Abstract:Diet is strongly associated with host metabolism and immune system. A number of studies have indicated that diets significantly affect the structure and function of gut microbiota, which further influence the physiological status of the host. Dietary strategies for the modulation of gut microbiota have become an area of ongoing research. This review concludes recent studies on the impacts of dietary patterns, dietary components and functional dietary supplements on gut microbiota and host health, aiming to facilitate the development of dietary strategies for gut microbiota modulation.

Abstract:At present, all links of the food industry chain are facing important opportunities and challenges. The food industry needs technological innovation and further development. The cross integration and innovation of the whole chain technology is becoming a new mode of innovation and development of the food industry. This study has analyzed the trend of the international situation and pointed out that it is an international trend to highlight the advantages of interdisciplinary integration and promote the systematization, scale and digitalization of food industry research with high and new technology. The study has also discussed the current situation and demand in China and further expounded the key development direction of China in the field of cross integration and innovation of technology in the whole chain.

Abstract: Haematococcus pluvialis is a major source of natural astaxanthin due to its ability to accumulate astaxanthin under stress conditions. In order to establish a technical system for the regulation of efficient synthesis of astaxanthin, this experiment analyzed the effect of exogenous melatonin(MLT) on the defense response of Haematococcus pluvialis under nitrogen deficiency combined with high light condition. The results showed that the induction of exogenous MLT significantly promoted the accumulation of astaxanthin under stress conditions, with the highest content reaching 32.37 mg/g, which was 2.25 times higher than that of the control group. In addition, exogenous MLT increased the levels of intracellular NO and mitogen-activated protein kinase (MAPK), and upregulated the expression levels of dxs and chy, which are the key enzyme genes for astaxanthin synthesis. This study showed that the efficient synthesis of astaxanthin in Haematococcus pluvialis induced by exogenous MLT under high light and nitrogen stress may be related to the increase of NO and MAPK and the expression of the enzyme genes dxs and chy.

Abstract:Heterologous over-expression of glutaminase in microorganisms has been extensively studied and its application in industrial production has been limited by its poor separation stability under nonresistant conditions with free plasmids. To obtain a strain used in industrial glutaminase production, glutaminase（from Micrococcus luteus K-3） was successfully over-expressed by integration of the Mglu gene in chromosome of GRAS strain Bacillus subtilis 168. Two genes encoding specific protease were blocked by integration of Mglu gene, and the zeo resistance marker was deleted by Cre recombinase catalyzing the recombination of DNA between lox sequences. After continuous cell culture without adding any antibiotics, the enzyme activity was basically unchanged when the recombinant strain was transmitted for 42 generations. By using 5 L bioreactor for fed-batch fermentation of recombinant glutaminase producing strain, the highest enzyme activity was about 41.5 U/mL. This study provides a reference for improving the genetic stability of glutaminase recombinant strain.

Abstract:In order to explore the inhibitory mechanism of acidic pH conditions for spore germination, the study investigated effects of different pH treatments on the activity and structure of spore cortical lyase (CwlJ). Using Fourier transform infrared spectroscopy and fluorescence spectroscopy, the relationship between the secondary and tertiary structures of CwlJ and its activity was analyzed. The pH values were set to 3, 5, 7, 9 and 11 in the experiment. The results showed that: 1) CwlJ was activated over time with pH 3 and 5; 2) The activity of CwlJ was closely related to the content of alpha-helix in its secondary structure; when pH value increased from 3 to 5, the content of alpha-helix also increased from 36.15% to 37.29%; when pH increased from 5 to 7, the content of alpha-helix basically unchanged; when pH increased from 7 to 11, the content of alpha-helix decreased; therefore, the enzyme may be activated in the pH range of 3-5; 3) the fluorescence intensity in pH 5 was strongest, the internal protein was fully unfolded, and the spatial structure was more loosely expanded, and the tertiary structure was more stable. In conclusion, the structure of CwlJ was stable and its activity was high in acidic pH conditions, so it was speculated that the inhibition of acidity for spore germination was not due to its inhibition for the activity of cortical lyase.

Abstract:Ferulic acid, a good natural plant extract, has many physiological functions and exhibits a wide range of therapeutic effects against various diseases, including cancer, diabetes, cardiovascular and neurodegenerative diseases. The study examined the effect of ferulic acid at different levels (0, 100, 300, 500 mg/kg) on histamine in smoked horse sausages using high performance liquid chromatography. Parameters such as microbiological growth, pH and moisture content were also evaluated. The results revealed that ferulic acid significantly reduced the numbers of Staphylococcus, Enterobacteriaceae and Pseudomonas compared to the control(P<0.05), but the inhibitory effects on Lactic acid bacteria were not significant (P>0.05). Moreover, ferulic acid suppressed the growth of histamine-producing bacteria based on traditional microbiological methods and PCR-DGGE analyses, and thus significantly reduced the accumulation of histamine(P<0.05). The content of histamine increased first, reaching a maximum after day 14, and then decreased. The treatment with 300 mg/kg ferulic acid gave the lowest content of histamine (30.71 mg/kg), which was reduced by 43.26% compared with the control after day 28. In conclusion, ferulic acid was an excellent additive which could inhibit histamine production remarkably and had a great application in food industry in fermented sausages.

Abstract:The gene cluster for pyrroquinoline quinone (PQQ) synthesis was cloned from Pseudomonas plecoglossicida JUIM01. Its genome composition and biological information were subsequently analyzed. According to the reported genome sequence of P. plecoglossicida JUIM01, primers were designed for amplification of the PQQ synthesis gene cluster via LA-PCR. The gene fragments were sequenced and analyzed by bioinformatics approaches. The results showed that the total length of the cloned gene fragment was 11 659 bp, which included 9 genes: pqqF, pqqA, pqqB, pqqC, pqqD, pqqE, pqqM, pqqH and pqqI, and encoded the related enzymes in PQQ biosynthesis pathway and precursor peptide PqqA. These encoding genes were similar to the PQQ synthesis gene cluster of P. fluorescens Pf0-1 with sequence identifity of 41~94%. This study, for the first time, reported cloning of the PQQ synthesis gene cluster from P. plecoglossicida JUIM01, and the bioinformatics analysis laid a foundation for the study of PQQ biosynthesis pathway and intracellular regeneration mechanism of Pseudomonas strains. Furthermore, it provided theoretical support for improving the production intensity of 2KGA.

Abstract:Fresh jellyfish contains abundant protein, essential amino acids, vitamins, carbohydrates and other nutrients. With the high nutrition, it is easy to cause the excessive growth of microbial in ready-to-eat jellyfish and then lead to the corruption and deterioration which will cause enormous economic losses and food safety issues. Therefore, the quality of the jellyfish should be controlled by identifying the dominant spoilage microorganisms that cause the metamorphism of the jellyfish and looking for the technology that can effectively inhibit their growth. The flora in ready-to-eat jellyfish was analyzed, and the dominant strains were isolated and identified by PCR. The results showed that the total number of colonies in ready-to-eat jellyfish after three months storage was 48 000 CFU/g which exceeded the national standard of 30 000 CFU/g. However, no pathogenic bacteria including Escherichia coli, Bacillus cereus, Salmonella and Staphylococcus aureus were identified in unqualified jellyfish. The dominant spoilage strain was Burkholderia cepacian which is gram-negative bacterium.

Abstract:In order to obtain red fermented oats (RFO) rich in monacolin K (MK), the study used a high MK but non-citrinin producing strain Monascus pilosus MS-1 and naked oats, optimized the medium and shortened the fermentation cycle by adding nutrients. The results showed that the basic fermentation parameters of RFO were moisture content 33.35%, comminution degree 20 mesh, lactic acid 0.6 mL/hg, MgSO₄·7H₂O 0.007 mol/kg, volume of sample loading 75 g and inoculum size 10 mL/hg, respectively. After fermentation at 30 ℃ for 3 days, the RFO were transferred to 25 ℃ up to 14 days. The MK yield (19.77 mg/g) was 32.63% higher than that of control when 2% soybean protein was added to the aforementioned optimized medium. The highest MK yield of 41.85 mg/g was obtained after 26 days fermentation. This study can provide a novel thinking for the deep processing of oats, and it can also be used as a reference for improving the productive efficiency of functional red yeast rice.

Abstract:Chondroitin-4-O-sulfotransferase-1（C4ST-1, EC 2.8.2.5） catalyzes the sulfation of 4-OH of GalNAc to generate chondroitin sulfate A（CSA）. C4ST-1 contains three pairs of disulfide bonds and is hard to correctly fold into active form. As a result, C4ST-1 mainly exists as inclusion bodies in E. coli. To increase the soluble expression, the effects of co-expression of thiol oxidase (Erv1p) and C4ST-1 or C4ST-1 and disulfide isomerase (DsbC) were investigated. The results showed that co-expression of DsbC significantly increased the expression level of intracellular soluble protein while no significant effect was observed for co-expression of Erv1p. Co-expression of C4ST-1 and Erv1p, or C4ST-1 and DsbC increased the enzyme activities to （12.32±0.76） U/L and （21.99±0.42） U/L, which were 1.30 and 2.33 times of that of the original strain, respectively. Then, C4ST-1, Erv1p and DsbC were co-expressed and the enzyme activities in shake flask and 3 L fermenter were improved to （29.12±0.66） U/L and 49.97 U/L, respectively. The present study provides a solid foundation for further applications.

Abstract:The study aimed to investigate the deodorization effect and mechanism of yeast extract for the small yellow croaker. The effects of yeast extract and other deodorants on the smell were determined using electronic nose and sensory evaluation. Single factor and orthogonal experiments were used to optimize the deodorizing time, temperature and dosage of yeast extract. The volatile substances in surimi were detected by head space solid phase microextraction (HS-SPME-GC-MS).The results of deodorization showed that the electronic nose could well distinguish the flavor of surimi treated with different deodorants and the yeast extract group had good deodorization effect and gentle flavor.The best deodorization process was to add 1% yeast extract to fish surimi at 40 ℃ for 60 min, leading to a decrease of 81.21% for the content of trimethylamine.Three volatiles with fishy smell, N,N-dimethylacrylamide, 1-octyl-3-alcohol and 1-ene-3-alcohol, were not detected. The contents of hexanal, glutaraldehyde and trimethylamine were reduced.

Abstract:In order to improve the ability of exogenous L-glutamate-dependent strain Bacillus subtilis HB-1 to produce γ-poly glutamic acid (γ-PGA), the study explored the effects of adding oxygen carrier and precursor L-glutamic acid on the cell growth and the yield of γ-PGA. Based on single factor tests, the optimum oxygen carrier was polydimethoxysilane (PDMS), and the cell density increased 3～5 times after the addition of 10% PDMS (v/v) in the initial fermentation medium; moreover, the optimum addition time of precursor L-glutamic acid was 18 h, and the optimum concentration was 10 g/L. With the optimal conditions, the concentration of γ-PGA increased to 45 g/L in a 3 L fermenter, and its yield reached 52 g/L by the combination of feeding carbon source and L-glutamic acid in 30 h. The fermentation product was confirmed to be a polypeptide compound by infrared and amino acid analyzers, and the molecular weight of γ-PGA was up to 10 million dalton.

Abstract:This article aimed to study the anti-inflammatory mechanism of Tricholoma mongolicum polysaccharide extract in LPS-treated RAW264.7 cells. The RAW264.7 cells were first treated with different concentrations of Tricholoma mongolicum polysaccharides, and the viability was determined by CCK-8. The release of NO was measured by Griess, and TNF-alpha and IL-1 beta were examined by ELISA. The expression levels of HIF-1α，NF-κB，STAT3，COX-2 and iNOS mRNAs and proteins were tested by qPCR and western blot. The results showed that the maximum safety dose of Tricholoma mongolicum polysaccharide extract was less than 100 μg/mL. Compared with the LPS model group, Tricholoma mongolicum polysaccharide extract at the concentrations of 0.01, 0.1, 1, 10 μg/mL could inhibit the production of NO,TNF-α and IL-1β. The inhibition rates of NO were 38.21%, 64.17%, 58.16%, 79.42%, respectively; the inhibition rates of TNF-α were 27.91%, 36.31%, 36.14%, 45.09%, respectively; the inhibition rates of IL-1?茁 were 47.75%, 58.47%, 60.21%, 64.55%, respectively. Tricholoma mongolicum polysaccharide extract at the concentration of 10 ?滋g/mL could down-regulate the mRNAs and proteins expression levels of HIF-1α, iNOS, STAT3 and COX-2. Therefore, anti-inflammatory effect of wild Tricholoma mongolicum polysaccharides on LPS-induced RAW264.7 cells may be exerted via STAT3 and HIF-1α pathways.

Abstract:The study compared the antioxidative activities of typical algal endophytes in Ulva lactuca L. and Undaria pinnatifida Suringar from Beibu Gulf in Guangxi and screened out the better ones. Among the first 12 strains with stronger antioxidative activities, 9 potent strains were screened out for the further study. Results indicated that the scavenging activities of algal endophytes on DPPH, hydroxyl radical and superoxide anions increased with concentrations. There was a significant difference in the antioxidative activity between Ulva lactuca L. and Undaria pinnatifida Suringar (P<0.05). The semi-inhibition concentrations (IC50) of endophytic bacteria from Ulva lactuca L. and Undaria pinnatifida Suringar for DPPH, hydroxyl radical and superoxide anions were significantly higher than those of endophytic fungi, indicating that the antioxidative activities of endophytic bacteria were significantly lower than those of endophytic fungi. SZ-5 strain from Ulva lactuca L. had the strongest potency to scavenge DPPH, hydroxyl and superoxide anions, and the IC_{50 was （0.59±0.06）, （1.30±0.36） mg/mL and (1.14±0.35) mg/mL, respectively. SZ-5 was identified as Aureobasidium spp.}

Abstract:The study investigated the plant growth promoting character and the phosphorus- solubilization in shell powder and soil of the strain Bacillus amyloliquefaciens YP6 (YP6) isolated from the rhizosphere of a plant in phosphorite mining area in Guizhou. The results showed the strain YP6 had good growth-promoting ability. Furthermore, after 7 days' fermentation by strain YP6, the soluble phosphorus contents in shell powders (oyster, clam and fresh oyster) and the mixtures of soil and shell powders were 44.9, 39.2, 40.3, 86.4, 73.1, 74.8 mg/L, respectively. This study showed that the strain YP6 had remarkable phosphorus solubilization in both soil and shell powder.