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Staphylococcus aureus (S. aureus) is known to be one of the most common foodborne pathogens capable of secreting a wide range of exotoxins such as enterotoxin, which severely threatens the health of consumers. Over the past few years, the development of safe and effective strategies in inhibiting the growth and enterotoxins generation of S. aureus in food turns out to be the research focus and emphasis. This research explores citronellal (CIT), a native compound with extensive existence in spices, which could effectively inhibit the growth and enterotoxins generation of S. aureus (ATCC 29213). Results from minimal inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill curves, showed that CIT could tremendously inhibit the growth of S. aureus. Analysis on hemolysin showed that CIT at sub-MIC could significantly (p 0.05) inhibit the hemolytic activity of S. aureus. As revealed by the results of ELISA, the production of enterotoxins in the culture supernatant and pork meat decreased significantly (p 0.05) after exposure to CIT at sub-MIC. Furthermore, a significant (p 0.05) decrease in dose-dependent was found in the transcription levels of virulence-related genes. In all, CIT proved to be a possible inhibitor of the growth and enterotoxins production of S. aureus with highly promising application in the food industry.

Gut microbiota balance and metabolites have become a potentially mechanism in maintaining health. The specific aim of this study was to compare the modulation of puerarin and puerarin acid esters on gut microbial composition and metabolites. Male mice were fed a control diet or diets supplemented with puerarin, puerarin propanoate ester, puerarin hexanoate ester, puerarin myristate ester for 24 h, respectively. The result revealed that puerarin acid esters with different chain lengths showed different activities to create more own impacted bacterial. Puerarin propanoate and puerarin hexanoate ester significantly improved the diversity of microbiota and promoted the relative abundance of beneficial gut microbiota such as Lactobacillus, Barnesiella, Clostridium IV, Prevotella. Additionally, the puerarin propanoate ester group showed the capacity to deliver specific propionic acid to the colon. But esters with medium-long chain lengths had more opportunity to alter gut microbiota for enhancing the short chain fatty acids production. As a whole, puerarin acid esters with different chain lengths supplements shaped different gut microbial and short chain fatty acids metabolism, which could improve human health.

The control of E. coli activity from forming biofilm and persister cells is an essential factor in both the health and food industries. The efficacy of antimicrobial treatment is often limited due to their low penetrability as biofilm formation protect cells within from physical or chemical threats. Among other factors, osmotic stress has shown to have a high capacity to enhance the antimicrobial activities against various pathogens. Thus, this study aimed to test the hypothesis that the antimicrobial activity of cineole (CN) could be enhanced under osmotic stress to inhibit biofilm and persister cells. Time-kill analysis revealed that CN under NaCl-induced osmotic stress (CN-S) had better inhibitory effect on E. coli biofilm. 5% CN-S altered the integrity, hydration, motilities and exopolysaccharide production of E. coli cells. Also, the outer membrane permeability, surface roughness and hydrophobicity which determine initial cell adhesion, aggregation and colony assembly were significantly perturbed. Furthermore, the expression levels of virulence genes stx1, stx2, eae, flhD, and the TA system antitoxin genes mazE, hipB were downregulated. When applied to cucumber, the rate of increase in internalized bacterial cells significantly reduced after storage at 4 °C for 48 h. Thus, the results suggested that the application of osmotic stress could minimize the working concentration of antimicrobials in real food systems, which could be helpful in counteracting the growing concern of microbial resistance.

This study was to explore the effect and mechanism of Let-7b nanocomposite on the expression of inflammatory factors in the cerebrospinal fluid (CSF) of purulent meningitis. 45 patients with purulent meningitis (PM) were selected as observation group (group A), and 38 patients with normal CSF without central nervous system diseases were selected as the control group (group B). The CSF of the two groups were collected to detect the inflammatory factors interleukin-8 (IL-8), macrophage inflammatory protein-1α (MIP-1α), matrix metalloproteinase 9 (MMP9), interleukin 1β (IL-1β), tumor necrosis factor-α (TNF-α), and Let-7b level with the double antibody sandwich enzyme-linked immunosorbent assay (ELISA). The Let-7b nanocomposite was prepared, and its morphology, particle size, and Zeta potential were analyzed. In addition, the degradation kinetics, cytotoxicity, and phagocytic efficiency (PE) of Let-7b nanocapsules were detected. 36 healthy adult New Zealand (NZL) rabbits were randomly grouped into a control group (group C) (0.9% normal saline (NS)), a model group (Escherichia coli (E. coli) modeling, group D), and a test group (E. coli modeling + Let-7b nanocapsules, group E), with 12 rabbits in each group. The changes of inflammatory factors in CSF of the three groups were detected and compared. It was found that the expression levels of IL-8 and IL-1 β in the group A were much higher than those in the group B (P < 0.01), and the MMP9 and TNF-α levels in the group B were much lower in contrast to the group A (P < 0.001). The expression of Let-7b in the group A was lower obviously in contrast to the group B (P < 0.001). Let-7b nanocapsules were irregularly spherical, with an average particle size (APS) of 23.1 nm, a polydispersity index (PDI) of 0.232, and the Zeta potential of around +15 mV. Let-7b nanocapsules showed obvious polymer shell absorption peaks at 1,015 cm-1, 1,228 cm-1, and 1,547 cm-1. The IL-8 and IL-1β levels of the group D were greatly different from those in the other two groups (P < 0.01). The levels of TNF-α and MMP9 in the group D were greatly different in contrast to the group C (P < 0.001) and the group E (P < 0.01). It indicated that Let-7b nanocomposite could lower the expression levels of IL-8, IL-1β, MMP9, and TNF-α in the CSF of patients with purulent meningitis dramatically, which provides a reliable basis for immunotherapy of purulent meningitis with Let-7b.

Tyrosinase is a key enzyme responsible for enzymatic browning of fruits and vegetables and skin disorders due to overproduction of melanin. Arbutin is an inhibitor of tyrosinase; however, its high polarity and weak transdermal absorption capacity limit its applications. In this paper, a green solvent system was developed to successfully synthesize arbutin esters with improved liposolubilities (Clog P values = 0.27-5.03). Among the obtained esters, arbutin undecenoate (AU) showed the strongest tyrosinase-inhibiting activity (15.6%), which was 9.0 times higher than that of arbutin. An enzyme kinetics study indicated that AU was a competitive inhibitor with reversible inhibition. The esters inhibited tyrosinase by making the secondary structure of tyrosinase looser and less stable; moreover, the interactions between tyrosinase and AU driven by metal interactions and hydrogen bonds also offered a mechanism for inhibition of AU on tyrosinase. In addition, AU (100 μM) reduced the melanin content of B16 mouse melanoma cells to 61.3% of the control group.

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 mounts specific acid-resistance systems against acid stress, making it more difficult to eradicate in food industry. To date, RNAseq-based analysi...

An efficient whole-cell biocatalytic method was developed for the cascade hydrolysis of flavonoid glycosides to their valuable hydrolyzates with high substrate conversions. Cells of Aspergillus niger showed both α-L-rhamnosidase and β-D-glucosidase activities, catalyzing the hydrolysis of hesperidin (HES) through two pathways in one pot: (1) α-L-rhamnosidase catalyzed HES hydrolysis to hesperetin-7-O-glucoside (HG) and subsequently β-D-glucosidase catalyzed HG hydrolysis to hesperetin, and (2) β-D-glucosidase catalyzed direct hydrolysis of HES to hesperetin. Both the HES conversion and product composition were controllable by adjusting the key reaction conditions and addition of different sugars. Remarkably, high conversions (above 90%) of HES were achieved by using green solvents in place of traditional organic solvents for dissolving polar substrates. The type and concentration of natural deep eutectic solvents (NADESs) in buffer solutions evidently influenced both the catalytic activity and selectivity of the cells. Inverted fluorescence microscopy and OD260/OD280 analysis suggested that NADESs can enhance the cellular membrane permeability, but high concentration of NADESs may damage cellular membranes and reduce the activity of enzymes. Furthermore, the whole-cell catalysts showed good scaled-up capability and stability. The whole cells also showed a relatively broad substrate spectrum towards various citrus flavonoid glycosides and their derivatives, with substrate conversions of 58.1%–98.2% and monoglycoside percentages of 73.3%–98.9%. This demonstration of whole-cell catalysis for one-pot cascade hydrolysis of flavonoid glycosides offers an eco-friendly, scalable and flexible platform method for the production of useful and valuable flavonoid monoglycosides and aglycones from inexpensive substances.

Aims To reveal the antibacterial mechanism of the combination of thymol and cinnamaldehyde to Listeria monocytogenes ATCC 19115 on autoclaved chicken breast. Methods and Results In this study, L. monocytogenes ATCC 19115 on autoclaved chicken breast was exposed to the stress of 125 μg/ml thymol and 125 μg/ml cinnamaldehyde, and transcriptome analysis was used to reveal the crucial antibacterial mechanism. According to the results, 1303 significantly differentially expressed genes (DEGs) were identified. Treated by thymol and cinnamaldehyde in combination, pyrimidine and branched-chain amino acid biosynthesis of L. monocytogenes were thwarted which impairs its nucleic acid biosynthesis and intracellular metabolism. The up-regulated DEGs involved in membrane composition and function contributed to membrane repair. Besides, pyruvate catabolism and TCA cycle were restrained which brought about the disturbance of amino acid metabolism. ABC transporters were also perturbed, for instance, the uptake of cysteine, D-methionine, and betaine was activated, while the uptake of vitamin, iron, and carnitine was repressed. Thus, L. monocytogenes tended to activate PTS, glycolysis, glycerol catabolism, and pentose phosphate pathways to obtain energy to adapt to the hostile condition. Noticeably, DEGs involved in virulence factors were totally down-regulated, including genes devoted to encoding flagella, chemotaxis, biofilm formation, internalin as well as virulence gene clusters. Conclusions The combination of thymol and cinnamaldehyde is effective to reduce the survival and potential virulence of L. monocytogenes on autoclaved chicken breast. Significance and Impact of Study This work contributes to providing theoretical information for the application and optimization of thymol and cinnamaldehyde in ready-to-eat meat products to inhibit L. monocytogenes.

A series-connected tetracation cross-linker, DB, was synthesized successfully from 1,4-diazabicyclo[2.2.2]octane (DABCO) and dibromomethane. Which had two terminal tertiary amine groups and reacted with the bromomethylated poly(aromatic ether sulfone) (BPAES) based on 9,9-bis(4-hydroxyphenyl)fluorene and the other copolycondensation monomers giving a series of series-connected hexacations cross-linked anion exchange membranes, QPAES-DBs, for acid recovery by diffusion dialysis (DD). When applied in mostly reported simulated solution mixture of HCl and FeCl2, QPAES-DB50 shows the best DD performances with separation factor of H+ to Fe2+ ( S H + / Fe 2 + ) value of 127 and dialysis coefficient of hydrogen ion ( U H + ) value of 18.92 × 10−3 m/h, which are much higher than that of the commercial membrane TWDDA1 ( U H + = 9.18 ×10−3 m/h, S H + / Fe 2 + = 38.08). The phenomena are possibly resulted from the strengthened DONNAN effect provided by the crosslinking network containing series-connected hexacation segments at a certain crosslink density. In addition, the application in DD of QPAES-DB50 was extended to the multi-metals ions chlorides system of Mn2+/Ni2+/Cu2+/Cd2+/Cr3+. The separation factors of H+ to Ni2+, Mn2+, Cr3+, Cu2+ and Cd2+ reach up to 137.48, 119.90, 54.59, 32.84 and 16.19 separately. Evidently, QPAES-DB50 exhibits excellent DD performances and great potential of acid recovery.

Acylation has become one of the most widely used methods to improve the lipid solubility and bioavailability of flavonoids. In this study, puerarin acid esters (PAES) with different chain lengths were synthesized via biocatalytic acylation. This was the first study to evaluate the digestion and transport profiles and immunocompetence of PAES. The relationship between the digestion and transport profiles and potential immunocompetence of the acylated derivatives in Caco-2 cell monolayers was also explored. Puerarin and PAES remained stable in gastric phases, whereas different degrees of hydrolysis of PAES were found in the intestine. PAES with less than 12 carbon chains were positively correlated with the degree of hydrolysis, while those with more than 12 carbon chains showed higher resistance to hydrolysis by the artificial human digestive juice. The apparent permeability coefficients of puerarin, puerarin acetate, puerarin propanoate, puerarin butyrate, puerarin hexanoate, puerarin octanate and puerarin laurate were 1.62 ± 0.09, 1.70 ± 0.15, 1.89 ± 0.19, 1.86 ± 0.18, 2.29 ± 0.12, 4.06 ± 1.01 and 2.32 ± 0.88 × 10-6 cm s-1, respectively, in Caco-2 cell monolayers. The results of the immune factor assays indicated that puerarin propanoate, puerarin hexanoate and puerarin myristate could significantly promote the secretion of IL-6, TNF-α and IL-10. These findings suggested that a better absorption could be predicted after oral intake using PAES. Meanwhile, the concentration of esters and their metabolites (puerarin) found in the digestion and transport profiles directly affected their potential immunocompetence.

Salmonella enterica serovar Enteritidis is a primary pathogen causing foodborne diseases and intestinal inflammatory responses. Acid tolerance response (ATR), as a strategy of adaption and resistance to acid stress, may contribute to enhanced virulence. In this study, there was a moderately acid adaption (pH 5.0) for S. Enteritidis cells prior to treatment with acid stress (pH 3.0). To figure out whether S. Enteritidis up-regulated the virulence or not, a global transcriptomic analysis was carried out by high-throughout RNA-sEq. The results showed 74 differentially expressed genes (DEGs) involved in virulence were identified after acid stress, among which, 62 DEGs were up-regulated and 12 DEGs were down-regulated. Afterwards, those virulence-linked DEGs were discussed and classified into four aspects based on the steps of infection, including flagellar functions, fimbrial adhesins, T3SS-mediated invasion and other virulent determinants. In conclusion, S. Enteritidis seemed to exhibit a trend of virulent genes towards high-expression under acid stress, revealing risks of Salmonella in acid-containing food. To our knowledge, there were few studies on comprehensively analyzing virulent genes expression changes of Salmonella, but it’s novel to put forward pathogenicity as the highest priority under acid environment.

Protein-based Pickering emulsions have received considerable attention as nutraceutical vehicles. However, the oral bioavailability of nutraceuticals encapsulated in Pickering emulsions was not well established. In this work, a simulated gastrointestinal tract/Caco-2 cell culture model was applied to investigate the oral bioavailability of quercetin encapsulated in zein-based Pickering emulsions with quercetin in zein particles as the control. Pickering emulsions with shell (ZCP-QE) and core quercetin (ZCPE-Q) were constructed, and quercetin bioaccessibility, cell uptake and secretion, and the overall bioavailability were evaluated and compared. The overall oral bioavailability of quercetin was increased from 2.71% (bulk oil) to 38.18% (ZCPs-Q) and 18.97% (ZCPE-Q), particularly reached 41.22% for ZCP-QE. This work took new insights into the contributions of bioaccessibility and absorption (cell uptake plus secretion) to the overall oral bioavailability of quercetin. A schematic representation is proposed to relate the types of colloidal nanostructures in the digesta to the uptake, cell absorption, and overall oral bioavailability of quercetin. This study provided an attractive basis for identifying effective strategies to improve the oral bioavailability of hydrophobic nutraceuticals.

A new Aspergillus niger whole-cell catalyst was cultured for the cascade hydrolysis of hesperidin (HES) to produce high-value hesperetin-7-O-glucoside (HG) and hesperetin with high conversion (above 90%). Moreover, the inducers used were shown to be useful for cell growth and to induce cells to produce specific enzymes. Remarkably, the type of inducers determined whether the cells can hydrolyze HES. The product composition was also controllable by adjusting different inducers. Transcriptome analysis suggested that both naringin-vs-blank group and saccharose-vs-blank group had obviously difference in gene expression. The naringin-vs-blank group was mainly up-regulated differentially expressed genes (DEGs), while saccharose-vs-blank group was mainly down-regulated DEGs. The Gene Ontology (GO) analysis showed that whether naringin or saccharose was added as an inducer would greatly affect the catalytic activity of cells. Furthermore, 3 genes related to rhamnosidase, 14 genes related to glucosidase and 5 genes related to hydrolase activity were found. These genes were not only involved in rhamnosidase and glucosidase activities, but also spliceosome and the sucrose and starch metabolic pathways. The quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that the results of transcriptome sequencing were reliable. This study gave a new approach to hydrolyze HES, and new perspectives to understand the mechanisms associated with the hydrolysis of whole-cell catalyst.

Antibacterial activity against Escherichia coli O157:H7 and Staphylococcus aureus of five typical plant-derived compounds [gallic acid (G.A), citral (Cit), thymol (Thy), salicylic acid (S.A), lauric acid (L.A)] were investigated by determining the minimum inhibitory concentration (MIC) and the fractional inhibitory concentration index (FICI). The results showed that only a combination of Thy and G.A (TGA), with a concentration of 0.1 and 1.25 mg/mL, respectively, had a synergistic effect (FICI = 0.5) on both E. coli O157:H7 and S. aureus. The amount of Thy and G.A in mixture were four-fold lower than the MICs of the individuals shown to cause the equivalent antimicrobial activity in trypticase soy broth (TSB). The microbial reduction obtained in TSB with addition of TGA were significantly higher (P 0.05) than the reduction shown for the broth supplemented with the separated phenolics. TGA caused the changes of morphology and membrane integrity of bacteria. Additionally, the application of TGA on fresh-cut tomatoes are investigated. Fresh-cut tomatoes inoculated with E. coli O157:H7and S. aureus were washed for 2min, 5min, 10min at 4 °C, 25 °C, 40 °C in 0.3% NaOCl, or water containing TGA at various concentrations. Overall, the reduction of TGA achieved against S. aureus is higher than E. coli O157:H7. Same concentrations of combined antimicrobials at a temperature of 40 °C further increased the degree of microbial inactivation, with an additional 0.89-1.51 log CFU/g reduction compared to that at 25 °C. Moreover, 1/2MIC

Porous materials derived from natural and biodegradable polymers have received growing interest. We demonstrate here an attractive method for the preparation of protein-based porous materials using emulsions stabilized by gliadin-chitosan hybrid particles (GCHPs) as the template, with the addition of gelatin and kosmotropic ions to improve the mechanical strength. The microstructure, mechanical properties, cytotoxicity, and fluid absorption behavior of porous materials were systematically investigated. This strategy facilitated the formation of porous materials with highly open and interconnected pore structure, which can be manipulated by altering the mass ratio of hexane or gelatin in the matrix. The Hofmeister effect resulted from kosmotropic ions greatly enhanced the Young's modulus and the compressive stress at 40% strain of porous materials from 0.56 to 6.84 MPa and 0.26 to 1.11 MPa, respectively. The developed all-natural porous materials were nontoxic to HaCaT cells; they also had excellent liquid (i.e., simulated body fluid and rabbit blood) absorption performance and advantages in resisting stress and maintaining geometry shape. The effects of different concentration amounts and type of salts in the Hofmeister series on the formation and performance of porous materials were also explored. Mechanical strength of porous materials was gradually enhanced when the (NH4)2SO4 concentration increased from 0 to 35 wt %, and the other four kosmotropic salts, including Na2S2O3, Na2CO3, NaH2PO4, and Na2SO4, also showed positive effects. This work opens a simple and feasible way to produce nontoxic and biodegradable porous materials with favorable mechanical strength and controllable pore structure. These materials have broad potential application in many fields involving biomedical and material science, such as cell culture, (bio)catalysis, and wound or bone defect healing.

To investigate the clinical effect of low molecular weight heparin sodium combined with antivenin in the treatment of severe and critical bite by Trimeresurus stejnegeri.The clinical data of 48 patients with severe or critical bite by Trimeresurus stejnegeri admitted to emergency department of Southeast Hospital Affiliated to Xiamen University from March 2017 to May 2019 were retrospectively analyzed. On the basis of early treatment of antivenom serum, internal administration and external application of Jidesheng snake tablet, and wound incision and detoxification, the patients were divided into heparin treatment group and non-heparin treatment group according to whether the low molecular heparin sodium was used or not. The patients in the two groups were compared in terms of gender, age, clinical classification, swelling degree of injured limbs, change of coagulation function index, bleeding of skin, mucous membrane or digestive tract, blood transfusion, local symptoms of bite, length of hospital stay and prognosis.There was no significant difference in terms of gender, age, clinical classification or swelling degree of injured limbs between the two groups. On the 3rd day of treatment, the platelet count (PLT) in the heparin treatment group was significantly higher than that in the non-heparin treatment group [×10For the patients with severe and critical bite by Trimeresurus stejnegeri, on the basis of injection of antivenom serum, internal administration and external application of Jidesheng snake tablet, and wound incision and detoxification, early application of low molecular weight heparin sodium anticoagulation and other comprehensive treatment is helpful to improve limb swelling and inflammation, reduce blood transfusion, promote the recovery of coagulation function, and shorten the length of hospitalization.

This study characterizes the impact of sdiA on biofilm formation under normal or osmotic stress conditions in Cronobacter sakazakii by constructing a sdiA deletion mutant (ΔsdiA). Here, the downregulation of flagellar assembly-related genes and upregulation of capsular, cellulose and lipopolysaccharide biosynthesis-associated genes in ΔsdiA were observed when compared to the wild type strain (WT) through transcriptomic analysis. Meanwhile, reduced ability of motility, enhanced cell surface hydrophobicity and stronger biofilms with extracellular matrix were observed in WT with deletion of sdiA. Both WT and ΔsdiA formed more biofilm in low osmotic stress medium, while in hyperosmolarity conditions, formation of biofilm was dramatically reduced. Our findings supported that sdiA might suppress biofilm formation of C. sakazakii by regulating biosynthesis of flagellar and extracellular polymeric substances. This study investigates the role of sdiA on biofilm formation in C. sakazakii, and provides the basis for the inhibition of C. sakazakii in food industry and infant-feeding.

The antibacterial effects of phenyllactic acid (PLA) against Vibrio parahaemolyticus and its application on raw salmon fillets (RSF) were investigated in this study. The minimum inhibitory concentration (MIC) of PLA against V. parahaemolyticus was 3.2 mg/mL. Interestingly, PLA at sub-MIC (0.4 mg/mL) completely inactivated planktonic V. parahaemolyticus under saline condition. The influence of PLA on bacterial membrane and genomic DNA was explored to reveal its antibacterial mechanism. Although no obvious morphological changes were observed by scanning electron microscope, the permeability of bacterial membrane was increased and the leakage of potassium was detected under PLA stress. DNA interaction analysis illustrated that PLA was intercalative with genomic DNA, which might influence normal physiological functions of bacteria. Besides, PLA at sub-MIC could effectively inhibit the motility (i.e., swimming and swarming) of V. parahaemolyticus, thereby inhibiting its biofilm formation. The in vivo antibacterial tests confirmed that PLA at 8 MIC was capable of eliminating the contamination of V. parahaemolyticus on RSF thoroughly, while low concentration of PLA could also be used as an antibacterial agent to inhibit the growth of V. parahaemolyticus on RSF, suggesting that PLA was a promising candidate for the control of foodborne pathogens in chilled aquatic products.

Design and synthesis of prodrugs is an effective strategy to develop new drugs. Puerarin is well-known for its pharmacological properties in the treatment of many cardiovascular and cerebrovascular related diseases. To cope with its poor liposolubility that limited practical applications, we successfully developed a new type of clean and efficient esterification medium for acylation modification of puerarin and studied the relative oral absorption, including pharmacokinetics, tissue distribution and metabolite after oral taking of puerarin acid esters in comparison with free puerarin in rats. In the 1-Ethyl-3-Methylimidazoliumacetate, puerarin had the good solubility, and the reaction showed great initial rate (46.71 mmol/(L*h)) and substrate conversion (63.91%). The results of oral absorption showed that the administration of long-chain fatty acid esters of puerarin, puerarin hexanoate and puerarin myristate, resulted in significantly higher levels of puerarin in the plasma and tissues, especially in the heart, cerebral cortex, hippocampus and corpus striatum. Overall, these findings collectively supported that puerarin acid esters administration led to greater circulating concentration of puerarin and had a reduced excretion rate, providing significant advantages and theoretical basis for their application in functional foods and pharmaceutical industries.

The adaptability of Escherichia coli O157:H7 to different environmental stresses, including prolonged cold stress, poses a threat to food safety. In order to elucidate the prolonged cold response in E. coli O157:H7, genes related to prolonged coldresistance and their expression changes in E. coli O157:H7 ATCC35150 were screened and identified by analyzing their transcriptomedifferences between normal (37 °C) and low temperature storage (4 °C or −20 °C, 10 d), using RNA-sequencing. According to our results, 425 differentially expressed genes (DGEs) were identified responding to cold stresses in this study. Gene rpoS was significantly up-regulated (more than two fold; p

Anion exchange membranes (AEMs) are the cores of electrodialysis (ED) desalination devices, which have attracted wide attention in recent years. However, the influence of the ions distribution of AEMs on ED performances has not been well explored, which is strongly instructive to design the ED AEMs. Here we synthesized two kinds of side-chain-ionic AEMs QPAES-a and QPAES-b, and main-chain-ionic AEM QPAES-c. To uncover the relationship between the AEMs structures and properties, these AEMs were characterized with 1H NMR and FTIR, and evaluated in terms of ion exchange capacity, water uptake, swelling ratio, λ, conductivity and transport number. Especially, we used NaCl aqueous solution to simulate seawater to investigate the ED performances of the synthesized AEMs by 180 min of ED processes. To distinguish our AEMs, the ED performance of commercial TWEDAI was similarly tested for comparison. The results confirmed that the ED performance with a lowest final conductivity of 430 μS·cm−1 of the main-chain-ionic QPAES-c is much better than that of TWEDAI and the side-chain-ionic AEMs. The ED performance stability tests convinced that QPAES-c had ED lifetime comparable to that of TWEDAI. These results show that the main-chain-ionic AEMs have their potential as ED AEMs.

Salmonella is a major foodborne pathogen throughout the world and able to resist extreme acid stress such as stomach gastric juice after mild acid adaptation, which makes it a potential hazard in food industry. We conducted a comparative transcriptomic analysis by high-throughout RNA-seq to elucidate the Acid Tolerance Response (ATR) in Salmonella Enteritidis. Among these 554 differentially expressed genes (DEGs) identified in this study, the expression of 280 DEGs were up-regulated and 274 DEGs were down-regulated. First, S. Enteritidis tried to survive the adverse environment by reducing the energy-consuming metabolisms and maintaining essential processes as an energy conservation strategy. Second, ATR S. Enteritidis underwent damages in DNA, an oxidization damage result in an iron-lacking circumstance and so on. Thus DEGs related to Fe/S cluster biogenesis, stress response regulating proteins and transport proteins were responsive to acid stress to repair damage caused by acid and ROS. Last, to balance extra protons, by increasing the intracellular NAD (+)/NADH ratio, S. Enteritidis could also decline the protein acetylation level by promoting the consumption of acetyl coenzyme A via TCA, to prevent the intracellular pH from further decline under acid stress.

Acylation modification of phenol glycosides is currently of great interest due to the improved bioavailability and multiple functions. In this work, mono- or diesters of arbutin, an important phenol glycoside derivative, can be controllably synthesized by using whole-cell biocatalytic systems. Among fourteen microbial strains selected, Candida parapsilosis cells showed the best catalytic activity and high organic solvent tolerance. Compared with the best pure solvent tetrahydrofuran, the use of a binary solvent pyridine-isooctane gave a slightly lower conversion (98.3% vs. 97.2%) and selectivity (85.3% vs. 80.5%) and much higher substrate solubility (37.1 vs. 214.0 mg mL−1), in a 24 h bioconversion of arbutin with a VP-arbutin molar ratio of 15 and whole cell dosage of 30 mg mL−1. The production of various arbutin esters with different fatty acid chain lengths can be realized by using this whole-cell strategy, with the substrate conversion and 6′-regioselectivity of 54.1–98.3% and 83.2–99.0%, respectively.

A combination method of real-time PCR and high-resolution melting (HRM) analysis for the rapid detection and specific classification of six pathogenic Cronobacter species based on gene cgcA was developed. HRM profiles with distinct Tm (melting temperature) peaks were consistently obtained with each species, represented by a single peak ranging from 86.02 to 86.80 °C. The detection limit ranged from 0.1 to 1 pg per reaction. Desiccated Cronobacter sakazakii and Cronobacter muytjensii of 2 cfu/25 g were successfully detected after 4-week storage at room temperature. The newly developed method provided a molecular tool for direct detection and simultaneous identification of pathogenic Cronobacter species in powdered infant formulae.

ATR in EHEC O157:H7 and the cross-protection effects thus induced lead to the uncertainty of food safety. This study aimed to identify factors that are associated with the ATR in EHEC O157:H7 under stomach acidity using RNA-seq. In total, 223 DEGs in E. coli O157:H7 and 110 DEGs in E. coli after acid treatment were identified, including 118 upregulated and 105 downregulated in EHEC O157:H7, and 89 upregulated and 21 downregulated in E. coli ATCC 25922. According to our results, when facing the ATR environment, protein Asr regulated the whole acid resistance process. In E. coli ATCC 25922, cadA and cadB mediate the lysine decarboxylation consumed the extra protons inside and keep the neutral pH value in cytoplasm to protect the E. coli from death. In contrast, oxidation-reduction mediated by ahpC, which was activated by the depression of oxyR , and hydrogenation mediated by mhpA consumed the protons inside keeping the neutral pH value to protect the EHEC O157:H7 from harm induced by a low pH environment. In addition, EHEC O157:H7 expressed more anti-oxidation enzymes to repair damage caused by acid stress, which enhanced its resistance to acid compared to E. coli ATCC 25922.

Cronobacter sakazakii is a common foodborne pathogen that can tolerate various stress conditions. Acidic environment is a common stress condition encountered by bacteria in food processing and gastrointestinal digestion, including both inorganic and organic acids. In order to elucidate the Acid Tolerance Response (ATR) of C. sakazakii, we performed high-throughput RNA-seq to compare gene expression under hydrochloric acid and citric acid stresses. In this study, 107 differentially expressed genes (DEGs) were identified in both acids, of which 85 DEGs were functionally related to the regulation of acid tolerance. Multiple layers of mechanisms may be applied by C. sakazakii in response to acid stress: Firstly, in order to reduce excessive intracellular protons, C. sakazakii pumps them out through trans-membrane proteins or consumes them through metabolic reactions. Secondly, under acidic conditions, a large amount of reactive oxygen species and hydroxyl radicals accumulate in the cells, resulting in oxidative damage. C. sakazakii protects cells by up-regulating the antioxidant stress genes such as soxS and madB. Thirdly, C. sakazakii chooses energy efficient metabolic pathways to reduce energy consumption and maintain necessary processes. Finally, genes involved in chemotaxis and motility were differentially expressed to respond to different acidic conditions. This study systematically analyzed the acid-resistant mechanism of C. sakazakii under the stress of organic and inorganic acids, and provided a theoretical basis for better control of its contamination in food.

Hexyl-modified series-connected bipyridine and 1,4-diazabicyclo[2.2.2]octane (DABCO) di-cations functionalized anion exchange membranes (QPPO-DP and QPPO-DABCO respectively) for electrodialysis (ED) were prepared via reactions of brominated poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and the self-designed quaternization agents containing mono-ionic bipyridine and DABCO moieties. These agents are precursors to the combinations of different di-cations and hydrophobic side chains. QPPO-DP (thickness: 95 μm) and QPPO-DABCO (thickness: 70 μm) with similar functionalization degrees were characterized in terms of ion exchange capacity (IEC), water uptake (WU), swelling ratio (SR), thermal and mechanical stabilities, morphology, area resistance ( R m ), transport number ( t - ) and limiting current density. QPPO-DP and QPPO-DABCO give IECs of 2.27 and 2.63 mmol g−1 respectively owing to the different unit masses of the di-cations. The conjugated aromatic bicyclic structure of bipyridine di-cations offers QPPO-DP higher WU than that of QPPO-DABCO. The relatively weaker hydrophilicity of DABCO di-cations ensures QPPO-DABCO moderate WU, superior R m and t - (2.77 Ω cm2 and 0.949). Thus, QPPO-DABCO displays more excellent ED performances than those of commercial AMX under the same ED conditions, including current efficiency of 89.58%, salt flux of 81.39 mg m−2 s−1 and reasonable energy consumption of 1.76 kWh kg−1 NaCl, revealing its potential in ED application.

We developed a series of anti-fouling anion exchange membranes (AEMs) by in-situ interpenetration of an ionomer of N-methylimidazole ionizing poly(2,6-dimethyl-1,4-phenylene oxide) (IM-QPPO) to lateralized gradient cross-linked hydrogel of Ca-Na alginate (CA). The CA surfaces repel negative-charged organic pollutants because of their inherent hydrophilicity and electronegative property. SEM and EDX characterizations reveal that the micron-sized anti-fouling CA layers are bonded firmly with the ionomer bulk by the interpenetration. The anti-fouling AEMs have qualified basic properties of thermal stability, water uptake and swelling ratio, area resistance and permselectivity for electrodialysis (ED) processes. IM-QPPO-0.10CA with optimal interpenetrating structure exhibits the highest current efficiency (η) of 88.88% and the lowest energy consumption (EC) of 2.53 kWh kg−1 NaCl among the group, which are comparable to those of commercial AMX (η = 89.38%, EC = 2.20 kWh kg−1 NaCl). IM-QPPO-0.10CA shows the strongest anti-fouling ability, which is confirmed by the lowest ascent speed of transmembrane voltage and no irreversible membrane-structure damages during the fouling tests. Moreover, the fouled IM-QPPO-0.10CA recovers 99.60% of the origin η value with an EC increase of 0.10 kWh kg−1 NaCl after immersion in NaCl solution. The properties of IM-QPPO-0.10CA are promising for the application of anti-fouling ED AEMs.

Salmonella enterica serovar Typhimurium can survive some extreme environment in food processing, and vanillin generally recognized as safe is bactericidal to pathogens. Thus, we need to explore the responses of S. Typhimurium to vanillin in order to apply this antimicrobial agent in food processing. In this study, we exposed S. Typhimurium to commercial apple juice with/without vanillin (3.2 mg/mL) at 45 °C for 75 min to determine the survival rate. Subsequently, the 10-min cultures were selected for transcriptomic analysis. Using high-throughput RNA sequencing, genes related to vanillin resistance and their expression changes of S. Typhimurium were identified. The survival curve showed that S. Typhimurium treated with vanillin were inactivated by 5.5 log after 75 min, while the control group only decreased by 2.3 log. Such a discrepancy showed the significant antibacterial effect of vanillin on S. Typhimurium. As a result, 265 differentially expressed genes (DEGs) were found when coping with vanillin, among which, 225 showed up-regulation and 40 DEGs were down-regulated. Treated with vanillin, S. Typhimurium significantly up-regulated genes involved in cell membrane, acid tolerance response (ATR) and oxidative stress response, cold shock cross-protection, DNA repair, virulence factors and some key regulators. Firstly, membrane-related genes, including outer membrane (bamE, mepS, ygdI, lolB), inner membrane (yaiY, yicS) and other proteins (yciC, yjcH), were significantly up-regulated because of the damaged cell membrane. Then, up-regulated proteins associated with arginine synthesis (ArgABCDIG) and inward transportation (ArtI, ArtJ, ArtP and HisP), participated in ATR to pump out the protons inside the cell in this scenario. Next, superoxide stress response triggered by vanillin was found to have a significant up-regulation as well, which was controlled by SoxRS regulon. Besides, NADH-associated (nuoA, nuoB, nuoK, nadE, fre and STM3021), thioredoxin (trxA, trxC, tpx and bcp) and glutaredoxin (grxC and grxD) DEGs led to the increase of the oxidative stress response. Cold shock proteins such as CspA and CspC showed an up-regulation, suggesting it might play a role in cross-protecting S. Typhimurium from vanillin stress. Furthermore, DEGs in DNA repair and virulence factors, including flagellar assembly, adhesins and type III secretion system were up-regulated. Some regulators like fur, rpoE and csrA played a pivotal role in response to the stress caused by vanillin. Therefore, this study sounds an alarm for the risks caused by stress tolerance of S. Typhimurium in food industry.

This study aimed to select for the quorum sensing receptor protein of C. sakazakii CICC 21544, and then evaluate the role of the receptor protein in stress tolerance. SdiA was identified as the receptor by sequence alignment. C. sakazakii CICC 21544 wild type (WT), the sdiA mutant strain (ΔsdiA), and the sdiA complemented strain (sdiA+) were subjected to heat treatment at 55 °C in tryptic soy broth (TSB) or reconstituted infant formula (RIF) and the results suggested that sdiA facilitated C. sakazakii to withstand thermal stress both in TSB and RIF. Similarly, the survival rate of ΔsdiA was significantly lower than that of WT and sdiA+ under osmotic pressure of 12% NaCl or desiccation conditions. Acid tolerance assay showed that loss of sdiA decreased the ability of C. sakazakii to grow in simulated gastric fluid. The survivability of the three strains under combined stress conditions was also evaluated in this study. After heating, evaporation, and drying stresses, ΔsdiA was undetectable, while WT and sdiA+ survived the treatments. This study demonstrates that sdiA contributes to the survival of C. sakazakii under different environmental stresses, and provides a basis for the sdiA-targeted inhibition of C. sakazakii in food.

The combined effects of four substances, carvacrol, citral, thymol and caprylic acid, on the growth of Cronobacter sakazakii CICC 21544 were evaluated. Among the six combinations, only the combination of citral and carvacrol demonstrated a synergistic effect. This combination had a stronger growth inhibition effect than treatment with citral or carvacrol alone, which led to more portions of cells in the propidium iodide (PI) fluorescent region and caused more severe cell damage. Citral and carvacrol also showed promising and potent antibiofilm activity against C. sakazakii, which was evaluated using crystal violet assay, field emission scanning electron microscopy (FESEM) and qRT-PCR. Mild heat treatment combined with citral and carvacrol at a concentration of 2 or 3 MIC completely eradicated C. sakazakii in reconstituted infant formula. Moreover, the combination at 2 MIC had no significant effect on the color and aroma scores of reconstituted infant formulae. The combination of citral and carvacrol could potentially be developed as an alternative or supplemental agent to reduce infections caused by C. sakazakii in reconstituted infant formula.

The effect of combining vacuum cooling with an ozone-based inhibition process (InhVac) on Clostridium perfringens spore germination and outgrowth in cooked pork meat after exponential chilling (from 54.4 to 7.2 °C in 12, 15, 18, or 21 h) and isothermal storage (20, 25, 30, 36, or 45 °C) was evaluated. Ice cooling (IC) and vacuum cooling (VC) were used to compare the effects with InhVac. The samples were inoculated with a three-strain mixture of C. perfringens spores to obtain concentration of ca. 3 log10 CFU/g. C. perfringens growth in samples treated by InhVac were 0.1, 0.37 and 0.9 log10 CFU/g after 15, 18 and 21 h of cooling from 54.4 to 7.2 °C respectively, significantly lower (P Industrial relevance In this study, an innovative inhibition approach (InhVac) was found to show a better antimicrobial effect on C. perfringens germination and outgrowth in cooked pork meat compared to ice cooling and vacuum cooling under temperature-abuse conditions. A primary modified Gompertz model and a secondary Square Root model could be used to predict the C. perfringens growth in samples subjected to InhVac treatment.

Fresh fish are highly perishable because their high content of protein and unsaturated fatty acids are easily oxidized and/or degraded under the influence of bacteria and the external environment. In this study, four natural preservatives (phenyllactic acid, kojic acid, tea polyphenols and thymol) were initially screened for antimicrobial activity against spoilage bacteria commonly found in fish by in vitro antibacterial tests. The results suggested that kojic acid (KA) and tea polyphenols (TP) exhibited a strong synergistic antibacterial effect against spoilage bacteria. Hence, the effects of KA and/or TP on the preservation of refrigerated sea bass (Lateolabrax japonicus) fillets after soaking treatments were determined. Changes in physicochemical parameters, indexes of fish freshness and microbial enumeration were examined. KA, TP and KA-TP treatments were effective in inhibiting bacterial growth and delaying lipid oxidation in fish flesh, resulting in lower TVB-N and TBARS than the control. Meanwhile, the freshness and physical qualities (color and texture) of fish fillets were also stabilized by the three treatments. Moreover, the KA-TP treatment showed the best effect on refrigerated fish preservation among the three treatments and extended the shelf-life by 5–6 days, suggesting that KA-TP have the potential to become a compound preservative for aquatic products.

Salmonella Enteritidis is a major cause of foodborne gastroenteritis and is thus a persistent threat to global public health. The acid adaptation response helps Salmonella survive exposure to gastric environment during ingestion. In a previous study we highlighted the damage caused to cell membrane and the regulation of intracellular reactive oxygen species (ROS) in S. Enteritidis. In this study, we applied both physiologic and iTRAQ analyses to explore the regulatory mechanism of acid resistance in Salmonella. It was found that after S. Enteritidis was subject to a 1 h period of acid adaptation at pH 5.5, an additional 1 h period of acid shock stress at pH 3.0 caused less Salmonella cell death than in non-acid adapted Salmonella cells. Although there were no significant differences between adapted and non-adapted cells in terms of cell membrane damage (e.g., membrane permeability or lipid peroxidation) after 30 min, intracellular ROS level in acid adapted cells was dramatically reduced compared to that in non-acid adapted cells, indicating that acid adaption promoted less ROS generation or increased the ability of ROS scavenging with little reduction in the integrity of the cell membrane. These findings were confirmed via an iTRAQ analysis. The adapted cells were shown to trigger incorporation of exogenous long-chain fatty acids into the cellular membrane, resulting in a different membrane lipid profile and promoting survival rate under acid stress. S. Enteritidis experiences oxidative damage and iron deficiency under acid stress, but after acid adaption S. Enteritidis cells were able to balance their concentrations of intracellular ROS. Specifically, SodAB consumed the free protons responsible for forming reactive oxygen intermediates (ROIs) and KatE protected cells from the toxic effects of ROIs. Additionally, acid-labile proteins released free unbound iron promoting ferroptotic metabolism, and NADH reduced GSSH to G-SH, protecting cells from acid/oxidative stress.