Advancing gelatin/cinnamaldehyde O/W emulsions electrospinability: Role of soybean lecithin in core-shell nanofiber fabrication.

The main objective of this study is to investigate the impact and mechanism of soy lecithin incorporation into the gelatin-cinnamaldehyde emulsion, focusing on how it influences emulsion stability during the electrospinning process. In this work, a cinnamaldehyde/gelatin/soy lecithin (CGS) fiber membrane with excellent antibacterial properties was successfully created. The addition of soy lecithin improves the stability of the emulsion and improves the loading performance and fiber morphology of the CGS fiber membrane. Fourier Transform infrared spectroscopy (FTIR) and urea addition confirmed that soy lecithin may strengthen the interface structure of gelatin in the oil and water phases through hydrogen bonds, thus enhancing the stability of the emulsion in electrospinning. The application tests also revealed that the CGS fiber membrane effectively preserved the sensory quality of beef. This study indicates that the vector construction method can extend the utilization of cinnamaldehyde in food industry.

Fabrication and characterization of pullulan/tapioca starch-based antibacterial films incorporated with Litsea cubeba essential oil for meat preservation.

Active packaging is a novel technology that utilizes active materials to interact with products and the environment, improving food shelf life. The purpose of this work was to fabricate a multifunctional film using Litsea cubeba essential oil (LC-EO) (1 %, 3 %, 5 %, and 7 %) as the active ingredient and pullulan(P)/tapioca starch (TS) as the carrier material. Adding essential oil improves the films properties, such as barrier ability, anti-oxidant, and antibacterial activity. However, tensile strength (TS) and elongation at break (EAB) were slightly reduced from 28.94 MPa to 11.29 MPa and 15.36 % to 12.19 %. The developed PTS3% films showed the best performance in mechanical properties, especially EAB (14.26 %), WVP (3.26 %) and OP (3.13 %), respectively. The inhibitory zone diameters in the agar-well diffusion test were 18.59 mm for Staphylococcus aureus and 17.32 mm for Escherichia coli. Further study was conducted to compare the preservation effects of film with low-density polyethylene bag (LDPE) on chilled beef. Remarkably, PTS3% film decreased the bacterial population in beef meat while maintaining the pH, color, texture, and TBARS levels within an acceptable range for ten days of storage at 4 °C rather than in a low-density polyethylene bag. The outcomes indicated the potential of PTS3% films in food packaging applications.

TRPV1 analgesics disturb core body temperature via a biased allosteric mechanism involving conformations distinct from that for nociception.

Efforts on developing transient receptor potential vanilloid 1 (TRPV1) drugs for pain management have been hampered by deleterious hypo- or hyperthermia caused by TRPV1 agonists/antagonists. Here, we compared the effects of four antagonists on TRPV1 polymodal gating and core body temperature (CBT) in Trpv1+/+, Trpv1-/-, and Trpv1T634A/T634A. Neither the effect on proton gating nor drug administration route, hair coverage, CBT rhythmic fluctuations, or inflammation had any influence on the differential actions of TRPV1 drugs on CBT. We identified the S4-S5 linker region exposed to the vanilloid pocket of TRPV1 to be critical for hyperthermia associated with certain TRPV1 antagonists. PSFL2874, a TRPV1 antagonist we discovered, is effective against inflammatory pain but devoid of binding to the S4-S5 linker and inducing CBT changes. These findings implicate that biased allosteric mechanisms exist for TRPV1 coupling to nociception and CBT regulation, opening avenues for the development of non-opioid analgesics without affecting CBT.

The effect of extraction methods on the components and quality of Camellia oleifera oil: Focusing on the flavor and lipidomics.

The objective of this study was to systematically elucidate the effects of conventional (Cold Pressing, CP; Hot Pressing, HP; Soxhlet Extraction; SE) and novel methods (Microwave-Assisted Extraction, MAE) on the physicochemical properties, bio-active substances, flavor and lipidomics of Camellia oleifera oil (COO). The cold-pressed COO contained the highest contents of squalene (176.38 mg/kg), α-tocopherol (330.52 mg/kg), polyphenols (68.33 mg/kg) and phytosterols (2782.55 mg/kg). Oleic acid was observed as the predominant fatty acid with the content of approximately 80%. HS-GC-IMS identified 47 volatile compounds, including 11 aldehydes, 11 ketones, 11 alcohols, 2 acids, 8 esters, 2 pyrazines, 1 furan, and 1 thiophene. A total of 5 lipid classes and 30 lipid subclasses of 339 lipids were identifed, among which TGs and DGs were observed as the major lipids. In summary, both cold-pressed and microwave-assisted technologies provided high-quality COO with high content of bio-active substances and diglycerides/triglycerides.

Transcriptome analysis reveals the inhibitory mechanism of phloretin on virulence expression of Staphylococcus aureus and its application in cooked chicken.

Staphylococcus aureus (S. aureus) enterotoxins have aroused great concern to food safety owing to its increased risk of food poisoning. The current research aimed to investigate the anti-virulence mechanisms of phloretin against S. aureus in terms of toxin activity and gene expression. The results indicated that phloretin could effectively inhibit the production of hemolysins and enterotoxins, and its anti-virulence effect was exerted in a concentration-dependent manner. Transcriptome results indicated that phloretin could downregulate the transcription level of majority virulence factors related genes (68 %) of S. aureus, including the quorum sensing-related genes (agrB, agrC, agrA, sspA, splF, splD and others) and bacterial secretion system-related genes (secDF, secY2, and yidC). In addition, it was speculated that phloretin was most likely to bind to the AgrA DNA binding domain, thereby affecting the expression of downstream virulence genes (hla, seb, spa, rot, geh, etc) based on molecular docking. Finally, the application in cooked chicken indicated that phloretin could effectively decrease the content of enterotoxins and improve the storage quality of cooked chicken. These findings not only evidenced the feasible anti-virulence activity of phloretin, but also provided a new strategy to prevent S. aureus food poisoning in cooked meat preservation.

Schiff base linkage of citral to zinc-casein hydrolysate chelates for preparing starch-based active films against L. monocytogenes on ready-to-eat foods.

Listeria monocytogenes (L. monocytogenes) is a foodborne pathogen often found in ready-to-eat (RTE) foods, posing significant threats to human health. In this study, an active film based on cross-linking via Schiff base and electrostatic interaction to inactivate L. monocytogenes on RTE foods was constructed. Zinc-casein hydrolysate chelates (Zn-HCas) was prepared and blended with cationic starch (CSt) to form the substrates of the film. Then, Citral (CI) with excellent antibacterial properties was added to enhance the biological and packaging properties of the film through covalent cross-linking (Schiff base). Based on the zinc ion-activated metalloproteinases produced by L. monocytogenes, the cross-linked film could be disrupted and the release of CI was accelerated. The variation in color, FTIR, and amino group content proved that Schiff base reaction had taken place. Enhanced mechanical properties, barrier properties, thermal stability and antimicrobial activity against L. monocytogenes (exceed 99.99 %) were obtained from the CI/Zn-HCas/CSt film. The application on RTE cheese results demonstrated that the cross-linked film could be employed in active packaging field with the ability in maintaining the original chroma and texture properties of RTE cheese. In summary, the prepared cross-linked film could be used as an active packaging against L. monocytogenes contamination with great potential.

Phosphoproteomics analysis reveals the anti-bacterial and anti-virulence mechanism of eugenol against Staphylococcus aureus and its application in meat products.

The increasing risk of food poisoning caused by Staphylococcus aureus (S. aureus) contamination has aroused great concern about food safety. Eugenol is highly favored due to its broad-spectrum antibacterial activity and non-drug resistance property. The study aimed to reveal the anti-bacterial and anti-virulence mechanisms of eugenol against S. aureus using phosphoproteomics. The results indicated that eugenol could inhibit the phosphorylation levels of enzyme I in the bacterial phosphotransferase system (PTS). Meanwhile, it could also inhibit the phosphorylation levels of key enzymes in bacterial carbon metabolism (such as glucose-6-phosphate isomerase of glycolysis and succinyl-CoA synthetase of tricarboxylic acid cycle), thereby decreasing the content of ATP and accelerating bacterial death. In addition, eugenol could inhibit the phosphorylation of AgrA in the quorum sensing system, thereby inhibiting the expression of agr operons (agrA and agrC) and downstream virulence genes (RNAIII, hla and seb). Finally, the application on beef indicated that eugenol could effectively decrease the content of enterotoxins and improve its storage quality. These findings provide a new way for eugenol to prevent S. aureus contamination and food poisoning in meat products.

An energy-efficient solution to sludge drying and combustion process through Camellia oleifera shells amended foaming.

Foaming pretreatment has been proven effective in promoting sludge drying, however, the variation in sludge properties significantly influences the foaming efficiency. Inspired by foam stabilizer of solid particles, Camellia oleifera shells (COS) was screened out from various biomasses as an additive incorporated with the CaO for promoting the sludge foaming. For the introduction of COS, this study analyzed the drying behaviors of foamed sludge, quantified the surface cracks information, characterized the combustion performance, and evaluated the energy consumption. The results indicated that 46.72-50.10% of time could be saved in foaming the sludge to 0.70 g/mL by addition of 3.0 wt% COS. Compared with the original sludge (OS), the 0.70 g/mL foamed sludge saved 47.43% of time for sludge drying at 80 °C, and this value further increased to 53.14% with 3.0 wt% COS addition. Combining the multifractal spectra and drying kinetics analysis, the foaming promoted the formation of complex surface cracks in the warm-up period, while COS further improved the complexity of cracks in the constant rate period, and the shrinkage of isolated sludge blocks in the falling rate period, thus enhanced the moisture diffusion and heat transfer. Furthermore, the appropriate porous structure and additional volatile matters promoted the combustion performance. The 0.90 g/mL foamed sludge with COS presented the lowest activation energy of 180.362 kJ/mol in combustion. Overall, compared with OS, the 0.70 g/mL foamed sludge with COS saved 40.65% energy consumption during the foaming, drying and combustion processes, providing an energy-efficient solution for the sludge treatment and disposal.

Cfp1 Controls Cardiomyocyte Maturation by Modifying Histone H3K4me3 of Structural, Metabolic, and Contractile Related Genes.

Cardiomyocyte maturation is the final stage of heart development, and abnormal cardiomyocyte maturation will lead to serious heart diseases. CXXC zinc finger protein 1 (Cfp1), a key epigenetic factor in multi-lineage cell development, remains underexplored in its influence on cardiomyocyte maturation. This study investigates the role and mechanisms of Cfp1 in this context. Cardiomyocyte-specific Cfp1 knockout (Cfp1-cKO) mice died within 4 weeks of birth. Cardiomyocytes derived from Cfp1-cKO mice showed an inhibited maturation phenotype, characterized by structural, metabolic, contractile, and cell cycle abnormalities. In contrast, cardiomyocyte-specific Cfp1 transgenic (Cfp1-TG) mice and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) overexpressing Cfp1 displayed a more mature phenotype. Mechanistically, deficiency of Cfp1 led to a reduction in trimethylation on lysine 4 of histone H3 (H3K4me3) modification, accompanied by the formation of ectopic H3K4me3. Furthermore, Cfp1 deletion decreased the level of H3K4me3 modification in adult genes and increased the level of H3K4me3 modification in fetal genes. Collectively, Cfp1 modulates the expression of genes crucial to cardiomyocyte maturation by regulating histone H3K4me3 modification, thereby intricately influencing the maturation process. This study implicates Cfp1 as an important molecule regulating cardiomyocyte maturation, with its dysfunction strongly linked to cardiac disease.

Physicochemical properties and pork preservation effects of lotus seed drill core powder starch-based active packaging films.

Lotus seed drill core powder starch (LCPS)-based active packaging films incorporated with cellulose nanocrystals (CNC) and grapefruit essential oil-corn nanostarch Pickering emulsion (ECPE) were characterized, and their pork preservation effects were investigated in this study. In contrast with corn, potato and rice starches, LCPS showed higher amylose content, elliptical and circular shape with more uniform size distribution. Furthermore, LCPS film exhibited lower light transmittance, stronger tensile strength, and smaller elongation at break compared to the other starch films. Then, the LCPS film containing 4 % CNC and 9 % ECPE was fabricated which had stronger mechanical properties, lower water vapor permeability and oxygen transmission rate, and denser network structure. FTIR and XRD analyses also confirmed that CNC and ECPE were successfully implanted into the LCPS matrix without damaging the crystalline structure of LCPS. Herein, the LCPS/CNC/ECPE film exerted potential antibacterial activity against Escherichia coli and Staphylococcus aureus. Besides, packaging with this composite film significantly preserved the pork during cold storage via decreasing its juice loss rate, pH value, total number of colonies, total volatile base nitrogen and thiobarbituric acid reactive substance values. The present study will provide a theoretical basis for the application of LCPS as new biodegradable active films.

Fabrication of Citrus bergamia essential oil-loaded sodium caseinate/peach gum nanocomplexes: Physicochemical, spectral, and structural characterization.

`The objective of current research was to encapsulate citrus bergamia essential oil (CBEO) in nanocomplexes composed of sodium caseinate (SC) and peach gum polysaccharide (PG) in various ratios (SC/PG-1:0, 0:1, 1:1, 1:3, and 3:1). The nanocomplexes formed by the combination of SC and PG in a ratio of 1:3 exhibited a zeta potential of -21.36 mV and a PDI of 0.25. The CBEO-loaded SC/PG (1:3) nanocomplexes revealed the maximum encapsulation efficiency (82.47 %) and loading capacity (1.85 %). FTIR also confirmed the secondary structure variations in response to different ratios of CBEO-loaded SC/PG nanocomplexes. In addition, the XRD and fluorescence spectroscopy analysis also revealed structural changes among CBEO nanocomplexes. The thermal capability of CBEO-loaded SC/PG (1:3) nanocomplexes via TGA showed the minimum weight loss among other complexes. SEM and CLSM analysis demonstrated the uniform distribution and spherical morphology of CBEO-loaded SC/PG (1:3) nanocomplexes. The antioxidant activity of free CBEO was significantly improved in CBEO-loaded nanocomplexes. Likewise, the inhibitory activity of CBEO-loaded nanocomplexes exhibited significantly higher antibacterial action against S. aureus and E. coli. The aforementioned perspective suggests that SC/PG nanocomplexes have potent potential to serve as highly effective nanocarriers with a broad spectrum of uses in the pharmaceutical and food sectors.

Apricot polysaccharides as new carriers to make curcumin nanoparticles and improve its stability and antibacterial activity.

Apricot polysaccharides (APs) as new types of natural carriers for encapsulating and delivering active pharmaceutical ingredients can achieve high-value utilization of apricot pulp and improve the solubility, the stability, and the antibacterial activity of insoluble compounds simultaneously. In this research, the purified APs reacted with bovine serum albumin (BSA) by the Maillard reaction, and with d-α-tocopheryl succinate (TOS) and pheophorbide A (PheoA) by grafting to fabricate two materials for the preparation of curcumin (Cur)-encapsulated AP-BSA nanoparticles (CABNs) and Cur-embedded TOS-AP-PheoA micelles (CTAPMs), respectively. The biological activities of two Cur nano-delivery systems were evaluated. APs consisted of arabinose (22.36%), galactose (7.88%), glucose (34.46%), and galacturonic acid (31.32%) after the optimized extraction. Transmission electron microscopy characterization of CABNs and CTAPMs displayed a discrete and non-aggregated morphology with a spherical shape. Compared to the unencapsulated Cur, the release rates of CABNs and CTAPMs decreased from 87% to 70% at 3 h and from 92% to 25% at 48 h, respectively. The antioxidant capacities of CABNs and CTAPMs were significantly improved. The CTAPMs exhibited a better antibacterial effect against Escherichia coli than CABNs due to the synergistic photosensitive effect between Cur and PheoA.

Inhibitory effects of citral on the production of virulence factors in Staphylococcus aureus and its potential application in meat preservation.

Foodborne diseases caused by Staphylococcus aureus contamination on meat and meat products has gained increasing attention in recent years, while the pathogenicity of S. aureus is mainly attributed to its virulence factors production, which is primarily regulated by quorum sensing (QS) system. Herein, we aimed to uncover the inhibitory effects and mechanisms of citral (CIT) on virulence factors production by S. aureus, and further explore its potential application in pork preservation. Susceptibility test confirmed the antibacterial properties of CIT against S. aureus, the minimal inhibitory concentration (MIC) was 0.25 mg/mL. Treatment with sub-MICs of CIT reduced the hemolytic activity by inhibiting the production of α-hemolysin, and staphylococcal enterotoxins (SEs) production was significantly inhibited by CIT in both culture medium and pork without affecting bacterial growth. Transcriptomic analysis indicated that the differentially expression genes encoding α-hemolysin, SEs, and other virulence factors were down-regulated after treatment with 1/2MIC CIT. Moreover, the genes related to QS including agrA and agrC were also down-regulated, while the global transcriptional regulator sarA was up-regulated. Data here demonstrated that CIT could inhibited S. aureus virulence factors production through disturbing QS systems. In a challenge test, the addition of CIT caused a remarkable inhibition of S. aureus population and delay in lipid oxidation and color change on pork after 15 days incubation at 4 °C. These findings demonstrated that CIT could not only efficiently restrain the production of S. aureus virulence factors by disturbing QS, but also exhibit the potential application on the preservation of meat products.

A shared mechanism for TNP-ATP recognition by members of the P2X receptor family.

P2X receptors (P2X1-7) are non-selective cation channels involved in many physiological activities such as synaptic transmission, immunological modulation, and cardiovascular function. These receptors share a conserved mechanism to sense extracellular ATP. TNP-ATP is an ATP derivative acting as a nonselective competitive P2X antagonist. Understanding how it occupies the orthosteric site in the absence of agonism may help reveal the key allostery during P2X gating. However, TNP-ATP/P2X complexes (TNP-ATP/human P2X3 (hP2X3) and TNP-ATP/chicken P2X7 (ckP2X7)) with distinct conformations and different mechanisms of action have been proposed. Whether these represent species and subtype variations or experimental differences remains unclear. Here, we show that a common mechanism of TNP-ATP recognition exists for the P2X family members by combining enhanced conformation sampling, engineered disulfide bond analysis, and covalent occupancy. In this model, the polar triphosphate moiety of TNP-ATP interacts with the orthosteric site, while its TNP-moiety is deeply embedded in the head and dorsal fin (DF) interface, creating a restrictive allostery in these two domains that results in a partly enlarged yet ion-impermeable pore. Similar results were obtained from multiple P2X subtypes of different species, including ckP2X7, hP2X3, rat P2X2 (rP2X2), and human P2X1 (hP2X1). Thus, TNP-ATP uses a common mechanism for P2X recognition and modulation by restricting the movements of the head and DF domains which are essential for P2X activation. This knowledge is applicable to the development of new P2X inhibitors.

Ethyl cellulose/gelatin-carboxymethyl chitosan bilayer films doped with Euryale ferox seed shell polyphenol for cooked meat preservation.

This study evaluated the effects of an edible bilayer containing polyphenols from the Euryale ferox seed shell on ready-to-eat cooked beef products, including the physical, mechanical, antioxidant, and antibacterial capabilities. Here, the bilayer films were prepared by layer-by-layer solution pouring using hydrophobic ethyl cellulose (EC) as the outer layer, and hydrophilic gelatin/carboxymethyl chitosan (GC) as the inner layer. By adjusting the proportion of gelatin to carboxymethyl chitosan, the optical, mechanical, and barrier characteristics of bilayer films were markedly enhanced. Extracted polyphenol (EP) from shell of the Euryale ferox seed performed potent antibacterial property against Listeria monocytogenes (L. monocytogenes). The addition of EP to the inner layer of the optimized bilayer film further improved the mechanical and barrier properties of films, and as expected, the film exhibited antioxidant and antibacterial abilities. Additionally, cooked beef and cooked chicken preservation tests indicated that the active bilayer film showed good inhibition of L. monocytogenes and delayed lipid oxidation in ready-to-eat meat products, and significantly delayed the pH, moisture loss, color and texture changes. This study developed multifunctional bilayer active edible films, which has a great potential in the preservation ready-to-eat cooked meat products.

The synergistic regulation of sewage sludge biodrying and greenhouse gas reduction by additives.

As a dewatering method of high moisture solid waste sludge, biodrying still faces environmental problems such as material loss and greenhouse gas emission in the process of treatment. In this study, biochar and magnesium chloride were used to explore the synergistic effect of enhancing sludge biodrying and reducing greenhouse gas emissions. The highest temperature of biodrying was raised to 68.2 °C within 3 days, extending the longest high-temperature period to 5 days, which reduced the water content to 28.8 % in the single addition of biochar treatment. The complex addition increased the NH4+-N content of materials by 57.49 % and decreased the NO3--N content of materials by 40.62 %. The use of additives significantly reduced the emissions of CO2, CH4, and N2O compared to the no-addition treatment. The increase in dominant Actinomycetes and Chloroflexibacter was the main reason for the reduction in gas emissions.

Effect of substrate composition on physicochemical properties of the medium-long-medium structured triacylglycerol.

BACKGROUND: Nutritional and functional qualities and applications of structured lipids (SL) depend on the composition and molecular structure of fatty acids in the glycerol backbone of triacylglycerol (TAG). However, the relationship between the substrate composition and physicochemical qualities of SL has not been revealed. The investigation aims to disclose the effect of substrate composition on the physicochemical properties of medium-long-medium structured lipids (MLM-SLs) by enzymatic interesterification of Lipozyme TLIM/RMIM. RESULTS: The medium-long-chain triacylglycerol (MLCT) yield could reach 70.32%, including 28.98% CaLCa (1,3-dioctonyl-2-linoleoyl glyceride) and 24.34% CaOCa (1,3-didecanoyl-2-oleoyl glyceride). The sn-2 unsaturated fatty acid composition mainly depended on long-chain triacylglycerol (LCT) in the substrate. The increased carbon chain length and double bond in triacylglycerol decreased its melting and crystallization temperature. The balanced substrate composition of MCT/LCT increased the size and finer crystals. Molecular docking simulation revealed that the MLCT molecule mainly interacted with the catalytic triplets of Lipozyme TLIM (Arg81-Ser83-Arg84) and the Lipozyme RMIM (Tyr183-Thr226-Arg262) by OH bond. The oxygen atom of the ester on the MLCT molecule was primarily bound to the hydrogen of hydroxyl and amino groups on the binding sites of Lipozyme TLIM/RMIM. The intermolecular interplay between MLCT and Lipozyme RMIM is more stable than Lipozyme TLIM due to the formation of lower binding affinity energy. CONCLUSION: This research clarifies the interaction mechanism between MLCT molecules and lipases, and provides an in-depth understanding of the relationship between substrate composition, molecular structure and physicochemical property of MLM-SLs. © 2023 Society of Chemical Industry.

Metabolic engineering of Yarrowia lipolytica for high-level production of squalene.

Squalene is an important triterpene with a wide range of applications. Given the growing market demand for squalene, the development of microbial cell factories capable of squalene production is considered a sustainable method. This study aimed to investigate the squalene production potential of Yarrowia lipolytica. First, HMG-CoA reductase from Saccharomyces cerevisiae and squalene synthase from Y. lipolytica was co-overexpressed in Y. lipolytica. Second, by enhancing the supply of NADPH in the squalene synthesis pathway, the production of squalene in Y. lipolytica was effectively increased. Furthermore, by constructing an isoprenol utilization pathway and overexpressing YlDGA1, the strain YLSQ9, capable of producing 868.1 mg/L squalene, was obtained. Finally, by optimizing the fermentation conditions, the highest squalene concentration of 1628.2 mg/L (81.0 mg/g DCW) in Y. lipolytica to date was achieved. This study demonstrated the potential for achieving high squalene production using Y. lipolytica.

Effects of maltodextrin and protein hydrolysate extracted from lotus seed peel powder on the fat substitution and lipid oxidation of lotus seed paste.

The fat substitution of maltodextrin from lotus seed peel powder (LSP-MD) and the lipid oxidation inhibitory effect of protein hydrolysate (LSP-PH) on lotus seed paste were investigated in this study. The LSP-MD with a dextrose equivalent value of 2.28 showed the smallest specific volume, strongest water-holding capacity and retrogradation. This LSP-MD effectively maintained the sensory quality, hardness and elasticity of low-fat lotus seed paste during storage at 25 °C. For protein hydrolysate, LSP-PH with a hydrolyzation degree of 13.45 % had the strongest DPPH· scavenging capacity and ferric reducing antioxidant power, which was further confirmed by FTIR spectra that enzymatic hydrolysis of LSP protein could facilitate the transformation of ß-sheet into ß-turn. Following 15 days of storage, supplementation with 0.5 % LSP-PH reduced the peroxide value and acid value of lotus seed paste, suggesting its excellent inhibitory effect on lipid peroxidation via interacting with hydrophobic polyunsaturated fatty acids.

Antibacterial effect of protease-responsive cationic eugenol liposomes modified by gamma-polyglutamic acid against Staphylococcus aureus.

Eugenol, as a natural antibacterial agent, has been widely studied for its inhibitory effect on the common food-borne pathogen Staphylococcus aureus (S. aureus). However, the widespread application of eugenol is still limited by its instability and volatility. Herein, γ-polyglutamic acid coated eugenol cationic liposomes (pGA-ECLPs) were successfully constructed by self-assembly with an average particle size of 170.7 nm and an encapsulation efficiency of 36.2%. The formation of pGA shell significantly improved the stability of liposomes, and the encapsulation efficiency of eugenol only decreased by 20.7% after 30 days of storage at 4 °C. On the other hand, the pGA layer can be hydrolyzed by S. aureus, achieving effective control of release through response to bacterial stimuli. The application experiments further confirmed that pGA-ECLPs effectively prolonged the antibacterial effect of eugenol in fresh chicken without causing obvious sensory effects on the food. The above results of this study provide an important reference for extending the action time of natural antibacterial substances and developing new stimuli-responsive antibacterial systems.