Preparation and characterization of zein-tannic acid nanoparticles/chitosan composite films and application in the preservation of sugar oranges

Chitosan-based food packaging film was prepared by incorporating zein-tannic acid nanoparticles (ZTNPs) into chitosan and was evaluated in terms of structure, physical, mechanical and functional properties. Results showed that there were hydrogen bonding interactions between ZTNPs and chitosan matrix, which is conductive to mechanical enhancements of chitosan films. Compared with the pure chitosan film, the composite films with 10% ZTNPs at pH 4 showed the increased tensile strength by 196.58%, increased elongation at break by 161.37%, decreased water vapor permeability by 70.76% and decreased oxygen permeability by 40.68%. The highest inhibition rates of this composite film-forming fluid against Escherichia coli and Staphylococcus aureus reached 83.32% and 72.35%, respectively. The composite film forming solution formed by adding 10% ZTNPs was used for sugar orange preservation. The weight loss rate of oranges was reduced and the nutrient retention rate was improved. This study expanded the application of chitosan-based packaging materials in fruit preservation.

Modified magnesium oxide/silver nanoparticles reinforced poly (butylene succinate-co-terephthalate) composite biofilms for food packaging application

MgO/Ag nanoparticles (NPs) were surface-modified with titanate coupling agent titaniumtriisostearoylisopropoxide (NDZ-130). A new antibacterial biofilm for food packaging was synthesized by combining the modified MgO/Ag NPs with poly (butylene succinate-co-terephthalate) (PBST). The modification improved the compatibility between the MgO/Ag NPs and the PBST matrix. The effects of the modified MgO/Ag NPs on biofilm mechanical, barrier, thermal, antibacterial and food preservation properties were evaluated. Compared with the PBST/MgO/Ag composite film, the modified PBST/MgO/Ag composite film showed an increase in tensile strength (TS) of 8.71% and elongation at break (EB) of 16.66%, additionally decreasing water vapor permeability (WVP) by 42.86%. The composite film also exhibited over 95% inhibition of Staphylococcus aureus and Escherichia coli. The modified PBST/MgO/Ag composite film avoided microbial contamination and preserved cherry tomatoes while maintaining moisture and firmness for six days. All results indicated that the prepared biofilms have a high potential for use as food packaging films.

Health-promoting properties of bioactive proteins and peptides of garlic (Allium sativum)

Garlic is a popular food spice with diverse and well-established medicinal properties. Many research interests have been directed toward the biological activities of the phytochemical constituents of garlic. However, prospects of its bioactive proteins and peptides have been understudied to date. With the advances in food proteomics/peptide research, a review of studies on garlic bioactive proteins and peptides, especially on their nature, extraction, and biological activities, is timely. Garlic has been reported to express several proteins, endogenous and protein-derived peptides with interesting bioactivities, including antioxidant, anti-inflammatory, antibacterial, antifungal, anti-proliferative, antiviral, anti-hypertensive and immunomodulatory activities, suggesting their therapeutic and pharmacological potentials. Compared to legumes, the low protein contents of garlic bulbs and their low stability are possible limitations that would hinder future applications. We suggest adopting heterologous expression systems for peptide overproduction and stability enhancement. Therefore, we recommend increased scientific interest in the bioactive peptides of garlic and other spice plants.

Biopolymer films incorporated with chlorogenic acid nanoparticles for active food packaging application

Food packaging is innovating towards more environmental-friendly polymers and broader applications of bioactive compounds. In this study, active packaging materials were successfully prepared by incorporating chlorogenic acid (CGA) nanoparticles into pullulan/gelatin polymer matrixes. The rhamnolipid (RL) and/or CGA were combined with chitosan (CS) to synthesize active nanoparticles by the ionic crosslinking method. The film containing CS/RL/CGA nanoparticles (F/CRC) exhibited both ultrahigh visible light (400-760 nm) transmittance (approximately 90%) and UVA (320-400 nm)-blocking efficiency (89.06%). Its fluorescent properties can be used for anti-counterfeiting. Significantly, the bacterial inhibition rates of F/CRC against E. coli and S. aureus were 92.14% and 98.72%. F/CRC also showed good antioxidant capability and biosafety. Finally, the packaging test further indicated that F/CRC could delay the browning of bananas and the bacteria growth of chicken samples. This work presents a green and feasible route to produce functional materials with UV-shielding properties for packaging applications.

Antimicrobial resistance characteristics and phylogenetic relationships of pleuromutilin-resistant Enterococcus isolates from different environmental samples along a laying hen production chain

Antimicrobial resistance in the laying hen production industry has become a serious public health problem. The antimicrobial resistance and phylogenetic relationships of the common conditional pathogen Enterococcus along the laying hen production chain have not been systematically clarified. 105 Enterococcus isolates were obtained from 115 environmental samples (air, dust, feces, flies, sewage, and soil) collected along the laying hen production chain (breeding chicken, chick, young chicken, and commercial laying hen). These Enterococcus isolates exhibited resistance to some clinically relevant antibiotics, such as tetracycline (92.4%), streptomycin (92.4%), and erythromycin (91.4%), and all strains had multidrug resistance phenotypes. Whole genome sequencing characterized 29 acquired antibiotic resistance genes (ARGs) that conferred resistance to 11 classes of antibiotics in 51 pleuromutilin-resistant Enterococcus isolates, and lsa(E), which mediates resistance to pleuromutilins, always co-occurred with lnu(B). Alignments with the Mobile Genetic Elements database identified four transposons (Tn554, Tn558, Tn6261, and Tn6674) with several ARGs (erm(A), ant(9)-la, fex(A), and optrA) that mediated resistance to many clinically important antibiotics. Moreover, we identified two new transposons that carried ARGs in the Tn554 family designated as Tn7508 and Tn7492. A complementary approach based on conventional multi-locus sequence typing and whole genome single nucleotide polymorphism analysis showed that phylogenetically related pleuromutilin-resistant Enterococcus isolates were widely distributed in various environments on different production farms. Our results indicate that environmental contamination by antimicrobial-resistant Enterococcus requires greater attention, and they highlight the risk of pleuromutilin-resistant Enterococcus and ARGs disseminating along the laying hen production chain, thereby warranting effective disinfection.

Detection of Methicillin-Resistant Staphylococcus Aureus using vancomycin conjugated silica-based fluorescent nanoprobe

Methicillin-Resistant Staphylococcus Aureus (MRSA) is a worldwide major pathogenic bacteria that has emerged over the past three decades as the leading cause of nosocomial and community-acquired infections. Biosensors can provide rapid, sensitive, and selective detection of the presence and number of bacteria in various environments. Herein, a novel fluorescence nanoprobe was designed as a biosensor for MRSA detection using dye-incorporated silica nanoparticles (FSiNP). Based on the results of specific surface area analysis using the Brauner Emmett-Teller (BET) method, the surface area of the nanoparticles was obtained at 377.127 m2/g, and the X-ray diffraction (XRD) analysis confirmed that it was in the amorphous phase. Vancomycin, as the bioreceptor, was immobilized on the silica surface through a hydrosilylation reaction, generating the biosensing platform FSiNP-Van. Each modification step was corroborated by the Fourier Transform Infra-Red (FTIR) spectroscopy. The sensing principle was based on the fluorescence-quenching mechanism of FSiNP-Van at 515 nm obtaining a rapid response time of 20 min. The FSiNP-Van nanoprobe provided a wide linear concentration range of 10-106 CFU/mL with a limit of MRSA detection calculated at 1 CFU/mL. The fluorescent nanoprobe demonstrated here is expected to find applications in point-of-care (POC) diagnostics to detect the presence of MRSA bacteria.

Graphene oxide influences transfer of plasmid-mediated antibiotic resistance genes into plants

As an emerging contaminant, antibiotic resistance genes (ARGs) are raising concerns about its significant threat to public health. Meanwhile, graphene oxide (GO), which also has a potential ecological damage with increasingly entering the environment, has a great influence on the transfer of ARGs. However, little is known about the effects mechanisms of GO on the migration of antibiotic resistance genes (ARGs) from bacteria into plants. In this study, we investigated the influence of GO on the transfer of ARGs carried by RP4 plasmids from Bacillus subtilis into rice plants. Our results showed that the presence of GO at concentrations ranging from 0 to 400 mg L-1 significantly reduced the transfer of ARGs into rice roots by 13-71 %. Moreover, the migration of RP4 from the roots to aboveground parts was significantly impaired by GO. These effects may be attributed to several factors. First, higher GO concentrations led to low pH in the culture solution, resulting in a substantial decrease in the number of antibiotic-resistant bacteria. Second, GO induced oxidative stress in rice, as indicated by enhanced Evans blue dye staining, and elevated levels of malondialdehyde, nitric oxide, and phenylalanine ammonia-lyase activity. The oxidative stress negatively affected plant growth, as demonstrated by the reduced fresh weight and altered lignin content in the rice. Microscopic observations confirmed the entry of GO into root cells but not leaf mesophyll cells. Furthermore, potential recipients of RP4 plasmid strains in rice after co-cultivation experiments were identified, including Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus cereus. These findings clarify the influence of GO on ARGs in the bacteria-plant system and emphasize the need to consider its potential ecological risks.

Do mould inhibitors alter the microbial community structure and antibiotic resistance gene profiles on textiles?

Mould inhibitors are closely associated with human health and have been extensively applied to textiles to prevent mould and insect infestations. However, the impact of these mould inhibitors on the microbial community structure on textiles and antibiotic resistance gene (ARG) profiles remains largely unexplored. In this study, testing techniques, including high-throughput quantitative PCR and Illumina sequencing, were employed to analyse the effects of three types of mould inhibitors -para-dichlorobenzene (PDCB), naphthalene, and natural camphor balls-on the composition of microbial communities and ARG profiles. The microbial mechanisms underlying these effects were also investigated. The experiments revealed that PDCB reduced the diversity of bacterial communities on textiles, whereas naphthalene and natural camphor balls exerted relatively minor effects. In contrast with bacterial diversity, PDCB enhanced the diversity of fungal communities on textiles, but significantly reduced their abundance. Naphthalene had the least impact on fungal communities; however, it notably increased the relative abundance of Basidiomycota. All three types of mould inhibitors substantially altered ARG profiles. Potential mechanisms responsible for the alterations in ARG profiles include microbial community succession and horizontal gene transfer mediated by mobile genetic elements. PDCB prominently increased the abundance of ARGs, mainly attributable to the relative enrichment of potential hosts (including certain γ-Proteobacteria and Bacillales) for specific ARGs. Thus, this study has important implications for the selection of mould inhibitors, as well as the assessment of microbial safety in textiles.

Co-exposure of microplastics and sulfamethoxazole propagated antibiotic resistance genes in sediments by regulating the microbial carbon metabolism

The concerns on the carriers of microplastics (MPs) on co-existing pollutants in aquatic environments are sharply rising in recent years. However, little is known about their interactions on the colonization of microbiota, especially for the spread of pathogens and antibiotic resistance genes (ARGs). Therefore, this study aimed to investigate the influences on the propagation of ARGs in sediments by the co-exposure of different MPs and sulfamethoxazole (SMX). The results showed that the presence of MPs significantly enhanced the contents of total organic carbon, while having no effects on the removal of SMX in sediments. Exposure to SMX and MPs obviously activated the microbial carbon utilization capacities based on the BIOLOG method. The propagation of ARGs in sediments was activated by SMX, which was further promoted by the presence of polylactic acid (PLA) MPs, but significantly lowered by the co-exposed polyethylene (PE) MPs. This apparent difference may be attributed to the distinct influence on the antibiotic efflux pumps of two MPs. Moreover, the propagation of ARGs may be also dominated by microbial carbon metabolism in sediments, especially through regulating the carbon sources of carboxylic acids, carbohydrates, and amino acids. This study provides new insights into the carrier effects of MPs in sediments.

Performance and mechanism of SMX removal by an electrolysis-integrated ecological floating bed at low temperatures: A new perspective of plant activity, iron plaque, and microbial functions

Improvements in plant activity and functional microbial communities are important to ensure the stability and efficiency of pollutant removal measures in cold regions. Although electrochemistry is known to accelerate pollutant degradation, cold stress acclimation of plants and the stability and activity of plant-microbial synergism remain poorly understood. The sulfamethoxazole (SMX) removal, iron plaque morphology, plant activity, microbial community, and function responses were investigated in an electrolysis-integrated ecological floating bed (EFB) at 6 ± 2 ℃. Electrochemistry significantly improved SMX removal and plant activity. Dense and uniform iron plaque was found on root surfaces in L-E-Fe which improved the plant adaptability at low temperatures and provided more adsorption sites for bacteria. The microbial community structure was optimized and the key functional bacteria for SMX degradation (e.g., Actinobacteriota, Pseudomonas) were enriched. Electrochemistry improves the relative abundance of enzymes related to energy metabolism, thereby increasing energy responses to SMX and low temperatures. Notably, electrochemistry improved the expression of target genes (sadB and sadC, especially sadC) involved in SMX degradation. Electrochemistry enhances hydrogen bonding and electrostatic interactions between SMX and sadC, thereby enhancing SMX degradation and transformation. This study provides a deeper understanding of the electrochemical stability of antibiotic degradation at low temperatures.

Abatement of antibiotics and resistance genes during catalytic ozonation enhanced sludge dewatering process: Synchronized in volume and hazardousness reduction

Based on the efficiency of the catalytic ozonation techniques (HDWS+O3 and MnFe2O4 @SBC+O3) in enhancing the sludge dewaterability, the effectiveness in synchronized abatement antibiotics and antibiotic resistance genes (ARGs) was conducted to determine. The results revealed that catalytic ozonation conditioning altered the distribution of target antibiotics (tetracycline (TC), oxytetracycline (OTC), norfloxacin (NOR), ofloxacin (OFL)) in the dewatered filtrate, the dewatered sludge cake and the extra-microcolony/cellular polymers (EMPS/ECPS) layers, achieving the redistribution from solid-phase adsorption to liquid-phase dissolution. The total degradation rate was over 90% for TC and OTC, 72-78% for NOR and OFL; the abatement efficiency of eleven ARGs reached 1.47-3.01 log and 1.64-3.59 log, respectively, and more than four eARGs were eliminated. The effective abatement of the absolute abundance of Mobile genetic elements (MGEs) (0.91-1.89 log) demonstrated that catalytic ozonation conditioning could also significantly inhibit horizontal gene transfer (HGT). The abundance of resistant bacteria was greatly reduced and the signal transduction of the typical ARGs host bacteria was inhibited. The highly reactive oxidation species (ROS) generated were responsible for the abatement of antibiotics and ARGs. These findings provided new insights into the sludge conditioning for ideal and synchronized reduction in volume and hazardousness by catalytic ozonation processes in sludge treatment.

Comparative study between three carbonaceous nanoblades and nanodarts for antimicrobial applications

The design of nanostructured materials occupies a privileged position in the development and management of affordable and effective technology in the antibacterial sector. Here, we discuss the antimicrobial properties of three carbonaceous nanoblades and nanodarts materials of graphene oxide (GO), reduced graphene oxide (RGO), and single-wall carbon nanotubes (SWCNTs) that have a mechano-bactericidal effect, and the ability to piercing or slicing bacterial membranes. To demonstrate the significance of size, morphology and composition on the antibacterial activity mechanism, the designed nanomaterials have been characterized. The minimum inhibitory concentration (MIC), standard agar well diffusion, and transmission electron microscopy were utilized to evaluate the antibacterial activity of GO, RGO, and SWCNTs. Based on the evidence obtained, the three carbonaceous materials exhibit activity against all microbial strains tested by completely encapsulating bacterial cells and causing morphological disruption by degrading the microbial cell membrane in the order of RGO > GO > SWCNTs. Because of the external cell wall structure and outer membrane proteins, the synthesized carbonaceous nanomaterials exhibited higher antibacterial activity against Gram-positive bacterial strains than Gram-negative and fungal microorganisms. RGO had the lowest MIC values (0.062, 0.125, and 0.25 mg/mL against B. subtilis, S. aureus, and E. coli, respectively), as well as minimum fungal concentrations (0.5 mg/mL for both A. fumigatus and C. albicans). At 12 hr, the cell viability values against tested microbial strains were completely suppressed. Cell lysis and death occurred as a result of severe membrane damage caused by microorganisms perched on RGO nanoblades. Our work gives an insight into the design of effective graphene-based antimicrobial materials for water treatment and remediation.

Targeting Anaerobic Respiration in Pseudomonas aeruginosa with Chlorate Improves Healing of Chronic Wounds

Objective: Pseudomonas aeruginosa is an opportunistic pathogen that can establish chronic infections and form biofilm in wounds. Because the wound environment is largely devoid of oxygen, P. aeruginosa may rely on anaerobic metabolism, such as nitrate respiration, to survive in wounds. While nitrate reductase (Nar) typically reduces nitrate to nitrite, it can also reduce chlorate to chlorite, which is a toxic oxidizing agent. Therefore, chlorate can act as a prodrug to specifically eradicate hypoxic/anoxic, nitrate-respiring P. aeruginosa populations, which are often tolerant to conventional antibiotic treatments. Approach: Using a diabetic mouse model for chronic wounds, we tested the role that anaerobic nitrate respiration plays in supporting chronic P. aeruginosa infections. Results: P. aeruginosa forms biofilm deep within the wound where the environment is anoxic. Daily treatment of P. aeruginosa-infected wounds with chlorate supported wound healing. Chlorate treatment was as effective as a treatment with ciprofloxacin (a conventional antibiotic that targets both oxic and hypoxic/anoxic P. aeruginosa populations). Chlorate-treated wounds showed markers of good-quality wound healing, including well-formed granulation tissue, reepithelialization and microvessel development. Loss- and gain-of-function experiments showed that P. aeruginosa requires nitrate respiration to establish a chronic wound infection and form biofilms. Innovation: We show that the small molecule chlorate, kills the opportunistic pathogen, P. aeruginosa, by targeting a form of anaerobic metabolism called nitrate respiration. Conclusion: Chlorate holds promise as a treatment to combat diverse bacterial infections where oxygen is limiting and/or where pathogens grow as biofilms because many other pathogens possess Nar and survive using anaerobic metabolism.

Gold nanoparticle conjugation enhances berberine's antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA)

Nanoparticle (NP) conjugation with various biomolecules is one of the most promising approaches for targeting Methicillin-resistant Staphylococcus aureus (MRSA). In this study, berberine (BER) was conjugated with gold nanoparticles (AuNPs) to enhance its antibacterial activity against MRSA. Chemically synthesized AuNPs were characterized by UV-vis spectroscopy, size distribution and Field Emission-Scanning Electron Microscope (FE-SEM) analysis. Berberine was conjugated with AuNPs and the conjugants were characterized using UV-vis spectroscopy and Fourier Transform Infrared (FTIR). The cytotoxicity of free and conjugated BER was also investigated. Comparative studies were conducted based on the Minimum Inhibitory Concentration (MIC) and anti-biofilm activities of conjugants and free BER against MRSA isolates. To verify cell membrane disruption and intracellular imbalance following treatment exposure, reactive oxygen species (ROS) and live-dead staining experiments were performed. In vivo antibacterial efficacy of treated groups was also assessed in a BALB/c mouse-infected skin model. DLS measurement, FE-SEM, and UV-vis spectroscopy confirmed the synthesis of AuNPs with a narrow size distribution of 49.38 nm and a zeta potential of -31.9 mV. The results from UV-vis spectroscopy and FTIR provided support for the functionalization of AuNPs by BER functional groups. The In vitro antibacterial results demonstrated that the conjugated BER exhibited a lower MIC value against MRSA (109.5 μg/ml) compared to free BER (165 μg/ml). Free and conjugated BER, at their MIC concentrations, demonstrated anti-biofilm activity, resulting in biofilm eradication of 13.9 and 22.33 %, respectively. The highest level of ROS production (93 %) was associated with the conjugated BER at a concentration of 27.37 μg/ml. This finding indicates a disruption in cell membrane integrity and a reduction in bacterial viability, as demonstrated by ROS and live/dead staining assays. The cytotoxicity study on the mouse L929 fibroblast cell line revealed approximately 100 % cell viability when exposed to free or conjugated BER at their MIC concentration. This result indicates the biosafety of both of the compounds. The in vivo study in the infected skin model groups treated with conjugated and free BER revealed MRSA survival rate of 2.7 % and 26 %, respectively. These findings suggest that conjugated BER could be an effective nanoformulation candidate with a potential role in managing MRSA associated infections.