Laser Scanning Microscopy Images Research Articles

Antimicrobial and anti-biofilm activity of Polygonum chinense L.aqueous extract against Staphylococcus aureus

Polygonum chinense Linn. (Polygonum chinense L.) is one of the main raw materials of Chinese patent medicines such as Guangdong herbal tea. The increasing antibiotic resistance of S. aureus and the biofilm poses a serious health threat to humans, and there is an urgent need to provide new antimicrobial agents. As a traditional Chinese medicine, the antibacterial effect of Polygonum chinense L. has been reported, but the antibacterial mechanism of Polygonum chinense L.aqueous extract and its effect on biofilm have not been studied in great detail, which hinders its application as an effective antibacterial agent. In this study, the mechanism of action of Polygonum chinense L.aqueous extract on Staphylococcus aureus (S. aureus) and its biofilm was mainly evaluated by morphological observation, flow cytometry and laser confocal experiments. Our findings demonstrate that Polygonum chinense L.aqueous extract has a significant bacteriostatic effect on S. aureus. The result of growth curve exhibits that Polygonum chinense L.aqueous extract presents a significant inhibitory effect against S. aureus. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) reveals that Polygonum chinense L.aqueous extract exerts a potent destruction of the cell wall of S. aureus and a significant inhibitory effect on the formation of S. aureus biofilm. In addition, flow cytometry showed the ability of Polygonum chinense L.aqueous extract to promote apoptosis by disrupting cell membranes of S. aureus. Notably, confocal laser scanning microscopy (CLSM) images illustrated the ability of Polygonum chinense L.aqueous to inhibit the formation of S. aureus biofilms in a dose-dependent manner. These results suggested that Polygonum chinense L.aqueous is a promising alternative antibacterial and anti-biofilm agent for combating infections caused by planktonic and biofilm cells of S. aureus.

Preparation and characterization of high internal phase Pickering emulsions stabilized by hordein-chitosan composite nanoparticles

In this study, hordein and chitosan were used to prepare composite nanoparticles (H-Cs) by anti-solvent precipitation method at pH 4.0. The addition of chitosan caused the increase in zeta-potential of H-Cs and the gradual decline in fluorescence intensity of H-Cs, indicating that chitosan was located on the hordein surface during the formation of H-Cs. Fourier transform infrared spectra of H-Cs illustrated that hordein and chitosan were combined to form composite nanoparticles by hydrogen bonds and hydrophobic interactions. The composite nanoparticle H-C25 (the mass ratio of hordein to chitosan 25:1) was chosen as Pickering stabilizer by measurement of three-phase contact angle. The O/W (oil-in-water) high internal phase Pickering emulsions (HIPPEs) stabilized by H-C25 (2.0 %, w/v) with oil fractions of 75 %− 85 % were further prepared. The confocal laser scanning microscope images and the rheological results indicated these HIPPEs had strengthen gel-like structure, leading to their excellent self-supporting capacity and storage stability. This study provides inspiration for designing protein-based food-grade HIPPEs in substitutes of partially hydrogenated vegetable oils (PHOs).

Impact of ethanol shock on the structural change and emulsifying capacity of bovine lactoferrin

The current study was focused on the structural change and emulsifying property of bovine lactoferrin (bLF) shocked by diverse ethanol levels (0%, 15%, 30%, 45%, 60%, and 75%, v/v). The fraction of β-sheet conformation was around 38.0% and dominated the bLF secondary structural component with the ethanol level from 0% to 75% (v/v). Both Try and Trp residues were involved in the interaction between bLF and ethanol. Hydrophobic effects and hydrogen bonds played crucial roles in the associations between bLF and ethanol molecules. Morphological observation revealed that the individual microstructures of bLF shocked by different levels of ethanol were irregular nanoparticles, worm-like structures, and short bars. The result of emulsifying capacity suggested that the bLF emulsion was stable at the ethanol level of 45% (v/v). Interfacial tensions were significantly decreased from 17.28 ± 0.27 to 1.78 ± 0.05 mN/m for single aqueous ethanol solutions, and from 13.58 ± 0.41 to 0.39 ± 0.01 mN/m for the bLF-E solutions with the ethanol level from 0% to 75% (v/v). Particle size distribution results and confocal laser scanning microscopy images evidenced that ethanol molecules were adsorbed at the oil-water interface, and bLF molecules escaped from the interface with the ethanol levels from 0% to 60% (v/v). As the level of ethanol was increased from 0% to 60% (v/v), the bLF surface load was significantly decreased from 98.44 ± 0.81 to 0.06 ± 0.06 mg/m 2 . The findings facilitated an understanding of the impacts of the structural variation of bLF and the concentration alteration of ethanol as a co-emulsifier on the emulsifying capacity of bLF. • Ethanol altered the tertiary conformation of bLF and led to its local denaturation. • BLF exhibited a prominent emulsifying capacity at the ethanol level of 45% (v/v). • Ethanol and bLF synergistically reduced the interfacial tension at the oil-water interface. • The structural change of bLF was intrinsically driven to enhance its emulsifying activity. • As a co-emulsifier ethanol modulated the emulsifying capacity of bLF.

Water distribution in maize starch-pea protein gels as determined by a novel confocal laser scanning microscopy image analysis method and its effect on structural and mechanical properties of composite gels

The objective of this study was to determine the water distribution in maize starch (MS) and pea protein isolate (PPI) composite gels and understand how the separate contributions of MS and PPI affect the mechanical properties of composite gels with varying MS/PPI ratios. A series of MS gels with increasing PPI contents and a series of PPI gels with increasing MS contents were prepared. The water distribution was evaluated with a novel image analysis method using confocal laser scanning microscopy (CLSM). This method was used to quantify the volume fraction of each phase, from which the water distribution between the starch phase and the protein phase within the gels was estimated. Depending on the MS/PPI ratios, either a dispersed or a bicontinuous gel was formed. The estimated stiffness of each phase was used to estimate the gel stiffness using models for either dispersed or bicontinuous structures. These predictions were shown to be in good agreement with experimental data obtained from compression tests. The determination of the properties of each phase separately allowed us to determine which phase dominated the properties of the composite gel. In filled gels, the MS network dominated the gel properties, unless the stiffness of PPI fillers was remarkably higher than that of the MS network. In bicontinuous gels, the stiffness of the composite gels was determined by the network with the highest stiffness. Dispersing pea protein aggregates (PPA) with different size into MS gels resulted in minor differences in mechanical properties compared to PPI-MS gel. These results show that this new analysis method can be used to predict water distribution within gels, and how this leads to changes in the stiffness, hardness and brittleness of the gels. • Water distribution can be estimated with a CLSM imaging analysis method. • Uneven water distribution was observed in all studied starch-protein gels. • Stiffness estimated based on theoretical models was in good agreement with experimental data. • In composite gels, the stiffer component dominates the gel properties.

Cover Image, Volume 71, Issue 1

GliaVolume 71, Issue 1 p. C1-C1 COVER IMAGEFree Access Cover Image, Volume 71, Issue 1 First published: 21 November 2022 https://doi.org/10.1002/glia.24194AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Cover Illustration: (Top) Image of the Cannabis sativa plant. (Bottom, left) Confocal laser scanning microscopy image of a mouse hippocampal astrocyte expressing GCaMP6f (green) (Alfonso Araque lab). (Bottom, center) Confocal laser scanning microscopy image of cultured oligodendrocytes stained for F-actin (phalloidin, red), alpha-tubulin (green) and DNA (Hoechst 3325-bisbenzimide, blue) (Eduardo Molina-Holgado lab). (Bottom, right) Confocal laser scanning microscopy image of mouse microglia immohistochemically stained for Iba1 (red) (Susana Mato lab). Volume71, Issue1Special Issue: Special Issue on Endocannabinoid signaling in glial cellsJanuary 2023Pages C1-C1 RelatedInformation

Development of dissolvable microneedle patches by CNC machining and micromolding for drug delivery

This study reports the fabrication of microneedles using computer numerical control (CNC) machining and micromolding for replicating dissolvable microneedles (DMNs) for drug delivery. Despite the ease of use and simple manufacturing by CNC, this method has not been extensively studied for the fabrication of microneedles. The master molds were fabricated using CNC machining; subsequently, DMNs embedded with fluorescent dye as a drug model were prepared using a hyaluronic acid (HA) and polyvinylpyrrolidone (PVP) solution in a rapid and comparatively simple micromolding process. The microneedles were evaluated for mechanical strength and penetration efficiency. The drug diffusion from DMNs was elucidated through confocal laser scanning microscopy (CLSM) imaging. The results show that fabricated DMNs are mechanically strong enough to penetrate the skin dermis layer and deliver their therapeutic cargo. In conclusion, CNC machining can provide rapid and low-cost fabrication of master molds, facilitating DMNs production for transdermal drug delivery.

Highly Emissive Luminogens in Both Solution and Aggregate States

Highly Emissive Luminogens in Both Solution and Aggregate States

A new approach to replace antibiotics with natural pigment derivatives: Surface modification on the titanium implants

Bacterial infections associated with metal implants and devices are an urgent challenge in biomedical materials, especially when bacterial biofilms form on the implant surface. Here, we developed a novel strategy to combat infections with bacteria-associated titanium implants. Curcumin molecular modification was carried out on the phenolic hydroxyl group to obtain curcumin carboxylic acid (Cur-COOH) with the β-diketone structure of curcumin retained. Cur-COOH was covalently immobilized on the (3-aminopropyl) triethoxysilane (APTES)-treated titanium surface via an amidation reaction to establish the curcumin-titanium implant interface (Ti-g-Cur). Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), water contact angle (WCA), and X-ray photoelectron spectroscopy (XPS) proved that Cur-COOH was successfully anchored on the titanium implants surface. Ti-g-Cur showed excellent antibacterial activity against E. coli and S. aureus, with antibacterial rates of 90.53 % and 94.38 %, respectively. Confocal laser scanning microscopy (CLSM) imaging showed that Ti-g-Cur could effectively inhibit bacterial biofilm formation for up to 5 days. In addition, Ti-g-Cur exhibited superior performance on mammalian hemocompatibility and cytocompatibility. Replacing antibiotics with natural pigment curcumin derivatives for application in biological materials can not only result in a high degree of biocompatibility but also fights bacteria and biofilm formation effectively.

High internal phase Pickering emulsion stabilized by sea bass protein microgel particles: Food 3D printing application

Food-grade high internal phase Pickering emulsions (HIPPEs) stabilized by protein-based particles have received widespread attention because of their potential applications in the food industry. Herein, HIPPEs stabilized by sea bass protein (SBP) microgel particles were prepared using a simple one-step method. Its internal phase volume fraction was as high as 88% oil-in-water emulsion. The impact of SBP microgel particles concentration on the physical and chemical properties of HIPPEs was investigated. The SBP microgel particles improved the environmental stability of HIPPEs. Confocal laser scanning microscope (CLSM) and cryo-scanning electron microscope (cryo-SEM) images showed a three-dimensional network structure formed around oil droplets through SBP microgel particles. The average particles size of the HIPPEs droplets decreased with the increased concentration of SBP microgel particles. In rheological analysis, as the concentration of SBP microgel particles increased, HIPPEs showed higher viscoelasticity, excellent recovery, and thixotropy, which further proved the potential application of HIPPEs in 3D printing. The physical and chemical stability of astaxanthin was improved after encapsulation of HIPPEs. Further, the lipolysis degree of HIPPEs and the bioaccessibility of astaxanthin during in vitro digestion were improved also by the SBP microgel particles. Interestingly, the bioaccessibility of astaxanthin in HIPPEs stabilized by 4 wt% SBP microgel particles reached 51.17%. Three-dimensional (3D) printing experiments confirmed the extrudability, printing performance, and self-supporting properties of HIPPEs. In short, the HIPPEs stabilized by SBP microgel particles could be used as a delivery vehicle for astaxanthin, and the HIPPEs loaded with astaxanthin might have potential as a 3D printing material for edible functional foods.

Phage Predation Promotes Filamentous Bacterium Piscinibacter Colonization and Improves Structural and Hydraulic Stability of Microbial Aggregates.

Although bacteria-phage interactions have broad environmental applications and ecological implications, the influence of phage predation on bacterial aggregation and structural stability remains largely unexplored. Herein, we demonstrate that inefficient lytic phage predation can promote host filamentous bacterium Piscinibacter colonization onto non-host Thauera aggregates, improving the structural and hydraulic stability of the dual-species aggregates. Specifically, phage predation at 103-104 PFU/mL (i.e., multiplication of infection at 0.01-0.1) promoted initial Piscinibacter colonization by 10-15 folds and resulted in 29-31% higher abundance of Piscinibacter in the stabilized aggregates than that in the control aggregates without phage predation. Transcriptomic analysis revealed upregulated genes related to quorum sensing (by 15-92 folds) and polysaccharide secretion (by 10-90 folds) within the treated aggregates, which was consistent with 120-172% higher content of polysaccharides for the treated dual-species aggregates. Confocal laser scanning microscopic images further confirmed the increase of filamentous bacteria and polysaccharides (both with wider distribution) within the dual-species aggregates. Accordlingly, the aggregates' structural strength (via atomic force microscopes) and shear resistance (via hydraulic stress tests) increased by 77 and 42%, respectively, relative to the control group. In the long-term experiments, the enhanced hydraulic stability of the treated aggregates could facilitate dwelling bacteria propagation in flow-through conditions. Overall, our study demonstrates that phage predation can promote bacterial aggregation and enhance aggregate structural stability, revealing the beneficial role of lytic phage predation on bacterial symbiosis and environmental adaptivity.

The impact of powdered activated carbon types on membrane anti-fouling mechanism in membrane bioreactors.

Dosing powdered activated carbon (PAC) has been proven to be an economical and effective method to mitigate membrane fouling. However, the effects of pretreated PAC with different redox properties on membrane fouling still need to be further investigated. Here, the impact of commercial PAC, oxidized-PAC, and reduced-PAC on membrane fouling was investigated in membrane bioreactors (MBRs). Surprisingly, the filtration cycles were extended from 12-36h to 132-156h only by dosing reduced-PAC and commercial PAC with a finial dosage of 3g/L, which were provided with reductive properties. However, few improvements of filtration cycle (less than 50h) were achieved by dosing oxidized-PAC in the same dosage, which had the same adsorption performance as reduced-PAC and commercial PAC. The biomass and foulant concentration suggested that the enhanced anti-fouling performances by PAC with reductive properties were mainly attributed to the reduction of extracellular polymer substances (EPS) and soluble microbial products (SMP) content in the bulk solutions after 14days of continuous operation. The model foulant degradation tests and the confocal laser scanning microscope (CLSM) images of activated sludge further demonstrated that PAC with reductive properties directly affected the microbial activities by controlling the EPS and SMP concentrations in the bulk solution, thereby suppressing membrane fouling. Such a finding provides new insights into anti-fouling mechanisms that the redox properties of PAC played a decisive role in membrane fouling mitigation, and also provides a strategy to prolong the anti-fouling effects by restoring the reductive properties of PAC. KEY POINTS: • The anti-fouling mechanisms of PAC with reductive property were investigated. • Reductive property was the main reason for fouling control instead of adsorption. • PAC with reductive property hindered the sludge activity to produce fewer foulants.

Nutritional and physical characteristics evaluation of giant panda (Ailuropoda melanoleuca) milk in comparison with bovine and caprine milk

The odour, particle size distribution, microstructure and nutrient profile of giant panda milk (GPM) was compared with bovine milk (BM) and caprine milk (CM). SDS-PAGE images of GPM showed clear, deep and uncertain bands different from those for BM and CM. GPM displayed significantly higher levels for free amino acids (p < 0.05), as well as more polyunsaturated and monounsaturated fatty acids. An electronic nose distinguished the three samples; GPM had the strongest response values to sensors. The effective diameter and polydispersity index of GPM were significantly higher than BM and CM (p < 0.05), and the same results were also observed in confocal laser scanning microscopy (CLSM) images. A giant panda milk substitute formulation with the following main nutrients is recommended: protein, 36%; fat, 50%; carbohydrates, 8%. It is also necessary to supplement a small quantity of isoglobotriose, and adjust the milk substitute amino acids and fatty acids ratios.

A novel approach for microalgal cell disruption and bioproducts extraction using non-thermal atmospheric plasma (NTAP) technology and chitosan flocculation

Microalgal cell disruption and bio-product extraction still remain as major challenging steps for biomass downstream processing. In this study, a sustainable approach of using non-thermal atmospheric plasma (NTAP) and chitosan flocculation was developed for microalgal cell disruption and bio-product recovery from wet C. Sorokiniana. For this purpose, the performance of NTAP treatment for cell disruption and extraction of protein, carbohydrate and lipid was investigated by using different applied voltages (8–16 kV). Then, the application of chitosan on recovery of bioproducts from the culture medium was evaluated. Fourier transform infrared (FTIR) analysis, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) images were used to analyze the flocculation mechanism and for flocs characterization. Additionally, the energy consumption and efficiency of the NTAP process were analyzed. According to the NTAP results, the highest cell disruption of 75% was achieved under the applied voltage of 16 kV. However, in the case of bioproducts extraction, the optimal applied voltage was 12 kV which was able to yield 41, 24 and 36 (%CDW) of protein, carbohydrate and lipid, respectively. Adding 100 mg/L chitosan efficiently recovered the released protein (65%) and carbohydrate (85%) from culture medium, while the highest lipid recovery (60%) was achieved at 150 mg/L chitosan addition. This study proved that the utilization of NTAP and chitosan treatment can be considered as a promising approach for valuable products extraction from microalgae.

Changes in Emulsifying and Physical Properties of Shrimp Oil/Soybean Oil‐in‐Water Emulsion Stabilized by Fish Myofibrillar Protein during the Storage

AbstractProperties of shrimp oil/soybean oil (30:70)‐in‐water emulsion stabilized using fish myofibrillar protein (FMP) at different concentrations (15, 30, and 45 mg mL−1) are investigated. When FMP concentration increases, emulsion activity index decreases (p &lt; 0.05). Conversely, emulsion stability index, adsorbed protein, and interfacial protein contents are augmented (p &lt; 0.05). During storage of 15 days, emulsion added with FMP at 45 mg mL−1 (FMP‐45) has the highest turbidity, zeta potential, viscosity, and viscoelastic properties (G′ and G″) than the others (p &lt; 0.05). Emulsions show shear‐thinning and non‐Newtonian behavior. The emulsion added with FMP at 15 and 30 mg mL−1 (FMP‐15 and FMP‐30, respectively) has dominant viscous properties (G′ &lt; G″), whereas FMP‐45 shows elastic gel‐like behavior (G′ &gt; G″) (p &lt; 0.05). Lower droplet size (d32 and d43), polydispersity index (PDI), flocculation (Fi), and coalescence (Ci) are observe in FMP‐45 (p &lt; 0.05). Microstructure reveals smaller droplet size and smaller increase in droplet size of FMP‐45 after storage. Overall, all emulsions remain stable with no obvious phase separation throughout the storage. Confocal laser scanning microscopic images show that increase in FMP concentration can yield monodisperse emulsion. Therefore, fish myofibrillar protein exhibits excellent emulsifying property and stability for shrimp/soybean oils‐in‐water emulsion.Practical Applications: Oil from shrimp hepatopancreas, a byproduct from hepatopancreas free whole shrimp, is well known for their health benefits. It can be used to produce functional food emulsion such as mayonnaise. The use of fish myofibrillar protein is proven to be a potential emulsifier, which can improve emulsifying properties. The obtained emulsion is stable without no phase separation during the extended storage. This finding can be beneficial for food industries to produce food emulsion rich in high quality protein and polyunsaturated fatty acid. Also, hepatopancreas can be fully exploited.

Acyclic cucurbit[n]urils-based supramolecular encapsulation for enhancing the protective effect of capsaicin on gastric mucosa and reducing irritation

Capsaicin (CAP) is an alkaloid isolated from pepper fruit, which possesses various pharmacological activities including antioxidant, anti-inflammatory, antibacterial and gastric mucosa protection. However, its inherent poor aqueous solubility and strong irritation impede the further clinical application. In our study, acyclic cucurbit[n]urils (ACBs, M1, M2 and M3) were rationally utilized to prepare a series of CAP inclusion complexes to improve the bioavailability and reduce stimulation. Their properties and inclusion behaviors were further investigated by multiple characterization methods, the data indicated that the inclusion complexes of ACBs/CAP were formed by a stoichiometric ratio of 2:1 with strong binding interaction. After complexation, the solubility of CAP was significantly increased by 12,076 times and its antioxidant activity also increased. Moreover, the anti-inflammatory activity and the ability to prevent gastric mucosal injury were both significantly improved, and the inhibition rate of nitric oxide (NO) and interleukin-1β (IL-1β) has been effectively improved while cytotoxicity against human normal hepatocytes cell (LO2), human lung fibroblasts cell (HLF) and the human gastric mucosal cell (GES-1) was greatly attenuated. Confocal laser scanning microscope (CLSM) images indicated that the complexes could be efficiently internalized by GES-1 cells and primarily located in cytoplasm. In vivo model of mouse, our complexes exhibited excellent biosafety. In summary, our study may provide a promising new strategy for the further clinical application of CAP.

Effects of microfluidization cycles on physicochemical properties of soy protein isolate-soy oil emulsion films

The effects of microfluidization cycles on the physicochemical properties of soy protein isolate–soy oil emulsion (SSE) films were studied. Surface weighted average diameter (d 3,2 ), volume weighted average diameter (d 4,3 ), and span of SSEs treated with two cycles of microfluidization were 0.78 μm, 1.21 μm, and 1.94, respectively. The d 3,2 , d 4,3 and span of SSEs significantly decreased with increasing number of microfluidization cycles, whereas the amount of protein adsorbed on oil droplets surfaces increased according to the confocal laser scanning microscopy (CLSM) images. The CLSM and scanning electron microscopy images indicated that phase separation occurred in the SSE films treated with two cycles of microfluidization, and uniform structures gradually formed with increasing the number of microfluidization cycles. The tensile strength, elongation at break, water vapor permeability, and surface hydrophobicity of the SSE films increased with the number of microfluidization cycles, whereas the transparency values and glass transition temperatures decreased. Microfluidization decreased the discrepancy between the intensities of infrared absorption peaks of the upper and lower surfaces and reduced the amorphous structures of the SSE films. • Microfluidization affected particle size and protein absorption on oil droplets. • Phase separation occurred in the SSE with a large droplet size during film formation. • The low elongation at break of the SSE films was caused by phase separation. • Water vapor barrier ability of SSE films was enhanced by phase separation. • WVP of SSE films can be controlled by phase separation through microfluidization.

Effect of konjac glucomannan and soy soluble polysaccharides on the rheological, microstructural and syneretic properties of rennet gels

This study investigated the rheological, microstructural and syneretic properties of rennet gels as influenced by the addition of soy soluble polysaccharides (2.5 g/kg, 5 g/kg) or konjac glucomannan (0.2 g/kg, 0.4 g/kg) to skim milk. The addition of all polysaccharides enhanced rennet coagulation properties, by reducing rennet coagulation time (RCT) and increasing development of gel firmness. There were also interactive effects between polysaccharide concentration and coagulation pH on parameters such as RCT, showing that the dynamics of gelation of such systems can be modulated by changing polysaccharide concentration and pH. Rennet gels containing 0.4 g/kg konjac glucomannan had significantly higher levels of syneresis (p < 0.05) than the other gels, which was linked to low yield stress and strain and a more open and porous microstructure. Quantitative analysis of 3-D confocal laser scanning microscopy image stacks showed that rennet gels containing konjac glucomannan had a significantly larger (p < 0.05) pore size than the other rennet gels. The ability of these polysaccharides to change the structure of rennet gels and their ensuing syneretic processes may provide a platform for development of novel cheese textures appealing to international consumers who may not be traditional cheese consumers.

Ternary hybrid Ag/SnO2-X/Bi4O5I2 photocatalysts: Impressive efficiency for photocatalytic degradation of antibiotics and inactivation of bacteria

Ag/SnO2-x/Bi4O5I2 ternary composites were prepared to further improve the photocatalytic properties by introducing Ag nanoparticles into SnO2-x/Bi4O5I2 binary composites. X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) proved that the ternary composites were successfully synthesized. Photocurrent and electrochemical impedance tests (EIS) confirmed that the photogenerated carrier separation efficiency of Ag/SnO2-x/Bi4O5I2 was much higher than SnO2-x and Bi4O5I2. Ag/SnO2-x/Bi4O5I2 showed high efficiency in degradation and antibacterial. The optimum sample of 3% Ag/SnO2-x/Bi4O5I2 can degrade 80 % tetracycline (TC) in 120 min, inactivate Escherichia coli (E. coil) in 15 min and Staphylococcus aureus (S. aureus) in 20 min under the LED light. The intermediates of the degradation of TC were identified by mass spectrometry (MS). Scanning electron microscopy (SEM) and confocal laser scanning microscope (CLSM) images intuitively showed the death process of E. coil caused by the photocatalytic reaction. The results of the capture experiment identified the active substance, and the possible photocatalytic degradation pathway was proposed. Ag/SnO2-x/Bi4O5I2 followed the Z-scheme charge transfer mechanism.

Characterization of Listeria monocytogenes biofilm formation kinetics and biofilm transfer to cantaloupe surfaces

Listeria monocytogenes biofilm is a consistent source of cross-contamination, both in housing storage and food processing environments. This study monitored the dynamic process of L. monocytogenes ST9 and ST87 biofilms, as well as their cross-contamination behaviors at various stages of formation. Scanning Electron Microscopy (SEM) captured the honeycomb-like structures and extracellular polymeric substances (EPS) during the biofilm formation. Confocal Laser Scanning Microscopy (CLSM) images illustrated that the ST87 strain formed a closed knitted chains network later than the ST9 strain. Moreover, structural parameters including bio-volume, mean thickness, porosity, and roughness could quantified the spatio-temporal differences of the biofilms. The transfer rates of biofilm cells to cantaloupes with the single contact had no significant difference at the initial adhesion, maturation, and dispersion stage (p > 0.05). Notably, the biofilm cells remained on the glass coupons when transferred to ten cantaloupe slices, indicating that biofilm cells transferred through cohesive failure. Meanwhile, the Logistic model could describe the transfer law of biofilm cells at different formation stages, as evaluated by Root Mean Square Error (RMSE) and R2adj. Additionally, the transfer rates were positively correlated with the hydrophobicity of L. monocytogenes ST87 biofilm cells measured by xylene. However, when the hydrophobicity of n-hexadecane was measured, the correlation was negative. This study illustrated the spatial and temporal differences during L. monocytogenes biofilms formation, and the transfer and residual of biofilm cells after a single and ten successive contacts at the specific stages. Our findings help in the quantitative microbiological risk assessment of fresh produce.

CaCO3 loaded lipid microspheres prepared by the solid-in-oil-in-water emulsions technique with propylene glycol alginate and xanthan gum.

Calcium carbonate (CaCO3) is difficult to deliver in food matrices due to its poor solubility. In this work, CaCO3 powders were encapsulated into Solid-in-Oil-in-Water (S/O/W) emulsions to fabricate delivery systems. The impact of the concentrations of propylene glycol alginate and Xanthan gum (PGA-XG) complexes on the physical stability and structural characteristics of S/O/W calcium-lipid emulsions microspheres were studied. The S/O/W calcium-lipid emulsions were characterized by the particle size, zeta potential, physical stability, and apparent viscosity. The S/O/W calcium-lipid emulsion has higher physical stability (including 6-week storage at 4°C), smaller mean particle size (7.60 ± 1.10 μm), and higher negative zeta-potential (45.91 ± 0.97 mV) when the concentration of PGA-XG complexes was 0.8 wt%. Moreover, Confocal laser scanning microscopy (CLSM) images confirmed that the CaCO3 powders were encapsulated in the O phase. Transmission electron microscopy (TEM) showed that S/O/W calcium-lipid emulsion was spherical. The X-ray diffraction (XRD) analysis further confirmed that CaCO3 was loaded in the S/O/W calcium-lipid emulsion as an amorphous state. The formation mechanism of S/O/W calcium-lipid microspheres was studied by Fourier transform infrared spectroscopy (FTIR) and Raman spectrum analysis. This study provided new ideas that accelerate the creation of a novel type of calcium preparation with higher quality utilization.