Mei Bai,Jinming Dai,Wei Hu,Changzhu Li,Haiying Cui,Lin Lin
This study investigated the use of Litsea cubeba essential oil (LC-EO) as an anti-virulence agent targeting listeriolysin O (LLO) of Listeria monocytogenes ( L. monocytogenes ). The hemolysis assay showed a significant decrease in the hemolytic activity of LLO by 90.7% and 70.2% after exposure to 500 μg mL −1 LC-EO or 700 μg mL −1 citral (the main component of LC-EO), respectively. This suggested that citral plays a major role in the anti-virulence function against LLO. The experiments including UV–visible absorption spectroscopy , fluorescence quenching and three-dimensional fluorescence spectroscopy demonstrated that exposure to citral leads to significant changes in the conformation of LLO, potentially resulting in the unfolding of its structure and the formation of a ground-state complex. Synchronous fluorescence spectra analysis indicated that the binding site of citral could be the undecapeptide region of LLO. Additionally, the results of molecular docking and the acid-base effect experiment of different aldehydes and phenols revealed that the cysteine residue of LLO and the α, β-unsaturated aldehyde of citral are likely to form a covalent bond through Michael addition . This interaction is believed to be the primary reason for the loss of hemolytic activity. As a result, this work provides a new approach for the development of LLO-targeting anti-virulence agents and holds promise for expanding the application of LC-EO in the field of food microbiological safety.
Yanbo Wang,Congnan Cen,Jian Chen,Chaosheng Zhou,Linglin Fu
Essential oils have attracted increasing attentions due to their broad-spectrum antimicrobial activities and generally recognized as safe (GRAS) regulatory status. However, their low-solubility in water and reduced effectiveness in food matrices limit the commercial application in food industry. In this study, we used ultrasonic emulsification , medium-chain triacylglycerol (MCT) and phosphate-buffered saline (PBS) to formulate a highly stable and water-dispersible litsea cubeba essential oil (LCEO) nanoemulsions. After emulsification, a minimizing droplet size of LCEO nanoemulsions was achieved at approximately 100 nm in diameter, resulting in an increase in the water solubility and better stability at 4 °C and 25 °C. Furthermore, the bioactivities (antibacterial, antioxidant and antibiofilm properties) of LCEO nanoemulsions were greatly improved after emulsification, suggesting that nano-emulsification is beneficial for the value development of various essential oils and the LCEO nanoemulsions could be used as a novel food preservative for controlling bacterial growth and preventing oxidative deterioration in foods.
With increasing demands for environmental protection and food safety, biodegradable active food packaging is gaining attention. Hereby, konjac glucomannan/carrageenan blend films (KCNTO) incorporating Litsea cubeba essential oil (LCEO) Pickering emulsion stabilized by cellulose nanocrystals/tannic acid were developed and evaluated for their preservation effect on pork. The formation, structure, physical properties, antioxidant and antimicrobial activities of KCNTO, as well as the release of LCEO were investigated. The results showed that the viscosity and pseudoplasticity of KCNTO film-forming solutions decreased due to LCEO Pickering emulsion interfering with the molecular entanglement network of konjac glucomannan/carrageenan. LCEO droplets were homogeneously distributed in KCNTO to make its structure loose. Hydrogen bonding interactions occurred between LCEO Pickering emulsion and the film matrix. The addition of LCEO Pickering emulsion improved KCNTO's elongation at break, water contact angle, water vapor barrier and UV shielding, while giving it excellent antioxidant and antimicrobial activities. LCEO was slowly and sustainably released from KCNTO at 25 °C in air. KCNTO-8 maintained the quality of pork by slowing down the increase in pH, aerobic plate count and thiobarbituric acid reactive substances during storage at 4 °C. The findings suggested that KCNTO was a promising active packaging material for pork preservation.
危险品化学品经营许可证（带存储）