and DNA ligase were discussed. Special attentions were paid to structures, activities and action modes of these enzyme inhibitors.Results:Among these enzymes, type II topoisomerase is the most validated target with abundant inhibitors. For type II topoisomerase inhibitors (excluding quinolones), NBTIs and benzimidazole urea derivatives are the most promising inhibitors because of their good antimicrobial activity and physicochemical properties. Simultaneously, DNA gyrase targeted drugs are particularly attractive in the treatment of tuberculosis as DNA gyrase is the sole type II topoisomerase in Mycobacterium tuberculosis. Relatively, exploitation of antimicrobial inhibitors of the other DNA replication enzymes are primeval, in which inhibitors of topo III are even blank so far.Conclusion:This review demonstrates that inhibitors of DNA replication enzymes are abundant, diverse and promising, many of which can be developed into antimicrobials to deal with antibioticresistance.

An electrocatalyst for BH4− electrooxidation is facilely achieved via a two-step method, which consists of carbon substrate, Ni(OH)2 nanospheres and Au nanoparticles. Results of scanning electron microcopy, transmission electron microscopy, and X-ray diffraction show that Au nanoparticles dispersedly grow on both surfaces of carbon substrate and carbon-supported Ni(OH)2 nanospheres. The electrocatalytic activity of the as-prepared catalysts loaded with different amounts of Au and Ni(OH)2 are explored through cyclic voltammetry, chronoamperometry, chronopotentiometry, and rotating disc electrode voltammetry. Among the prepared catalysts, Au(50)/Ni(OH)2(50)/C catalyst displays the best electrocatalytic activity for BH4− electrooxidation, and the lower content of noble metal and the higher catalytic activity for BH4− electrooxidation make Au(50)/Ni(OH)2(50)/C a promising anode catalyst in application of direct borohydride fuel cells.

Pd/C and Pd-Co/C nanocatalysts are prepared via a simple and environmentally friendly method and are used as anodic catalyst for direct borohydride–hydrogen peroxide fuel cells. X-ray diffraction and transmission electron microscopy results indicate that Pd and Pd-Co nanoparticles adhere on carbon with the mean diameter of about 4 nm. The cyclic voltammetry, chronoamperometry, chronopotentiometry, and rotating disc electrode voltammetry results show that the electrocatalytic activity of Pd-Co/C is higher than that of Pd/C, especially Pd67Co33/C which shows the highest electrocatalytic activity for BH4− electro-oxidation with the electron-transfer number of 4.9 related to BH4− electro-oxidation reaction. The single direct borohydride–hydrogen peroxide fuel cell with Pd67Co33/C anode obtains the maximum power density as high as 66.84 mW cm−2 at 25 °C.

Microbial antagonists are effective and environmentally friendly in controlling postharvest diseases of fruit. The present study investigated the influence of D. nepalensis on epiphytic microbiome and postharvest decay of jujube. Results showed that D. nepalensis notably reduced fungal decay, maintained the fruit firmness and delayed discoloration. The epiphytic microbiome revealed that D. nepalensis changed the fungal communities, but few influence on bacterial communities were observed. D. nepalensis, as the dominant population in the treatment group, decreased the abundance of pathogenic fungi of Alternaria, Penicillium, Fusarium and Botrytis, while increased the beneficial bacteria of Pantoea. The canonical correspondence analysis revealed that Debaryomyces was negatively correlated with the decay rate, whereas Penicillium, Acremonium, Rhodosporidiobolus and Hansfordia were positively correlated. In conclusion, D. nepalensis altered the successional process of fungal and bacterial communities to reduce the decay rate of jujube during storage.

Loss and waste of postharvest vegetables are the main challenges facing the world’s vegetable supply. In this study, an innovative method of value-added transformation was provided: production of bacteriocin from vegetable waste, and then its application to preservation of vegetables. Antibacterial activity to soft rot pathogen Pectobacterium cartovorum (Pcb BZA12) indicated that tomato performed best in the nutrition supply for bacteriocin production among 12 tested vegetables. Moreover, the antibacterial activity was from Lactobacillus paracasei WX322, not components of vegetables. During a fermentation period of 10 days in tomato juice, L. paracasei WX322 grew well and antibacterial activity reached the maximum on the tenth day. Thermostability and proteinase sensitivity of the bacteriocin from tomato juice were the same with that from Man-Rogosa-Sharpe broth. Scanning electron microscope images indicated that the bacteriocin from tomato juice caused great damage to Pcb BZA12. At the same time, the bacteriocin from tomato juice significantly reduced the rotten rate of Chinese cabbage from 100% ± 0% to 20% ± 8.16% on the third day during storage. The rotten rate decrease of cucumber, tomato, and green bean was 100% ± 0% to 0% ± 0%, 70% ± 14.14% to 13.33% ± 9.43%, and 76.67% ± 4.71% to 26.67% ± 4.71%, respectively. Bacteriocin treatment did not reduce the rotten rate of balsam pear, but alleviated its symptoms.

Chitosan (CS) has been widely used to prepare natural hydrogel duo to its characteristics. However, most of the methods of preparing CS-based hydrogel are complicated and not green, which limits its further application. In this work, a green and antibacterial CS-based hydrogel was prepared by simple Schiff base reaction between CS and water-soluble 2,3-dialdehyde cellulose (DAC) obtained by simple heat treatment of DAC of high oxidation degree. The effect of DAC dosage on the properties of hydrogel, including water content, swelling behavior, water retention, hydrogel strength and viscoelasticity, was evaluated. Fourier transform infrared spectroscopy, scanning electron microscopy, elemental analysis and thermogravimetric analysis were employed to characterize the hydrogel. The antibacterial activity of hydrogels against Escherichia coli and Staphylococcus aureus was confirmed in vitro experiments. The green and antibacterial CS-based hydrogel prepared with this facile strategy would be a promising candidate for the application in the area of biomedicine, food storage, etc.

Food-borne pathogenic bacteria are dispersed throughout the entire chain of the food industry. However, many food preservatives are limited by poor biocompatibility such as cumulative poisoning. The antimicrobial peptide is increasingly regarded as a promising preservative in food research due to its high bioactivity and low cytotoxicity. In this study, thirteen peptides were designed, synthesized, and screened for application as food preservatives. One of them, termed zp65, whose sequence is GIOAOIIIOIOO-NH2, demonstrated potent bactericidal effect against common Gram-negative strains including enterohemorrhagic Escherichia coli, Salmonella, and Citrobacter freundii. Encouragingly, zp65 showed negligible cytotoxicity to both mammalian cells and Galleria mellonella larvae. Peptide zp65 was prone to form α-helix structure in amphiphilic environments, facilitating its affinity with bacterial membrane. Furthermore, the proteolytic stability of zp65 was much higher than its derivatives consisting of totally natural amino acids. Isothermal titration calorimetry indicated that zp65 has a strong binding affinity to lipopolysaccharide with Kd = 1.3 μM, suggesting its possible action target on the bacterial envelope. Mechanistic studies revealed that this peptide also influenced the membrane potential of E.coli O157:H7 (O157) in a dose-dependent manner. Surprisingly, peptide zp65 did not induce disruption of membrane permeability even at a higher concentration of 4-fold minimal inhibitory concentration. By employing confocal microscopy, peptide zp65 labeled by fluorescein isothiocyanate mainly aggregated on the bacterial membrane. These results suggested that the bactericidal mode of action of zp65 is likely attributed to depolarization of the cell membrane. The minced lean beef experiment indicated that the maximum reduction of O157 reached 1.46 log colony-forming unit (CFU) per gram on day 1 after zp65 treatment at the dosage of 40 μg/g. Compared with the untreated cooked beef sample, the CFU of the zp65-treated group remained at a much lower level after 10-day storage. Subsequently, treatment with zp65 at concentrations above 32 μM also significantly reduced O157 viable counts in fresh tomato juice. And the zp65 treatment could rescue about 40% of Galleria mellonella larvae injected with O157-contaminated tomato juice. The peptide zp65 exhibits great potential and deserves further study as a candidate for food preservative.

Biofilm-producing pathogens, such as Acinetobacter baumannii, have aroused escalating attention. Because these bacteria could secrete mixture with close-knit architecture and complicated components to resist traditional antibiotics. Here, we reported an amphiphilic peptide denoted as zp3 (GIIAGIIIKIKK-NH2), which showed favorable bioactivity against Acinetobacter baumannii ATCC 19606 (minimal inhibitory concentration, MIC = 4 μM) and low cytotoxicity to mammalian cells Vero (half maximal inhibitory concentration, IC50 > 100 μM). Importantly, zp3 could inhibit the formation of biofilm at micromole level and eliminate around 50% preformed biofilm at 32 μM after 6 h treatment. This peptide was able to bind with biofilm while maintaining a helical structure in a mimic biofilm-rich environment. In vivo test demonstrated that zp3 rescued 33.3% of larvae after 48 h infection and reduced 1 log live bacteria inside the animal body after 6 h treatment. The bactericidal mode for zp3 was attributed to the combination of influencing ions balance at low concentration and inducing permeability alteration and pore formation on the Acinetobacter baumannii membrane at high concentration. Application on medical textiles also proved that zp3 could perform a good antibacterial activity in practice.

Multidrug-resistant (MDR) bacterial infection still poses a serious threat to public health, therefore, effective and safe antimicrobial agents are urgently needed. In this study, recombinant bacteriocin BMP32 (BMP32r) prepared by the Escherichia coli expression system had a broad-spectrum antibacterial activity even against some MDR bacteria and its minimum inhibitory concentration ranged from 9.2 to 36.8 mg/L. Furthermore, BMP32r showed good stable performance in heat, pH and storage. Moreover, the scanning electron microscope and transmission electron microscope revealed that BMP32r killed indicator strains through cell wall destruction, pore formation, and the membrane permeability increasing which was proved by propidium iodide uptake investigation. The wound healing of an animal MDR S. aureus infected model was promoted by BMP32r, and the safety was verified by the cytotoxicity assay that the viability of HFF cells remained 87.3% in even when the concentration of BMP32r was as high as 147.2 mg/L. In addition, no abnormalities or damages to major organs was found in vivo assessments after treatment with BMP32r. In conclusion, BMP32r has great potential to be developed as a safe antimicrobial agent to treat MDR bacterial infections.

Au nanoparticle coated carbon-supported Co(OH)2 (Co(OH)2@Au/C) composites are prepared by a two-step method and are used as electrocatalysts for BH4− electrooxidation. Transmission electron microscopy and X-ray diffraction analysis show that the as-prepared composites are only a few tens of nanometers in size, and the Co(OH)2 nanoparticles are coated with Au completely. The electrocatalytic activity of the as-prepared composites are tested by cyclic voltammetry, chronoamperometry, chronopotentiometry, and rotating disc electrode voltammetry, and the results show that the Co(OH)2(50)@Au(50)/C catalyst shows the highest electrocatalytic activity for BH4− electrooxidation among the as-prepared composites, and the electron-transfer number related to BH4− electrooxidation is 5.0 on the Co(OH)2(50)@Au(50)/C electrode.

This study investigated the effect of arginine (Arg) on the antagonistic activity of Metschnikowia citriensis against sour rot caused by Geotrichum citri-aurantii in postharvest citrus, and evaluated the possible mechanism therein. Arg treatment up-regulated the PUL genes expression, and significantly induced the pulcherriminic acid (PA) production of M. citriensis, which related to the capability of iron depletion of M. citriensis. By comparing the biocontrol effects of Arg-treated and untreated yeast cells, it was found that Arg treatment significantly enhanced the biocontrol efficacy of M. citriensis, and 5 mmol L−1 Arg exerted the best effect. Additionally, the biofilm formation ability of M. citriensis was greatly enhanced by Arg, and the higher population density of yeast cells in citrus wounds was also observed in Arg treatment groups stored both at 25 °C and 4 °C. Moreover, Arg was shown to function as a cell protectant to elevate antioxidant enzyme activity [including catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPX)] and intracellular trehalose content to resist oxidative stress damage, that directly helped to enhance colonization ability of yeasts in fruit wounds. These results suggest the application of Arg is a useful approach to improve the biocontrol performance of M. citriensis.

Photocatalytic water splitting for H2 evolution is appealing for transforming solar energy into clean chemical fuel. This technique generally requires noble metals as H2 evolution cocatalysts to fa...

Listeria monocytogenes and Cronobacter sakazakii are notorious pathogens involved in numerous foodborne outbreaks after ingested contaminated food. Bacteriocins are natural food preservatives, some of which have antimicrobial activity comparable with antibiotics. In this study, a plasmid encoded novel bacteriocin BMP11 produced by Lactobacillus crustorum MN047 was innovatively identified by combining complete genome and LC-MS/MS. The BMP11 was found to have rich α-helix conformation after prediction. Moreover, the antimicrobial activity of BMP11 was verified after its heterologous expression in E. coli with 1280 and 640 AU/mL against L. monocytogenes and C. sakazakii, respectively. After purification by anion-exchange chromatography and HPLC, BMP11 had MIC values of 0.3–38.4 μg/mL against tested foodborne pathogens. Further, it was found that BMP11 had bactericidal action mode with concomitant cell lysis to pathogens by growth curve and time-kill kinetics. The results of scanning electron microscope (SEM) and transmission electron microscope (TEM) indicated that BMP11 destroyed the integrity of cell envelope of pathogens with cell wall perforation and cell membrane permeabilization. The destruction of cell envelope integrity was further verified by propidium iodide (PI) uptake and lactic dehydrogenase (LDH) release. BMP11 increased inner-membrane permeability of C. sakazakii in a concentration-dependent manner. Meanwhile, BMP11 exhibited antibiofilm formation activity. In addition, BMP11 inhibited the growth of L. monocytogenes in milk. Therefore, BMP11 had promising potential as antimicrobial to control foodborne pathogens in dairy products.

A structure evolution map of face-centered cubic (fcc)-structured thiolate-ligand protected gold nanoclusters is outlined on the basis of total structure determination of a new 6e Au21(SR)15 (R = tert-butyl, t-Bu) cluster. The structural evolution map described some basic structural evolution patterns such as a triangle-Au3 and tetrahedron-Au4 associated gold-core evolution pattern and the periodic or symmetric growth of gold cores and ligand shells. According to the structural evolution map, a topological structure–electronic structure relationship is also proposed. The delocalized valence electronic properties of any fcc-structured gold clusters may be expressed as the linear combinations of the molecular orbitals of the fragment 2e units (Au3+ and Au42+). The structural disciplines and topological structure–electronic structure relationships reported in this work laid a basis for understanding the structural evolution and electronic structure of fcc-structured thiolate-protected gold nanoclusters. Part...

Carbon-supported bimetallic platinum–iron nanocatalysts (Pt–Fe/C) with various proportions of atoms, applied to direct borohydride/peroxide fuel cell (DBHFC) anode catalyst, are facilely prepared via a simple and low-cost chemical route in aqueous solution at ambient temperature. Transmission electron microscopy and X-ray diffraction results show the Pt–Fe alloy structure’s existence as well as the mean crystallite size of around 3 nm for Pt–Fe nanoparticles. Enhanced catalytic activity of Pt–Fe/C to BH4– electro-oxidation has been observed in electrochemical test (chronoamperometry, cyclic voltammetry, single fuel cell test, and rotating disc electrode voltammetry) results, and Pt67Fe33/C shows the best catalytic performance. High maximum power density of 65 mW cm–2 for DBHFC is acquired by using Pt67Fe33/C as anode at 25 °C. Furthermore, the electron-transfer number (n) related to BH4– oxidation is evaluated, and n of 4.9 can be achieved on Pt67Fe33/C electrode.

Foodborne pathogens cause diseases by food chain transmission, therefore preservatives or antimicrobials are essential for food products, among which bacteriocins are considered as promising alternatives of chemical preservatives. Moreover, bacteriocins can potentially be used as antibiotic alternatives. In this study, two genes of novel bacteriocins (BM1157 and BM1300) from probiotic Lactobacillus crustorum MN047 were identified, cloned, and then expressed in Escherichia coli expression system. The genes were inserted into expression vector pET-28a and transformed into competent E. coli BL21 (DE3) pLysS, after which the two bacteriocins were successfully heterologously expressed. Further, it showed that the BM1157 and the BM1300 had broad spectrum activity against gram-positive and gram-negative bacteria, including multidrug-resistant strains. The characteristics and action mode of the BM1157 were further investigated because of its higher antimicrobial activity. It was found that the BM1157 had MIC value of 5.2 μg/mL against both S. aureus and E. coli. Moreover, it was stable at high temperature and resistant to proteinases. The BM1157 had bactericidal action mode according to time-kill curve. The results of scanning electron microscope and transmission electron microscope demonstrated that the BM1157 killed Listeria monocytogenes by biofilm destruction and pore formation. The antibiofilm activity and pore formation were further verified by crystal violet dye and lactic dehydrogenase release. In addition, the BM1157 inhibited the growth of L. monocytogenes in milk.

Pathogens can stick to the surfaces of leaves and ready-to-eat leafy greens are usually eaten without any lethal treatment to remove them. In this study, the peptide zp80 was chemically synthesized and purified. It had α-helix structure by circular dichroism spectroscopy analysis. zp80 reduced aerobic bacteria in ready-to-eat vegetable salad and lettuce. zp80 had MIC values of 2–8 μM against 7 foodborne pathogens, it was 2 μM to Listeria monocytogenes. Growth curve and time-kill curve showed that zp80 exhibited bactericidal mode with partial cell lysis. Confocal microscope indicated that zp80 was able to penetrate inside the cell membrane and distributed in cytoplasm and nucleus. Cell deformation with sunken surface was observed using scanning electron microscope. Further, results of SYTOX green and DiSC3(5) showed that zp80 had membrane depolarization caused by pore formation. After entering cytoplasm of L. monocytogenes, zp80 could bind to DNA, and then precipitated DNA. In addition, zp80 induced the production of intracellular reactive oxygen species (ROS), which played a key role on lethal effect by analysis using SYTO9 and PI. Hurdling treatment with 64 μM zp80 reduced 4.18 log units of L. monocytogenes in fresh-cut lettuce and alleviated browning after 7-day storage.

Metschnikowia citriensis FL01 has great potential for biocontrol applications for its excellent biocontrol efficacy on postharvest diseases of citrus fruit, and the iron depletion by pulcherriminic acid (PA) and then formation of insoluble pigment pulcherrimin had been speculated as an important action mechanism. To identify the genes involved in pulcherrimin synthesis and reutilization in M. citriensis FL01, we de novo assembled the genome of M. citriensis FL01 based on long-read PacBio sequencing. The final assembled genome consisted of 12 contigs with a genome size of 25.74 Mb, G + C content of 49.16% and 9310 protein-coding genes. The genome-wide BLAST of the PUL genes of M. pulcherrima APC 1.2 showed that the four PUL genes were clustered and located on Contig 4 of M. citriensis FL01. In order to further clarify the role of pulcherrimin pigment on biocontrol of M. citriensis FL01, CRISPR/cas9 technology was used to knock out PUL2 gene that was responsible for PA synthesis and the pigmentless mutants with stable phenotype were obtained. The mutant strains of M. citriensis FL01 lost the ability to produce pulcherrimin pigment, and simultaneously lost the ability to inhibit the growth of Geotrichum citri-aurantii in vitro. Moreover, the biocontrol efficacy of pigmentless mutant strains against sour rot was about 80% lower than that of wild-type M. citriensis FL01. These results directly proved that the iron depletion was an important mechanism of M. citriensis FL01.