Abstract:Functional oligosaccharides have drawn increasing attention due to their remarkable effects and have been used in many fields such as healthy foods. However, their utilized dosage and safety analysis still lack the support of effective and extensive research data. Therefore, the study of three common functional oligosaccharides is reviewed, including their source and manufacture technology, their food safety and recommended dosage, as well as their application in the health food industry, based on the investigation of literature progress and industry development, the comparison of domestic and international regulations, and the combination of health evidence and test results. In addition, the existing problems in the functional oligosaccharide industry are also discussed.

Abstract:Bacteriocin is a kind of antibacterial peptide synthesized by ribosomes during the metabolism process, which is widely used in the food industry as a natural and non-toxic antibacterial agent. Quorum sensing is an act of regulating the genes expression by response to the concentration of autoinducers among the bacterial cells. The quorum sensing of lactic acid bacteria has been proved to play a key role in the bacteriocin synthesis.The current research progress of bacteriocin of lactic acid bacteria, including the systematic classification of the bacteriocin, the transduction mechanism of quorum sensing signals and the regulation of LAB bacteriocin synthesis, was reviewed in this article, aiming to give reference and inspiration to the development and application of bacteriocin.

Abstract:Monascus red pigment is a natural pigment produced by Monascus with medicinal and nutritional values. In order to improve the yield of Monascus red pigment through liquid fermentation, the mutagenesis of Monascus purpureus LBBE was performed based on atmospheric and room temperature plasma (ARTP), and the fermentation optimization was also conducted. The mutagenesis condition of ARTP was set with 107/mL of Monascus spore and 10 SLM of aeration at 80 W of power for 42 s. After 10 rounds mutagenesis under the mentioned condition, the positive mutation rate of the strain decreased from 44.6 % to 3.8 %, and the mutant LBBE-15 achieved 1 244 U/mL of the red pigment, which was 1.26 times of the original strain. The optimal culture condition of Monascus was determined as follows:7% inoculation quantity, 1 g/L manganese sulfate, and initial pH 3.7. Then, the yield of the red pigment reached 1 376 U/mL under the optimized culture condition. As indicated by batch fermentation, the mutant strain produced 642 U/mL red pigmentin 50 L jar-fermenter. The results here provided reference data for realizing industrial scale production of Monascus red pigment.

Abstract:Fermented whey was prepared with L.bulgaricus ND02 in this study to investigate the metabolic characteristics of L. bulgaricus ND02 during fermentation. The effects of metabolites on the physiological functions of fermented whey was evaluated based on the dynamic changes of metabolites during whey fermentation. The metabolites in whey fermentation were detected by LC-MS. The screening and analysis of the differential metabolites were conducted through multivariate statistical method. Potential biomarkers were screened out according to database searching. A total of 37 metabolites, including isoleucine, peptides, methyl-D-galactopyranoside, oleic acid, amber acid, jaundice, cytosine adenosine and etc., were significantly identified (P<0.05). The relative content of 23 metabolites, such as homocysteine, Tyr-Trp, phenyllactic acid, cytidine monophosphate and etc., increased significantly in fermented whey(P<0.05). L. bulgaricus ND02 produced a large number of essential amino acids, oligopeptides, organic acids and nucleotides during fermentation, giving the special physiological functions and nutritional values of fermented whey.

Abstract: Bacillus subtilis, generally recognized as safe (GRAS),waswidely used as host strain to express heterologous proteins due to its good secretion ability and easy geneticmanipulations. In B. subtilis, most of the signal peptide-mediated secretion was depended on Sec-pathway(General secretion pathway) or Tat-pathway(Twin-arginine translocation pathway). In this study, through signal peptide prediction and protein N terminal sequencing, the secretion of Pyrococcus yayanosii L-asparaginase in B. subtilis was confirmedto depend onnon-classical protein secretion pathway. By signal peptidescreening, the Tat-pathway signal peptide SP_{phoD was found to bebeneficial for the L-asparaginase secretion in B. subtilis. With the co-expression of SPphoD and molecular chaperone PrsA, the L-asparaginase secretion was increased by 72.11% compared with that of the original one.}

Abstract:The main causes of the browning changes of medlar wine during fermentation and aging were investigated by determination of changes in polyphenol oxidase (PPO) and peroxidase (POD) activities, the discussion of variation rules of the total phenol, flavonoids, 10 monomer phenols, VC and the 5-Hydroxymethyl furaldehyde (5-HMF), as well as the analysis of browning degree changes of the Maillard reaction. The results showed that a large amount of monomers phenol rutin, chlorogenic acid, ferulic acid, p-hydroxybenzoic acid and p-coumaric acid in the zymotic fluid which greatly affected the degree of browning. At meanwhile, the oxidative degradation of VC and the Maillard reaction of sugars and amino acids also participated in the browning. In conclusion, enzymatic browning as well as non-enzymatic browning co-existed in the process of fermentation. The main cause of the browning was the participation of phenolic substances in both enzymatic and non-enzymatic browning reactions.

Abstract:To explore the changes of polyphenols and flavonoids content and antioxidant activity during in vitro simulated gastrointestinal digestion of kiwifruit(pulp and juice), the antioxidant activity was evaluated by the ferric reducing antioxidant power assay and the radical scavenging capacity of DPPH, superoxide anion and hydroxyl. The results showed that the release of polyphenols and flavonoids increased after digestion. For kiwifruit pulp, the maximum amounts of polyphenols and flavonoids were 1.62 and 2.40 times of that before digestion, while 1.63 and 2.90 times for juice. The radical scavenging rates of DPPH, superoxide anion and hydroxyl, as well as ferric reducing antioxidant power of juice and pulp reached the maximum after 1 h digestion, then declined and gradually stabilized. Different antioxidant capacity with similar variation of pulp and juice is observed. Studies indicate that simulated gastrointestinal digestion can promote the release of polyphenols and flavonoids, and improve antioxidant activity.

Abstract:This study aimed to obtain the vitamin K₂ dominant mutant and to further improve its yield via the fermentation medium optimization using response surface design. The mutagenesis breeding of bacillus natto was carried out through room temperature plasma (ARTP) in combination with the structural analog resistance screening under atmospheric pressure, subsequently rescreened by 24 bore plates fermentation. The fermentation medium was then optimized by Box-Behnken design. A dominant mutant strain of vitamin K₂ was obtained by ARTP mutagenesis with a yield of 3.23 times higher than that of the original strain. The optimal values based on Box-Behnken design were 0.69 g/L of K₂HPO₄, 66.01 g/L of glycerol and 25.12 g/L of yeast powder, with an increase of 56.7% of vitamin K₂ yield. A dominant mutant strain of vitamin K₂ was achieved by ARTP mutagenesis and the fermentation medium was effectively optimized by response surface methodology. The experimental results showed that the mutant strain has potential value in production and application, establishing the breeding method with a beneficial reference for the selection and breeding of other industrial microorganisms, which is of great significance to improve human health.

Abstract:An ethidium monoazide in combination with real-time PCR method (EMA-PCR) was newly developed for selective detection of live Listeria monocytogenes cells from dead cells. The primers and TaqMan probes were designed using the hly gene which encoded listeriolysin O (LLO). The sensitivity and specificity of the assay were confirmed by intensive validation tests with a large number of Listeria monocytogenes strains and other pathogenic bacteria strains (n=56). A qPCR assay was detected with EMA of different concentrations. Sodium deoxycholate solution (SD) was used to strengthen the inhibitory effect. In addition, 73 various artificial contaminated food and environmental samples (braised chicken, milk, minced meat and garbage leachate) were investigated for L. monocytogenes. The primer probe accurately detected L. monocytogenes without specific amplification for other strains. EMA could penetrate dead cells resulting in the covalent links of DNA upon 15 min light exposure and therefore inhibition of amplification under an optimal concentration of 2.5 μg/mL with a detection limit of 150 CFU/mL. The Ct value of live Lm increased under SD treatment. The diagnostic accuracy of EMA-qPCR method was up to 100 % compared to the traditional culture method. This method with simple operation, time-saving and high efficiency has a promising application on accurate microbiological monitoring of food safety and environmental source.

Abstract:L-threonine is an essential amino acid widely used in food, feed and medicine. In the process of L-threonine synthesis from glucose, transcription and translation of some non-essential genes consume carbon source. In this study, CRISPR-Cas9 and site-specific recombination system Cre/loxP were used to delete 34 non-essential genes (30.372 kb) between puuE and ynaI genes in the genome of E.coli MG1655, resulting the mutant strain MG003. The genes thrA*, thrB and thrC, the key genes in the L-threonine biosynthetic pathway, and the genes rhtA and rhtC encoding the L-threonine transporters, were then overexpressed in MG003 to increase the L-threonine production. Compared to the control strain MG1655/pFW01-thrA*BC, MG003/pFW01-thrA*BC grew faster and produced 25.5% more L-threonine, MG003/pFW01-thrA*BC-rhtA produced 43.3% more L-threonine, and MG003/pFW01-thrA*BC-rhtC produced 74.5%more L-threonine. The results indicate that deletion of the 34 non-essential genes in E. coli could improve L-threonine production.

Abstract:A fast, specific and sensitive method for detection of crocodile-derived components was developed by designing specific primers on the cytb gene sequence of crocodiles. Mutton, beef, pork, chicken, duck, fish and shrimp were used as reference animals for specific detection. The feasibility of the method was verified by the detection limit and sensitivity test. The results showed that the method was effective in rapid detection of crocodile-derived components, with strong specificity, and the detection limit of DNA of crocodile-derived components was up to 0.001 ng/μL, and the sensitivity was up to 0.01%. The method has the characteristics of strong specificity and high sensitivity, which can be used for the detection of crocodile-derived components in processed meat products.

Abstract:Stevioside is demonstrated to regulate the cholesterol levels in body. The steviol is the main natural hydrolysate of stevioside in the intestine. The regulation of adenosine triphosphate binding cassette transporter A1 protein (ABCA1) in mouse macrophages J774A via steviol was studied and its possible molecular mechanism was investigated. The conditions and concentration of steviol were first established by MTT method. The detection of western blot, immunofluorescence and quantitative fluorescence PCR confirmed that steviol could significantly increase the expression of ABCA1 at protein and gene transcription level in collaboration with 8-(4-chlorophenylthio) adenosine 3',5'-cyclic monophosphate (CPT), the analogue of cyclic adenosine monophosphate (cAMP). Moreover, steviol could significantly up-regulate the expression levels of both mRNA and protein in upstream regulatory genes LXRα and PPARα of ABCA1, however, insignificant regulation on the expression of PPARγ was observed. The regulation of the ABCA1 protein expression through steviol might be related to the expression of PPARα and LXRα. This study is extremely instructive to the subsequent treatment and prevention of atherosclerosis, providing a reference for the application of stevioside in food.

Abstract:A virulent phage, named as ΦSHDA-1, was isolated from sewage by a double-layer plate method using Salmonella typhimurium (CMCC50115) as the host strain. The preliminary study of its biological characteristics and genome was conducted. The results showed that ΦSHDA-1 plaque was bright and the edge was clear. The transmission electron microscopy showed that ΦSHDA-1 had a head diameter of (53±8) nm and a tail length of (112±12) nm which belong to the Siphoviridae family. The best multiplicity of infection was 0.00001. The one-step growth curve showed the latent period was 25 min and the burst period was 30 min with an average lysis amount of 36.52 PFU/cell. ΦSHDA-1 was stable at 30~50 ℃ and pH 2~10, exhibiting a good lysis effect on Salmonella typhimurium. A total of 6 coutig with length of 40 523 bp and 51% of GC were obtained by whole-genome sequence. A total of 59 coding sequences were obtained by Prokka annotation, which contained an lysin gene without tRNA and rRNA. Through the open reading frame and the analysis of CARD and VFDB, no drug resistance genes and virulence genes were detected.

Abstract:Zein was treated by ultrasound oscillation at 225 W for 90 minutes to improve its structural characteristics and reduce the formation of viscoelastic gluten dough at 50 ℃. The treated zein was characterized by scanning electron microscopy, differential scanning calorimeter and Fourier transform infrared spectroscopy, respectively. The microscopic surface morphology of zein was clearly observed which changed from lamellar toughness to bulk looseness. Meanwhile, the denaturation peak and absorption intensity of amide I band (1 700~1 600 cm^-1) decreased significantly after ultrasound oscillation. Corn crude peptides with a Fisher's ratio of 4.07 were obtained after hydrolyzation by alkaline protease (Alcalase 2.4L), ultrafiltration and nanofiltration. The fraction with molecular weight less than 1 000 accounted for 97.62% in the crude peptides. Furthermore, the directed hydrolysis of corn crude peptides was performed by sequential using of α-chymotrypsin and carboxypeptidase A. Combined with the adsorption of aromatic amino acids by activated carbon, corn oligopeptides with a Fisher's ratio of 41.87 was prepared. The fraction with the molecular weight of 180~1 000 was determined to be 71.37% in the oligopeptides, where the proportion of Phe and Tyr was only accounted for 0.73% within total amino acids.