Abstract:Mycotoxins are important pollutants that have long been a serious problem of food security, especially for cereal crops. Therefore, the detection and degradation of mycotoxins has always been a focus of food safety research. According to the existing research, the main degradation methods are physicochemical and biological methods. In addition, a variety of synergistic degradation methods have emerged with a diversified trend. Therefore, the recent research efforts in different strategies used to control the contamination of various mycotoxins in food and other products were reviewed in this article, aiming to further promote the application of more convenient and efficient mycotoxin degradation methods to the relevant food fields, to reduce the impact of degradants on food quality, and to inspire new mycotoxin degradation methods. The corresponding toxin production mechanisms were analyzed, and the advantages and disadvantages of various methods to prevent and control mycotoxins at present were discussed. At the same time, the future development trend of mycotoxin degradation methods in food industry was prospected, and new research points were put forward.

Abstract:The infectious diseases caused by pathogenic microorganisms seriously threaten human public safety, especially the multi-drug resistant bacteria (MDR). Antimicrobial peptides (AMPs) have attracted much attention because their non-drug resistance or lower drug resistance for bacteria with the advantages of good thermal stability, high antimicrobial activity, high specificity and few mammalian cytotoxic side effects. AMPs have the physiological functions of active defense and immunity, and are expected to be ideal antibiotic substitutes. AMPs possess single or synergistic bacteriostasis effect on cells with multiple targets, and thus they are of great significance to clarify the antibacterial mechanism with multiple targets for the application of AMPs. In this paper, the antibacterial mechanism of AMPs was systematically reviewed from the perspectives of multiple targets including cell wall damage, cell membrane damage, the mechanisms of intracellular biomacromolecule synthesis, the mechanisms of material and energy metabolism affecting key enzymes activity, and the mechanisms of mitochondrial injury and immunoregulation. The antibacterial mechanism of AMPs was prospected to provide theoretical reference for antibacterial mechanism of AMPs.

Abstract:Bacillus subtilis is an important industrial production strain, widely used in the expression of foreign proteins. At present, among the common constitutive promoters in Bacillus subtilis, P_spovG, as a high-strength constitutive promoter, has the advantages of high expression, good stability and wide application when expressing foreign proteins. This study first truncated the upstream sequence of P_spovG, and the strength of the promoter was still maintained when the upstream sequence of promoter was shortened form the original 251 bases to 26. And the three bases 'AGC' adjacent to the upstream of element -35 was identified as the key bases affecting the promoter strength. Secondly, random mutations of the upstream A-T rich region of promoter and the G-C rich region of spacer region were conducted, which proved that the arrangement of the A-T bases in the upstream activation sequence had an important influence on the promoter strength, and a mutant with increased strength was obtained. Finally, a novel promoter SP_spovG-P_lytR with a promoter strength of 135.1% of the original promoter was obtained by inserting the key regulatory sequences of promoters at different expression periods into the upstream and downstream of mutant. This study provides an important reference for the development of new strong constitutive promoters for the Bacillus subtilis expression system.

Abstract:Ethyl carbamate (EC) is a potential carcinogenic chemical in yellow rice wine. Urease has attracted much attention because of its degradation of urea, the precursor of EC. To guarantee the food safety of rice wine, the gene encoding Bacillus amyloliquefaciens IT-45 urease (Ba-urease) was realized by gene mining and expressed in recombinant Bacillus subtilis. The enzyme activity of urease increased from 6.85 U/mL to 9.01 U/mL after the urease gene cluster reconstructed by the optimization of codon and ribosome binding site. The urease activity was further increased to 10.15 U/mL by adjusting the position of gene ureC. The optimal reaction condition of recombinant urease was 37 ℃ and pH 6.5~7.0. Under the optimal fermentation conditions, the enzyme activity reached 12.5 U/mL. The production of food-grade recombinant urease has potential application in traditional fermented food industry.

Abstract:This study aims to explore the feasibility and effectiveness of functionalized glycogen as a gene vector. Aminated glycogen (NH₂-Gly) was synthesized through functionalization of glycogen with diethylenetriamine. The structure of NH₂-Gly was characterized by infrared spectra. The encapsulation and protection of pEGFP by NH₂-Gly was studied by gel retardation assay. The biocompatibility of NH₂-Gly was investigated by MTT and hemolysis assay. The transfection efficiency of NH₂-Gly/pEGFP in NIH 3T3 cells was analyzed by confocal laser scanning microscope and flow cytometry. The results showed that the prepared NH₂-Gly was uniformly dispersed with a particle size of about 80 nm and a significant positive charge. Compared with PEI 25 k, NH₂-Gly had good biocompatibility. NH₂-Gly could effectively encapsulate pEGFP and protect it from degradation by nuclease. NH₂-Gly significantly increased the transfection efficiency of pEGFP in NIH 3T3 cells, which was almost equivalent to that of PEI 25 k. Therefore, glycogen is expected to be a safe and efficient gene vector.

Abstract:Carrots are susceptible to spoilage by oxygen and microorganisms after peeling and cutting. Therefore, appropriate preservation methods are needed to delay their quality deterioration. In this study, microwave blanching and modified atmosphere packaging (MAP) used as preservation methods and their effects on the quality of carrots during storage were investigated. After the treatment of microwave blanching and modified atmosphere packaging, the firmness, β-carotene content, moisture content, water activity, moisture status, peroxidase activity, colour, and microbial load of carrots were evaluated in an interval of 5 days. Microwave blanching effectively reduced the microbial load and decreased water mobility in carrot. In contrast, free water (T₂₄) was more prominent in the control sample. Microwave blanching under 360 W for 300 s combined with modified atmosphere packaging (80% O₂,10% CO₂, 10% N₂) reduced the degradation of β-carotene, loss of firmness and peroxidase activity of carrots during storage, and the increases of water activity and moisture content were better controlled. Low power microwave blanching combined with high oxygen modified atmosphere packaging is an effective preservation technology which could be used to maintain and improve the storage quality of carrot.

Abstract:This study aimed to establish the bacteriostasis and antioxidant relationship among different parts of artificially cultivated Isaria cicadae Miquel (IcM) and screen the active components. Ultra-performance liquid chromatography (UPLC) fingerprints of different parts of IcM were established, and in vitro antibacterial and DPPH antioxidant activity were performed on the extracts of spore powder and sterigmata. The pharmacodynamic data was correlated with the common peaks of chromatographic fingerprints by the cluster analysis and grey relational analysis to establish the spectrum-activity relationship. The extracts from different parts of IcM were effective in inhibiting Staphyloccocus aureus and scavenging free radicals. The extract from IcM spore powder showed better therapeutic effect than that form sterigmata. Grey relational analysis showed that the bacteriostasis and antioxidant activities of IcM were the combined effects of various components, and the characteristic peaks were No.23, No.2, guanosine and adenosine (correlation degree>0.85), which greatly contributed to the pharmacodynamics. The preliminary spectrum-activity relationship of different parts of IcM was established in this study, and the characteristic peaks which greatly contributed to the pharmacodynamics of IcM were screened out, providing reference for the further study of the pharmacodynamics and pharmacology of IcM.

Abstract:There are problems in acidified milk beverage including protein precipitation and whey isolation, and polysaccharides such as pectin are often used as stabilizers. Soluble soybean polysaccharide(SSPS) has low viscosity, good solubility and refreshing taste, however, its stabilization mechanism of acidified milk beverage is still unclear. Acidified milk beverage processed by formulation and fermentation with skim milk was studied, and the differences of mechanism between SSPS and pectin stabilizing three kinds of acidified milk proteins (skim milk, casein and whey protein) were investigated by the LUMiSizer instability index, the complex content quantified by SEC-HPLC, the particle size, ζ potential and the 14-day cold storage stability. The results showed that for three acidified milk proteins processed by formulation, 2 g/L SSPS could not form effective complex with casein and stabilize acidified casein, and 2 g/L pectin could not form complex with 3 kinds of acidified milk proteins and failed to stabilize these milk proteins. SSPS and pectin under other mass concentrations could form complexes with three acidified milk proteins of 10 g/L, and showed good stability during 14-day cold storage. The fermented acidified skimmed milk could only be effectively stabilized by 6 g/L pectin. The stability tests of whey protein and casein could not predict the stability of fermented acidified skim milk beverage. The results of average particle size showed that the particle size of formulated acidified milk beverage was far smaller than that of the fermented acidified milk. The increasing of SSPS could not effectively reduce the average particle size of fermented skim milk. However, for three kinds of formulated acidified milk proteins and fermented acid whey protein or casein, the average particle size decreased significantly with the increasing of SSPS. The ability of pectin to reduce the particle size of acidified milk proteins was not as good as that of SSPS. These results indicated that the particle size of acidified milk protein was one of the factors affecting the formation of polysaccharide complex. Besides, the viscosity of milk beverage might also be an important factor affecting the stability of milk beverage if the complexes effectively formed. The long-term storage stability could not be characterized by centrifugation stability. For formulated acidified milk proteins, the complex amount and average particle size might be more important for predicting the long-term storage stability, while for fermented acidified milk proteins, the average particle size and viscosity might be more useful.

Abstract:D--allulose is a C-3 epimer of D--fructose. It has similar sweetness to sucrose but provids significantly lower calorie, which makes it a functional sweetener with important application potentials. The enzymatic preparation of D--allulose from D--fructose catalyzed by D--psicose 3-epimerase (EC 5.1.3.30, DPEase) has attracted much attention owing to its simple purification process and high product concentration. To obtain higher expression of enzyme, DPEase was produced by a previously constructed strain, <>Biacillus subtilis 1A751/pUB-P43dpe-dal, in a 3 L fermentor. By optimizing the dissolved oxygen (DO), pH, temperature and initial carbon source concentration, the optimal fermentation conditions were determined as follows: DO 30%, pH 6.0, 37 ℃, initial glucose concentration of 15 g/L. And the maximum enzyme activity reached 78.3 U/mL. On this basis, the fed-batch fermentation was applied, and the optimal fed fermentation time was 5 h. At a constant feeding rate of 8.0 g/（L·h）, the whole-cell enzyme activity reached 123.0 U/mL after 9 h fermentation. This strategy of fermentation could provide a theoretical basis for the expanding the industrial production of D--allulose.

Abstract:The effects of different storage years and pressing methods on the flavor quality of Shoumei were investigated based on the sensory evaluation and biochemical composition determination, in which Shoumei loose tea, PFTS Shoumei cake tea (pressed first and then stored, PFTS) and SFTP Shoumei cake tea (stored first and then pressed, SFTP) were used as the experimental materials. The results of sensory evaluation showed that with the increase of storage years, the aroma of PFTS and SFTP Shoumei cake tea was superior to that of Shoumei loose. PFTS Shoumei cake tea in 2016 presented plum fragrance, and its tea soup showed the weakest astringency. The results of biochemical analysis showed that with the increase of storage years, the contents of tea polyphenols in PFTS Shoumei cake tea decreased gradually, while the contents of non-ester catechin C, EC and EGC increased. The main different aroma substances in the three kinds of Shoumei tea were linalols, which might be related to the plum fragrance of PFTS Shoumei cake tea in 2016. In general, the PFTS storage method was most favorable to reduce the bitter and astringent substance in Shoumei, increase the concentration of taste substance, improve the pure and mild taste, and enhance the aroma.

Abstract:In order to solve the hidden danger of food safety, gas chromatography-mass spectrometry (GC-MS) combined with headspace solid phase microextraction (HS/SPME) was constructed to explore the volatile metabolites of Staphylococcus aureus, and the different metabolites and metabolic pathways of Staphylococcus aureus in milk were analyzed by the combination of metabonomics and genomics. The results showed that the different metabolites of Staphylococcus aureus included N-methylthioformamide, 1-butanol, acetic acid, ethylbenzene, mesitylene, octanoic acid, benzoic acid, n-decanoic acid, dodecanoic acid, ethanol, phenol and propylene glycol. After genomic analysis, Staphylococcus aureus was mainly based on the basic life metabolism, and the metabolic pathways and related genes of the substances involved in metabolism (ethanol, acetic acid, 1-butanol) in the metabolic network were identified. This study could provide a theoretical basis for the study of biomarkers of Staphylococcus aureus.

Abstract:A method for simultaneous determination of 22 organochlorine pesticides residues in eggs, chicken and milk powder was established. The samples were extracted by acetonitrile solution, purified by Captiva EMR-Lipid solid phase extraction column, determined by gas chromatography (ECD) after n-hexane dissolution, and quantified with external standard method. The results showed that the linear relationship between the mass concentration of 22 organochlorine pesticides and their corresponding peak areas were good in the range of 0.005~0.2 mg/L, and the R² were greater than 0.995. At spiked levels of 0.01, 0.02, 0.1 mg/kg, the recoveries of 22 organochlorine pesticides were between 60%~100% with RSD less than 10% after 6 repeated determinations, fitting the coefficient of variation in laboratory according to GB 27404-2008. This method could effectively remove animal fat and lipophilic interference in eggs, chicken and milk powder. Besides, the sensitivity, accuracy and precision of this method could meet the requirements of pesticides residue detection, providing an efficient and reliable analytical method for monitoring organochlorine pesticide residues in eggs, chicken and milk powder.

Abstract:There are a large number of inorganic ions in D--ribose fermentation broth, which will affect the subsequent purification of D--ribose if not removed. At present, ion exchange resins are often adopted for desalination in industry. The cost of desalination increases proportionally with the increase of feed liquid salt content, and generates a large amount of wastewater, which is neither economical nor environmentally friendly. In order to determine the feasibility of electrodialysis desalination, the specific cost of desalination and the best desalination process, the desalting experiment of electrodialysis was carried out with the filtrate of D--ribose fermentation broth as the raw material and Lanran-40-2040 composed of homogeneous cation exchange membrane CMX and anion exchange membrane AMX as the laboratory-scale equipment. The results showed that when the desalination rate was controlled at 54%, the product yield reached 97.68%. However, when the desalination rate was further increased, a certain amount of D--ribose would permeate into the electrodialysis concentration chamber, and the D--ribose content in the concentration chamber increased rapidly with the increase of operation time. Compared with the whole resin desalination process, the product yield of electrodialysis combined with ion exchange resin desalination process was increased by 1.9%, which saved half of the ion exchange resin, acid and alkali, and reduced half of the wastewater discharge. Therefore, this study could provide a good reference for the industrial production ofD--ribose.