Abstract:

Abstract:[Objective] Lake sediments store huge amount of specific microorganisms that greatly contribute to biogeochemical processes in lake ecosystems. However, there is little information about the vertical distribution of microbial community along lake sediment profile. In this study, we investigated the abundance and structure of pristine sediment bacterial communities along a depth gradient (0?20 cm) in a freshwater lake Puma Yumco and a saline lake AWongco on the Tibetan Plateau. [Methods] Real-time quantitative PCR (qPCR) and denaturant gradient gel electrophoresis (DGGE) were used to determine the bacterial abundance and community structure, respectively. [Results] Bacterial abundance consistently decreased along vertical depth in the two lake sediments and the abundance decreased from 1012 to 1010 in freshwater lake and from 1011 to 108 in saline lake, respectively. Bacterial abundances in freshwater lake were one order of magnitude higher than those in saline lake at each vertical depth. DGGE analysis showed that the bacterial richness was significantly higher (p=0.014) in freshwater lake than saline lake sediments; the bacterial community composition was clearly different between these two lake sediments, and the communities differed between upper (0?7 cm) and lower (7?20 cm) depths. Phylogenetic analysis showed that Gamma-proteobacteria, Bacteroidetes, Deinococcus-Thermus and Cyanobacteria were present in saline sediments while Delta- and Beta-proteobactria, Acidobacteria and Chloroflexi were only detected in freshwater sediment. [Conclusion] These results indicated that bacterial abundance and community structure differed dramatically between freshwater lake and saline lake sediments, and the microbial community composition also differed along the depth of sediments. Our results could provide the scientific base on how microbes in lake ecosystems respond to climate change on the Tibetan Plateau.

Abstract:

Abstract:[Objective] The aim of this study was to screen a low pH, lactic acid and succinic acid tolerant strain from the artificial acidic ecosystem. [Methods] A strain resistant to low pH, lactic acid and succinic acid was isolated from the artificial acidic ecosystem by acidic plates. We identified the strain by morphological and physiological traits, combined with 18S rDNA gene sequence and phylogenetic trees. [Results] A strain named WJ-2 with low pH, lactic acid and succinic acid tolerance was obtained and identified as Saccharomyces cerevisiae. Its optimal growth temperature was 30 °C, and it could survive in acidic plate at pH 2.5 and grow in the plate with a lactic acid concentration of 9% (w/v). WJ-2 also showed a succinic acid tolerance (8% succinic acid, w/v). WJ-2 also displayed a relative neutral intracellular pH when being challenged at pH 2.5, 9% lactic acid and 8% succinic acid. [Conclusion] Artificial ecosystem is a good alternative to screen strain with specific characteristics.

Abstract:[Objective] Heterofermentative lactic acid bacteria (LAB) can convert fructose to mannitol efficiently using the intracellular mannitol dehydrogenase enzyme, but fructose as a substrate is relatively expensive and not suitable for industrial production. In order to reduce cost, inexpensive substrates must be selected. Sucrose, abundantly in nature, is relatively cheap and can be used by recombinant Escherichia coli to produce mannitol. Sucrose hydrolase and mannitol dehydrogenase are the key enzymes to convert sucrose into mannitol. This paper was focused on the construction of sucrose hydrolase and mannitol dehydrogenase co-expression strain. [Methods] The target genes sacA and mdh, 1 502 bp and 1 032 bp respectively, were derived from the Lactobacillus plantarum and Lactobacillus buchneri. The genes were cloned into the expression vector pET-28a(+), resulting in the generation of the recombinant expression vector pET-28a-sacA-mdh, which was transformed into the E. coli BL21. The expression of the target protein was analysed by SDS-PAGE and the enzyme activity measurement. [Results] SDS-PAGE showed that the molecular weight of the expressed protein was 55.1 kD and 37.8 kD, respectively, which was consistent with the expected molecular weight, demonstrating the expression of genes sacA and mdh. The enzyme activity of sucrose hydrolase and mannitol dehydrogenase was 25.78 U/mL and 14.56 U/mL, respectively. The concentration of mannitol reached 45.19 g/L and the conversion was 37.66% after optimizing the fermentation conditions. [Conclusion] Compared with the mannitol production by LAB fermentation using sucrose, the yield was increased six-fold, with the advantages of short fermentation period and high stability. The successful construction of recombinant strain laid the foundation for the industrial production of mannitol.

Abstract:[Objective] Sucrose:sucrose 1-fructosyltransferase (1-SST) catalyzes the transfer of a fructosyl residue from one sucrose to another sucrose, forming 1-kestose and glucose. 1-Kestose has the highest prebiotic activity among fructooligosaccharides. In this study, 1-SST displayed on the cell-surface of Yarrowia lipolytica was used to prepare 1-kestose. [Methods] 1-SST gene from Lactuca sativa was cloned into the surface-display vector and expressed in the cells of Y. lipolytica. Biochemical characteristics of the displayed 1-SST were investigated with sucrose as its substrate. [Results] Immunofluorescence microscopy assay and high performance liquid chromatography (HPLC) indicated that the expressed protein was displayed on the cell-surface of Y. lipolytica and possessed 1-SST activity. The displayed 1-SST showed the highest activity at 45 °C and pH 7.5. The activity of the displayed 1-SST was inhibited by Zn2+ and Cu2+, while stimulated by Ca2+. The enzyme activity reduced 50% of initial activity after the displayed 1-SST was repeatedly used for seven times. The highest content of 1-kestose reached 20.8 mmol/L after the reaction mixture containing the displayed 1-SST and 3% sucrose was incubated at 40 °C for 30 min. [Conclusion] 1-SST was successfully expressed and displayed on the cells of Y. lipolytica, and the fructosyltransferase activity was detected. The surface-displayed 1-SST as a whole-cell catalyst can be applied to the 1-kestose preparation.

Abstract:[Objective] In order to improve the production of proteinase K and setup purification method. [Methods] We first optimized the codons of proteinase K gene and transfered it into Pichia pastoris (GS115) to realize secretory expression. And culture conditions including methanol concentration, temperature and pH were investigated. The purification methods, such as ammonium sulfate precipitation, affinity chromatography, were further optimized. [Results] Through the optimization of codons of proteinase K gene and cultural conditions, we obtained high-level expression of proteinase K. The results showed optimal fermentation condition was supplement of methanol 0.75%, fermentation temperature 25 °C and pH 7.0. The yield of proteinase K was 2.2 g per liter under the optimized fermentation condition. The efficient purification way is Ni-NTA affinity chromatograph after comparing with the other methods. [Conclusion] The results showed that proteinase K can be expressed at high level expression in P. pastoris and can be efficient purified with Ni-NTA affinity chromatograph.

Abstract:[Objective] A bacterial strain, L206, which could degrade seaweed polysaccharides was isolated from the rotten brown algae. This research aims to analyze its ability to degrade different polysaccharides of seaweed. [Methods] The morphologic, biochemical and physiological characteristics and 16S rRNA gene were analyzed to identify the taxonomic position of strain L206. Then the activity of seaweed polysaccharide degrading enzyme was measured by DNS. [Results] The bacterial strain was a Gram-negative short bacillus. Its logarithmic growth phase was 3?21 h, with NaCl concentration range from 0 to 3% (w/v) for suitable growth. Phylogenetic analysis based on 16S rRNA gene sequence comparisons indicated that the strain L206 was Agarivorans albus. The comprehensive enzyme activity reached maximum level after strain L206 was induced for 72 h by the powder of Laminaria japonica, amylase present the highest enzymatic activity (28.17 U/mL), and followed by xylanase (23.83 U/mL). [Conclusion] As a multi-functional polysaccharide-degrading bacterium, Agarivorans albus L206 shows a special ability to degrading brown algae polysaccharide and has a great development potential.

Abstract:[Objective] To understand the diversity of cultivable bacteria associated with Atrina pectinata collected from the tidal flat of Naozhou Island (20°52′–20°56′N, 110°33′–110°38′E) in the South China Sea. [Methods] Bacteria strains were isolated from homogenates of the sample by using the conventional culture-dependent method and then investigated by using phylogenetic analyses based on 16S rRNA gene sequence comparisons. [Results] We isolated 125 bacteria strains from the sample on MA (marine agar), MH (moderate halophilic medium agar) and NA (nutrient agar) supplemented with 0–25% (W/V) NaCl. Based on partial morphological, physiological and biochemical characteristics, out of them, 90 strains were selected and subjected to a molecular systematic study based on 16S rRNA gene sequences. The results showed that the 90 isolates were members of 10 genera (Marinobacter, Chromohalobacter, Halomonas, Salinivibrio, Vibrio, Bacillus, Halobacillus, Virgibacillus, Staphylococcus, Micrococcus) of 6 families (Alteromonadaceae, Halomonadaceae, Vibrionaceae, Bacillaceae, Staphylococcaceae, Micrococcaceae) in 3 phylogenetic groups (Gamma-proteobacteria, Firmicutes, Actinobacteria). The most abundant and diverse isolates were within the phylum Firmicutes (56 strains, 62.2%) and the subphylum Gamma-proteobacteria (31 strains, 34.5%). The results of phylogenetic analyses suggested that there were obvious genetic divergences between most isolates and their closestly related type strains (16S rRNA gene sequence similarities ranging from 95.7%–99.9%). The results also showed that, out of the 90 isolates, at least 5 JSM strains (112019, 112024, 114045, 114058, 114083) should represent potential new taxa. Strain JSM 112024 could represent a novel genus in the family Halomonadaceae, and strains JSM 112019, JSM 114045, JSM 114058 and JSM 114083 could represent four novel species with in 4 characterized genera Salinivibrio, Bacillus, Halomonas and Virgibacillus, respectively. [Conclusion] There are abundant bacterial species diversity and phylogenetic diversity in the Atrina pectinata.

Abstract:[Objective] Understanding the characteristics of simultaneous carbon and nitrogen removal under different conditions. [Methods] We took strain Y5, which was isolated in the medium with sodium acetate as the sole carbon source and capable of removing carbon and nitrogen simultaneously, as the model microorganism in this study. The 16S rRNA gene sequence of strain Y5 was analyzed. The carbon and nitrogen removal dynamics of strain Y5, as well as the influencing factors such as carbon source, ratio of carbon to nitrogen (C/N), dissolved oxygen concentration (DO), temperature, and pH were investigated. [Results] Strain Y5 belonged to Alcaligenes faecalis. Compared with glucose and other organic acids, strain Y5 showed higher total organic carbon (TOC) and NH4+-N removal rates in the medium with sodium acetate as the sole carbon source. When the initial TOC and NH4+-N were 1 000 mg/L and 110 mg/L, the NH4+-N, TOC and TN removal rates were 99.54%, 92.95% and 86.55% after 48 hours aerobic incubation, respectively. [Conclusion] Alcaligenes faecalis Y5 had efficient carbon and nitrogen simultaneous removal ability when taking sodium acetate as the sole carbon source and its optimal conditions were C/N=10, pH 7?8, DO>6.20 mg/L, 30 °C.

Abstract:[Objective] In order to understand the diversity and succession change of endophytic fungal communities of Aloe barbadensis at different habitats. [Methods] Healthy perennial samples were collected in Yunnan, Sichuan, Guangdong and Shaanxi provinces. The endophytic fungi were isolated from the foliage and roots of the samples. Then they were identified based on morphological and molecular methods. And the endophytic fungal communities were analyzed by statistical?evaluation. [Results] A total of 1 442 isolates were obtained which were belonged to twenty-nine different genera. Among which 96.88% only been observed to produce asexual or no spores, others were belonged to Ascomycotina (0.83%), Basidiomycotina (0.07%) and Zygomycota (2.22%) respectively. The Alternaria (35.63%), Fusarium (12.69%) and Phomopsis (11.65%) were the dominant genera. [Conclusion] The community of endophytic fungi from Aloe barbadensis of Yunnan and that of Sichuan has the highest similarity (Cs=0.88), while the community similarity of Guangdong and that of Yunnan was the lowest (Cs=0.73). Alternaria, Fusarium and Rhizoctonia were the dominant genera in root, but Alternaria, Phomopsis and Phoma were the primary one in foliage. Additionally, the isolation rate of Hypomycetes was the highest (31.42%) in spring, but that of Coelomycetes (31.01%) was the highest in autumn.

Abstract:[Objective] In order to investigate bacteria diversity and community composition in Bole river entrance soil of the Ebinur Lake wetland National Nature Reserve, Xinjiang. [Methods] Total DNA was directly extracted from the soil of the Ebinur Lake wetland Bole river entrance using the culture independent method. 16S rRNA gene was amplified using bacterial primer set Eubac27F and Eubac1492R. 16S rRNA gene clone library was constructed. Positive clones were identified by amplified rDNA restriction analysis (ARDRA) using Msp I and Afa I, and unique rDNA pattern clones were sequenced, analysed, and then the phylogenetic tree was constructed. [Results] seventy-five different clones of Macrorestriction Map was classified into 58 operational taxonomic units (OTU), which were associated with 8 phyla by phylogenetic analysis, including Chloroflexi, Cyanobacteria, Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, Verrucomicrob and Gemmatimonadetes. Among them, the most abundant phyla was Proteobacteria, followed by Bacteroidetes, accounting for about 65% of the total clones. [Conclusion] The bacterial diversity is abundant in the Ebinur Lake wetland Bole river entrance soil, and exist a certain amount of new unknown taxon in this environment.

Abstract:[Objective] The influence of different metal ions on the growth and nitrogen removal ability were studied to identify the suitable metal ions and their concentrations for strain C16. [Methods] Mg2+, Mn2+, Fe2+, Cu2+ and Zn2+ ions were selected to study their influence on the growth, nitrogen removal ability, NO2?-N accumulation and activity of relative enzymes of strain C16. [Results] Mg2+ significantly promoted the growth and NH4+-N oxidation rate of strain C16; C16 could not grow in higher concentrations of Mn2+; lacking of Fe2+ in original medium inhibited the growth and NH4+-N oxidation rate of C16; adding 0.1 mmol/L Cu2+ in the original culture medium could stimulate the growth and nitrogen removal rate of strain C16, meanwhile NO2?-N and NH2OH were only present in trace amounts; the existing of Zn2+ of different concentrations inhibited the growth and NH4+-N oxidation rate of C16. A further enzyme testing results showed that, 0.1 mmol/L Mg2+ promoted the activity of hydroxylamine oxidase (HAO); 0.1 mmol/L Cu2+ promoted nitrate reductase (Nar) and nitrite reductase (Nir) activity. [Conclusion] Mg2+ was necessary for the growth and nitrogen removal of strain C16. The addition of Cu2+ could avoid excessive accumulation of nitrite.

Abstract:[Objective] To isolate and screen the efficient phenol-degrading microorganisms from the coal chemical wastewater and preliminary investigate the feasibility to construct the bioaugmentation process combined with microorganisms and DTRO technology for phenolic wastewater treatment. [Methods] The phenol concentration gradient medium were used for isolation and screening of phenol-degrading microorganisms. The strains were preliminary identified based on the cell electron microscopy observation, physiological and biochemical characteristics analysis and 16S rRNA gene phylogenetic tree construction. The bioaugmentation-DTRO process was built combined with high efficient phenol-degrading bacteria inocula and disc-tube reverse osmosis (DTRO) technology and this system was on trial for phenolic wastewater treatment. [Results] Seven bacteria strains were purified and among which strain Phe-03 and Phe-05 have the high-efficiently phenol degradable potential and can use phenol as the sole carbon source. The strain Phe-03 was preliminary determined as a strain of Agromyces and the Phe-05 as a strain of Corynebacterium. With initial 1 300 mg/L phenol concentration, the phenol degradation rate of the above two strains reached more than 70% within 44 h and over 90% at 76 h. So far, the phenol degradation activities of Agromyces genus microbes have not been reported. The new bio-augmentation process can not only effectively remove phenolic compounds in wastewater, reduce pollution of reverse osmosis membrane but also increase membrane permeability. [Conclusion] This research indicated that the bioaugmentation process can be built combined with microbial and DTRO technology for phenolic wastewater treatment. This work can provide an alternative idea for the study of phenolic wastewater treatment technology.

Abstract:[Objective] In order to lay the foundation for the further development and utilization of biocontrol strains with good colonization ability, bacterial strains with antifungal activity were isolated, screened and identified from soil. [Methods] Antagonistic experiment was used to screen the specific bacteria against pathogenic fungi and evaluate its inhibitory ability. The strain was classified and identified by morphological characteristics, physiological and biochemical characteristics, sequencing of 16S rRNA gene and analysis of sequences similarity in GenBank. Protease activity of the test strain was measured by Folin-Ciocalteu method. [Results] Brevibacillus laterosporus, preservation number AMCC 100017, was isolated from various kinds of?soil in Tai’an, Shandong province. Plate confrontation experiment indicated that the strain has strong antagonistic effect against various plant pathogenic fungi, especially Fusarium. In addition, it was also verified that the strain could produce highly reactive extracellular protease. [Conclusion] Brevibacillus laterosporus AMCC 100017 is a biocontrol strain wih the development and utilization potential against fungal diseases of crops and fruit trees, as well as the biological control of nematodes.

Abstract:[Objective] Based on a 6-years greenhouse cropping field, the objective of the present study was to find out the differences of the structure and function of denitrifier community under different carbon and nitrogen managements. [Methods] We used terminal restriction fragment length polymorphism (T-RFLP) and denaturing gradient gel electrophoresis (DGGE) methods to analyze the structure of microbial communities containing nirK/nirS and nosZ, respectively, a robotized incubation system to measure NO/(NO3?+NO2?) and N2O/(N2O+N2) product ratio and an acetylene inhibition method to determine denitrification enzyme activity. [Results] Conventional N management (CN) significantly changed the structure of denitrifier communities containing nirK and nosZ and increased the NO/ (NO3?+NO2?) and N2O/(N2O+N2) product ratio. nirS-denitrifiers were less affected by carbon and nitrogen managements. Reduced N (RN) and reduced N plus straw (RN+S) management had significant changed the denitrifier communities containing nirK and nosZ and reduced NO/(NO3?+NO2?) and N2O/(N2O+N2) product ratio compared with CN treatment. In contrast to CN and RN treatments, RN+S significantly increased denitrification enzyme activity. [Conclusion] Conventional N management significantly changed the structure and function of denitrifier community, and promoted the formation of NO and N2O. RN and RN+S managements could form new denitrifier community structure and reduced the risk of NO and N2O emissions. In addition, straw application promoted potential denitrification rates and reduced the risk of NO3? leaching in greenhouses.

Abstract:[Objective] Selecting biocontrol agents for preventing three kinds of soil-borne diseases (Fusarium oxysporum, Sclerotinia sclerotiorum and Rhizoctonia solani), promoting plant growth and clarifying their inhibitory efficiency as well. [Methods] Seventeen plant growth promoting rhizobacteria (PGPR) strains, acquired from preliminary studies, were used to test antagonism on pathogenic fungi by panel confrontation method and to measure the inhibition of mycelial growth by the PGPR strains. [Results] There were six strains efficiently antagonized Rhizoctonia solani. Among the six strains, the inhibition rate FX2 and LM4-3 was higher which could rise up to 73.82%. Seven strains efficiently antagonized Fusarium oxysporum, the inhibition rate of FX2 reached 66.81%. Four strains efficiently antagonized Sclerotinia sclerotiorum, the inhibition rate of strain LHS11 reached 85.71%. The strains of JM170 and LHS11 could prevent disease by secondary metabolites. All strains had a certain impact on mycelial growth of pathogenic fungi. [Conclusion] Strains LHS11 and FX2 that were screened had better biocontrol effects on three soil-borne fungous pathogen.

Abstract:[Objective] To isolate specific bacteria capable of biotransforming isoflavones daidzein and genistein from fresh feces of rabbit. [Methods] In an anaerobic chamber, fresh fecal samples of rabbit were diluted before being spread on agar plate. Single colonies were picked randomly and incubated with daidzein or genistein. High performance liquid chromatography (HPLC) was used to detect whether the isolated bacteria were able to biotransform the substrate daidzein or genistein. [Results] A Gram-positive obligate anaerobic bacterium, which we named AUH-JLR41 (KJ188150), capable of biotransforming isoflavones daidzein and genistein was isolated. Based on the HPLC retention time, UV spectra and electrospray ionization mass spectrometry (ESI-MS) analysis, the metabolites of daidzein and genistein were identified as dihydrodaidzein (DHD) and dihydrogenistein (DHG), respectively. Chiral stationary-phase HPLC successfully separated the two peaks which had the same peak area, indicating that the enantiomeric excess of biosynthesized DHD and DHG was zero. Biotransformation kinetics showed that daidzein was reduced to DHD completely after 48 h incubation and genistein was reduced to DHG after 72 h incubation under anaerobic conditions. Moreover, the maximal concentrations of daidzein and genistein that strain AUH-JLR41 was able to convert were 0.6 mmol/L. BLAST search on the GenBank revealed that the 16S rRNA gene sequence for strain AUH-JLR41 had the highest similarity to that of Slackia equolifaciens DZE (EU377663), the similarity of which was 99.6%. [Conclusion] Bacterium strain AUH-JLR41 isolated from rabbit feces was able to reduce isoflavones daidzein and genistein to DHD and DHG, respectively, under anaerobic conditions.

Abstract:[Objective] This study aimed to investigate the diversity of intestinal Lactobacillus in normal diet rats (NDR), high-fat diet rats (HFDR) and antibiotic diet rats (ADR). [Methods] Culture-dependent and culture-independent methods (16S rRNA gene sequencing, DGGE and q-PCR) were applied to isolation, identification and diversity analysis of intestinal Lactobacillus in above three groups. [Results] According to the 16S rRNA gene sequencing analysis, L. johnsonii, L. murinus, L. acidophilus, L. reuteri, L. plantarum, L. intestinals, L. animalis and L. vaginalis were isolated from the intestinal of NDR. Whereas L. animalis were not able to find in HFDR, L. intestinals and L. vaginalis were not isolated from ADR. The DGGE results showed that there was an obvious contrast in the composition of intestinal Lactobacillus among 3 groups, and a high similarity in the same group as well. Comparing the richness of Lactobacillus in three groups, ADR was the lowest one. Moreover, the intestinal Lactobacillus of NDR owed the highest diversity than the others. The q-PCR data indicated that the population of Lactobacillus in NDR was higher than that in other two groups, there was a significantly different (P<0.01) among three groups. [Conclusion] The diversity of the intestinal Lactobacillus can be reduced with the interference of high-fat diet or antibiotic.

Abstract:[Objective] To study the effect of type III secretion system (TTSS) inhibitors on virulence factors, TTSS, bacterial flagella and pilin, of Pseudomonas aeruginosa PAO1. [Methods] The transcriptional reporters of exoT and exoY genes were used to monitor the exoT and exoY expression in the wild type strain PAO1 supplemented with TTSS inhibitors. The protein level of FliC was analyzed by SDS-PAGE. The twitching motility mediated by bacterial pilin was examined on the BM2 medium. [Results] Transcriptional fusion assay indicated that the expression of exoT and exoY was decreased when the TTSS inhibitors were supplemented. Although the production of PcrV was not changed in the cells when compounds TS52, TS53 and TS94 were added in the medium, the translocation of PcrV protein in the medium was decreased. The level of flagella structural protein FliC was decreased when the compound TS53 was supplemented in the medium. In addition, compounds TS52, TS53 and TS88 inhibited the ability of twitching motility, whereas TS94 increased the twitching motility. [Conclusion] Besides the TTSS effector genes, TTSS inhibitors influence other virulence factors, such as flagella and type IV pilus-dependent twitching motility. These data will provide the theoretical basis for further clinical trials.

Abstract:[Objective] To study the infection by Legionella pneumophila and the relative biological activities between bacteria and host cells in real time. [Methods] We constructed a strain of L. pneumophila that can stably express green fluorescent protein by method of gene knockout and retro-complementation, and established an infection model with murine Raw264.7 macrophage. [Results] The recombinant strain was applied in cell infection successfully. The entire process of infection can be observed in real time by fluorescence microscope, including the variety of bacterial cell morphology, intracellular proliferation, and lysing the host cells. [Conclusion] Our result provides a new mean to study the relationship between L. pneumophila and infected cells, the preparation of some models related to the drugs, and the drug screening and the mechanism of drug resistance.

Abstract:Algogenic organic matter (AOM) is released from algae cells. AOM could become a really significant pollutant when algae bloom. Membranes have emerged as a key means of water treatment with high efficiency and excellent effect. However, membrane fouling by AOM remains a critical factor limiting the efficiency of low pressure membrane treatment systems including microfiltration and ultrafiltration. This paper overviewed the components and categories of AOM, different membrane processes and former research conclusions. Some suggestion was also given to facilitate further study in this field.

Abstract:Cordyceps is precious Traditional Chinese Medicine, having a wide range of pharmacological effects such as anti-cancer, anti-bacterial, immune regulation, lowering blood lipid, lowering blood sugar, etc. Selenium is an essential trace element, which has broad physiological functions including anti-cancer, anti-oxidation, anti-aging, etc. and closely associated with a variety of diseases. Combinating Cordyceps fungus and Selenium to produce Selenium-enriched Cordyceps has important significance as medicine, health care products and food Selenium supplementation. This article gives a review on Selenium-enriched Cordyceps research in the past 20 years.

Abstract:Knowledge internalization is essential for improving students’ practical abilities. Microbiology, as the basic lesson for the undergraduates, has a variety of knowledge points. How to help the students internalize the knowledge is an important issue that needs teachers keep thinking and learning. This paper described our experience in internalizing knowledge by daily life examples and the feedback of the students indicated this teaching strategy was successful.

Abstract:[Objective] In this study, since hydrolyzed feather powder is a kind of good nitrogen-containing material rich in a wide variety of amino acids, it is used to replace the tryptone, a common component in Luria-Bertani medium for cultivating bacteria, thus to develop a novel bacterial culture medium and recycle the waste resource. [Methods] Absorbance at 600 nm of the fermentation broths detected by turbidimetry and culture-dependent method were used to analyze the effect of media on cell growth. [Results] Compared to the LB medium, no significant difference or more abundance in the growth of the tested bacteria was observed when peptone was completely replaced by hydrolyzed feather powder and the biomass of type strains (Escherichia coli and Bacillus subtilis) tested, increased by 21.59% and 27.83%, respectively. Results of bacteria-growth curves showed that a bit delay at the initial phase and an extended logarithmic phase of the tested strains were observed in the novel medium. However, the biomasses of the strains tested at stable phase in the novel medium were higher than those in the control. Meanwhile, results from culture-dependent method also showed that no significant differences for the number of type strains were observed between the two media. [Conclusion] In conclusion, the hydrolyzed feather powder was able to replace tryptone to create a novel low-cost but high-quality medium.

Abstract:[Objective] To study the effects of different stirrers on laccase production with white-rot fungus Cerrena unicolor Y-G07 during fermentation. [Methods] Y-G07 is a non-spore forming filamentous fungus, whose laccase synthesis is coupled with its cell growth. Considering the aerobic nature and shear force sensitivity of the strain, five different stirrers were designed to compare the effects on hyphal morphology, growth rate, dissolved oxygen, glycometabolism and laccase production. [Results] Different stirrers resulted in the difference in hyphal morphology, cell concentration, growth cycle, and thus affected laccase production. The six-hinge-blade DT602 impeller formed reticular mycelia with appropriate density, high concentrations of mycelium cells and less hypha fracture during fermentation. The laccase production was increased up to 690 U/mL, which is 54% higher than that by using usual Six-flat-blade impeller. [Conclusion] Proper design of agitator in fermentor can be favorable for aerobic and shear-force sensitive microorganisms.

Abstract:[Objective] This study aimed to develop a rapid and simultaneous detection method for Salmonella, Shigella, and Staphylococcus (S.) aureus in food. [Methods] Magnetic beads coated with speci?c antibodies were used to capture target pathogens from 250 mL at 37 °C. After quick DNA extraction, multiplex RT-PCR was applied to detect the target pathogens with three sets of specific primers and probes. [Results] The limit of detections of immunomagnetic separation (IMS)-multiplex real-time PCR (RT-PCR) method were 2.0 CFU/g for Salmonella, 6.8 CFU/g for shigella and 9.6 CFU/g for S. aureus. The sensitivity, specificity, and accuracy of this method were 99.2%, 100%, and 99.5%, respectively. One hundred fifty-one samples were tested using the IMS-multiplex RT-PCR and GB methods, and only one negetive deviation was detected. [Conclusion] The IMS-multiplex RT-PCR method with high sensitivity, specificity and accuracy could enable the simultaneous detection of Salmonella, Shigella, and S. aureus in food within 8 h and offers the opportunity for a quick response in an emergency when these bacteria are detected.