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Clostridium perfringens is an important foodborne pathogen, which has caused serious public health problems worldwide.

This study aims to analyze the contamination and biofilm formation of foodborne and opportunistic pathogens in yellow-feathered chicken carcasses sampled in different seasons and to prove the relationship between biofilm-forming ability and bacterial extracellular polysaccharide (EPS) production. A total of 78 strains were isolated from chicken samples. The strains consisted of 30.8% Escherichia coli, 14.1% Pseudomonas aeruginosa, 12.8% Salmonella enteritidis, 12.8% Klebsiella pnenmoniae, 10.2% Enterobacter cloacae, 8.9% Proteus mirabilis, 5.1% Klebsiella oxytoca, 1.3% Staphylococcus aureus, and 1.3% Citrobacter braakii. Crystal violet staining assay revealed six strains with strong biofilm-forming ability, namely, E. coli S7, K. oxytoca B12, K. pnenmoniae B6, S. enteritidis H4, P. aeruginosa M5, and S. aureus G1, which showed had high abilities of cell motility and EPS production. Confocal laser scanning microscopy and scanning electron microscopy showed that all six strains can form mature biofilm architectures after 5 d of cultivation. This study may serve as a reference to control the contamination of foodborne pathogens in yellow-feathered chicken and enhance the quality and shelf life of these chicken products.

In this study, antibacterial nanofiber films were prepared by electrospinning gelatin, chitosan, and 3-phenyllactic acid (PLA). The addition of PLA improved the microstructures of the nanofibers, and the nanofiber films (GCP-1 and GCP-2) had uniform and continuous structures with a diameter range of 40‐–70 nm when the PLA concentrations in the polymers were 1% and 2%. Under acidic conditions, chitosan and PLA interacted and formed hydrogen bonds, which decreased the crystallinity of the nanofiber films. The GCP-2 nanofiber film had the best thermal stability, water stability, and water vapor permeability. Compared with the control GCP-0 film, the four nanofiber films with PLA (GCP-1, GCP-2, GCP-3, and GCP-4) had more effective antibacterial effects, and GCP-2 film reduced approximately 4 log CFU/mL of Salmonella enterica Enteritidis and Staphylococcus aureus in 30 min. Results suggested that the GCP-2 nanofiber film mat can be used as an active food packaging.

Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic infection-causing pathogen that threatens human health. Accordingly, a rapid and ultrasensitive analytical method is required urgently. Herein, an ultrasensitive multicolor electrochromic sensing platform was established on the basis of a closed bipolar electrode (BPE). Prussian blue (PB), the blue spot that can be easily electrodeposited, was selected as an electrochromic indicator at the closed BPE cathode. Integrating with the anodic emitter, Ru(bpy)

An effective antibacterial nanofiber film was prepared through the incorporation of ε-polylysine (ε-PL) into gelatin/chitosan-based polymers. All nanofiber films had uniformly disordered fibrous structure with good diameter distribution. The weight ratio of the gelatin/chitosan/ε-PL (G/C/P) influenced the solution property and nanofiber morphology. The addition of ε-PL can decrease the viscosity and increase the conductivity of solutions, which lead to a decrease in the diameter of nanofibers. The three polymers of gelatin, chitosan, and ε-PL were interacted by hydrogen bonding, and the crystallinity of nanofiber films was decreased by the electrospinning process. The addition of ε-PL can enhance the thermal stability, and decrease the water vapor permeability and oxygen permeability of the films, and ε-PL did not easily release from the nanofiber films. The G/C/P (6:1:0.125) nanofiber film was more effective to control six foodborne pathogens than the G/C nanofiber films by destroying the bacterial cell membranes. The result indicated that the gelatin/chitosan/ε-PL nanofiber films can be used as a food-packaging material to reduce the risk of foodborne pathogens.

The inhibitory and bactericidal activities of thyme oil against the foodborne multiple antibiotics-resistant Enterococcus faecalis biofilm were evaluated in this study. Gas chromatography-mass spectrometry revealed that more than 70% of the composition of thyme oil is thymol. Crystal violet staining assay showed that 128 and 256 μg/mL thyme oil significantly inhibited the biofilm formation of E. faecalis. The cell adherence of E. faecalis, as shown by its swimming and swarming motilities, was reduced by thyme oil. The exopolysaccharide (EPS) quantification assay showed that thyme oil inhibited the EPS synthesis in E. faecalis biofilms. The 3D-view observations through confocal laser scanning and scanning electron microscopy suggested that cell adherence and biofilm thickness were decreased in thyme oil–treated biofilms. Quantitative real-time analyses showed that the transcription of ebp and epa gene clusters, which were related to cell mobility and EPS production, was inhibited by thyme oil. Thus, thyme oil effectively inhibited the biofilm formation of E. faecalis by affecting cell adherence and EPS synthesis. Furthermore, 2,048 and 4,096 μg/mL thyme oil can effectively inactivate E. faecalis population in the mature E. faecalis biofilms by 5.75 and 7.20 log CFU/mL, respectively, after 30 min of treatment. Thus, thyme oil at different concentrations can be used as an effective antibiofilm or germicidal agent to control E. faecalis biofilms.

Chlorogenic acid (CA), an ester of caffeic acid, is a major phenolic compound in herbs. The antimicrobial activity of CA against Pseudomonas aeruginosa P1, a foodborne pathogen, was investigated in this study. To understand how CA injured target cells, the influence of CA on cell morphology was assessed. A sunken cell surface and detachment of outer membrane components in P. aeruginosa P1 were observed after being treated by CA. Following this, the intracellular membrane permeability and the content of lipopolysaccharide (LPS), a main component of outer membrane, were determined. The release of intracellular protein and ATP from P. aeruginosa P1 indicated that CA increased intracellular membrane permeability and resulted in the leakage of intracellular materials. The uptake of propidium iodide, a compromised cell membrane nucleic acid stain, further demonstrated that CA acted on the intracellular membrane. CA resulted in the decrease of LPS contents of P. aeruginosa P1, which supported the detachment of outer membrane. CA also downregulated the expression of major genes in LPS biosynthesis, suggesting that CA may inhibit intracellular metabolism of P. aeruginosa P1 cells. Thus, CA increased the intracellular membrane permeability, induced the exfoliation of outer membrane, and disturbed the intracellular metabolism. Damage of intracellular and outer membranes as well as disruption of cell metabolism resulted in cell death eventually. The finding suggested that CA has the potential to be developed as a preservative to control P. aeruginosa-associated foodborne diseases.

Highlights • The synergistic bactericidal effect had produced by ultrasound (US) and chlorogenic acid (CA). • US plus CA changed the morphology of S. aureus cells.. • US plus CA led the leakage of internal constituents. • US plus CA reduced the concentration of polysaccharide in biofilms. • US plus CA reduced S. aureus in mutton by 1.14 log CFU/g., This study aimed to investigate the mechanism of different treatments, namely, ultrasound (US), chlorogenic acid (CA), and ultrasound combined with chlorogenic acid (US plus CA) on the inactivation of Staphylococcus aureus planktonic and biofilm cells. Results showed that the combined treatment of US and CA exhibited remarkable synergistic antibacterial and antibiofilm effects. Scanning electron microscopy images indicated that the combined treatment of US and CA caused the most serious damage to the cell morphology. Confocal laser scanning microscopy images revealed that the combined treatment led to sharp increase and severe damage to the permeability of the cell membrane, causing the release of ATP and nucleic acids and decreasing the exopolysaccharide contents in S. aureus biofilm. Finally, the combined treatment of US plus 1% CA for 60 min inactivated S. aureus cells by 1.13 lg CFU/g on mutton. Thus, the combined treatment of US and CA had synergistic effect against S. aureus under planktonic, biofilm, and food systems.

The antibacterial and antibiofilm mechanisms of ultrasound combined with chlorogenic acid treatment for Salmonella enteritidis under biofilm and planktonic condition were investigated. S. enteritidis under biofilm and planktonic cells were treated with ultrasound, chlorogenic acid, and their combination for 5, 10, 20, 30, and 60 min. Results showed that the combined treatments exhibited synergistic effects that inactivated the S. enteritidis biofilm and planktonic cells. The nucleic acids and ATP leakage and CLSM imagines showed that the combining chlorogenic acid and ultrasound treatment significantly increased the permeability of the S. enteritidis cell membrane. SEM indicated that the combining chlorogenic acid and ultrasound treatment quickly destroyed the integrity of the S. enteritidis cell membrane, and the activity of respiratory chain dehydrogenase sharply decreased. Additionally, the amounts of polysaccharides in the S. enteritidis biofilms significantly decreased after the combined treatments. Hence, the combining chlorogenic acid and ultrasound treatment have potential applications in food preservation.

This study investigated the synergistic efficacy of ultrasound (US, 50 kHz, 400 W) in combination with chlorogenic acid (CA; 0, 0.5, 1, and 2%) to inactivate Pseudomonas fluorescens planktonic and biofilm cells. The P. fluorescens planktonic and biofilm cells were treated with CA with and without US for 5, 10, 20, 30, or 60 min. Results showed that US enhanced the efficacy of CA for inactivation of both P. fluorescens planktonic and biofilm cells. Treatment with 2% CA and US could completely inactivate P. fluorescens planktonic cells within 10 min and the biofilm cells within 30 min. Confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), ATP, and nucleic acid release assays indicated that the combination of US and CA could quickly damage the integrity of P. fluorescens planktonic and biofilm cell membranes. The combined treatment effectively inactivates P. fluorescens planktonic and biofilm cells via the synergetic destruction of the biofilm structure and bacterial cell integrity.

Biodegradable and eco-friendly food packaging materials have attracted attention. Novel blending films were prepared with polylactic acid (PLA) and Perilla essential oil (PEsO). The morphological features of the nanofibers were modulated by adjusting process parameters (e.g. PLA solution concentration, applied voltage and ultrasonic power). The optimal spinning concentrations, applied voltages and ultrasonic power of the PLA solutions were set at 15% (m/v), 20 kV and 640 W, respectively. Compared with the PLA films, the addition of PEsO increased the diameter of the nanofibers and solvent resistance and reduced the swelling rate of the PLA/PEsO films. The breakage elongation and the gas barrier properties significantly improved when 2% (w/w) PEsO was used. Fourier infrared spectroscopy, X-ray diffractometer, thermogravimetry and differential scanning were used in analyzing the potential interactions of the film matrices. The PLA/PEsO films had good biocompatibility and antibacterial and antioxidant properties. The PLA/PEsO (1:0.02) film loaded with 2% PEsO extended the shelf life of chilled chicken to 12 days, as indicated by the measured total volatile basic nitrogen (TVB-N), total viable count and pH value. Therefore, PLA/PEsO films have great potential as fresh-keeping packaging.

This study evaluated the effect of the combination of ultrasound and phenyllactic acid (PLA) on inactivating Staphylococcus aureus and Salmonella enteritidis biofilm cells and determined the possible antibiofilm mechanism. S. aureus and S. enteritidis biofilm cells were separately treated with ultrasound (US, 270 W), phenyllactic acid (PLA, 0.5% and 1%), and their combination (US + 0.5% PLA, and US + 1% PLA) for 5, 10, 20, 30, and 60 min. Biofilm inactivation, polysaccharide, and respiratory chain dehydrogenase assays were conducted. US and PLA had a synergistic effect on inactivating bacterial cells in S. aureus and S. enteritidis biofilms. The combination of US and PLA significantly decreased the contents of soluble and insoluble polysaccharides and the activity of respiratory chain dehydrogenase in the biofilm cells compared to the single treatment. Confocal laser scanning microscopy, scanning electron microscopy, and intracellular adenosine-triphosphate (ATP) analyses indicated that the combination of US and PLA seriously destroyed the cell membrane integrity of the S. aureus and S. enteritidis biofilms and caused the leakage of intracellular ATP. These findings demonstrated the synergistic antibiofilm effect of US combined with PLA and offered a research basis for its application in the food industry.

Perillaldehyde is a natural antibacterial agent extracted from perilla essential oil. In our methodology, five antibacterial nanofiber packaging films are prepared by loading different concentrations of perillaldehyde (P) into gelatin/zein (G/Z) polymers. Morphology observations show that the G/Z/P film had a good uniform microstructure and nano-diameter as the weight ratio of 5:1:0.02 (G/Z/P). Fourier transform infrared spectroscopy, and X-ray indicate that these three ingredients had good compatibility and strong interaction via hydrogen bonding. Water contact angle results show that the G/Z/P films gradually change from hydrophilic to hydrophobic with the increase of perillaldehyde. Thermal analysis indicates that the G/Z/P (5:1:0.02) film has good thermal stability. Antibacterial and storage analysis indicates that G/Z/P (5:1:0.02) film is effective to inactivate Staphylococcus aureus and Salmonella enteritidis, and obviously reduces the increasing rate of total bacteria counts and volatile basic nitrogen of chicken breasts. This study indicates that the G/Z/P (5:1:0.02) is a kind of potential antibacterial food packaging film.

An efficient antibacterial nanoemulsion was prepared using zein and NaCas to encapsulate ginger essential oil (GEO). Physical, optical, and mechanical properties as well as the antibacterial activities of GEO nanoemulsion were investigated. At 1:1 mass ratio of zein/NaCas, the GEO nanoemulsion possessed the highest solubility, entrapment efficiency and stability. The GEO/zein/NaCas complex was confirmed by ultraviolet and fluorescence spectroscopy. The addition of GEO led to more amorphous structure formation and the secondary structure changes of zein/NaCas improved the solubility and stability of GEO. GEO nanoemulsion inactivated two common foodborne bacteria, namely, Staphylococcus aureus and Pseudomonas aeruginosa, by destroying the cell membrane. Meanwhile, the GEO nanoemulsion exhibited better preservation effects on chilled chicken breasts than non-emulsified GEO and could effectively prolong the shelf life of chicken breasts for 6 days. This research provides a green and low-cost method for preparing GEO nanoemulsion to control the risk of foodborne pathogens.

Three edible food packaging films loaded with perillaldehyde (P), thymol (T), or ɛ-polylysine (ɛ-PL) in gelatin/zein (G/Z) nanofibers were prepared and characterized. Their effects on the preservation of chilled chicken breast were evaluated. Results showed that the addition of perillaldehyde, thymol, and ɛ-polylysine improved the morphology and diameter of the G/Z. Loading with perillaldehyde improved the elongation and tensile strength of the G/Z/P by 18% and 55%, respectively. The water vapor permeability and oxygen permeability of the G/Z/P were lower than those of the G/Z/T and G/Z/ɛ-PL. X-ray diffraction, differential scanning calorimetry suggested that perillaldehyde enhanced the thermal stability of the G/Z/P. Measurements of 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), total volatile basic nitrogen, and total viable bacterial counts demonstrated that the G/Z/P had good bio-compatibility and effectively prolonged the shelf life of chilled chicken breasts by over 6 days. Therefore, the G/Z/P developed herein has potential application in chilled meat packaging.

The study evaluated the antibacterial activity of chlorogenic acid (CA) against Salmonella Enteritidis S1, a foodborne pathogen in chilled fresh chicken. Its minimum inhibitory concentration for S. Enteritidis S1 was 2 mM. 1 MIC CA treatment reduced the viable count of S. Enteritidis S1 by 3 log cfu/g in chilled fresh chicken. Scanning electron microscopy examination indicated that CA induced the cell envelope damage of S. Enteritidis S1. Following this, 1-N-Phenylnaphthylamine assay and LPS content analysis indicated that CA induced the permeability of outer membrane (OM). Confocal laser scanning microscopy examination further demonstrated that CA acted on the inner membrane (IM). To support this, the release of intracellular protein and ATP after CA treatment was also observed. CA also suppressed the activities of malate dehydrogenase and succinate dehydrogenase, two main metabolic enzymes in TCA cycle and electron transport chain. Thus, damage of intracelluar and outer membranes as well as disruption of cell metabolism resulted in cell death eventually. The finding suggested that CA has the potential to be developed as a preservative to control S. Enteritidis associated foodborne diseases.

The aim of this study was to optimize and characterize Flavourzyme hydrolysis conditions for the preparation of antioxidant peptides from duck meat, using response surface methodology. The results indicated that optimal Flavourzyme hydrolysis conditions for preparation of antioxidant peptides from duck protein were a temperature of 50.19°C, pH 5.45, and a reaction time of 1.03 h. Compared to non-hydrolyzed duck meat, Flavourzyme hydrolysis significantly improved the hydroxyl-radical scavenging, DPPH radical-scavenging, ferrous ion-chelating, reducing, and ABTS radical cation-scavenging activities of duck meat. Therefore, Flavourzyme can be regarded as an effective hydrolytic enzyme for the preparation of antioxidant peptides from duck meat.

3-Phenyllactic acid (PLA) and slightly acid electrolyzed water (SAEW) are effective antimicrobial agents with broad-spectrum activity. The combined effects of PLA and SAEW on the inactivation of Klebsiella oxytoca planktonic and biofilm cells were evaluated in this study. The K. oxytoca K6 planktonic and biofilm cells were treated with PLA (0.5%, 1% and 2%), SAEW (30 and 60 mg/L), 0.5% PLA plus 30 mg/L SAEW, and 1% PLA plus 30 mg/L SAEW for 5, 10, 20, 30, and 60 min. The planktonic and biofilm cell assays showed that 2% PLA was more effective for the inactivation of K. oxytoca planktonic and biofilm cells than the other agents, and the combination of PLA and SAEW was more effective than the single agents at the same concentrations. Confocal laser scanning microscopy and ATP leakage analysis showed that the combined treatment of PLA and SAEW at different concentrations destroyed the cell membrane integrity of K. oxytoca planktonic and biofilm cells and caused ATP leakage at different levels. Scanning electron microscopy (SEM) assays showed that the morphologies of K. oxytoca planktonic and biofilm cells changed after treatment with the antibacterial agents at different levels. The cells were seriously damaged after treatment with 1% PLA and 30 mg/L SAEW for 60 min. The biofilm polysaccharide detection assays showed that SAEW-containing antibacterial agents were effective for disrupting the biofilm extracellular polymeric matrix, as shown in SEM images. The combination of PLA and SAEW effectively inactivated K. oxytoca planktonic and biofilm cells by damaging the cell membrane and disrupting the biofilm matrix.

The aim of the present study was to evaluate the effect of ultrasound pre-treatment on the characterization and in-vitro digestion properties of collagen from turtle calipash and the antioxidant activity of its hydrolysates. The results showed that ultrasound significantly increased the collagen yield compared with that from conventional extraction (ASC, P

This work investigated the impact of ultrasound assisted extraction on the physicochemical, structural and functional properties of duck liver protein isolate (UDLPI). Degreased liver powders were extracted by ultrasound working at a single frequency of 24 kHz and a fixed power of 266 W by a pulsed on-time of 2 s and off-time of 3 s for 42 min in pH11.2 solution. The results revealed that UDLPI yield and the protein content increased by 67.7% and 4.6% respectively compared to that of the conventional alkaline extraction (DLPI). Ultrasound treatment could cause partial protein hydrolysis and unfolding as suggested by differential scanning calorimetry, circular dichroism and fluorescence spectroscopy analysis, leading to increased surface hydrophobicity, surface net charge and gelling property. The particle size reduced from 177.8 nm of DLPI to 156.0 nm of UDLPI. Ultrasound also promoted the storage modulus (G′) and solubility of the isolate. Moreover, the foaming expansion was especially strong, compared to DLPI. However, the results of the foam stability, reactive-/total-sulfhydryl groups and sodium-dodecyl sulfate-polyacrylamide gel electrophoresis showed no significant change between UDLPI and DLPI ( P > 0.05). Therefore, UDLPI with better functional property could be utilized as new materials in the food industry.

This study aimed to evaluate the inhibitory activity of phenyllactic acid (PLA) against the biofilm formation of Enterococcus faecalis and to explore its potential molecular mechanism. The MIC value of PLA that inhibited the growth of E. faecalis R612-Z1 in BHI broth was 5 mg/mL. PLAs at subinhibitory concentrations of 1.25 and 2.50 mg/mL were found to inhibit biofilm formation by a crystal violet staining assay. The cell swimming and swarming motilities of E. faecalis were reduced in the presence of PLA. An apparent decrease in the thickness of PLA-treated biofilms was observed through confocal laser scanning microscopy analysis. The exopolysaccharide production in E. faecalis biofilms was inhibited by EPS quantification assay and scanning electron microscopy (SEM). qRT-PCR analyses showed that PLA down-regulated the transcription of Ebp pili genes (ebpABC) and Epa polysaccharide genes (epaABE). PLA inhibited the biofilm formation by interfering with cell mobility and EPS production of E. faecalis. In addition, PLA at concentrations of 10.0 mg/mL can effectively control the bacterial cells in a three-day-old mature biofilm of E. faecalis grown on 24-well flat-bottom polystyrene plates and stainless-steel surfaces. Thus, PLA is potentially an effective agent to control E. faecalis biofilms.

This study aimed to analyze the effect of carvacrol oil on biofilm formation of Enterobacter cloacae. The minimum inhibitory concentration of carvacrol oil against E. cloacae was 256 μg/mL. The biofilm formation was inhibited by carvacrol oil at sub-inhibitory concentrations of 64 and 128 μg/mL. The bacterial cell motilities and biofilm exopolysaccharide (EPS) production were both inhibited by carvacrol oil. Correlation analysis indicated that the inhibition of biofilms in mature stages was related to the decrease of EPS production. The biofilm thickness and excretion of extrapolymeric matrix were reduced by carvacrol oil, as shown by scanning electron microscopy and confocal laser scanning microscopy analyses. Transcriptional analysis showed that carvacrol oil down-regulated 24 of 29 selected genes, including curli fimbriae genes (csgABCEFG) and colonic acid polysaccharide genes (wcaABCDEFKLM, wza, wzb, wzc, gmd, manB, manC) which are required for biofilm formation of E. cloacae. In addition, different antimicrobial agents, including 1% lactic acid, 1% phenyllactic acid, and 1024 μg/mL of carvacrol oil considerably inactivated the bacterial cells in carvacrol-treated biofilms. Hence, carvacrol oil effectively inhibited biofilm formation and EPS production of E. cloacae, which is useful for further inactivating E. cloacae biofilms by other antimicrobial agents.

3-Phenyllactic acid (PLA) was reported to have an effective antimicrobial activity. This study evaluated the antimicrobial activity of PLA against foodborne Enterococcus faecalis and its effect on cell membrane. The minimum concentration of PLA to inactivate E. faecalis in brain heart infusion broth was 5 mg/mL. PLA solutions of 5 and 10 mg/mL can inactivate E. faecalis population ≥6 log CFU/mL within 60 and 30 min, respectively. The cell membranes of most E. faecalis cells were damaged after PLA treatment according to the images of scanning electron microscopy and transmission electron microscopy. The differences in the regions of cell membrane protein, fatty acid, and polysaccharide were revealed by Fourier transform infrared spectroscopy, which further indicated cell membrane damages. The cell membrane permeability was increased when the concentration of PLA treatment was increased in the membrane permeability assays. Finally, almost all bacterial cells were damaged after treatment with 10 mg/mL PLA for 30 min, further confirmed by flow cytometry analysis. This study concluded that PLA is effective in inactivating E. faecalis cells through the leakage of intracellular components caused by cell membrane damage.

The aim of present study was to investigate the effect of different ultrasound power on physicochemical property and functional performance of chicken actomyosin (CAM). The treated CAM had the lowest particle size and the highest absolute zeta potential at 150 W. The conformation changes of treated CAM exhibited the reduction in α-helix as well as the improvement of fluorescence intensity. Ultrasound power at 150 W could significantly increase protein hydrophobicity and reactive SH groups compared to the others (P 0.05). The disappearance of specific peaks and lower endothermic peaks implied that the treated CAM became thermally instable. The microstructure of CAM revealed small and homogeneous sub-bunches treated by 100-150 W. Furthermore, the solubility and emulsion property of CAM was significantly increased at 150 W (P 0.05). These results demonstrated that ultrasound treatment at the power of 100-150 W may be an appropriate range to modify CAM for enhancing its functional properties.

Summary Supplying microalgae with extra CO2 is a promising means for improving lipid production. The molecular mechanisms involved in lipid accumulation under conditions of elevated CO2, however, remain to be fully elucidated. To understand how elevated CO2 improves lipid production, we performed sequencing of Chlorella sorokiniana LS-2 cellular transcripts during growth and compared transcriptional dynamics of genes involved in carbon flow from CO2 to triacylglycerol. These analyses identified the majority genes of carbohydrate metabolism and lipid biosynthesis pathways in C. sorokiniana LS-2. Under high doses of CO2, despite down-regulation of most de novo fatty acid biosynthesis genes, genes involved in carbohydrate metabolic pathways including carbon fixation, chloroplastic glycolysis, components of the pyruvate dehydrogenase complex (PDHC) and chloroplastic membrane transporters were upexpressed at the prolonged lipid accumulation phase. The data indicate that lipid production is largely independent of de novo fatty acid synthesis. Elevated CO2 might push cells to channel photosynthetic carbon precursors into fatty acid synthesis pathways, resulting in an increase of overall triacylglycerol generation. In support of this notion, genes involved in triacylglycerol biosynthesis were substantially up-regulated. Thus, elevated CO2 may influence regulatory dynamics and result in increased carbon flow to triacylglycerol, thereby providing a feasible approach to increase lipid production in microalgae.

Heat shock proteins of 90kDa (Hsp90) are molecular chaperones essential for protein homeostasis. Besides chaperone activity, Hsp90 exhibits other cellular functions at membranes, yet how it interacts with membranes remains elusive. We report here that Hsp90B1 interacts with phospholipid membranes. We first cloned the full-length open reading frame of Hsp90B1 from Anas platyrhnchos (ApHsp90B1), and the gene was then heterologously expressed and purified. SPR analysis show the purified ApHsp90B1 interacts with phospholipid membranes with high affinity (KD 176±25nM), and the interaction occurs over a wide range of pH, which is especially distinct under acidic conditions. Tryptophan fluorescence and far-UV CD spectra studies find that the interaction of ApHsp90B1 with phospholipid membrane induces microenvironment changes of tryptophan residues and conformational change of some regions in ApHsp90B1, which might be the reason of its increased ATPase activity upon addition phospholipid vesicles. Importantly, the interaction of ApHsp90B1 with phospholipid vesicles significantly reduces lipolysis of the membrane phospholipid, suggesting that the interaction of Hsp90B1 with membrane could preserve membrane integrity. The present study therefore demonstrates for the first time that Hsp90B1 exhibits high affinity for phospholipid membrane and suggest Hsp90B1 play an important role in membrane-stabilizing via its interaction with membrane phospholipids.

The antioxidative role of Hsp90 purified from duck muscle on phospholipid was investigated in this study. Lipid oxidation was assessed by ferric thiocyanate method, and particle size, zeta potential measurements and transmission electron microscopy were employed to detect physical and chemical changes during oxidation of liposomes. Increase of the peroxidation products, decrease of the particle size and disruption of the spherical unity of the liposomes were detected when liposome was exposed to hydrogen peroxide (H2O2) oxidation, and Hsp90 was shown to protect liposome against oxidation. To further test the protection of Hsp90 on cell membrane, the Hsp90 transformed E. coli cell model was built. The Hsp90-containing E. coli showed higher survival and better membrane integrity as compared to the control upon H2O2 exposure. It is expected that Hsp90 plays an important role in the prevention of phospholipids oxidation in meat and has potential use as a food antioxidant.

SlpB, a surface layer protein isolated from Lactobacillus crispatus, has the potential to enhance the antimicrobial activity of nisin. Previous research indicated that, when combined with nisin, SlpB acted synergistically to inhibit Staphylococcus saprophyticus growth, thus extending the shelf life of chicken meat. In order to understand how SlpB enhances the antibacterial activity of nisin, electron microscopy, confocal laser scanning microscopy, flow cytometry and transmembrane electrical potential analysis were used to study cell wall organization and cell membrane integrity. No remarkable bacteriolytic effects were observed, indicating that cell death could not be attributed to cell lysis, although SlpB caused dramatic modifications of cell wall, thereby altering cell shape. The combination of SlpB and nisin also induced the release of ATP or UV-absorbing materials, as well as sudden dissipation of the transmembrane electrical potential by compromising membrane integrity. Considering that SlpB led to structural disorganization of the cell wall, and nisin access is enhanced to form a stable pore, cell death is a predictable outcome. SlpB significantly enhanced the effect of nisin at half of the minimum inhibitory concentration, which resulted in cell death by destroying the cell wall and cell membrane, therefore providing a new, feasible approach in food preservation.

The aim of the present study was to evaluate the physicochemical and functional properties of acid-soluble collagen by ultrasound assisted extraction (UASC) from calipash of soft-shelled turtle (Pelodiscus sinensis). The results showed the collagen content was increased by 16.3% in UASC over the collagen from the conventional extraction (ASC). Both ASC and UASC contained a moderate amount of imino acid (197 and 216 residues/1000 residues, respectively) and hydrophobic amino acid (353 and 391 residues/1000 residues, respectively) in amino acid composition. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analyses confirmed that the ultrasound treatment did not disrupt the triple-stranded helical structures in UASC. UASC had higher thermal stability compared with ASC by viscosity and differential scanning calorimetry (DSC) measurements, therefore, UASC might have the advantage to be used. In dynamic elastic behavior measurement, UASC showed a larger elasticity than ASC. With a mild modification by ultrasound, UASC had superior functional properties to ASC, including water/oil absorption capacity, water-holding capacity, emulsifying properties and foaming properties. These results suggested that UASC from the soft-shelled turtle calipash had a potential to be used widely in food, medicine, cosmetics and biomedical materials.

This research investigated the physiochemical and functional characteristics of chicken liver protein isolate, which was extracted by alkali (CLPI) and ultrasound-assisted alkali (UCLPI), respectively. Protein yield of UCLPI was increased by 55.4% over that of CLPI (P 0.05). Several amino acids were significantly higher and methionine was lower in UCLPI (P 0.05). Ultrasound treatment reduced the particle size and prolonged the stability of the protein isolate during 7 d storage. Lower pH and a higher amount of total solubilized proteins (68.5%) were found in UCLPI by comparison with CLPI (61.8%). Surface hydrophobicity increased greatly by 63.0% compared with CLPI, but the total/reactive sulfhydryl groups and the primary structure molecular weight profile between them were not significantly different (P 0.05). However, the enthalpy of denaturation in UCLPI decreased by 41.7%, which was related to the changes in its second structure. This resulted in better water/oil holding capacity and emulsifying properties for UCLPI. The changed physiochemical characteristics and improved functional properties of UCLPI demonstrated the potential utilization of ultrasound-assisted alkaline extraction in the food industries.