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Being nutritious, aquatic products are loved by consumers. However, aquatic products are prone to bacterial spoilage, posing safety risks to consumers. The current research proves that bacterial spoilage capacity and virulence are often regulated by its quorum sensing (QS) system, so using quorum sensing inhibitors (QSIs) to intervene in the QS system is an effective way to control bacteria. Currently, more and more QSIs have been discovered from microorganisms, plants and animals. Along with the development of biological engineering, cheminformatics and nanotechnology, artificial QSIs have been synthesized. In order to provide a reference for quality and safety control of aquatic products based on QS inhibition, this article reviews the QS systems of seveal common aquatic product-borne pathogenic and spoilage bacteria and the modes of regulatory effects of the QS systems on virulence factors, with a focus on the current status of research on microbial-, plant-, animal-derived and synthetic QSIs.

Hafnia sp. was one of the specific spoilage bacteria in aquatic products, and the aim of the study was to investigate the inhibition ability of the silver nanoparticles (AgNPs) biosynthesis by an aqueous extract of Prunus persica leaves toward the spoilage-related virulence factors of Hafnia sp. The synthesized P-AgNPs were spherical, with a mean particle size of 36.3 nm and zeta potential of 21.8 ± 1.33 mV. In addition, the inhibition effects of P-AgNPs on the growth of two Hafnia sp. strains and their quorum sensing regulated virulence factors, such as the formation of biofilm, secretion of N -acetyl-homoserine lactone (AHLs), proteases, and exopolysaccharides, as well as their swarming and swimming motilities were evaluated. P-AgNPs had a minimum inhibitory concentration (MIC) of 64 μg ml−1 against the two Hafnia sp. strains. When the concentration of P-AgNPs was below MIC, it could inhibit the formation of biofilms by Hafnia sp at 8–32 μg ml−1, but it promoted the formation of biofilms by Hafnia sp at 0.5–4 μg ml−1. P-AgNPs exhibited diverse inhibiting effects on AHLs and protease production, swimming, and swarming motilities at various concentrations. [ABSTRACT FROM AUTHOR]

BACKGROUND: Composite nanofiber films loaded with ε‐polylysine (PL) and gallic acid (GA) were prepared using a zein/gelatin (ZG) electrospinning method to develop effective active packaging films for tuna preservation. The morphology, structure, thermal stability, hydrophobicity, antibacterial, and antioxidant properties of the films, and their application for tuna during a period of storage of 4 °C were investigated. RESULTS: PL reduced the average diameter of ZG fibers, whereas GA increased it. The PL/GA/ZG film possessed a well distributed fiber morphology with an average diameter of 810 ± 150 nm. Fourier‐transform infrared spectroscopy and X‐ray diffraction results showed the physical loading of PL and GA in ZG film with the main chemical bonds and crystal structure unchanged. The addition of both PL and GA reduced hydrophobicity of the ZG film while the PL/GA/ZG film was still hydrophobic. GA enhanced its thermal stability and contributed to its antioxidant activity. PL and GA synergetically enhanced the antibacterial activity of ZG film against Shewanella putrefaciens. PL combined with GA is more suitable for modifying ZG film than GA alone. The PL/GA/ZG film effectively inhibited total viable counts, total volatile base nitrogen, fat oxidation, and texture deterioration of tuna fillets at 4 °C storage, and could extend the shelf life by 3 days. CONCLUSIONS: The PL/GA/ZG nanofiber film demonstrated promising potential for application in the preservation of aquatic products as a new antibacterial and antioxidant food packaging. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Quorum sensing (QS) is a communication pattern between bacteria, hence the inhibition of bacterial QS system could be used as a new strategy to the control the spoilage caused by bacteria, and to some extent could avoid the bacteria drug resistance. In the study, dandelion water extract mediated biosynthesis Ag nanoparticles (D-AgNPs) was prepared with AgN03 as silver source and dandelion water extract as reducing agent. Its structure was characterized by ultraviolet visible absorption spectroscopy (UV-vis), dynamic light scattering (DLS), Zeta potential, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray energy spectrum (EDS). It was found that the synthesized D-AgNPs were spherical, with an average particle size of 13.9 nm and Zeta potential of (-14.07±0.25) mV. The effects of D-AgNPs on the growth of two Hafnia strains and quorum sensing regulated virulence factors such as biofilm, AHLs, proteases, exopolysaccharides, swimming and swarming motilities were determined. It was found that the minimum inhibitory concentration of D-AgNPs against Hafnia was 128 |g/mL, and could inhibit the formation of the biofilms of Hafnia at 1/16-1/2 MIC (8-64 |g/mL), whereas promoted its biofilm formation at 1/128-1/32 MIC (1-4 µg/mL). D-AgNPs showed different inhibition abilities on the AHLs and protease production, as well as swimming and swarming motilities; however, sub-MIC D-AgNPs promoted the production of exopolysaccharides. It is proved that D-AgNPs could be used as quorum sensing inhibitor. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria (LAB) and yeasts are the dominant microorganisms in the fermentation process of pickled vegetables, and their relationship and fermentation characteristics are important factors affecting the quality of products. In the study, high-yield AI-2 LAB and aroma-producing yeasts were screened from commercial pickled vegetable using Vibrio harveyi BB170 report method and total ester titration method. The mixed fermentation conditions of LAB and yeast were further optimized by orthogonal test. The differences in AI-2 production, acid production rate, acid resistance, salt tolerance, and nitrite degradation between the mixed strains and LAB alone fermentation were compared. Effect of yeasts on the fermentation characteristics of LAB with high production AI-2 was explored. These results showed that Lactobacillus plantarum SR with high yield of AI-2 and Pichia membranaceus S-0-1 with ester content of 0.6 g/L were obtained. The mixed fermentation conditions were as follows: inoculation amount 2%, inoculation ratio 1 : 1 (SR: S-0-1), culture temperature 28 °C. Under optimized fermentation conditions, compared with L. plantarum SR alone fermentation, the AI-2 synthesis ability, acid tolerance rate (pH = 3) and the salt tolerance rate at 5% of the mixed strains was increased by 1.4 times, 4.8 times and 24.66%, respectively. Meanwhile, the acid production rate of the mixed strains was increased. but there was no significant change in the degradation rate of nitrite of the mixed strains, which basically maintained at 98%. The above results indicated that Pichia membranaceus S-0-1 could increase the yield of AI-2 signal molecules in L. plantarum SR, result in enhancing the fermentation characteristics of the LAB and yeasts. This study aimed to provide a theoretical basis for further exploring the mutual regulation mechanism of AI-2 / LuxS quorum sensing in mixed fermentation system of LAB and yeasts. [ABSTRACT FROM AUTHOR]

A total of 10 protease-producing strains were isolated from homemade fermented seafoods, and were identified as Bacillus velezensis S1YBB, S1YB, Serratia marcescens S2DD, S2DB, C2Y3, M1B, C2J2, Micrococcus luteus C1Y1, Shewanella alga C2J1, and Enterococcus hirae M1R. The biological and enzymatic characteristics of S1YB, S2DB, C1Y1, C2J1, and M1R from different species with relatively higher enzyme activities were evaluated. The optimum growth temperature, pH and salinity of the strains were 37 &, 6.0, and 20 g/L, respectively. The optimum temperature and pH for the enzyme activities were 50 & and 6.0-8.0, respectively. Relative enzyme activities of the strains were decreased under the treatment of Na+, Ke, Ca2e, Fe2e, Fe3e, Zn2e, Cu2e and ethylene diamine tetraacetic acid (EDTA) and in response to their concentrations. The results provided theoretical supports for exploring strains with excellent fermentation performance in seafood fermentation and controlling unexpected protease -producing strains in seafood fermentation processes. [ABSTRACT FROM AUTHOR]

objective: Pseudomonas fluorescens is the dominant spoilage organism in frozen foods, and its spoilage-caus¬ing genes are regulated by quorum sensing system. In order to accurately quantify the expression of spoilage genes and thus investigate the mechanism of quorum sensing regulation in food spoilage, it is required to screen reference genes of Pseudomonas fluorescens. Methods: Using Pseudomonas fluorescens PF-08 as the research object, eight common reference genes (dsbA, carA, rpsL, gyrB, atpD, rpoD, gltA, 16S rRNA) were selected and their gene expression was measured by quantitative real-time PCR (qPCR) after incubation with different types of quorum sensing signal molecules. geNorm, Normfinder, BestKeeper and RefFinder were used to evaluate the expression stability of the candidate reference genes and to screen out the most appropriate reference genes. Results: Under different types of exogenous signal molecules incuba¬tion, the least change in Ct value of Pseudomonas fluorescens was gltA and the Ct value of 16S rRNA was too low. The most stable reference genes by geNorm analysis were atpD and rpoD and the combination of the two could more accu¬rately quantify the expression levels of target genes. gltA was the most stable reference gene analyzed by Normfinder and BestKeeper. Further comprehensive evaluation with RefFinder showed rpoD and gltA were the most stable reference genes. Conclusion: Both rpoD and gltA were stably expressed in Pseudomonas fluorescens after incubation with different QS sig¬nal molecules. They could be used for the subsequent study of Pseudomonas fluorescens spoilage gene expression, and could also provide reference genes for studying the expression of QS-related genes in other spoilage bacteria. [ABSTRACT FROM AUTHOR]

This review summarizes current studies on fermented vegetables, analyzing the changes in nutritional components during pickling, the health benefits of fermented vegetables, and their safety concerns. Additionally, the review provides an overview of the applications of emergent non-thermal technologies for addressing these safety concerns during the production and processing of fermented vegetables. It was found that vitamin C would commonly be lost, the soluble protein would degrade into free amino acids, new nutrient compositions would be produced, and the flavor correlated with the chemical changes. These changes would be influenced by the variety/location of raw materials, the original bacterial population, starter cultures, fermentation conditions, seasoning additions, and post-fermentation processing. Consuming fermented vegetables benefits human health, including antibacterial effects, regulating intestinal bacterial populations, and promoting health (anti-cancer effects, anti-diabetes effects, and immune regulation). However, fermented vegetables have chemical and biological safety concerns, such as biogenic amines and the formation of nitrites, as well as the existence of pathogenic microorganisms. To reduce hazardous components and control the quality of fermented vegetables, unique starter cultures, high pressure, ultrasound, cold plasma, photodynamic, and other technologies can be used to solve these problems. [ABSTRACT FROM AUTHOR]

In this study, lactic acid bacteria (LAB) with producing γ-aminobutyric acid (GABA) were screened from traditional pickled vegetables in Northeast China using thin-layer chromatography (TLC) and the Berthelot colorimetric method. LAB were identified by the physiological and biochemical test and 16S rRNA sequencing analysis. And then their biological properties, including acid tolerance, bile salt tolerance, antioxidant, antibacterial activity, antioxidant activity and acid production rate, were analyzed using principal component analysis (PCA). These results showed that five strains LAB with typical GABA-producing were obtained from forty strains LAB from traditional pickled vegetables, including one strain Weissella kandleri HJL2 and four strains Lactobacillus plantarum PJ-7, HJG1-3, L-9, and L-11. Among them, L. plantarum PJ-7 isolated from fermented radish had better ability to synthesize GABA, and the yield reached 0.48 mg/mL. There were significant differences in acid tolerance, bile salt tolerance, antioxidant and other biological characteristics of the five strains LAB. Based on PCA, L. plantarum PJ-7 ranked the first in the comprehensive score of biological characteristics. Therefore, L. plantarum PJ-7 has excellent GABA synthesis ability and good biological characteristics, which would provide a theoretical basis for the development of GABA-rich pickled vegetables. [ABSTRACT FROM AUTHOR]

Five Bacillus strains were isolated from the traditional homemade shrimp paste, and were identified as Bacillus amyloliquefaciens Yll, Bacillus velezensis Y12, Bacillus subtilis Y13, Bacillus safensis Y32, and Bacillus cereus BI6Y. All five strains could grow normally at 10% NaCl concentration, had different protease and lipase and antibacterial substances production capacities. Among them, Bacillus cereus BI6Y has β-hemolysis and is insensitive to chloramphenicol, vancomycin and norfloxacin, hence is not suitable for a probiotic. The other four Bacillus strains are y-hemolytic, insensitive to chloramphenicol, with a self-aggregation rate between 25% and 35%, and tolerant to acid and bile salts; they were found to secrete surfactin and could survive after treatment with artificial gastrointestinal fluid, the strain that had the highest survival rate in artificial gastric juice (pH 2.0) was found to be B. subtilis Y13 (95.3%), and in artificial intestinal juice it was B. safensis Y32 (85.1%). The bacterial cell, cell-free supernatant, and cellular contents had different antioxidant activities, and the cell-free supernatant could scavenge 1,1 -diphenyl -2 -trinitrophenylhydrazine (DPPH) and hydroxyl radicals simultaneously, the scavenging rate is between 40% and 60%. The results of the study showed that in addition to B. cereus BI6Y, B. amyloliquefaciens Y11, B. velezensis Y12, B. subtilis Y13, B. safensis Y32 have certain safety and probiotic properties, hence could be used as potential probiotics, which would provide a theoretical basis for the development of Bacillus, spp-based probiotic products. [ABSTRACT FROM AUTHOR]

In this study, quorum-sensing quenching activity of Lactobacillus crustorum ZHG2-1 was verified with the Chromobacterium violaceum CV026 as a indicator strain. Based on the change of biofilm, phenotypes of spoilage factors and the expression levels of related genes, the quorum sensing quenching mechanism of Lb. crustorum ZHG2-1 on P. fluoresces was detected. The results showed that the degradation rate of cell-free supernatant from strain ZHG2-1 to P. fluoresces AHLs reached 100%. The sub-inhibitory concentration (1.0, 2.0, 3.0 mg/mL) of strain ZHG2-1 crude extract could inhibit and remove the biofilm of P. fluoresces, and the inhibition rate and clearance rate reached 9.66%-31.32% and 28.62%-62.82%, respectively. In addition, the inhibition rate of strain ZHG2-1 crude extract with sub-inhibitory concentration on P. fluoresces spoilage factors (exopolysaccharides, proteases, lipases, biogenic amines) reached 7.23%- 100%. Meanwhile, the inhibition rate was mass concentration-dependent. Scanning electron microscope showed that the sub-inhibitory concentration of strain ZHG2-1 crude extract treatment significantly reduced the amount of biofilm and the bacterial colonies were in a dispersed state. The results of qRT-PCR showed that the crude extract of strain ZHG2-1 down-regulated the quorum-sensing genes rhlI and rhlR of P. fluoresces by 0.93 and 0.99, respectively, and the expression levels of aprX, algA, orm, flgA, ldcA and other biofilm and spoilage genes was significantly inhibited. The results indicated that Lb. crustorum interfered with the expression of quorum-sensing genes of P. fluoresces, thereby affecting the production of biofilm and spoilage factors. [ABSTRACT FROM AUTHOR]