马尾松优良菌根真菌(S.l)液培条件的研究

作者经过对褐环乳牛肝菌［Ｓｕｉｌｕｓｌｕｔｅｕｓ（Ｌ．ｅｘＦｒ．）Ｇｒａｙ］的一系列研究，业已证明它是我国亚热带地区特有树种马尾松（ＰｉｎｕｓｍａｓｏｎｉａｎａＬａｍｂ．）共生的优良菌根真菌。它具有生长快速、繁殖容易、拮抗性强、适生范围广、制剂简便、...

Preparation of BCEC-Astrocyte Co-culturing Membrane Plate Insert

To prepare a hand-made micropore membrane culture plate insert forco-culture. Methods The plate insert was made using plastic centrifuge tube and micropore membrane.After seeding brain capillary endothelial cells (BCECs) on it (under the effect ofastrocyte-conditioned medium), the plate insert was assessed by analysis of trans-endothelialelectrical resistance (TEER). Results The plate insert has a stability of at least 15 d underculture condition. TEER increased significantly under co-culture condition from (66.1 +- 13.3)Ωcm^2 to (182.2 +- 6.7) Ωcm^2. Conclusion This micropore membrane culture plate insert can beeasily made, on which BCEC culture can be successfully performed. Moreover, it is adjustable andrecyclable. It follows that the plate insert is a useful tool for co-culture and the relatedresearch fields.

Production and characterization of exopolysaccharides in mycelial culture of Cordyceps sinensis fungus Cs-HK1 with different carbon sources

The effects of different carbon sources(sugars) on the production and molecular properties of exopolysaccharides(EPS) were evaluated in the mycelial liquid culture of a medicinal fungus Cordyceps sinensis Cs-HK1. Galactose or mannose was used(at 5 g·L^(-1)) as a secondary carbon source with glucose(35 g·L^(-1)) at the mass ratio of 1:7. Mannose was consumed notably since the first day of culture, but galactose was not even after glucose was exhausted.The volumetric yield of EPS in culture was increased slightly with the addition of galactose and decreased with mannose. The monosaccharide composition of EPS was also different, e.g., on day 8, the glucose contents of EPS were 76%with the addition of mannose, 59% with galactose, compared with 62% with glucose only. The molecular weight distribution of EPS was also affected by the secondary carbon source, being generally lower compared with that with glucose only. The results suggested that the addition of galactose improved the total yield of EPS in culture while mannose can improve the yield of glucan constituent of EPS.

Optimum Production and Characterization of an Acid Protease from Marine Yeast Metschnikowia reukaufii W6b

The marine yeast strain W6b isolated from sediment of the South China Sea was found to produce a cell-bound acid protease.The crude acid protease produced by this marine yeast showed the highest activity at pH 3.5 and 40 ℃.The optimal pH and temperature for the crude acid protease were in agreement with those for acid protease produced by the terrestrial yeasts.The optimal medium of the acid protease production was seawater containing 1.0% glucose, 1.5% casein, and 0.5% yeast extract, and the optimal cultivation conditions of the acid protease production were pH 4.0, a temperature of 25 ℃ and a shaking speed of 140 rmin-1.Under the optimal conditions, 72.5 UmL-1 of acid protease activity could be obtained in cell suspension within 48 h of fermentation at shake flask level.The acid protease production was induced by high-molecular-weight nitrogen sources and repressed by low-molecu-lar-weight nitrogen sources.Skimmed-milk-clotting test showed that the crude acid protease from the cell suspension of the yeast W6b had high skimmed milk coagulability.The acid protease produced by M.reukaufii W6b may have highly potential applications in cheese, food and fermentation industries.

Optimization of the Culture Conditions for the Endophytic strain 4-3

Bacillus amyloliquefaciens 4-3 is an excellent plant endophyte that can be used as a good raw material for microecological preparations.For this reason,it is important to optimize the culture conditions of this strain.The number of viable bacteria of strain 4-3 in this study was the evaluation index,and the culture conditions of the liquid fermentation were optimized by single factor experiment.The optimized culture condition was as follows:incubating temperature 32°C,initial pH value 7.2,rotation speed 220 r/min,inoculum concentration 3%and incubating 56 h,under which higher concentrations of Bacillus amyloliquefaciens could be obtained.

Isolation and Production of Novel β-galactosidase from a Newly Isolated, Moderate Thermophile, Bacillus sp. Strain B1.1

The enzyme β-galactosidase （lactase; EC 3.2.1.23） is a commercially important enzyme due to its various applications in dairy and food industries, which are based on the β-galactosidase-catalysed hydrolysis of lactose into glucose and galactose. The objectives of this work were to identify novel and attractive sources of this industrially relevant enzyme, and to study the effect of selected growth parameters （carbon source, lactose concentration, nitrogen source, peptone concentration, initial pH and temperature） on the formation of β-galactosidase. Based on a screening of isolates from Tha Pai hot spring, Mae Hong Son Province, Thailand, strain BI.1 was selected for further studies. Strain BI.1 is a Gram-positive, rod-shaped, catalase-positive bacterium that forms endospores. Based on the sequence of the 16S rDNA determined, this isolate is most closely related to Anoxybacillus sp. and Bacillus sp., and hence the strain is designated as Bacillus sp. B 1. I.β-Galactosidase was produced by this strain with lactose and peptone as carbon and nitrogen sources, respectively. Optimal enzyme production occurred at an initial culture pH of 8.5 and at 45 ℃. Under these optimum culture conditions, maximal volumetric and specific β-galactosidase activity of 0.478 U mL^-1 and 0.338 U mg^-1 protein, respectively, were obtained after 13 h of cultivation in a medium contain 2.5% lactose, 2.0% peptone, 0.3% K2HPO4, 0.1% KH2PO4 and 0.05% MgSOa·7H2O.

Tissue culture of three species of Laurencia complex

To establish a micropropagation system of three Laurencia complex species （Laurencia okamurai, Laurencia tristicha, and Chondrophvcus undulatus） by tissue culture techniques, we studied the regeneration characteristics and optimal culture conditions of axenic algal fragments cultured on solid medium and in liquid medium. Regeneration structures were observed and counted regularly under a reverse microscope to investigate the regeneration process, polarity and optimal illumination, and temperature and salinity levels. The results show that in most cultures of the three species, we obtained bud regeneration on solidified medium with 0.5% agar and in liquid medium. Rhizoid-like regeneration was filamentous and developed from the lower cut surface of fragments in L. okamurai, but was discoid and developed from the apical back side of bud regeneration in L. tristicha and C. undulatus. Regeneration polarity was localized to the apical part of algal fronds in all three species, and on fragments cut from the basal part of algae buds could develop from both the upper and the lower cut surfaces. Buds could develop from both the medullary and the cortical portions in L. okamurai and C. undulatus, while in L. tristicha, buds only emerged from the cortex. The optimal culture conditions for L. okamurai were 4 500 lx, 20℃ and 35 （salinity）; for C. undulatus, 4 500 lx, 20℃ and 30; and for L. tristicha, 4 500 lx, 25℃ and 30.

Protective effect of astrocyte-conditioned medium on neurons following hypoxia and mechanical injury

Objective： To investigate the protective effect of mouse astrocyte-conditioned medium （ACM） on hypoxic and mechanically injured neurons by a cell model in vitro, and to explore the possible mechanism. Methods： The model of hypoxic neuronal injury was caused by 3% 02 in three-gas incubator. Neurons were cultured with ordinary medium or 20% ACM respectively and randomly divided into hypoxic group （hypoxia for 4, 8, 24 h and marked as H4R0, H8R0, H24R0） and hypoxia reoxygenation group （H4R24, H8R24, H24R24）. Mechanical injury model was developed by scratching neurons cultured in 20% ACM or ordinary medium to different degrees. Neu- rons in both medium were divided into normal control group, mild, moderate and severe injury groups. The 20% ACM was added 24 h before hypoxia/reoxygenation or mechanical injury. The morphology and survival of neurons were observed and counted by trypan blue staining. The concentration of NO, lactic dehydrogenase （LDH） and membrane ATPase activity were detected by corresponding kits. Results： It was showed that 20% ACM can obviously promote the survival rate of hypoxia/reoxygenated neurons and scratched neurons as well. The morphology and num- ber of neurons exposed to hypoxia or scratch injury showed great difference between groups with or without ACM treatment. Compared with control group, the concentration of NO and LDH was much lower in hypoxic/reoxygenated neurons treated with 20% ACM, and the ATPase activity was higher. For the mechanical injury model, neurons with moderate injury also revealed a lower NO and LDH concen- tration than the control group. All the differences were sta- tistically significant （P〈0.05）. Conclusion： ACM can promote the survival and func- tional recovery of neurons following hypoxia or scratching to a certain degree. The mechanism may be associated with reducing the synthesis and release of NO and LDH as well as increasing the activity of membrane ATPase.

Stiffness heterogeneity-induced double-edged sword behaviors of carcinoma-associated fibroblasts in antitumor therapy

Carcinoma-associated fibroblasts(CAFs) function as a double-edged sword in tumor progression. However,factors affecting the transition between tumor promotion and inhibition remain to be investigated. Here, we found that the transition was determined by stiffness heterogeneity of the tumor stroma in which tumor cells and CAFs were grown.When tumor cells were grown on a rigid plastic substrate,supernatants from CAFs inhibited the cytotoxic effects of 5-fluorouracil. In contrast, when tumor cells were grown on a soft substrate(5.3 kPa), supernatants from CAFs grown on a soft substrate increased the cytotoxicity of 5-fluorouracil. The diverse effects of CAFs were mediated by mechanotransduction factors, including stroma stiffness-induced cytokine expression in CAFs and signal transduction associated with stress fiber formation of CAFs. Moreover, we found that the cytokine expression in CAFs was regulated by nuclear Yesassociated protein, which changed according to cell stiffness,as characterized by atomic force microscopy. Overall, these findings suggested that modulating the mechanotransduction of the stroma together with CAFs might be important for increasing the efficacy of chemotherapy.