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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)

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.

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.

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.

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.

Bacterial soft rot caused by Pectobacterium carotovorum has brought huge economic losses to post-harvest vegetables. In this study, vegetables were used as raw materials to produce food-grade antibacterial products, fermented by lactic acid bacteria, to control P. carotovorum. A total of 32 kinds of vegetables were fermented by Lactobacillus paracasei WX322, results showed that 31 vegetable fermentation products had antibacterial activities at different levels. The green pepper fermentation antibacterial product (GPFA) had the highest activity and was selected for further analysis. On the 7th day of fermentation, the antibacterial activity of GPFA reached the maximum, with 640 AU/mL. Two bacteriocins, GP-19 and EP-20, were identified by LC-MS/MS. Growth curve and time-kill curve showed that the GPFA could effectively inhibit and kill P. carotovorum at a dose-dependent manner. SYTO9TM/PI staining observation further confirmed its bactericidal ability. Meanwhile, GPFA treatment led to irregular deformation of cells with rough surface observed using scanning electron microscopy (SEM). Moreover, in vivo assay showed that GPFA treatment significantly reduced the disease incidence and decay degree of pepper soft rot. In addition, GPFA treatment could prolong the shelf life of fresh-cut bell pepper. This study indicates that antibacterial products based on vegetable fermentation can provide a new method for the control of vegetable soft rot.

Superbugs or multi-drug resistant pathogens are not only clinical issue but also highlighted in food safety. However, development of new antibiotics and safe preservatives is declining. A novel workflow was used to purify antimicrobial substance produced by Lactobacillus rhamnosus LS-8, in which ethyl acetate extraction, polypeptide column and HPLC were involved in the purification process. Subsequently, a novel antimicrobial substance was purified and identified as 4,6-dimethyl-1,2,5-triazepane-3,7-dione (C6H11N3O2) by mass spectrum, 1H NMR and 13C NMR analysis. Fortunately, it has significant inhibitory effect on both gram-positive and gram negative strains including multi-drug resistance pathogens. Also it had good heat stability and resistant to proteolytic enzymes, however, it was only active in acidic condition. The results of scanning electron microscopy (SEM) and transmission electron microscope (TEM) showed that LS-8-25 destroyed the ultrastructure of S. aureus and E. coli. The discovery is adding a new variety of antimicrobial substance produced by lactic acid bacteria.

Due to frequent outbreaks of sprouts-associated foodborne illness, sprouts have been considered as a “high risk” food. In this study, the antimicrobial peptide zp37 (GIKAKIIIKIKK-NH2), which possesses a helical structure, was found to exhibit a minimum inhibitory concentration (MIC) value of 16 μM on E. coli O157:H7, effectively killing such strain in vitro and reducing its population size by 94.7% in sprouts upon storage for seven days. The effect of zp37 on cell membrane was investigated, with results showing that zp37 caused membrane depolarization and weak membrane permeabilization, which in turn resulted in cellular deformation observable by scanning electron microscope (SEM). Peptide zp37 was labeled by FITC to track the cellular location of zp37. Fluorescence microscopy studies showed that a larger amount of FITC-zp37 entered the bacterial cells when exposed to a higher concentration of the labeled peptide. Confocal microscopy showed that FITC-zp37 was detectable in cell membrane and cytoplasm. Upon entering the cytoplasm, zp37 was found to bind to the DNA of E. coli O157:H7, causing DNA aggregation and precipitation. Moreover, in vitro (HEK293 cell) and in vivo (Galleria mellonella) assays demonstrated that zp37 exhibited low toxicity.

Many citrus farmers are deprived of their profits as a result of post-harvest losses in citrus production. Diverse microbial environments including fermented foods are necessary to be explored in the quest to get more novel biocontrol yeasts to control post-harvest pathogens in citrus. 90 yeasts were isolated from kimchi in this investigation. Inhibition tests in vitro showed that 10 of the 90 yeasts reduced the development of fungal mycelia by the formation of an inhibition zone. Molecular methods were used to identify the yeast isolates, and they were Pichia sp., Kluyveromyces marxianus, Yarrowia lipolytica, and Issatchenkia orientalis. Three isolates tested in vivo in citrus were able to reduce disease incidence within the range from 18 % to 57 %. The action mechanisms of the three yeasts were studied subsequently by determining the biofilm formation ability of the yeast isolates, screening of yeast isolates for extracellular lytic enzyme activity, evaluating the effect of yeast isolates’ volatile organic compounds (VOCs) on P. digitatum, investigating the competition for nutrients between P. digitatum and yeast isolates, etc. For Pichia kudriavzevii, the most effective one, reduced the incidence of green mold caused by Penicillium digitatum (Pd1 / CECT 20795) by biofilm formation, competition for nutrients, and emitting volatile organic compounds. K. marxianus showed antifungal activity by inducing resistance, and colonization on wound sites. Whereas Y. lipolytica inhibited P. digitatum by adhesion to pathogen mycelia and production of extracellular lytic enzymes. Evidence from this study suggests that some yeast strains isolated from kimchi have the potentials to inhibit green mold in citrus.

E. coli and C. sakazakii are both opportunistic pathogenic bacteria that widely found in food. Emerging of antibiotic resistance makes the treatment of Gram-negative bacteria infection become ever more difficult. Therefore, it is urgent to find new antibacterial compounds against Gram-negative bacteria. Our previous study showed that bacteriocin BM1157 had broad antibacterial activity against both Gram-positive and Gram-negative bacteria. However, its antimicrobial mechanism against Gram-negative bacteria is still unknown. In this study, propidium iodide uptake and lactate dehydrogenase release experiments showed that the membrane integrity and permeability of the two indicator strains were not affected by BM1157 treatment. Observation of the ultrastructure of both bacteria by SEM and TEM also indicated that BM1157 did not damage the cell membrane. However, it significantly inhibited the biofilm formation of both bacteria. Furthermore, the lable-free proteome showed that BM1157 disturbed the carbohydrate metabolism, amino acid metabolism, lipid metabolism and nucleic acid metabolism, and then bioactive molecule synthesis and intracellular metabolism were blocked, resulting in cell death. Down-regulation of gene expression was further confirmed by real-time quantitative PCR. This study indicates that bacteriocin BM1157 inhibited Gram-negative bacteria by non-pore mechanisms.

Bacterial soft rot is a devastating disease that harms vegetables. Lactic acid bacteria (LAB) can be effective antagonist against soft rot pathogens. In this study, Lactobacillus paracasei WX322 and its produced bacteriocin had antibacterial activities against a variety of foodborne pathogens and spoilage bacteria, including both Gram-positive and Gram-negative bacteria, especially the soft rot pathogen Pectobacterium carotovorum subsp. brasiliense BZA12 (Pcb BZA12). The in vivo antibacterial test proved that the bacteriocin produced by the L. paracasei WX322 could control soft rot disease of peppers caused by Pcb BZA12. The L. paracasei WX322 produced bacteriocin after fermentation for 36 h, which had broad antimicrobial activity. In addition, the bacteriocin produced by L. paracasei WX322 had good thermal stability and broad pH adaptation. Then, the complete genome of L. paracasei WX322 was sequenced with one circular chromosome and eight plasmids. Three bacteriocin gene clusters were identified in the genome by antiSMASH. Furthermore, seven genes in the three gene clusters were identified to be bacteriocins. Moreover, three of the seven bacteriocins were novel. The complete genome sequences of the L. paracasei WX322 can provide a better molecular basis of its antibacterial activity and biocontrol effect on bacterial soft rot disease.

Mesoporous Ni-P@NiCo2O4 composite materials have been fabricated via a facile strategy including solvothermal synthesis of Ni-P and subsequent chemical deposition of NiCo2O4. Due to the synergistic effect between Ni-P and NiCo2O4, the Ni-P@NiCo2O4 composite materials exhibit an enhanced performance (1240 F g−1 at 1 A g−1, 668 F g−1 at 16 A g−1) compared with the bare Ni-P materials (717 F g−1 at 1 A g−1, 106 F g−1 at 16 A g−1) and NiCo2O4 materials (741 F g−1 at 1 A g−1, 457 F g−1 at 16 A g−1). Furthermore, the AC//Ni-P@NiCo2O4 asymmetric capacitor exhibits superior energy/power densities (13.3 Wh kg−1/5.7 kW kg−1) and cycling behavior (78.3% retention after 10,000 cycles at 4 A g−1) than the AC//Ni-P asymmetric capacitor (7.4 Wh kg−1/5.7 kW kg−1, 63.4% retention after 10,000 cycles at 4 A g−1) and AC//NiCo2O4 asymmetric capacitor (10.4 Wh kg−1/5.6 kW kg−1, 32.4% retention after 10,000 cycles at 4 A g−1). The high performance makes the mesoporous Ni-P@NiCo2O4 composite materials promising electrode materials for supercapacitors.

In this study, preparation of nitrogen- and oxygen-codoped porous carbonaceous foam and its application as metal nanoparticles catalysts support for direct methanol fuel cell (DMFC) were presented. Tadpole-like single chain polymer nanoparticles stabilized water-in-acrylonitrile/divinyl benezene high internal phase emulsion (HIPE) was firstly prepared, and the formed HIPE was then converted into polymer of high internal phase emulsion (polyHIPE) through a radical polymerization reaction. Subsequently, the formed acrylonitrile/divinyl benezene based polyHIPE was hypercrosslinked via FeCl3 catalyzed Friedel-Crafts reaction in 1,2-dichloroethane. After pyrolysis of the hypercrosslinked polyHIPE at elevated temperature under N2 atmosphere, nitrogen- and oxygen-codoped porous carbonaceous foam exhibiting highly interconnected macroporous cells and a micro-/mesoporous carbon skeleton (carboHIPE) was obtained. The resultant carboHIPE was further applied as the support for Pt and Ru bimetal nanoparticles. Well-dispersed PtRu bimetal nanoparticles with a smaller size were perfectly dispersed on the surface of carboHIPE in the form of alloy phase. The PtRu alloy nanoparticles decorated carboHIPE (PtRu/carboHIPE) demonstrated superior electrocatalytic performances towards the methanol electrooxidation by comparison with Pt/carboHIPE and commercial PtRu/C with almost same Pt content, such as the higher current density, the better long term stability and the improved CO-resistance.

The multidrug-resistant strains of food spoilage bacteria and foodborne pathogenic bacteria in food are badly in need of being controlled by effective bio-preservatives. In this study, the XN8 strain was isolated from Jiangshui and identified as Lactobacillus coryniformis according to 16S rRNA gene sequence. One of the bacteriocins produced by XN8 was purified by ammonium sulfate precipitation and a series of chromatographic column, and designated as lactocin XN8-A (LXA). The molecular mass of LXA was 3100.0242 Da by MALDI-TOF MS. The LXA showed good heat, pH and storage stabilities. However, it was sensitive to proteases. The LXA was found to have a broad antimicrobial spectrum on both Gram-positive and Gram-negative bacteria including multidrug-resistant strains and Listeria monocytogenes. Its minimum inhibitory concentration (MIC) for both Escherichia coli and Staphylococcus aureus was 6.85 μg/mL. The LXA had a bactericidal mode without cell lysis by the growth curve and time-kill assay. The results of electron microscope showed that the LXA destroyed membrane permeability and induced pore-formation of target cells. Furthermore, the LXA induced cell cycle arrest at both G1 and G2/M phase by cell cycle analysis. This research suggests that the LXA has promising potential as bio-preservative in food industry.

Staphylococcus aureus is one of the most common foodborne pathogens, and it can cause food poisoning. As a promising alternative to antibiotic, bacteriocin has been widely used in food as bio-preservative. In this study, the bacteriocin BM1157 had good antibacterial activity against S. aureus according to growth curve. BM1157 treatment reduced positively charged hydrophilic group of cell surface and caused an increase of cell hydrophobicity. SEM and TEM images showed that BM1157 treatment damaged cell wall and caused nonuniform distribution of cytoplasmic materials. Results of propidium iodide (PI) uptake and lactic dehydrogenase (LDH) release indicated that BM1157 treatment damaged cell envelope integrity of S. aureus. Proteome analysis showed that 117 proteins were up-regulated and 408 proteins were down-regulated after BM1157 treatment, among which enzymes involved in peptidoglycan biosynthesis and proteins related to DNA replication and repair were included. Further, real-time quantitative PCR verified the gene down-regulation of proteins of peptidoglycan biosynthesis and DNA replication and repair of S. aureus. Moreover, agarose gel electrophoresis showed that BM1157 could bind to the DNA of S. aureus. This study suggested that BM1157 killed S. aureus by damage of cell wall and DNA.

The presence of pathogens in fresh-cut fruits represents a risk for the public health since these products generally do not receive any further treatment before consumption. In this study, a Lactobacillus pentosus MS031 was isolated from Sichuan Paocai with broad antibacterial activity against foodborne pathogens. Antimicrobial peptides produced by the L. pentosus MS031 had broad activity and resistance to heat, but they were sensitive to proteinases and their activity vanished under alkaline condition. Bacteriocin-like substance obtained by pH-absorption related methods showed activity only against Staphylococcus aureus. However, cell-absorbed substance and cell-secreted into culture substance had activity against both S. aureus and Escherichia coli. Foodborne pathogens in fresh-cut fruit mixture were controlled by the metabolites of the L. pentosus MS031 that Listeria monocytogenes was reduced by 96.3 %, Salmonella typhi and E. coli were decreased to an undetectable level. The complete genome of the L. pentosus MS031 was sequenced using Illumina and MinION nanopore platform with a size of 3,805,216 bp, consisting of one chromosome and eight plasmids. After mining using BAGEL4, two novel bacteriocins, pentocin MS1 and pentocin MS2, were identified. Furthermore, fragments of 5 antimicrobial peptides were identified by LC–MS/MS in the fermentation supernatant. In addition, antimicrobial cyclic dipeptides and small compounds were identified in the antimicrobial metabolites. The results indicate antimicrobial metabolites of the L. pentosus MS031 can control foodborne pathogens in fresh-cut product during subsequent cold storage, which is significant for food industry.

This study investigated the biocontrol efficiency of Metschnikowia citriensis strain FL01 against Geotrichum citri-aurantii, and evaluated possible mechanisms. The results showed that M. citriensis could effectively control the development of sour rot, and significantly inhibit the mycelial growth and spore germination of G. citri-aurantii. The population dynamics results and Scanning electron microscopy (SEM) analysis indicated that M. citriensis could rapidly colonize wounds and tightly adhere to the surface of the wounds to compete with G. citri-aurantii for nutrition and space. M. citriensis also showed the biofilm formation action in vitro. The response of G. citri-aurantii to different components of M. citriensis culture showed that only the yeast cells but not the extracellular metabolites and the volatile organic compounds (VOCs) exhibited inhibitory effect on the growth of G. citri-aurantii. M. citriensis adhered to the hyphae of G. citri-aurantii loosely and sparsely, and the production of lytic enzymes β-1, 3-glucanase (GLU) and Chitinase (CHI) could not be induced by G. citri-auranti. Iron affected the pulcherrimin pigment production and antagonism of M. citriensis indicating iron depletion as the most important antagonistic mechanism. Besides, M. citriensis also induced resistance of fruit against sour rot. These results suggested that M. citriensis could be used as the potential alternative of fungicides to control postharvest pathogens on citrus fruit.

The control of foodborne pathogens in raw/processed foods is urgently needed. Lactic acid bacteria (LAB) bacteriocins are promising natural food preservatives. In this study, 81 antibacterial LAB strains were isolated from pickles and dry-cured meats, among which 38 LAB isolates inhibited both Staphylococcus aureus and Escherichia coli. Broad antibacterial LAB strains consisted of Lactobacillus, Pediococcus, Staphylococcus, and Weissella after identification according to 16S rDNA sequences. Antimicrobial activity of crude bacteriocins of the 38 strains was tested against multiple foodborne pathogens and L. pentosus DZ35 was selected to investigate further. L. pentosus DZ35 started to produce bacteriocin at 36 h during fermentation. The bacteriocin of L. pentosus DZ35 had good thermostability and broad pH adaption ranging from pH 2 to pH 11. Its antibacterial activity was partially lost after treated by proteinases. Genome of L. pentosus DZ35 was sequenced using Illumina sequencing and MinION nanopore sequencing platform with a size of 3,962,622 bp, including nine circular plasmids. Two novel bacteriocins, pentocin DZ1 and pentocin DZ2, were identified using BAGEL4. The present study indicates that pickle has abundant bacteriocin-producing LAB and the probiotic L. pentosus DZ35 has promising potentials to control pathogens in food.

Nanoporous carbon (NPC) supported Pt-Cu nanocomposites (PtxCu/NPC) with different Pt/Cu molar ratios have been successfully synthesized via NaBH4 reduction method and used as anode catalysts for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The as-synthesized PtxCu/NPC electrocatalysts are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), cyclic voltammetry (CV), chronoamperometry (CA), rotating disc electrode (RDE) and fuel cell test. It has been found that the PtCu nanoparticles are uniformly dispersed on the surface of the NPC support with average size of about 2.3 nm. Besides, the PtxCu/NPC catalysts show higher activities for borohydride oxidation than that of monometallic Pt/NPC and Vulcan XC-72 carbon supported Pt2Cu (Pt2Cu/XC-72) catalysts. Especially, the DBHFC equipped with Pt2Cu/NPC as anode catalyst shows the maximum power density of 89 mW cm−2 at 25 °C.

A series of nanoporous carbon supported Pd–Zn catalysts (Pd x Zn/NPC, x = 1, 2, 3) have been successfully prepared via impregnation-reduction method and firstly employed as anode catalysts for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The properties of the Pd x Zn/NPC electrocatalysts are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV), chronoamperometry (CA) and single fuel cell test. The TEM images of Pd 2 Zn/NPC catalyst reveal that the metal particles with a size of approximately 3.1 nm are uniformly dispersed on the nanoporous carbon (NPC). Besides, all the Pd x Zn/NPC catalysts exhibit enhanced catalytic activity and stability for BH 4 − electrooxidation compared to monometallic Pd/NPC in the electrochemical tests. Especially, the Pd 2 Zn/NPC catalyst exhibits the highest electrocatalytic activity toward borohydride oxidation among the four catalysts. Moreover, the DBHFC equipped with the Pd 2 Zn/NPC anode also presents an excellent cell performance with the maximum power density as high as 103.93 mW cm −2 at 25 °C.

Bacteriocins produced by LAB comprise a variety of antimicrobial proteins or peptides which can be used as food biopreservatives and/or possible antibiotic alternatives. Bacteriocin-producing Lactobacillus coryniformis MXJ 32, which was identified based on its 16S rRNA gene sequence, was isolated from a traditional fermented vegetable ( Jiangshui Cai ) of Xixiang county, Shaanxi province, China. Thereafter bacteriocin (designated as lactocin MXJ 32A) produced by L. coryniformis MXJ 32 was purified by ammonium sulfate precipitation, dialysis and ion exchange chromatography. The molecular mass of lactocin MXJ 32A was 3520 Da determined by LC-ESI/MS and the N-terminal sequence of lactocin MXJ 32A was NH 2 -GEPGPMGPAGAD. Lactocin MXJ 32A had a broad antimicrobial spectrum including many Gram-positive and Gram-negative foodborne pathogens, in which even some antibiotic-resistant foodborne pathogenic strains could also be inhibited. The MIC of lactocin MXJ 32A for Staphylococcus aureus and Escherichia coli was 10 mg/mL. Lactocin MXJ 32A showed good pH-stability and heat stability and was sensitive to proteolytic enzymes. It was shown by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) that the possible mode of action of lactocin MXJ 32A was pore formation of the cytoplasmic membrane of target cells.

The nanoporous carbon (NPC) is synthesized by carbonization of metal–organic framework-5 (MOF-5, [Zn4O(bdc)3], bdc = 1,4-benzenedicarboxylate) with furfuryl alcohol (FA) as carbon source and used as the carrier of the anode catalyst for the direct borohydride–hydrogen peroxide fuel cell (DBHFC). Then the NPC-supported Pt anode catalyst (Pt/NPC) is firstly prepared by a modified NaBH4 reduction method. The obtained Pt/NPC catalyst is characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS), cyclic voltammetry, chronopotentiometry, chronoamperometry and fuel cell test. The results show that the Pt/NPC is made up of the spherical Pt nanoparticles which disperse uniformly on the surface of the NPC with average size 2.38 nm, and exhibits 36.38% higher current density for directly borohydride oxidation than the Vulcan XC-72 carbon supported Pt (Pt/XC-72). Besides, the DBHFC using the Pt/NPC as anode electrocatalyst shows the maximum power density as high as 54.34 mW cm−2 at 25 °C.

The present study evaluated the antifungal properties of tetrapeptide H-OOWW-NH2 (O3TR) and its derivative lipopeptide C12-OOWW-NH2 (C12O3TR) against Penicillium digitatum, one of the main postharvest pathogens in citrus, and the possible mechanisms of their antifungal action. The results showed that the peptides O3TR and C12O3TR could inhibit conidial germination, induce conidia death and reduce the survival of mycelia of P. digitatum in vitro. The antifungal properties of O3TR and C12O3TR against P. digitatum were thermostable (40 °C–80 °C), insensitive to the change of pH (3–10) and varying sensitive to the presence of cations (Na+, Ca2+). In addition, the two peptides could effectively control green mold on citrus in vivo study. In terms of safety evaluation, the hemolytic activity of O3TR was neglectable, and significantly lower than that of C12O3TR, both of which were much lower than that of commercial prochloraz. The signals and intensity of fluorescent dye SYTOX Green (SG) and Propidium Iodide (PI) showed that O3TR and C12O3TR could enhance the mycelial and conidial membrane permeabilization. The antifungal action of O3TR and C12O3TR was further demonstrated by the release of cellular constituents and extracellular conductivity. In conclusion, the two peptides have a promising prospect to be applied as antifungal agents for the control of the green mold of citrus postharvest diseases.

With the appearance of superbug and environment pollution, it is urgent to find a viable alternative to synthetic fungicide for controlling postharvest disease on citrus, especially for the control of the main pathogen Penicillium digitatum. The aim of this study was to isolate lactic acid bacteria (LAB) with antifungal activity against P. digitatum and investigate their antifungal characteristics. Sixty-eight LAB were isolated from surface of citrus fruit, leaves of citrus and peanuts, and soil in citrus orchards. Ten strains which belonging to three species (Lactobacillus sucicola, Weissella paramesenteroides, Pediococcus acidilactici) had strong inhibitory effects in vitro. After neutralization and catalase treatment, the cell-free supernatants of the L. sucicola JT03, W. paramesenteroides JT13 and P. acidilactici JY03 still exhibited partial inhibitory effect. However, their antifungal activities were partially lost after treated by proteinases. Moreover, they were especially sensitive to trypsin that antifungal activity of cell-free supernatants of the three LAB strains was totally lost. This result indicated that proteinaceous compounds might play an important role in antifungal activity for the LAB strains.

Lithium titanium phosphate (LiTi 2 (PO 4 ) 3 ) has been successfully synthesized by a polyvinyl alcohol (PVA) assisted sol–gel method. To further improve its electrochemical properties, a ball-milling process with various amount of acetylene black (AB) has been used to form LiTi 2 (PO 4 ) 3 -AB nanocomposites (the weight ratio of acetylene black is 5 wt.%, 10 wt.%, 15 wt.% and 20 wt.%). The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Electrochemical performance of the samples is characterized by the charge–discharge test, cyclic voltammetry (CV), electrochemical impedance spectroscopic studies (EIS), and galvanostatic intermittent titration technique (GITT). The results show that the ball-milling process enables LiTi 2 (PO 4 ) 3 nanoparticles to network with conductive acetylene black, which offers better electrochemical performance. Especially, LiTi 2 (PO 4 ) 3 -AB nanocomposite with 15 wt.% acetylene black shows the best electrochemical properties, which delivers the highest specific capacity and the best cycle performance. Besides, the thermodynamics properties of as-prepared samples are also been studied.

A spherical lithium-rich layered cathode material with an average composition of Li 1.13 [Mn 0.534 Ni 0.233 Co 0.233 ] 0.87 O 2 was successfully synthesized via co-precipitation route. In this material, each particle was consisted of an inner core and a stable concentration-gradient outer layer in which manganese content was gradually increased. The concentration-gradient material showed a typical rhombohedral LiNiO 2 -like layered structure with the existence of the monoclinic Li 2 MnO 3 -type integrated component. It can be found from the cross-sectional SEM images that the concentration-gradient particle was quite homogeneous without any apparent gap between the inner core and the concentration-gradient outer layer. Furthermore, according to the EDXS analysis, the concentrations of Mn, Ni, and Co kept almost constant throughout the core, and the concentration of Mn increased gradually within the outer layer of the particle. The lithium-rich layered material can deliver a very high capacity of 220 mAh g −1 , and the excellent cycle life and improved thermal stability were achieved by the concentration-gradient outer layer. The results here indicate that the lithium-rich layered material with a manganese-rich concentration-gradient outer layer will be a promising cathode material for advanced lithium ion batteries with high capacity, long cycle life, and improved safety.

With the direct carbonization using polyaniline/activated mesocarbon microbead (PANI/ACMB) composites as the precursor and subsequent activation treatment with 16 M HNO 3 , the activated nitrogen-enriched novel carbons (a-NENCs) can be prepared. Scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption/desorption isotherm at 77 K are utilized to characterize the structure, morphology and physicochemical properties of the a-NENCs. The result shows that the a-NENCs keep the original leechee-like morphology of the PANI/ACMB composites. The supercapacitive performances of the a-NENCs are investigated with cyclic voltammetry (CV), galvanostatic charge/discharge tests, impedance spectroscopy (EIS) and cycle life measurements in 6 M KOH. The results based on galvanostatic charge/discharge tests demonstrate that the maximum specific capacitance of the a-NENCs electrode is 385 F g −1 . Meanwhile, the specific capacitance of the button supercapacitor using a-NENCs as electrode active material is as high as 89.5 F g −1 at the charge/discharge current density of 500 mA g −1 . These remarkable results demonstrate the exciting commercial potential for high performance, environmentally friendly and low-cost electrical energy-storage devices based on this new material.

Porous calcium carbide-derived carbon (CCDC) has been prepared by one-step route from CaC2 in a freshly prepared chlorine environment at lower temperature, and following activated by ZnCl2 to get activated CCDC. The performances of the supercapacitors based on activated CCDC as electrode active material in aqueous KOH, K2SO4, KCl and KNO3 electrolytes are studied by cyclic voltammetry, constant current charged/discharged, cyclic life and electrochemical impedance spectroscopy. It has been found that the supercapacitor using 6 M KOH as electrolyte shows an energy density of 8.3 Wh kg−1 and a power density of 1992 W kg−1 based on the total weight of the electrode active materials with a voltage range 0 V–1 V. Meanwhile, the specific capacitance of the supercapacitor in 6 M KOH electrolyte is 68 F g−1 at the scan rate of 1 mV s−1 in the voltage range of 0 V–1 V, the charge-transfer resistance is extremely low and the relaxation time is the least of all. The supercapacitor also exhibits a good cycling performance and keeps 95% of initial capacity over 5000 cycles.

In current study, nanowhisker-like NiO/carbon aerogel microbead (NiO/CAMB) composites with chestnut-like core–shell structure are prepared by in situ encapsulating method. The structure and morphology of NiO/CAMB are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results indicate that the appearance of composite becomes chestnut-like morphology with core–shell structure when NiO is coated. Electrochemical performances of the NiO/CAMB composites with different NiO contents are evaluated by using cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS). Results show that the supercapacitive behaviors of NiO/CAMB composites are largely improved due to the combination of electrical double-layer capacitance of CAMB and pseudo-capacitance based on the redox reaction of NiO. Especially, the 15%-NiO/CAMB composite exhibits the best capacitive properties, its specific capacitance is up to 356.2 F g −1 . Besides, the symmetric supercapacitor using 15%-NiO/CAMB composite as the electrode active material shows stable cycling performance.

Carbon supported Pt–Sn bimetallic nanoparticles (Pt–Sn/C) are prepared by a modified NaBH 4 reduction method in aqueous solution at room temperature, and used as the anode electrocatalyst for direct borohydride–hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared electrocatalysts are investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV), chronoamperometry (CA) and fuel cell test. XRD results show that the diffraction peaks in Pt–Sn/C catalyst shift slightly to lower 2θ values with the increase of Sn content compared with that of Pt/C catalyst, suggesting the formation of Pt–Sn alloying. TEM results show that the morphologies of Pt–Sn bimetallic nanoparticles are uniformly spherical with the particle size of about 3 nm on the carbon surface. Besides, it has been found that the Pt–Sn/C catalysts have much higher catalytic activity for the direct oxidation of BH 4 − than Pt/C catalyst, especially the Pt 67 Sn 33 /C catalyst presents the highest catalytic activity among all as-prepared catalysts. The DBHFC with Pt 67 Sn 33 /C anode catalyst and Pt/C cathode catalyst obtains the maximum power density as high as 91.5 mW cm −2 at 25 °C.

The graphene supported Pt nanoparticles are prepared by ethylene glycol reduction method. The obtained Pt/graphene (Pt/G) nanocomposites are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). TEM images show that the spherical Pt nanoparticles with sizes of 3.1 nm disperse uniformly on the surface of the graphene, which is consistent with the XRD date of 2.97 nm. The Pt/G nanocomposites show electrochemically active surface area (ECSA) of 62.7 m2/g. It has been found by electrochemical measurements (i.e., cyclic voltammetry, chronoamperometry) that the Pt/G nanocomposites exhibit good electrocatalytic activity and stability toward borohydride oxidation. Besides, the Pt/G nanocomposites are used as anode electrocatalyst in a direct borohydride fuel cell at 298 K, and the maximum power density is 42 mW/cm2, which is apparently higher than Vulcan XC-72R supported Pt (Pt/C) nanoparticles (34 mW/cm2).

Carbon-supported Pt–Co nanoparticle catalysts (Pt–Co/C) with a mean crystallite size of approximate 2 nm are prepared by a modified NaBH4 reduction method in aqueous solution at room temperature and employed as anode catalyst for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), chronoamperometry (CA) and fuel cell test. The results show that Pt–Co/C catalyst presents more excellent performance as DBHFC anode catalyst compared with Pt/C catalyst, especially, Pt67Co33/C catalyst presents the highest catalytic activity for BH 4 − electrooxidation among all as-prepared catalysts. The single DBHFC using Pt67Co33/C as anode catalyst and Pt/C as cathode catalyst obtains the maximum power density as high as 79.7 mW cm−2 at 25 °C.

Carbon supported Pd hollow nanospheres (HN-Pd/C) are prepared by employing cobalt nanoparticles as sacrificial templates at room temperature in aqueous solution, and used as the anode electrocatalyst for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared nanospherical electrocatalysts are investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), linear sweep voltammetry (LSV), chronoamperometry (CA), chronopotentiometry (CP) and fuel cell test. The results show that the Pd nanospheres supported on the carbon are coreless and composed of a series of Pd nanoparticles with the average crystallite size of about 3.8 nm. Besides, the HN-Pd/C exhibits distinctly higher electrocatalytic activity for BH 4 − electrooxidation than the carbon supported Pd solid nanoparticles (SN-Pd/C), and the DBHFC using HN-Pd/C as anode electrocatalyst shows as high as 48.4 mW cm −2 power densities at a discharge current density of 54.8 mA cm −2 . Therefore, the HN-Pd/C catalyst can apparently improve the catalytic activity of BH 4 − electrooxidation and imply a promising application in the DBHFC.

The carbon supported AuNi electrocatalyst (AuNi/C) for electrochemical oxidation of borohydride is prepared in water-in-oil microemulsion of water/AOT/n-heptane. The effects of the molar ratios of water to AOT (Rω) on the particle size and catalytic performance are systemically investigated. It has been found that when the Rω is less than 10, the particle size increases with the increase of Rω value, and the particle size is decreased after Rω > 10 due to two-phase separation of the microemulsion. The morphology and structure of as-prepared AuNi/C electrocatalysts are examined by transmission electron microscopy (TEM) and X-ray diffractometer (XRD). It is confirmed that all AuNi nanoparticles are spherical with average diameters in the range of 3–9 nm and uniformly distributed on the surfaces of carbon. The electrooxidation behaviors of BH 4 − on the AuNi/C anodic electrocatalyst have been investigated. The results show that the catalytic activity of BH 4 − oxidation on AuNi/C electrocatalyst is apparently improved and the smaller particle size can get a higher catalytic activity.

Carbon supported Au–Cu bimetallic nanoparticles are prepared by a modified NaBH 4 reduction method in aqueous solution at room temperature. The electrocatalytic activities of the Au–Cu/C catalysts are investigated by cyclic voltammetry, chronoamperometry, chronopotentiometry and fuel cell experiments. It has been found that the Au–Cu/C catalysts have much higher catalytic activity for the direct oxidation of BH 4 − than Au/C catalyst. Especially, the Au 67 Cu 33 /C catalyst presents the highest catalytic activity for BH 4 − electrooxidation among all as-prepared catalysts, and the DBHFC using Au 67 Cu 33 /C anode catalyst and Au/C cathode catalyst shows the maximum power density of 51.8 mW cm −2 at 69.5 mA cm −2 and 20 °C.

Carbon supported Pt–Cu bimetallic nanoparticles are prepared by a modified NaBH4 reduction method in aqueous solution and used as the anode electrocatalyst of direct borohydride–hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared electrocatalysts are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP) and fuel cell test. The results show that the carbon supported Pt–Cu bimetallic catalysts have much higher catalytic activity for the direct oxidation of BH4− than the carbon supported pure nanosized Pt catalyst, especially the Pt50Cu50/C catalyst presents the highest catalytic activity among all as-prepared catalysts, and the DBHFC using Pt50Cu50/C as anode electrocatalyst and Pt/C as cathode electrocatalyst shows as high as 71.6 mW cm−2 power density at a discharge current density of 54.7 mA cm−2 at 25 °C.

A series of Mn2O3/carbon aerogel microbead (Mn2O3/CAMB) composites for supercapacitor electrodes have been synthesized by in situ encapsulation method. The structure and morphology of Mn2O3/CAMB are characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrum and scanning electron microscopy (SEM). Electrochemical performances of the synthesized composites are evaluated by cyclic voltammetry and galvanostatic charge/discharge measurement. All the composites with different Mn2O3 contents show higher specific capacitance than pure CAMB due to the pseudo-capacitance of the Mn2O3 particles dispersed on the surface of CAMB. The highest specific capacitance is up to 368.01 F g−1 when 10 wt% Mn2O3 is coated on the surface of CAMB. Besides, 10%-Mn2O3/CAMB supercapacitor exhibits excellent cyclic stability, the specific capacitance still retains 90% of initial capacitance over 5000 cycles.

Bismuth–vanadium oxyfluoride (Bi 2 VO 5 F) has been synthesized using a simple, solid-state reaction process at different sintering temperatures. The structure and performance of the samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge experiments. The results show that bismuth–vanadium oxyfluoride belongs to a tetragonal crystal system with space group I4mm . The sample that was synthesized at 550 °C (P550) exhibits relatively good electrochemical properties. Sample P550 shows a high, initial discharge capacity of 222 mAh g −1 at a rate of 100 mA g −1 between 1.4 and 3.5 V. Sample P550 also shows acceptable electrochemical cycling properties. After the first cycle, the discharge specific capacity remains between 106 and 155 mAh g −1 , which plateaus between 2.1 and 1.9 V during the first 15 cycles.

The carbon supported Pt hollow nanospheres were prepared by employing cobalt nanoparticles as sacrificial templates at room temperature in aqueous solution and used as the anode electrocatalyst for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared electrocatalysts were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP) and fuel cell test. The results showed that the carbon supported Pt nanospheres were coreless and composed of discrete Pt nanoparticles with the crystallite size of about 2.8 nm. Besides, it has been found that the carbon supported Pt hollow nanospheres exhibited an enhanced electrocatalytic performance for BH 4 − oxidation compared with the carbon supported solid Pt nanoparticles, and the DBHFC using the carbon supported Pt hollow nanospheres as electrocatalyst showed as high as 54.53 mW cm −2 power density at a discharge current density of 44.9 mA cm −2 .

Co 3 O 4 /carbon aerogel microbead (Co 3 O 4 /CAMB) composites are prepared by in situ coating method and their supercapacitive behaviors are investigated. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrum, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectrum are used to characterize the structure and morphology of Co 3 O 4 /CAMB. The results show that nano-sized Co 3 O 4 particles are homogenously encapsulated on the surface of CAMB. Electrochemical performances of the composite electrodes with different Co 3 O 4 amount are studied by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements. It is found that Co 3 O 4 /CAMB composites show better electrochemical performance than CAMB, and the optimum content of Co 3 O 4 in Co 3 O 4 /CAMB composites is 10 wt.%. The specific capacitance of 10%–Co 3 O 4 /CAMB composite in 6 mol L −1 KOH electrolyte is about 350.18 F g −1 at a current density of 1 A g −1 . Moreover, 10%–Co 3 O 4 /CAMB composite supercapacitor exhibits relatively good high-rate capability and excellent cycle life.

The carbon supported Au-base electrocatalysts (Au (1−x) Zn x /C, 0 ≤ x (1−x) Zn x nanoparticles all were uniformly spherical no matter what Zn content changed, and the average particle size of Au (1−x) Zn x bimetallics varied from 3 to 6 nm. The electrochemical measurements revealed that the Au (1−x) Zn x /C electrocatalysts showed no activity toward the NaBH 4 hydrolysis reaction and obviously improved the catalytic activity of borohydride oxidation. Compared with Au/C anode electrocatalyst, the stability of DBFC using the Au 0.65 Zn 0.35 /C as anode electrocatalyst was apparently improved, and the maximum power density of 39.5 mW cm −2 was obtained at 20 °C.

Carbon aerogel (CA) microspheres have been successfully synthesized by an inverse emulsion polymerization and characterized by scanning electron microscopy (SEM), N2 sorption isotherm and X-ray diffraction (XRD). The results show that the size and pore characteristics of carbon microsphere obviously depend on stirring speed and concentration of surfactant in the emulsion polymerization process. The resultant CA microspheres are amorphous carbon structure with the size ranging from about 2 to 50 μm by changing the stirring speed. CA microspheres with SBET of 414–603 m2 g− 1 and Vmeso of 0.028–0.432 cm3 g− 1 are synthesized using different SPAN80 concentrations. The results of cyclic voltammetry indicate that the CA microspheres prepared at a stirring speed of 480 rpm and at Vs/Vh = 0.01 have ideal supercapacitive behavior in 6 M KOH electrolyte, the maximum specific capacitance of the electrode reaches 180 F g− 1.