Abstract:Benzo[a]pyrene (B[a]P), as a polycyclic aromatic hydrocarbon (PAHs) with the highest toxicity and a potent carcinogen, widely exists in the high-temperature processed food. A large number of epidemiological studies have shown that B[a]P is closely related to the occurrence and development of many diseases. MicroRNA (miRNA) is a short (17-25 nucleotides) non-coding RNA, which negatively regulates specific target genes through mRNA degradation or translation inhibition. MiRNA plays an important role in the process of B[a]P-induced carcinogenicity, reproductive toxicity, neurotoxicity, and other processes. Based on the existing findings, this study reviews the mechanism of miRNA in the toxicity process induced by B[a]P, aiming to further reveal the toxicological mechanism of B[a]P and to provide new research directions and ideas for the disease prevention and food safety control.

Abstract:As one of the traditional staple foods in China, the safety standards of fried food affect the health and nutrition level of the entire population. This paper summarizes the progress in the legalization of fried food safety standards. First of all, on the basis of emphasizing the importance of legalization of food safety standards, the current state of governance for the safety of fried food in China is analyzed. Secondly, the current research and practice progress of legalization are introduced from the aspects of scientific nature, standard system, governance model and legal norm framework of fried food safety control. Finally, prospects for advancing the legalization of fried food safety standards are prospected.

Abstract:Heat treatment in electric cookers can give rice pleasant characteristic flavors, but there are still some limitations in improving the odor quality of aged Japonica rice. The characteristic compounds causing the off-flavor of aged Japonica rice were determined by gas chromatography-olfactometry-mass spectrometry and odor activity value. Gas chromatography-mass spectrometry was used to analyze the odor characteristics of aged Japonica rice with different soaking treatments. The effect of vacuum-assisted soaking on lipid oxidation degree of aged Japonica rice was investigated by analyzing the changes of lipase activity, composition of free fatty acid, peroxide value, and malondialdehyde content. The results showed that vacuum-assisted soaking at 50℃ for 10 min could regulate the process of lipid oxidation by inhibiting the catalytic activity of lipase in rice grains, and reduce the accumulated content of key aged flavor compounds such as hexanal, (E)-2-heptenal, nonanal and (E, E)-2, 4-decadienal by 12.4%, 4.2%, 100% and 53.8%, respectively, significantly improving the odor quality of aged Japonica rice cooked with an electric rice cooker.

Abstract:β1,3-galactosyltransferase(CgtB) from bacterium Campylobacter jejuni is mainly responsible for the second elongation of proteins O-glycosylation by transferring a galactose to O-linked N-acetylgalacosamine (O-GalNAc). Presently, CgtB has been widely applied in the synthesis of O-glycoproteins. To develop a recognition tool for O-GalNAc modification, the CgtB protein was used for mutant design. Cgt1 was generated by deleting 30 amino acids from both the N- and C-terminal regions at the gene level. Cgt1 was constructed in pMal-c5x expression plasmid and expressed in the Escherichia coli. The soluble Cgt1 was purified by affinity chromatography with maltose binding protein(MBP) column and the activity assay was carried out by glycan binding activity. The results suggested that the soluble recombinant Cgt1 with the molecular weight of approximately 70 000 could be successfully expressed in the system of Escherichia coli. The recombinant Cgt1 possessed the activity of binding O-GalNAc modified proteins. For different standard glycoproteins, Cgt1 only recognized mucin containing O-GalNAc modification. For complex cellular samples, Cgt1 could specifically recognize intracellular O-GalNAc modification. The developed recognition tool for O-GalNAc modification in this research will provide a foundation for further research on the function of O-GalNAc modification.

Abstract:In order to explore the microbial diversity and sugar metabolism process in pit mud of Chenggu Baijiu, traditional culture-dependent and high-throughput sequencing technology were used for analysis. The results showed that the bacteria in pit mud could be divided into 68 genera, and the core-microbiome were Petrimonas, Bacillus, Septinibacter and Clostridium. The fungi could be divided into 149 genera and the core-microbiome included Issatchenkia, Debaryomyces, Pichia and Aureobasidium. A total of 236 022 unigenes were annotated in KEGG database, with carbohydrate metabolism as the main metabolic activity and pyruvate metabolism as the most important process. The CAzY and COG databases annotated 23 functional categories and 210 major carbohydrate-active enzymes, respectively, among which the number of predicted proteins with unknown functions was the highest, followed by glycoside hydrolase and glycosyltransferase, accounting for 31% of the predicted protein sequence and 74% of the carbohydrate-active enzymes. In the sugar metabolism pathway, there were three different sugar transport protein systems with the key enzyme genes of phosphorylated sugars which could be converted sugars into intermediate products of glycolysis. Among them, there were 477 genes controlled by mannose transporter system, indicating the strongest ability to transport mannose. This study identified the dominant microbial community and related sugar metabolism pathway in pit mud of Chengguo Baijiu, providing a theoretical basis for improving the quality of Chenggu Baijiu.

Abstract:The alterations of gene expression profile of RAW 264.7 cells before and after infection by Listeria monocytogenes (LM) were explored, and the key functional genes and pathways were screened to lay a foundation for investigating the pathogenic mechanism. The RAW264.7 cells were treated with LM at a multiplicity of infection (MOI) of 10 for 6 h, and RNA was extracted for transcriptome sequencing. Differentially expressed genes (DEGs) in the infection group compared to the control group with a 1.5 fold change and a P<0.05 were screened and analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Some DEGs were validated by RT-qPCR. The transcriptome results showed that the expression of 1 782 genes in RAW264.7 cells changed significantly before and after infection with LM, including 989 up-regulated and 793 down-regulated genes. GO enrichment analysis mainly involved the immune system process, immune response, and regulation of programmed cell death and so on. KEGG analysis showed that the significantly enriched pathways included cytokine-receptor interaction, tumor necrosis factor, and IL-17 signaling pathway and so on. The RT-PCR verification experimental results showed that the trend of fold change of expression in the randomly selected 11 significantly DESs was consistent with the sequencing results. This study lays a foundation for further in-depth exploration of the pathogenic mechanism of LM.

Abstract:This study evaluated the safety of Pediococcus pentosaceus 10-a-1 with high resistance and adsorption properties to heavy metal lead, which was isolated and screened from sheep manure in Baotou Iron and Steel Mining Area, Baotou City, Inner Mongolia Autonomous Region. Clean grade Kunming mice were selected and administered with high, medium, and low doses of Pediococcus pentosaceus 10-a-1 by oral gavage. The negative control group was administered with the same amount of 0.85 g/dL physiological saline by oral gavage, and the positive control group was administered with 40 mg/kg cyclophosphamide solution by oral gavage. The changes in physical signs, weight gain and food intake of mice were observed during the experiment. Furthermore, the changes of serum biochemical indexes, sperm malformation rate, bone marrow cell malformation rate, organ index and intestinal mucosa morphology were compared among the groups. The results showed that in the acute toxicity test, the mice showed normal signs and no bacterial translocation occurred in the internal organs. In the mouse sperm abnormality test and erythrocyte micronucleus test, the mutation effect of the positive control group was significant, while no significant difference was observed between the Pediococcus pentosaceus 10-a-1 dose groups and the physiological saline control group (P>0.05). In the 28-day toxicity test, there was no significant difference between the Pediococcus pentosaceus 10-a-1 dose groups and the physiological saline group in terms of reproductive performance, organ index, serum biochemical indexes and intestinal mucosal thickness P>0.05). Collectively, Pediococcus pentosaceus 10-a-1 is discovered to be safe without toxic side effects in use.

Abstract:In order to obtain a better feather meal degrading enzyme, a keratinase gene (baker1) was screened from the genome of Bacillus velezensis SYBC H47. Subsequently, baker1 was cloned and its heterologous expression was achieved in Escherichia coli BL21 (DE3). Finally, the recombinant keratinase (BaKer1) was isolated and purified, characterized, and was studied for its practical application. The results showed that the optimal pH and temperature for BaKer1 were 9.5 and 55 ℃, respectively, and it exhibited good stability under moderately-temperature and alkaline conditions. BaKer1 was significantly activated by 1 mmol/L Ca²⁺ ion, slightly inhibited by 5 mmol/L Mn²⁺ ion, and insignificantly affected by other metal ions. BaKer1 had significant inhibitory effect on the activity of PMSF, indicating that BaKer1 is a typical serine protease. The kinetic parameters of BaKer1 were determined using feather meal, azocasein and casein as substrates. The K_m values were 5.06, 1.09, 1.39 mmol/L, respectively, and their k_cat/K_m values were 1 058.24, 2 536.54, 3 733.79 s·mmol/L, respectively. An acid hydrolysis efficiency of 33.51% could be achieved during the degradation of feather meal by BaKer1, indicating its potential application value in the degradation of feather meal.

Abstract:Excellent acetic acid bacteria and yeasts were separated and screened as fermentation strains from different producing areas of kombucha. The yellow big tea in Dabie Mountains was used as the main raw material, and strawberry juice was added to develop the strawberry-flavored yellow big tea fermented beverage. By optimizing the fermentation process and product formulation, the optimal process parameters were identified. This includes the use of two exceptional fermentation strains, acetic acid bacteria DZ-001 and yeast LN-001, with an inoculation ratio of 2∶1 and a total inoculation amount of 5%. The optimal initial pH value is 5.5, with a fermentation temperature of 30 ℃ for a duration of 12 days. The addition amount of strawberry juice is 4.66 g/L, while the addition amount of crystalline syrup is 5.08 g/L. The addition amount of citric acid and sodium citrate is 0.20 g/L, with the optimal addition amounts of VC and D-sodium erythorbate at 0.02 g/L and 0.03 g/L, respectively. Finally, the optimal addition amount of strawberry flavor is 0.1%.

Abstract:To elucidate the non-cytoplasmic membrane damage antimicrobial mechanism of metal antimicrobial peptide SIF₄ against foodborne Escherichia coli(E. coli) based on cell wall target, the effect of SIF₄ on cell wall damage, the competitive binding mechanism of SIF₄ with cell wall lipopolysaccharide (LPS), and the effect of SIF₄ on cell wall membrane components were investigated, and the changes in cell morphology of strain were analyzed using scanning electron microscopy. Results displayed that SIF₄ could destroy the bacterial cell wall. Within a certain concentration range, the damage to the cell wall was positively correlated with the treatment time and treatment dose of SIF₄, and the difference between groups was significant (P<0.05). SIF₄could competitively bind with lipopolysaccharides(LPS), however, no antibacterial activity was observed when the binding amount exceeded 256 mg/L. Fourier transform infrared spectroscopy (FT-IR) analysis revealed that SIF₄ had a significant impact on cell wall polysaccharide information area, as well as the mixed information area of protein and fatty acid, indicating that cell wall was the potential antimicrobial targets. Scanning electron microscope (SEM) analysis showed that SIF₄ could destroy the cell wall membrane structure and alter strain morphology. This study suggests that SIF4 can exert efficient antimicrobial activity against E. coli based on cell wall damage target. Research results could provide supports for elucidating the mechanism of non-cytoplasmic membrane damage based on cell wall targets and biological control of foodborne E. coli.

Abstract:This study aimed to investigate the antibacterial properties effect of common metal ions doping on antibacterial tablets, providing a technical basis for the preparation and improvement of novel nano-TiO₂ antibacterial tablets. The fixed mass fractions of Ag⁺、Zn²⁺and Fe³⁺ doped on TiO₂ antibacterial tablets were selected for comparative research, and the antibacterial properties were in-depth evaluated by antibacterial circle, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. The microscopic structure was characterized and analyzed to investigate the reasons for the differences in antibacterial properties. The results showed that the order of antibacterial activity was Ag@TiO₂>Zn@TiO₂>Fe@TiO₂. Zn@TiO₂ had higher antibacterial activity but poorer antibacterial stability. The MIC and MBC of Ag@TiO₂ for Escherichia coli and Staphylococcus aureus were 10 mg/L and 20 mg/L, while those of Zn@TiO₂ were 30 mg/L and 50 mg/L, respectively. Characterization revealed that the antibacterial activity was mainly attributed to the number and stability of active sites produced by the interaction between the nano-TiO₂ surface and metal ions, and it was not closely related to the pore structure or surface functional groups.

Abstract:Traditional culture-dependent approaches and single molecule real-time sequencing technology were applied to investigate the fungal community composition and characteristics during the fermentation process of sauce-flavor baijiu using the biomimetic machine-produced Daqu and the traditional manual Daqu. The results showed that Wicherhanmomyces anomalus, Pichia kudriavzevii, Candida tropicalis, Kodamaea ohmeri, Kazachstania humilis, Kluveromyces marxianus, and Aspergillus could be simultaneously detected by both approaches. The fungal diversity gradually decreased from the formation of Daqu to the end of fermentation. In addition, compared with the results of second-generation high-throughput sequencing, single-molecule real-time sequencing technology was more suitable to identify the diversity of minor fungal. Moreover, the dominant fungal genera the high-temperature Daqu showed a significant positive correlation regulation mechanism, including 55 fungal genera showing a significant positive correlation, and 6 fungal genera showing a significant negative correlation. This study revealed fungal community composition and characteristics during high-temperature Daqu fermentation of sauce-flavor baijiu, and aimed to lay a theoretical foundation for exploiting functional microorganisms and clarifying the fermentation mechanism of high-temperature Daqu.

Abstract:The twigs of Ligustrum robustum (Rxob.) Blume are the waste generated during the production of small leaf Kuding tea. The large quantity of waste is typically incinerated, resulting in significant environmental pollution and resource waste. To promote the resource utilization of the twigs of Ligustrum robustum (Rxob.) Blume, Lactobacillus plantarum was used to ferment its water extract, and then the composition, distribution and changes of the substances before and after the fermentation were detected by LC-MS non-targeted metabolomics technology. Multivariate statistical analysis methods including PCA and PLS-DA identified 175 different metabolites that demonstrated significant changes in metabolites before and after the fermentation of Ligustrum robustum (Rxob.) Blume twigs extracts, with 100 up-regulated and 75 down-regulated. The top 25 differential metabolites in univariate statistics included 3 peptides, 1 carbohydrate, 4 nucleic acids, 1 lipid, 1 organic acid, 1 flavonoid, and 14 other metabolites, involving 11 significantly different metabolic pathways, of which 6 were amino acids metabolic pathways. The differential metabolites included 915-fold increased Nobiletin and 11-fold enhanced Anserine, both of which have physiological activities such as antioxidant, anti-inflammatory, anticancer, and hypoglycemic effects. Meanwhile, the content of antibiotics Gentamicin. C1a and Lincomycin after fermentation were increased by 22 000 times and 66 times, respectively. The results demonstrate that Lactobacillus plantarum fermentation technology for the resource utilization of Ligustrum robustum (Rxob.) Blume twigs is feasible, but further safety assessment is required.