Gram-positive Bacteria Bacillus Subtilis Research Articles

Preparation, spectroscopic characterization and antitumor-antimicrobial studies of some Schiff base transition and inner transition mixed ligand complexes

Mixed ligand complexes of Mn(II), Ni(II), Zn(II), La(III), Er(III) and Yb(III) metal ions were prepared from bidentate Schiff base ligand (L) as a primary ligand, derived from condensation of benzophenone and 1,8-naphthylenediamine, and 1,10-phenanthroline (Phen) as a secondary ligand. The new Schiff base ligand (N1-(diphenylmethylene)naphthalene-1,8-diamine) and its mixed ligand complexes were characterized by using elemental microanalysis, conductometric measurements, magnetic susceptibility and spectroscopic studies (UV–Vis, mass spectral analysis, IR, 1H NMR and SEM). In addition, their thermal analytical (TG and DTG) behavior has been reported. Measurements of the molar conductivity of the complexes in DMF solvent pointed out the electrolytic nature of all complexes except Mn(II) and Zn(II) complexes were non electrolytes. According to the elemental analyses data, it was observed that the mixed ligand chelates had the general formulae [M(L)(Phen)Cl2]Cl.2H2O (M = La(III), Er(III) and Yb(III)), [M(L)(Phen)Cl2].H2O (M = Mn(II) and Zn(II)) and [Ni(L)(Phen)Cl(H2O)]Cl.H2O. Based on these findings, all mixed ligand complexes had octahedral geometry. The SEM image of the Schiff base ligand illustrated its rods like morphology with and average particle size of 77 nm while, the image of Ni(II) complex showed non-uniform platelets structure with some scattered rods with an average particle size of 54 nm. Considerable applications were done to ensure the biological significance of Schiff base ligand and its new mixed ligand complexes with Phen against Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Bacillus subtilis) and fungal (Aspergillus flavus and Candida albicans) strains and anti-cancer activities against (MCF7 breast cancer cell line). The results obtained revealed that the complexes exhibited promising biological and anticancer activity. Moreover, molecular docking studies were applied to determine the probable binding mode among the Schiff base ligand and the active site of the crystal structure of E. coli YcbB acylated with meropenem (PDB ID: 6NTW) and breast cancer estrogen mutant L536S (PDB ID: 6SBO) receptors.

Bio-synthesis of ZnO nanoparticles and their in-situ coating on cotton fabric using Azadirachta Indica leaf extract for enhanced antibacterial activity

ABSTRACT ZnO nanoparticles (NPs) of average size of ~36 nm have been successfully synthesised using a low-temperature bio-synthesis method employing Azadirachta Indica leaf extract. Also cotton fabrics have been coated in-situ during synthesis of ZnO NPs for time durations of 30 , 45 , and 60 min. Amount of ZnO NPs on the cotton fabrics has been found to increase with increase in time. The bio-synthesized ZnO NPs have been found to be crystalline in structure without formation of any impurity phases. The agar diffusion method of antibacterial assay shows that ZnO NPs modified cotton fabrics is more efficient to perform antibacterial effect against Gram-negative bacteria (Escherichia coli) than Gram-positive bacteria (Bacillus subtilis). It has also been observed that better antibacterial effects are obtained for the fabric samples coated with ZnO NPs with more ageing time. That means, the modified fabrics with more NPs coated in longer deposition time show better antibacterial properties.

A Gut-Specific LITAF-Like Gene in Antheraea pernyi (Lepidoptera: Saturniidae) Involved in the Immune Response to Three Pathogens.

Antheraea pernyi (Guérin-Méneville 1855) is an important resource for silk, food, and biohealth products; however, exogenous pathogens largely affect the commercial application potential of this species. Since the gut is a key organ for the digestion and absorption of nutrients as well as for immune defense, we used comparative transcriptome analysis to screen for a gut-specific molecular tool for further functional research in A. pernyi. In total, 3,331 differentially expressed genes (DEGs) were identified in the gut compared with all other pooled tissues of A. pernyi, including 1,463 upregulated genes in the gut. Among these, we further focused on a lipopolysaccharide-induced tumor necrosis factor-α factor (LITAF) gene because of its high gut-specific expression and the presence of a highly conserved SIMPLE-like domain, which is related to the immune response to pathogenic infections in many species. The cDNA sequence of ApLITAF was 447-bp long and contained a 243-bp open reading frame encoding an 80-amino acid protein. Immune challenge assays indicated that ApLITAF expression was significantly upregulated in the gut of A. pernyi naturally infected with nucleopolyhedrovirus (NPV) or fed leaves infected with the gram-negative bacterium Escherichia coli (Migula 1895) and the gram-positive bacterium Bacillus subtilis (Ehrenberg 1835). Cell transfection showed that ApLITAF localized to the lysosome. Collectively, these results suggested that ApLITAF played a role in the immune response of A. pernyi and could facilitate the future research and breeding application in this species.

Evaluation of Ruthenium(II) N-Heterocyclic Carbene Complexes as Antibacterial Agents and Inhibitors of Bacterial Thioredoxin Reductase.

A series of ruthenium(II) complexes with N-heterocyclic carbene (NHC) ligands of the general type (arene)(NHC)Ru(II)X2 (where X = halide) was prepared, characterized, and evaluated as antibacterial agents in comparison to the respective metal free benzimidazolium cations. The ruthenium(II) NHC complexes generally triggered stronger bacterial growth inhibition than the metal free benzimidazolium cations. The effects were much stronger against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) than against Gram-negative bacteria (Escherichia coli, Acinetobacter baumannii, Pseudomonas aeruginosa), and all complexes were inactive against the fungus Candida albicans. Moderate inhibition of bacterial thioredoxin reductase was confirmed for selected complexes, indicating that inhibition of this enzyme might be a contributing factor to the antibacterial effects.

Functional Redundancy and Specialization of the Conserved Cold Shock Proteins in Bacillus subtilis.

Many bacteria encode so-called cold shock proteins. These proteins are characterized by a conserved protein domain. Often, the bacteria have multiple cold shock proteins that are expressed either constitutively or at low temperatures. In the Gram-positive model bacterium Bacillus subtilis, two of three cold shock proteins, CspB and CspD, belong to the most abundant proteins suggesting a very important function. To get insights into the role of these highly abundant proteins, we analyzed the phenotypes of single and double mutants, tested the expression of the csp genes and the impact of CspB and CspD on global gene expression in B. subtilis. We demonstrate that the simultaneous loss of both CspB and CspD results in a severe growth defect, in the loss of genetic competence, and the appearance of suppressor mutations. Overexpression of the third cold shock protein CspC could compensate for the loss of CspB and CspD. The transcriptome analysis revealed that the lack of CspB and CspD affects the expression of about 20% of all genes. In several cases, the lack of the cold shock proteins results in an increased read-through at transcription terminators suggesting that CspB and CspD might be involved in the control of transcription termination.

Myco-nanotechnological approach to synthesize silver oxide nanocuboids using endophytic fungus isolated from Citrus pseudolimon plant

The current study reports the isolation of Colletotrichum plurivorum, an endophytic fungus from a Citrus pseudolimon plant and its utilization in the green synthesis of silver oxide nanocuboids (Ag2O NCs) at room temperature. The synthesized nanocrystals were thoroughly characterized by UV–vis, FTIR spectroscopy, field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray diffraction (XRD) analyses. Electron microscopic images confirmed the formation of cuboid shaped particles having size 200−250 nm in length and 80−150 nm in width, whereas, XRD and selected area electron diffraction (SAED) pattern confirms the formation of cubic Ag2O nanocrystals. Then these Ag2O NCs are applied in antibacterial activities against a pathogenic gram-negative bacteria Escherichia coli and gram-positive bacteria Bacillus subtilis and found very good activities against them. Currently these types of nanocuboids have drawn great interest in the field of catalysis, photocatalysis to biomedical applications.

Fluorescent papain-encapsulated platinum nanoclusters for sensing lysozyme in biofluid and gram-positive bacterial identification

Fluorescent metal nanoclusters, a new class of fluorophores, have been widely used in the fields of biosensing, biological imaging, catalysis and advanced therapeutics. In this study, papain-encapsulated platinum nanoclusters (papain-Pt NCs) were synthesized via a biomineralization process, which showed intense green fluorescence with maximum excitation and emission wavelengths at 380 and 490 nm. A panel of characterizations was performed to investigate the optical properties, morphology and surface chemistry of Pt NCs, demonstrating the accurate formation of papain-Pt NCs with good dispersity and stability. As a “turn-off” fluorescence biosensor, papain-Pt NCs exhibited selective and relatively sensitive detection of lysozyme with an excellent linear concentration in the range of 70−1000 nM and a detection limit of 16.94 nM at a signal-to-noise ratio of 3. Meanwhile, Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus and Microbacterium) cells stained with papain-Pt NCs could emit obvious green fluorescence, whereas their counterparts of Gram-negative bacteria (Escherichia coli, Rhodobacter and Rhizobium) exhibited no fluorescence signal. These results indicate that papain-Pt NCs could be used as fluorescent label-free nanoparticles for the purpose of identifying Gram-positive bacteria. Our current study provides a highly promising fluorescent nanomaterial for lysozyme detection and bacterial differentiation, and opens crucial insights into the design of hybrid bioinspired systems intended for various diseases.

Cytotoxic and antimicrobial activities of secondary metabolites isolated from the deep-sea-derived Actinoalloteichus cyanogriseus 12A22.

The online version contains supplementary material available at 10.1007/s13205-021-02846-0.

Investigating the Possibility of Green Synthesis of Silver Nanoparticles Using Vaccinium arctostaphlyos Extract and Evaluating Its Antibacterial Properties.

Objective Vaccinium genus plants have medicinal value, of which Vaccinium arctostaphylos (Caucasian whortleberry or Qare-Qat in the local language) is the only available species in Iran. Public tendency to use herbal remedies and natural products such as synthesized nanoparticles is increasing due to the proof of the destructive side effects of chemical drugs. Nanosilver products have been effective against more than 650 microbe types. This study was aimed at assessing the possibility of green synthesis of silver nanoparticles using Vaccinium arctostaphylos aqueous extract and at evaluating its antibacterial properties, as well. Materials and Methods In order to synthesize silver nanoparticles, different volumes of Vaccinium arctostaphylos aqueous extract (3, 5, 10, 15, and 30 ml) were assessed with different silver nitrate solution concentrations (0.5, 1, 3, 5, and 10 mM) and different reaction time durations (1, 3, 5, 10, and 20 minutes) at room temperature using a rotary shaker with a speed of 150 rpm. Ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction analysis (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were carried out. The antibacterial activity of the aqueous extract and the synthesized nanoparticles was evaluated, as well. Results Silver nanoparticle formation process was confirmed with XRD analysis, transmission electron microscopy (TEM), and FTIR spectroscopy. The UV-Vis spectroscopy of silver colloidal nanoparticles showed a surface plasmon resonance peak at 443 nm under optimal conditions (3 ml aqueous extract volume, 1 mM silver nitrate solution concentration, and 3 min reaction time under sunlight exposure). The reduction of silver ions to silver nanoparticles in solution was confirmed, as well. Based on X-ray diffraction analysis, the size of silver nanoparticles was in the range of 7-16 nm. TEM images showed an even distribution of silver nanoparticles, with a spherical shape. FTIR spectroscopy demonstrated the presence of different functional groups of oxygenated compounds such as carboxyl, hydroxyl, and nitrogenous groups. The antibacterial properties of the synthesized nanoparticles were confirmed. Conclusion The synthesized nanoparticles showed more antibacterial properties against gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) than gram-negative ones (Escherichia coli and Salmonella enteritidis).

Ent-Clerodane diterpenoids from the stems of Croton krabas

The first phytochemical investigation from the stems of Croton krabas resulted in the isolation of three new ent-clerodane diterpenoids, crotonkrabases A–C (1–3), along with two known compounds, 12-oxohardwickiic acid (4) and crotonpyrone B (5). Their structures were elucidated using extensive spectroscopic methods. The structure of 3 was unambiguously proven by X-ray crystallography. Furthermore, the absolute configurations of compounds 1–3 were identified by NOESY and the comparison of their experimental ECD spectra with those of calculated ECD spectra reported in the literature. Compounds 1, 2, and 5 showed antibacterial activities against two Gram-positive bacteria (Bacillus cereus and Bacillus subtilis); whereas compound 4 exhibited weak antibacterial against B. cereus. In addition, compound 4 showed potent α-glucosidase inhibitory activity, which was lower than the reference standard acarbose.

Antibacterial Activity and Flavonoids Content of Artemisia cina Berg. ex Poljakov Ethyl Acetate Extracts

The medicinal plant-derived bioactive compounds have a potential for many biological activities, including antimicrobial activity. Artemisia cina is a medicinal plant from the Compositae family with the potential of having antitumor, antifungal, and antibacterial activity. This study aimed to determine the antibacterial activity and the flavonoid content of A. Cina’s ethyl acetate extract. Plants samples were extracted by ethyl acetate maceration method. Antibacterial activity was tested against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) by a disk diffusion method using 25, 50, and 100 mg/l extract concentrations. The flavonoid contents (quercetin and kaempferol) were measured using High-Performance Liquid Chromatography. The extracts of diploid and polyploid A. cina displayed some antibacterial activity, with the Gram-negative bacteria being more resistant than the Gram-positive counterpart. However, no significant difference was observed between the diploid and polyploid extracts. As for the flavonoid content, the highest quercetin content (0.5501 mg/ml) was found in the polyploid A. cina (J), while the highest kaempferol content (0.5818 mg/ml) was observed in the diploid A. cina (KJT). Although A. cina is widely grown in Indonesia, compared to other Artemisia species, A. cina has not been widely studied, especially its antibacterial potential and in related to its flavonoid content and the use of ethyl acetate as the extraction solvent.  This study reveals the potential of A. cina as a natural antibacterial agent.Â

Stochastic Spatial Simulation of Genetic Information Processes in the Minimal Cell

JCVI-syn3A is a genetically minimal cell whose genome consists of 493 genes, of which 452 are protein-coding. The genetic information processing reactions in JCVI-syn3A were recently solved stochastically using a well-stirred assumption which predicts the times of DNA replication initiation and elongation to be 8 and 50 minutes on average respectively after averaging over 1,000 replicate cells. This model approximately doubles the number of proteins according to genome-wide proteomics data as well as the number of ribosomal components over the course of a cell cycle. We introduce spatial heterogeneity and diffusion by constructing a 3D spatial model of JCVI-syn3A using cryo-electron tomograms to infer placement of large cellular components such as membrane boundaries and ribosomes. The ensemble of DNA configurations for the circular chromosome were generated using a random polymer where self-intersections and intersections with ribosomes were forbidden. Membrane-bound degradosome complexes were randomly distributed across the interior of the cell membrane. We fixed positions of the DNA, degradosomes, and ribosomes while simulating diffusion of RNA and proteins with more than 3,000 reactions including transcription of all 452 protein-coding genes and translation and degradation of all 452 mRNA under a reaction-diffusion master equation formulation using our GPU-based software, Lattice Microbes. Introducing spatial heterogeneity and requiring mRNA to diffuse to ribosomes and degradosomes to be translated or decayed results in a distribution of mRNA half-lives in agreement with measurements in other gram-positive bacteria Mycoplasma gallisepticum and Bacillus subtilis.

Cobalt(II) Complexes of (E)-2-(2-Hydroxy-3-methoxybenzalidene)hydrazinecarbo(thio)amides: Synthesis, FT-IR studies and their antimicrobial activity

In this present work, six new Co(II) complexes {1-6, [Co(L3)] (1); [Co(L2)] (2); [Co(L1)] (3); [Co(L2)(L3)] (4); [Co(L1)(L2)] (5); [Co(L1)(L3)] (6)} of (E)-2-(2-hydroxy-3-methoxybenzalidene)-N4-methylhydrazinecarbothioamide (HL1), (E)-2-(2-hydroxy-3-methoxybenzalidene)-hydrazinecarbothioamide (HL2) and (E)-2-(2-hydroxy-3-methoxybenzalidene)-hydrazinecarboamide (HL3), have been synthesized and characterized by elemental analysis, analytical and FT-IR spectral investigations. The FT-IR spectral data advocated the attachment of Co2+ ion to the Schiff's base ligand moiety through the azomethine nitrogen, thioketonic sulfur and phenolic-O atom. The synthesized complexes 1-6 were screened for their antibacterial activities in contradiction of on two gram-positive bacteria (Bacillus subtilis and Escherichia coli) and two gram-negative bacteria (Pseudomonas aeruginosa and Staphylococcus aureus) and also screened for their antifungal in contradiction of Aspergillus Niger and Candida Albicans. Those complexes showed reasonable to substantial inhibitory effect on tested bacteria strains, whereas they exposed an admirable inhibitory effect on tested fungal strains.

Green Synthesis of Nickel Oxide Nanoparticles using Populus ciliata Leaves Extract and their Potential Antibacterial Applications

ABSTRACT Green synthesis of nanoparticles has received a lot of attention from scientists globally because it is eco-friendly, relatively rapid, and a cost-effective method. This work presents a method for the green synthesis of nickel oxide nanoparticles (NiO-NPs) using leaf extracts of Populus ciliata as a reducing and stabilising agent. The synthesised NiO-NPs were characterised by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. It was found that the synthesised NiO-NPs shapes varied, were highly crystalline, and had a face-centred cubic geometry. The calculated crystallite size of the synthesised nanoparticles was 44 nm. Moreover, the antibacterial activity of the synthesised NiO-NPs was also conducted against Gram-positive bacteria (Bacillus subtilis, Bacillus licheniformis) and Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae). Bacillus subtillus showed a maximum inhibition zone of 28.1±1.6 mm, whereas Klebsiella pneumonia showed a minimum inhibition zone of 9.2±0.5 mm. It was also found that the antibacterial activity increased with an increase in the concentration of NiO-NPs. Keywords: antibacterial activity, green synthesis, nanoparticles, NiO, Populus ciliata.

Molecular and functional identification of a β-defensin homolog in large yellow croaker (Larimichthys crocea).

β-defensin (BD) is a cysteine-rich cationic antibacterial peptide that is active against a wide range of bacteria. Here, a β-defensin homolog (LcBD2) was identified in large yellow croaker (Larimichthys crocea). The open reading frame of LcBD2 contains 195 nucleotides, encoding a protein of 64 amino acids that possesses a typical arrangement of six conserved cysteine residues (C31 , C37 , C41 , C53 , C59 and C60 ). LcBD2 transcripts were constitutively expressed in all examined tissues and significantly increased in head kidney, spleen and gills by Vibrio alginolyticus. The synthetic LcBD2 peptide imparted antimicrobial effects on both Gram-negative bacteria (V. campbellii, V. parahaemolyticus, V. alginolyticus, V. harveyi and Pseudomonas plecoglossicida) and Gram-positive bacteria (Bacillus subtilis). We also observed that after treatment with synthetic LcBD2 peptide, numerous blisters appeared on the membrane of P. plecoglossicida, which in turn may result in cell membrane breakage and bacterial death. Moreover, the synthetic LcBD2 peptide significantly upregulated the expression levels of TNF-α2, IL-1β and CXCL8_L1 in monocytes/macrophages, while downregulated expression level of IL-10. The LcBD2 peptide also remarkedly enhanced the phagocytosis of monocytes/macrophages. These results indicate that LcBD2 not only protects large yellow croaker against multiple bacterial pathogens but also plays a role in activation of monocytes/macrophages.

Synthesis, structural, optical, dielectric properties, gamma radiation attenuation, and antimicrobial activity of V-doped hydroxyapatite nanorods

The nanoscale hydroxyapatite (HAp) is a significant material applied for bone tissue engineering in the human body. This study focuses on the impact of vanadium addition on nano-sized HAp synthesized by sol-gel/hydrothermal technique and microwave device. The as-prepared nanocomposites were analyzed by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transformed infrared spectroscopy (FTIR), and Raman spectroscopy. The calculated crystallite size of the pure and V-HAp ranged from 15.73 nm to 20.77 nm, as supported by the XRD technique. The surface morphology of V-HAp samples is nanorods. Furthermore, the diffused reflectance helps to obtain the absorption spectra and the bandgap of the investigated samples. The dielectric constant and AC electrical conductivity are varied with the applied frequency and recorded at room temperature for HAp and different V-concentrations HAps. The gamma ray's absorption was also studied to consider the gamma attenuation of the tested samples using Cs-137 and Am-241 radioactive sources. The antimicrobial activity of the synthesized nanopowders was considered against pathogenic Gram-negative bacteria (P aeruginosa and Klebseilla sp), Gram-positive bacteria (Micrococcus sp and Bacillus subtilis), and yeast pathogen (Candida albicans). Therefore, vanadium-doped HAp nanostructured can be used as a multifunctional material vis microbial inhibitory and gamma radiation shielding materials.

Profiling of Silk Sericin from Cocoons of Three Southern African Wild Silk Moths with a Focus on Their Antimicrobial and Antioxidant Properties.

Silk sericin was extracted from the cocoons of three Southern African wild silk moth species, namely Gonometapostica, G. rufobrunnae (Lepidoptera: Lasiocampidae), and Argema mimosae (Lepidoptera: Saturniidae); these three sericin extracts were analysed to determine the relationship that exists between their chemical structures and their functional properties. The relationship was investigated by utilising several methods that include the determination of the amino acid composition, and characterisation of the secondary structures with Fourier transformation infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The antibacterial properties of these three sericin extracts were evaluated by an agar well diffusion assay with three Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus, and Staphylococcus epidermidis) as test microorganisms; and, lastly, the antioxidant properties of the three sericin extracts were determined using several scavenging methods that include the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS˙+), and the ferric reducing antioxidant power (FRAP) assay. The amino acid composition in the silk sericin extracts from G. postica, G. rufobrunnea, and Argema mimosa in terms of the polar/non-polar ratio (P/NP) was found to be 65:35, 56:44, and 59:41, respectively. The FTIR spectra of these three silk sericin extracts showed distinct major bands such as amide A (3265 cm−1), amide B (3062 cm−1), amide I (1644 cm−1), amide II (1538 cm−1), and amide III (1244 cm−1). The XRD patterns of the silk sericin extracts revealed both amorphous and α-helical structures, with small crystalline regions. All three silk sericin extracts presented potent antibacterial efficacy against the three Gram-positive bacteria and were found to have excellent antioxidant activities against the tested free radicals.

Novel Biodegradable Starch Film for Food Packaging with Antimicrobial Chicory Root Extract and Phytic Acid as a Cross-Linking Agent.

The aim of the study was to obtain and evaluate the properties of biodegradable starch film with the addition of phytic acid (0.05%) as a cross-linking agent and chicory root extract (1–5%) as an antimicrobial agent. To prepare biodegradable film, extracts from chicory root obtained with water or methanol were used. The content of bioactive compounds (sesquiterpene lactones and total polyphenols) was evaluated in chicory extracts. The antibacterial activity of the extracts was tested against Gram-negative bacteria (Pseudomonas fluorescens, Escherichia coli) and Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) using the microculture method. The extracts acted as bacteriostatic agents, decreasing the growth rate (µmax), and extending the lag phase (tlag). The most sensitive bacterium in terms of film bacteriostatic activity was P. fluorescens; all extracts, irrespective of the solvent used, decreased its µmax value. S. aureus was the least sensitive. The obtained films were tested for their properties as food packaging (color, thickness, permeability, mechanical strength). Phytic acid improved the tensile strength and barrier properties of the films. The antimicrobial activity of the films was studied by the disk diffusion method against Gram-negative (P. fluorescens, E. coli) and Gram-positive (B. subtilis, S. aureus) bacteria, as well as fungi (Candida albicans, Aspergillus niger). The growth-inhibiting activity of each obtained film was observed for all tested microorganisms, and the most beneficial effect was observed for films with the 5% level of added extracts obtained with water. The growth-inhibiting activity for fungi, in particular for the yeast C. albicans, was low.

Facile synthesis of new composite, Ag-Nps-loaded core/shell CdO/Co3O4 NPs, characterization and excellent performance in antibacterial activity

Here, we report for the first time the synthesis of new composite Ag-NPs-loaded core/shell mixed oxides NPs, CdO/Co3O4. First, nano-precursors (1) and (2) consist of mixed (cadmium oxalate/cobalt oxalate) and (silver oxalate/cadmium oxalate/cobalt oxalate), respectively, have been synthesized and characterized. Then, thermal treatment of 1 and 2 at 400 °C resulted in the formation of composites CdO/Co3O4 (3) and Ag-NPs@CdO/Co3O4 (4), respectively. The materials have been characterized by IR, SEM, TEM, TGA and XRD. The morphologies of the materials were described from SEM images. TEM images revealing the formation of core–shell structure with average particles size 5–20 nm. The crystal sizes were calculated from XRD patterns and resulted in 14.21, 14.65, 15.06 and 15.79 nm for 1, 2, 3 and 4, respectively. All the materials undergo tests as antibacterial agents against Gram-positive bacteria (Bacillus subtilis and Enterococcus spp.) and Gram-negative bacteria (E. coli and Pseudomonas aeruginosa). Precursor 2 and composite 4 impart higher inhibition against all the bacterial strains compared to precursor 1 and composite 3.

Antioxidant and antibacterial properties of lemon, sweet, and cereal grasses

Total phenolic content (TPC), antioxidant and antibacterial activity of ethanol, water, and water:ethanol (50/50 vol/vol) extracts from wheat, spelt, rye, barley, sweet, and lemon grasses were studied. Both grass type and solvent used significantly (p < .05; MANOVA) affected the extracts’ properties. The water:ethanol extract from lemon grass showed the highest TPC (107.24 ± 2.22 mg GAE/g d.m.), DPPH radical scavenging activity (87.8% inhibition), and FRAP value (1,445.2 ± 14.1 µmol Trolox/g d.m.). Rye and barley grass extracts also exhibited strong antioxidant potential. Spelt and lemon grass demonstrated the highest antimicrobial activity among the ethanol and water:ethanol extracts, whereas among the water extracts, only rye grass showed antibacterial activity against all of the tested indicator microorganisms. Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) were inhibited by extracts at a concentration of 0.3 mg/ml, whereas gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) needed higher extract concentrations (5–20 mg/ml). Grass extracts are thus a potential source of biologically functional compounds. Practical applications There is an ongoing, extensive search for natural ingredients that either prevent or retard undesirable changes, such as oxidation or microbiological contamination, which take place in food products. In this study, extracts from different types of grasses exhibited strong and moderate antioxidant and antibacterial activities, which thus makes it possible to use them as additives (antioxidants or preservatives) in the design of novel beverages and food products. The results obtained in this study could be an important asset to the food industry, as they provide new insight into plant extracts that have the potential to be used in food supplements, health drinks, or food products with enhanced health properties.