Abstract:To select excellent probiotics of fish origin, tilapia fish (Oreochromis niloticus) was used as the experimental material to isolate and identify intestinal Bacillus and lactic acid Bacteria. The isolated strains were subjected to in vitro probiotic characteristics analysis, including antibacterial activity, acid tolerance, bile salts tolerance, artificial gastrointestinal fluid tolerance, hemolytic activity, and antibiotic susceptibility. The results showed that a total of 109 strains were isolated from tilapia fish intestine, including 79 strains of Lactobacillus and 30 strains of Bacillus. After a series of experiments, three strains of Lactococcus lactis were finally screened out. Biological characteristic studies indicated that all three strains exhibited no hemolytic activity. They showed a certain level of sensitivity to antibiotics and displayed tolerance to strong acids, bile salts, and artificial gastrointestinal fluids. Moreover, they demonstrated different antibacterial activities against aquatic pathogens. The three selected strains enriched the probiotic resources derived from fish, making them excellent candidates for fish-derived probiotics. Among them, strain R1 exhibited the highest tolerance to strong acids and artificial gastrointestinal juices, while strain R29 displayed the strongest bile salt tolerance. Further studies on their probiotic properties can be conducted to explore their probiotic effects as food-source probiotics.

Abstract:As a crucial part of epigenetics, DNA methylation plays an indispensable role in various physiological processes in bacteria. Here, we compared the metabonomics of DNA methylation of mutant strain Lactobacillus casei (L. casei) Zhang ΔpglX and wild strain L. casei Zhang in the early logarithmic growth phase(4 h) using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) non-targeted metabolomics technology. A total of twenty-three significantly different metabolites were identified(P <0.05), primarily enriched in pathways such as aminoacyl-tRNA biosynthesis, un-saturate fatty acids biosynthesis, D-glutamine and D-glutamate metabolism, and galactose metabolism. The results suggest that DNA methylation phenotype may affect the synthesis and utilization of amino acids in bacterial strains during early logarithmic growth. On the other hand, DNA methylation phenotypes may modulate the composition of cellular membrane fatty acids, altering membrane permeability and fluidity.

Abstract:This study was conducted to explore the feasibility to use Enterococcus faecium NRRL B-2354 (E. faecium) as a surrogate for Salmonella typhimurium ATCC 14028 (S. typhimurium) in black pepper during thermal processing. The thermal resistance parameters of E. faecium and S. typhimurium in black pepper were detected by isothermal experiments. Furthermore, an experimental verification of radio frequency sterilization for black pepper kernels (A_w=0.65) was carried out. The results of the isothermal experiments indicated that the heat resistance of E. faecium was higher than that of S. typhimurium in black pepper kernels. In the radio frequency (RF) sterilization experiment, 2 g of inoculated black pepper kernels with both bacteria strains were vacuum-sealed and placed in the center of 45 g of black pepper kernels. The samples were then heated in a 40.68 MHz RF field for 15 min. The population reduction of S. typhimurium in black pepper kernels was greater compared to E. faecium, indicating that E. faecium could exhibit higher heat resistance during RF heating and could be used a suitable surrogate for S. typhimurium during the sterilization process of black pepper kernels.

Abstract:Bird's nest, a traditional health food with rich nutritional value, has received little research attention regarding the effect of heat treatment temperature on its product quality. In this study, the bird's nest imported through Chinese customs was used as raw material. The fresh stewed bird's nest products were prepared through heat treatments at different temperatures. The microbial indicators, in vitro digestion rate of protein and sialic acid, and sensory properties of edible bird’s nest (EBN) products were investigated. The results indicated that EBN products showed commercial sterility during one month of storage after sterilized for 30 min at 110 ℃ and above. The results of in vitro simulated digestion revealed that sialic acid release rate of EBN increased significantly with the increase of temperature, reaching 90.19% at 120 ℃, significantly higher than that achieved from stewing at 100 ℃(P＜0.05), which was 46.22%. There was no significant difference between EBN treated at 115 ℃ and 120 ℃ (P＞0.05). Quantitative descriptive sensory analysis indicated that EBN stewed at 110 ℃ and 115 ℃ exhibited moderate hardness, smoothness, chewiness, elasticity, and egg white flavor with appropriate intensity. However, further increasing the temperature to 120 ℃ caused sensory quality deterioration. Overall, EBN stewed at 115 ℃ for 30 min could provide the optimal heat treatment parameters, ensuring safety, nutrition, and sensory quality.

Abstract:In order to understand the co-pigmentation effect of metal ions on the coloration of anthocyanin under different conditions, cyanidin-3-O-glucoside was used as the raw material, and CIELab color evaluation was used to analyze the relevant color indicators. The results showed that the addition of K⁺, Mg²⁺, and Al³⁺ could lead to a deepening in the color of pigment solution, effectively enhancing its storage stability. Notably, the co-pigmentation effect of Al³⁺ was superior to that of K⁺ and Mg²⁺. The inclusion of metal co-pigments could effectively delay the color change of anthocyanin during storage. Additionally, the addition of K⁺, Mg²⁺, and Al³⁺ could alleviate the color loss caused by an increase in pH, especially under strong acid conditions(pH<3.0), which facilitated a more pronounced color expression. Moreover, the effects of ethanol, glucose, and phenolic acids on the co-pigmentation effect of metal ions were also studied. These results could provide data and reference for the in-depth study of the co-pigmentation effect of metal ions and their application in preserving food color.

Abstract:There are various types of fresh waxy corn, which exhibit differences in edible quality after cooking. In order to explore the factors affecting the edible quality of fresh waxy corn, four varieties of fresh waxy corn were selected and an ordinary corn was used as the control. Based on sensory evaluation, texture characteristics, component composition and starch gelatinization degree analysis, starch components were extracted to further study their thermodynamic properties, gelatinization characteristics, and starch structure features. The results showed that the amylopectin mass fraction of four kinds of fresh waxy corn ranged from 95% to 98%. The texture hardness value ranged from 2 987 g to 3 633 g, and the gelatinization degree after cooking ranged from 68% to 91%. The sensory evaluation results showed that ‘Sukenuo 1505’ and ‘Sukenuo 1704’ with higher gelatinization degrees exhibited better taste. The correlation analysis revealed that there was a significant positive correlation between the scores of waxiness and taste with gelatinization degree (P<0.05), with correlation coefficients of 0.698 and 0.651, respectively. At the same time, amylopectin mass fraction was positively correlated with taste score(P<0.05), with correlation coefficient of 0.642. There was a significant negative correlation between amylopectin mass fraction and hardness(P<0.05), with correlation coefficient of -0.742. The correlation analysis showed that the starch gelatinization degree of fresh waxy corn had a great effect on the taste. This study provides a reference for the relationship between the edible quality of fresh waxy corn and the properties of starch. It offers a new research direction and data support in identifying key factors affecting the quality of fresh waxy corn, guiding the development of fresh waxy corn industry.

Abstract:In order to improve the comprehensive development and utilization of Premna puberula Pamb. (P. puberula) resources, the fermented bread was produced by the leaves juice of P. puberula, wheat flour and strains. The production process of bread was screened according to the solid-to-liquid ratio of P. puberula leaves juice, amount of starter culture, amount of white granulated sugar, baking time, and baking temperature. Furthermore, the effects of P. puberula leaves juice, the amount of Lactobacillus sakei-DPC addition, the amount of Saccharomyces cerevisiae-L23 addition, and baking time on the fermented bread of the P. puberula leaves were further studied to determine the optimal production process. The results showed that the solid-to-liquid ratio, Lactobacillus sakei, Saccharomyces cerevisiae, sugar, baking time, and temperature all affected the quality of fermented bread of P. puberula leaves. Furthermore, the optimal process was determined as a solid-to-liquid ratio of 1 g∶8 mL, 100 mL of Lactobacillus sakei, 700 mL of Saccharomyces cerevisiae, and a baking time of 25 min, achieving a score of 82.59. Physicochemical analysis of the bread under these optimized conditions demonstrated that the fermented bread of P. puberula leaves met the requirements of the national standard. Besides, the addition of P. puberula leaves juice could improve the content of active ingredients and antioxidant capacity. The research could provide technical references for the utilization of P. puberula resources.

Abstract:For understanding the effect of OmpU on antibiotics resistance of Vibrio parahaemolyticus, a deletion mutant strain of the highly abundant outer membrane protein(OmpU) in Vibrio parahaemolyticus, designated as ΔompU, was constructed in this study. Minimum inhibitory concentration (MIC) assay revealed altered antibiotic resistances of ΔompU to 12 antibiotics, with the highest increase observed in resistance to ampicillin. Quantitative reverse transcription PCR showed a general downregulation in the transcription level of peptidoglycan synthesis genes in both wild-type (WT) and ΔompU cells under ampicillin stimulation. However, the gene VP_RS17515 encoding β-lactamase exhibited the higher transcription level in WT strains than ΔompU. The results suggest that V. parahaemolyticus responds to ampicillin through expressing β-lactamase and reducing peptidoglycan synthesis rates, while OmpU changes the cell membrane permeability to affect the penetration of ampicillin.

Abstract:In order to enhance the quality of air-dried beef, this study aimed to select the starter culture of lactic acid bacteria with excellent characteristics for its production. Three different protease-producing lactic acid bacteria (Lactococcus lactis S-1, Pediococcus pentosaceus S-2, Lactococcus gasseri S-3) were separately inoculated into beef. At different stages of curing, fermentation, air drying and maturation of the air-dried beef, the physical and chemical analysis techniques were used to detect its moisture content, pH value, thiobarbituric acid reactive substances (TBARS) value, color, texture and microorganisms. In addition, high-performance liquid chromatography was employed to analyze the variations in the mass fraction of biogenic amines in air-dried beef, and safety assessment of the added strains was conducted. The results revealed that protease-producing lactic acid bacteria could significantly reduce the pH value and TBARS value (P＜0.05), improve the color and texture of air-dried beef. However, there was no significant effect on the change of moisture mass fraction(P＞0.05). All three starters could effectively inhibit the growth of Enterobacter, with S-2 demonstrating the strongest antibacterial effect. The three starters could efficiently inhibit the formation of biological amines (putrescine, cadaverine, histamine, and tyramine) in the air-dried beef, with S-2 and S-3 exhibiting the best inhibitory effects. Therefore, three strains of lactic acid bacteria used as the starters in air-dried beef can improve the quality and safety of products, thereby providing a theoretical basis for the application of protease-producing lactic acid bacteria in air-dried beef.

Abstract:Methyltransferases can protect the host genomic DNA from digestion by restriction endonucleases. Based on this property, the classical strategy for preparing restriction endonuclease involves first expressing their paired methyltransferases to protect the host strain, followed by co-expression of the restriction endonuclease, i.e. a 'one-to-one' recombinant expression pattern. In this study, we proposed a novel strategy for generating restriction endonucleases by co-expressing a methyltransferase that could recognize overlapping sequences to protect the host strain. Initially, a methyltransferase recognizing the overlapping sequences was transferred into E. coli ER2566 to protect the host genomic DNA. Subsequently, multiple restriction endonucleases capable of recognizing the overlapping sequences were individually transferred into the host strain to achieve the recombinant expression of restriction endonucleases in a 'one-to-many' recombinant pattern. According to this approach, a series of restriction endonucleases recognizing overlapping sequences (TTAA, AGCT and GCGC) were successfully achieved using methyltransferases M. EsaDix5 I, M. Alu I and M. Hha I, respectively. Additionally, the recombinant expression of two new R. Sac I isozymes, i.e., R.EcoSP4ORF25090P and R.Gma5ORF28P, was also successfully achieved through methyltransferase M. Alu I. This approach simplifies the labor-intensive screening process for host strains resistant to restriction endonuclease digestion, while providing the capability for large-scale preparation of restriction endonucleases. Furthermore, this method can be utilized for the discovery of new isoenzymes or isoschizomers in other microorganisms.

Abstract:This study aimed to explore the inhibitory effect and related mechanisms of the extracted Lucid Ganoderma total saponins (LGTS) on colon cancer HCT116 cells. Ganoderma lucidum fruiting bodies were used as the raw materials, and the LGTS was extracted by alcohol and then purified. The inhibitory effect of LGTS on colon cancer HCT116 cells was detected by CCK8 method. Meanwhile, the state of cell apoptosis was detected by flow cytometry. The intracellular mitochondrial membrane potential and intracellular reactive oxygen species levels were recorded by fluorescence spectrophotometer. The expression of apoptosis-related genes such as p53, noax, bax, bcl-2, caspase-9 and caspase-3 were measured by real-time fluorescent quantitative PCR. The results showed that the concentration of LGTS above 40 mg/L could significantly inhibit the proliferation of HCT116 cells compared with the blank group, with the inhibitory effect becoming positively correlated with time. Through the intervention of GLTS, the apoptosis rate of cells increased significantly. At a GLTS concentration of 150 mg/L, the apoptosis rate reached 50.2%. Additionally, GLTS significantly reduced the intracellular mitochondrial membrane potential, increased the intracellular reactive oxygen species levels, upregulated the expression of pro-apoptotic genes (p53, noax, bax, caspase-9 and caspase-3), and downregulated the expression of anti-apoptotic gene(bcl-2). In conclusion, GLTS have the significant inhibitory effect on colon cancer cells and the effect could be achieved through the mitochondrial apoptosis pathway, suggesting GLTS as promising candidates for further research as potential anti-colon cancer drugs and food additives.

Abstract:This study was conducted to investigate the effects of Nongxiangxing Baijiu on the gut microbiota in SD rats. A SD rat model of chronic alcoholic-induced liver injury was established by intragastrically administering with appropriate doses of ethanol for 8 weeks. At the same time, an equivalent dose of Baijiu was administered intragastrically to investigate the effects of Baijiu and ethanol on blood lipids and liver indicators of SD rats, and the changes in gut microbiota. The results showed that the intragastric administration of ethanol for 8 consecutive weeks caused a certain degree of alcoholic liver injury to SD rats, while the severity of liver damage was significantly lower in the Baijiu group compared to the ethanol group. The diversity analysis revealed that the ethanol intervention resulted in decreased abundance and diversity of the gut microbiota of SD rats, while the intake of Baijiu could reverse this phenomenon. Moreover, the analysis of microbial community structure demonstrated significant differences between the ethanol and Baijiu interventions, with the species composition in the Baijiu intervention group being closer to that of the control group. Three potential differential microbial biomarkers in the Baijiu and ethanol groups were identified by difference analysis, which were g_Eubacterium_rumminantium_group, g_U29-B03 and g_unclassified_f_Oscillospiraceae. These results indicate that Baijiu may alleviate the mild ethanol-induced liver injury by regulating the gut microbiota.