Antibacterial Products Research Articles

High-Throughput Fabrication of Antibacterial Starch/PBAT/AgNPs@SiO2 Films for Food Packaging.

In this current work, antimicrobial films based on starch, poly(butylene adipate-co-terephthalate) (PBAT), and a commercially available AgNPs@SiO2 antibacterial composite particle product were produced by using a melt blending and blowing technique. The effects of AgNPs@SiO2 at various loadings (0, 1, 2, 3, and 4 wt%) on the physicochemical properties and antibacterial activities of starch/PBAT composite films were investigated. AgNPs@SiO2 particles were more compatible with starch than PBAT, resulting in preferential distribution of AgNPs@SiO2 in the starch phase. Infusion of starch/PBAT composite films with AgNPs@SiO2 marginally improved mechanical and water vapor barrier properties, while surface hydrophobicity increased as compared with films without AgNPs@SiO2. The composite films displayed superior antibacterial activities against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The sample loaded with 1 wt% AgNPs@SiO2 (SPA-1) showed nearly 90% inhibition efficiency on the tested microorganisms. Furthermore, a preliminary study on peach and nectarine at 53% RH and 24 °C revealed that SPA-1 film inhibited microbial spoilage and extended the product shelf life as compared with SPA-0 and commercial LDPE packaging materials. The high-throughput production method and strong antibacterial activities of the starch/PBAT/AgNPs@SiO2 composite films make them promising as antimicrobial packaging materials for commercial application.

Susceptibility pattern of methicillin resistance Staphylococcus aureus (MRSA) by flow cytometry analysis and characterization of novel lead drug molecule from Streptomyces species

BackgroundActinomycetes particularly, Streptomyces species are producing wide variety of natural products with potential bioactivities. The microbial-derived metabolites hold a strong position to combat emerging and re-emerging antimicrobial drug-resistant pathogens. ObjectivesA diverse group of actinomycetes strains were isolated from unexplored regions of mangrove sediment. Further, a polyphasic approach based on 16S rRNA gene sequence analysis and to evaluate their antibacterial potential against a panel of bacterial pathogens and methicillin resistance Staphylococcus aureus (MRSA). MethodsThe mangrove sediment samples were serially diluted with sterile water and plated on inorganic starch agar medium. A total of 20 isolates were pure cultured and 16S rRNA gene sequences were deposited in the public nucleotide databases (GenBank, NCBI). All the isolates were screened for the antibacterial activity by agar overlay method. Further, the susceptibility pattern of MRSA by flow cytometry and fluorescence microscopy was analysed. ResultsThese twenty different isolates were grouped under nine major clad and they shared 95–99% sequence identity to the 16S rRNA gene sequences of the genus Streptomyces in the public nucleotide databases. Among these strains, the isolates namely JRG-02, JRG-03, JRG-04, JRG-10 and JRG-12 exhibited a broad-spectrum antibacterial activity against Methicillin-resistant Staphylococcus aureus(MRSA) and Gram negative bacteria Klebsiella pneumoniae MTCC109. Furthermore, we have characterized the antibacterial compound production and its properties from the isolate JRG-02, a potential drug candidate. The culture conditions and various nutrient components of strain Streptomyces sp. JRG-02 were optimized for enhanced antibiotics production of the isolate. The FT-IR and LCMS spectrum analysis envisaged the chemical nature of the substance. The effect of antibacterial compound on the viability of MRSA was alone examined by flow cytometry (FACS) and fluorescence microscopy analysis. ConclusionsThe present study clearly shows that the survival of diverse inhabitants of Streptomyces in the mangrove sediments. Hence, the mangrove sediment inhabiting strain Streptomyces sp. JRG-02 has potential pharmaceutical activity and genetic diversity.

A novel antibacterial and biocompatible wound cover made of gelatin/chitosan with silver nanoparticles of green synthesis

A dressing material based on the combination of gelatine, chitosan and silver nanoparticles with a suitable proportion has been developed and can be successfully applied in biomedical fields. The new gelatin/chitosan membranes were prepared using the chitosan suspension mixed with gelatin and silver nanoparticles (AgNPs), resulting in a biocompatible and antibacterial product. AgNPs were obtained by the reduction of silver nitrate with chitosan solution and added to chitosan/gelatin (GCs) blend solutions to obtain membranes by the casting method. Thus, membranes with three different AgNPs concentrations were produced: 30 mM, 20 mM and 10 mM AgNPs. To evaluate the characteristics of the membranes, physicochemical and morphological tests were carried out, such as infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission (TEM), and in vitro cytotoxicity and bacterial assays. The formation of AgNPs was confirmed by Visible Ultraviolet to Ultraviolet to Visible (UV–vis) and TEM, where the nanoparticles were observed by the formation of the peak spectrum at a wavelength at 560 nm. According to the TEM images, polymorphic nanoparticles with an average size of 30 nm were obtained. Furthermore, the results of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) indicated the presence of silver evenly distributed within the membranes. The results obtained by (FTIR) showed spectral peaks characteristic of the membrane materials, that is, typical spectra of gelatin, chitosan and silver. These results could be explained by addition of free −OH, −NH2 and −NHOCOCH3 groups of the amorphous chitosan in the blends and a network structure through electrostatic interactions between the ammonium ions (−NH3+) of the chitosan and the carboxylate ions (−COO−) of the gelatin. The concentrations of AgNPs 30 mM and 20 mM in the membranes attributed to them a high hydration rate and high water vapor permeability (WVP). Membranes with 30 mM AgNPs showed bacterial effect against Staphylococcus aureus and Pseudomonas aeruginosa, concentrations of 20 mM AgNPs and 10 mM AgNPs, bacteriostatic effect against Staphylococcus aureus and bacterial effect against Pseudomonas aeruginosa. In the results of the in vitro assays, 10 mM AgNPs membranes were not cytotoxic. With the results obtained, GC membranes with up to 10 mM AgNPs are candidates for use in the fields of biomaterials and biomedicine.

Development of a High-Throughput Strategy for Functional Enhancement and Alteration of Antibacterial Natural Products

Development of a High-Throughput Strategy for Functional Enhancement and Alteration of Antibacterial Natural Products

Freeze-thawed hydrogel loaded by Piper crocatum extract with in-vitro antibacterial and release tests

Indonesian red betel ( Piper crocatum ) has been used traditionally to cure wounds and to prevent diseases as well as an antiseptic, while the leaves were also reported to inhibit the growth of bacteria. On the other hand, polyvinyl alcohol (PVA) is a suitable biomaterial with a wide range of applications after being transformed into hydrogels. This paper reports on the encapsulation of P. crocatum extract in PVA hydrogel synthesized by the freeze-thaw method with varying compositions and its characterizations. The internal morphology of the composite hydrogels did show some phase separation between the liquid and solid phases, while the analysis of the Fourier-transform infrared spectra confirmed that the P. crocatum extract was successfully encapsulated in the hydrogels. The hydrogels were amorphous due to the scattering of the liquid trapped within the pores. The extract was stable within the range of the room to body temperature since no significant mass decomposition of the extract was observed. The compressive modulus and the fracture stress of the composite hydrogel decreased as the fraction of extract increased due to the unfrozen ethanol fraction during the freeze-thaw process. The composite hydrogels loaded by P. crocatum extract possessed antibacterial activity against Staphylococcus aureus (gram-positive) and Pseudomonas aeruginosa (gram-negative). The release of extract from the hydrogels was immediate release following the pseudo-fickian diffusion for most of the composite hydrogels. This report thus suggests that the composite hydrogels are potential antibacterial products and can be applied for a biomedical device that requires antibacterial activity.

Challenges for the application of bacteriophages as effective antibacterial agents in the food industry.

Food contamination caused by foodborne pathogens is one of the most important concerns in public health worldwide, and accounts for a significant portion of food loss every year. The emergence of antimicrobial resistant bacteria has turned the attention of researchers back to the potential of bacteriophages as antibacterial agents, and their use has been attempted in various pre-and post-harvest food production settings. The application of phage-based antibacterial products has achieved considerable success but a number of technical, environmental and administrative challenges remain unaddressed. In this review, we summarize the current status of bacteriophage application in the food industry. We discuss the obstacles facing the further development of phage-based antibacterial products from the aspects of technology, environmental safety, and administrative policy. We also advance some possible solutions to these challenges. © 2021 Society of Chemical Industry.

Strategies toward development of antimicrobial biomaterials for dental healthcare applications.

Several approaches for elimination of oral pathogens are being explored at the present time since oral diseases remain prevalent affecting approximately 3.5 billion people worldwide. Need for antimicrobial biomaterials in dental healthcare include but is not restricted to designing resin composites and adhesives for prevention of dental caries. Constant efforts are also being made to develop antimicrobial strategies for clearance of endodontic space prior root canal treatment and for treatment of periimplantitis and periodontitis. This article discusses various conventional and nanotechnology-based strategies to achieve antimicrobial efficacy in dental biomaterials. Recent developments in the design and synthesis of antimicrobial peptides and antifouling zwitterionic polymers to effectively lessen the risks of antimicrobial drug resistance are also outlined in this review. Further, the role of contemporary strategies such as use of smart biomaterials, ionic solvent-based biomaterials and quorum quenchers incorporated biomaterials in the elimination of dental pathogens are described in detail. Lastly, we mentioned the approach of using polymers to print custom-made three-dimensional antibacterial dental products via additive manufacturing technologies. This review provides a critical perspective on the chemical, biomimetic, and engineering strategies intended for developing antimicrobial biomaterials that have the potential to substantially improve the dental health.

Changes of color and antibacterial characteristics of knitted fabrics dyed with reactive dyes after treatment with a nanocomposition of silver and carboxymethyl starch

Changes in the color characteristics of knitted fabrics after bactericidal finishes were studied by the colorimetric method. Antibacterial activity was tested with regard to gram-negative bacterium E. coli and gram-positive bacterium S. aureus. The strongest color changes due to the presence of Ag NPs were observed on samples dyed with lighter shades, where the color difference was mainly caused by the change in lightness and brightness. After treatment with silver NPs, the colors in samples dyed with Navy K-EN and Black NN are deepened, that is, the color intensity increases many times and the reflection coefficient decreases. Due to this effect, darker color tones can be achieved using less dye. The dyed knitted fabrics modified with Ag-carboxymethyl starch (AgCMS) NPs exhibited excellent antibacterial properties regardless of the dye color used. The dyeing did not affect the antibacterial activity of fabrics modified with AgCMS nanocomposites. The research on the resistance of the dyed knitted fabrics treated with nanocomposite AgCMS solution to washing showed the preservation of a sufficiently high antimicrobial activity, slightly decreasing only after the 10th wash in a washing solution. This is proved by exceptional resistance to washing of knitted fabrics modified with AgCMS. The results of the research allow one to solve the problem of expanding the range of antibacterial products and special clothes by treating textile materials with silver and carboxymethyl starch NPs.

Fabricating Ag@MOF-5 nanoplates by the template of MOF-5 and evaluating its antibacterial activity

MOF-5 was prepared by hydrothermal method and Ag@MOF-5 nanoplates were obtained to improve the antibacterial activity and dispersion of Ag nanoparticles. MOF-5 and Ag@MOF-5 were characterized by scanning electron microscope (SEM), high-resolution transmission electron microscope and energy spectrum (HR-TEM&EDS), X-ray diffraction (XRD), infrared spectrum (FTIR) and thermal gravimetric analysis (TGA). MOF-5 was flaky crystals accumulated and complexed to form cube-like crystalline particles with the size of 20–50 micrometers, and it was destroyed in the process of loading nano-silver particles. Ag@MOF-5 nanoplates were nanoscale sheets, and 3–5 nm Ag nanoparticles were uniformly dispersed and loaded on nanoplates of MOF-5. The content of silver nanoparticles reached 13 wt% of Ag@MOF-5 total weight. The results of antibacterial experiment indicated that antibacterial ability of MOF-5 was limited, while Ag@MOF-5 showed good antibacterial ability to Escherichia coli and Staphylococcus aureus. The 3–5 nm nano-Ag particles were uniformly loaded on the flaky crystals of MOF-5, and Ag@MOF-5 nanoplates were obtained. EDS showed that the content of Zn and Ag was 18.13 wt% and 38.87 wt%, respectively. Ag@MOF-5 nanoplates are expected to be further used in tissue engineering materials, drug carriers, antibacterial products and other similar fields.

The involvement of CgCaspase-8-2 in regulating the expressions of cytokines, antibacterial peptide and autophagy-related genes in oysters

Caspase-8 has been reported to be involved not only in apoptosis, but also in many other important immune response processes, such as inflammation and autophagy. In the present study, the open reading frame of CgCaspase-8-2 was cloned from the Pacific oyster Crassostrea gigas, which was of 2160 bp encoding 737 amino acids. There were two death effector domains (DEDs) and a cysteine aspartase cysteine structural (CASc) domain in the deduced amino acid sequences of CgCaspase-8-2. The mRNA expressions of CgCaspase-8-2 in haemocytes and gills all increased significantly after Vibrio splendidus stimulation at 3 h, 6 h, and 24 h. The cleaved CgCaspase-8-2 protein was observed in haemocytes at 3 h after V. splendidus stimulation and the expression of CgCaspase-8-2 protein was relatively higher in granulocytes, compared with that in agranulocytes. In CgCaspase-8-2-RNAi oysters, the mRNA expressions of CgIL17s (CgIL17-1, −2, −3, −4, −6), CgTNF, CgIFNLP and CgBigDef1 all decreased significantly at 12 h after V. splendidus stimulation. Meanwhile, the mRNA expressions of CgATG5 and CgBeclin1 decreased significantly at 12 h after V. splendidus stimulation, while CgBcl2 increased significantly. These results indicated that CgCaspase-8-2 was involved in not only the regulation of cytokine and antibacterial peptide production, but also autophagy-related gene expressions.

Total Syntheses of Hikosamine and Hikizimycin.

Hikizimycin (1) is a potent anthelmintic and antibacterial natural product. The core 4-amino-4-deoxyundecose sugar (hikosamine) of 1 consists of an 11-carbon linear chain substituted with one amino group and 10 hydroxy groups. The C1 and C6O positions of the 10 contiguous stereocenters are further appended by a cytosine base and a 3-amino-3-deoxyglucose sugar (kanosamine), respectively. Since the structural determination in the early 1970s, synthetic chemists have been attracted by this exceedingly complex structure and have investigated the full chemical construction of 1. These synthetic efforts culminated in four syntheses of the protected hikosamines and two total syntheses of 1. In this Perspective, we summarize the strategies and tactics utilized in these syntheses to showcase the evolution of modern natural product synthesis.

In Vitro and In Vivo Evaluation of Lacticaseibacillus rhamnosus GG and Bifidobacterium lactis Bb12 Against Avian Pathogenic Escherichia coli and Identification of Novel Probiotic-Derived Bioactive Peptides.

Avian pathogenic E. coli (APEC), an extra-intestinal pathogenic E. coli (ExPEC), causes colibacillosis in poultry and is also a potential foodborne zoonotic pathogen. Currently, APEC infections in poultry are controlled by antibiotic medication; however, the emergence of multi-drug-resistant APEC strains and increased restrictions on the use of antibiotics in food-producing animals necessitate the development of new antibiotic alternative therapies. Here, we tested the anti-APEC activity of multiple commensal and probiotic bacteria in an agar-well diffusion assay and identified Lacticaseibacillus rhamnosus GG and Bifidobacterium lactis Bb12 producing strong zone of inhibition against APEC. In co-culture assay, L. rhamnosus GG and B. lactis Bb12 completely inhibited the APEC growth by 24h. Further investigation revealed that antibacterial product(s) in the culture supernatants of L. rhamnosus GG and B. lactis Bb12 were responsible for the anti-APEC activity. The analysis of culture supernatants using LC-MS/MS identified multiple novel bioactive peptides (VQAAQAGDTKPIEV, AFDNTDTSLDSTFKSA, VTDTSGKAGTTKISNV, and AESSDTNLVNAKAA) in addition to the production of lactic acid. The oral administration (108CFU/chicken) of L. rhamnosus GG significantly (P < 0.001) reduced the colonization (~ 1.6 logs) of APEC in the cecum of chickens. Cecal microbiota analysis revealed that L. rhamnosus GG moderated the APEC-induced alterations of the microbial community in the cecum of chickens. Further, L. rhamnosus GG decreased (P < 0.05) the abundance of phylum Proteobacteria, particularly those belonging to Enterobacteriaceae (Escherichia-Shigella) family. These studies indicate that L. rhamnosus GG is a promising probiotic to control APEC infections in chickens. Further studies are needed to optimize the delivery of L. rhamnosus GG in feed or water and in conditions simulating the field to facilitate its development for commercial applications.

Phyto-fabrication of selenium nanorods using extract of pomegranate rind wastes and their potentialities for inhibiting fish-borne pathogens

Abstract The invasion of fish/seafoods by zoonotic pathogens causes health threats to humans. Plant derivatives and phytosynthesized nanometals could promisingly overcome bacterial infections/contaminations. The extract of pomegranate rinds (PRE) was innovatively employed for biosynthesizing selenium nanorods (Se-NRs). These agents were assessed as antibacterial candidates against diverse fish-borne pathogenic species (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Salmonella typhimurium, and Sphingomonas paucimobilis). The PRE-synthesized Se-NRs, within 60 min of contact, were negatively charged (‒32 mV) and had mean diameter of 62.31 nm and length range of 443.5–1236.9 nm. The designated infrared spectra for PRE and PRE/Se-NRs composite validated the biosynthesis, bonding, and interactions of the nanocomposite. The antibacterial potentialities of PRE, phytosynthesized Se-NRs, and PRE/Se-NRs composite was confirmed toward the entire challenged pathogens; S. aureus had the highest resistance (with inhibitory concentrations of 72.5, 60.0, and 55.0 mg/L, respectively) and S. paucimobilis was the most sensitive (with inhibitory concentrations of 55.0, 45.0, and 42.5 mg/L, respectively). The ultrastructure of the treated S. paucimobilis with PRE/Se-NRs emphasized the composite potentiality for deforming/distorting cells within 4 h and causing full cells’ destruction and deformation within 8 h of exposure. The PRE-phytosynthesized Se-NRs are advocated as potent antibacterial products against fish-borne pathogens for decontaminating fisheries farms and products.

Tıbbi Aromatik Bitki Ekstraktının Ahşabın Anatomik Yapısına Etkileri

In Since the beginning of history, the global world structure and medicinal aromatic plants in our country have been used in very rich areas (medical, cosmetic, food, spice, agriculture, animal husbandry, spice, paint industry, etc.). New human / environment friendly wood protective materials are being developed, thus efforts are made to create an antioxidant / antibacterial product structure in various areas such as hygienic furniture structure, children's toys, hospitals, etc. It has been reported by the World Health Organization (WHO) that the number of herbs used as medicinal and spice in the world is around 20,000. Preparing extracts from plants and using them as medicine, in China in BC. It dates back to 2700 BC. Rapid depletion of forest resources and exposure to synthetic / chemical effects in the environment in which human beings have lived pose serious threats. The anatomical properties of this material, which was aimed to create a much more organic structure by obtaining extracts (1%, 3%) of various medicinal and aromatic plants (meadow onion, chives) and bringing it into relationship with borax by double process, were examined and the scale of attachment was determined in relation to this. Due to its anatomical structure, the level of adhesion on spruce wood cross-sectional surfaces was evaluated microscopically and the net dry impregnation amount was calculated. In spruce wood, especially the passage aspiration structure is known to be among the most important elements that make it difficult to hold the material in the impregnation process.

The CARB-X Portfolio of Nontraditional Antibacterial Products.

The growing prevalence of antibiotic-resistant bacterial pathogens and the lack of new medicines to treat the infections they cause remain a significant global threat. In recent years, this ongoing unmet need has encouraged more research groups to focus on the discovery and development of nontraditional antibacterial agents, ranging from anti-virulence strategies to bacteriophage and ways to modulate the microbiome. The Combating Antibiotic-Resistant Bacteria Biopharmaceutical Accelerator (CARB-X) is a global nonprofit public-private partnership dedicated to accelerating antibacterial-related research. Importantly, the CARB-X portfolio supports a wide variety of novel and innovative nontraditional programs to help the global antibacterial research ecosystem understand the potential that these modalities can play in the management or prevention of serious infections. We describe here the breadth of the CARB-X pipeline of novel nontraditional products.

Synthesis and Antimicrobial Evaluation of Bis-morpholine Triazine Quaternary Ammonium Salts.

Efficient, environmentally and economically sustainable, and nontoxic antibacterial products are of global relevance in the fight against microorganism contamination. In this work, an easy and straightforward method for the synthesis of bis‐morpholino triazine quaternary ammonium salts (bis‐mTQAS) is reported, starting from 2,4,6‐trichloro‐1,3,5‐triazine or 2,4‐dichloro‐6‐methoxy‐1,3,5‐triazine and various N‐alkylmorpholines. Bis‐mTQAS were tested as antimicrobials against Gram‐negative and Gram‐positive bacterial strains. The best‐performing bis‐mTQAS were found to achieve total disinfection against Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922 at 50 and 400 μg/mL, respectively. Distinctively, bis‐mTQAS with the highest antimicrobial efficiency had lowest cytotoxicity.

Biologically synthesized silver nanoparticles, mediated by Bothriochloa laguroides, inhibit biofilm formation and eradicate mature biofilm of Yersinia enterocolitica and Staphylococcus aureus.

To phytosynthesize silver nanoparticles (AgNPs) and determine their antibacterial and antibiofilm capacity against gram-positive and gram-negative bacterial strains. AgNPs were synthesized using Bothriochloa laguroides aqueous extract as reducing and stabilizing agent. After characterization, a phytochemical screening to the extract and the AgNPs was performed. Antibacterial activity, inhibition and eradication of biofilms against Staphylococcus aureus and Yersinia enterocolitica strains were tested. Spherical AgNPs with an average size of 8nm were obtained. Tannins, flavonoids, carbohydrates, proanthocyanidins, anthocyanins and saponins were identified in aqueous extract; meanwhile, only carbohydrates were identified in AgNPs. The MIC and MBC were determined at pmol L-1 levels for all tested strains. Furthermore, AgNPs inhibited more than 90% of biofilms formation and eradicated more than 80% of mature biofilms at concentrations higher than MIC. The AgNPs obtained in this study inhibited planktonic and sessile growth, and eradicated mature biofilms of pathogenic bacterial strains at very low concentrations. The current study showed the promising potential of AgNPs as antibiofilm agents opening the way for the future development of a new class of antibacterial products.

Antibacterial and antioxidant potential of ethyl acetate extract from Streptomyces AIA12 and AIA17 isolated from gut of Chanos chanos

Abstract. Kurnianto MA, Kusumaningrum HD, Lioe HN, Chasanah E. 2021. Antibacterial and antioxidant potential of ethyl acetate extract from Streptomyces AIA12 and AIA17 isolated from gut of Chanos chanos. Biodiversitas 22: 3196-3206. Streptomyces has been recognized as a promising and productive source of antibacterial and antioxidant compounds. The phenotypic and genomic characterizations indicated AIA12 and AIA17 are closely related to the S. globisporus ARGB01 and S. misionensis S1-SC15, respectively. Incubation on yeast-malt extract broth for nine days (AIA12) and 11 days (AIA17) proved to be the best growth medium and optimum antibacterial production time for these two strains. Crude-extract of extracellular secondary metabolites, obtained by ethyl acetate extraction, demonstrated broad-spectrum inhibitory activity against Pseudomonas aeruginosa InaCC B52, Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 10876, Escherichia coli ATCC 25922, Salmonella Typhimurium ATCC 14028, and Listeria monocytogenes with minimum inhibitory and minimum bactericidal concentrations from 2.5 to 0.31 and 5.0 to 0.31 mg mL-1, respectively. Evaluation of antioxidant showed AIA17 crude-extract had moderate DPPH scavenging and antioxidant activities of 65.122% ± 0.56 and 28.178 ± 0.24 mg ascorbic acid equivalent antioxidant capacity (AEAC g-1), respectively. The identification of compounds through profiling with RP-HPLC showed optimum absorbance at 210 and 214 nm, which showed the presence of peptide groups in the constituent compounds' molecular structure. These findings indicate that Chanos chanos-derived Streptomyces produces valuable bioactive compounds with various promising biological activities.

A new way to reduce postharvest loss of vegetables: Antibacterial products of vegetable fermentation and its controlling soft rot caused by Pectobacterium carotovorum

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.

Annulation of Enals with Carbamoylpropiolates via NHC-Catalyzed Enolate Pathway: Access to Functionalized Maleimides/Iso-maleimides and Synthesis of Aspergillus FH-X-213.

Herein we report the N-heterocyclic carbene (NHC)-catalyzed [3 + 2] annulation of α,β-unsaturated aldehydes with carbamoylpropiolates via an unusual enolate pathway leading to the construction of highly functionalized maleimides or isomaleimides. The electronic effect imposed by the alkyl/aryl group present on the amide nitrogen of carbamoylpropiolates plays a crucial role in the selective formation of these important five-membered heterocyclic building blocks. The developed protocol is mild and tolerates a wide range of substituents on both substrates. The application of this protocol in the synthesis of the antibacterial natural product Aspergillus FH-X-213 has also been demonstrated.