沿海沙岸风蚀地黄泥客土和深埋造林效果分析

论述了广泛省汕头潮阳市田心镇华林管理区沙质海岸风蚀地试验示范林的造林存在蒸发量大于降水量,降水量过于集中,常年风大和冬连春旱等４个极为不利因素。试验采用黄泥客土和深埋造林可缓解这些不利因素,从而提高了造林成活率和保存率,是沙质海岸风蚀地造林的好方法。     

Generation of high rapamycin producing strain via rational metabolic pathway‐based mutagenesis and further titer improvement with fed‐batch bioprocess optimization

Rapamycin is a triene macrolide antibiotic produced by Streptomyces hygroscopicus. Besides its wide application as an effective immunosuppressive agent, other important bioactivities have made rapamycin a potential drug lead for novel pharmaceutical development. However, the low titer of rapamycin in the original producer strain limits further industrialization efforts and restricts its use for other applications. Predicated on knowledge of the metabolic pathways related to rapamycin biosynthesis in S. hygroscopicus, we have rationally designed approaches to generate a rapamycin high producer strain of S. hygroscopicus HD‐04‐S. These have included alleviation of glucose repression, improved tolerance towards lysine and shikimic acid, and auxotrophy of tryptophan and phenylalanine through the application of stepwise UV mutagenesis. The resultant strain produced rapamycin at 450 mg/L in the shake flask scale. These fermentations were further scaled up in 120 and 20,000 L fermentors, respectively, at the pilot plant. Selected fermentation factors including agitation speed, pH, and on‐line supplementation were systematically evaluated. A fed‐batch strategy was established to maximize rapamycin production. With these efforts, an optimized fermentation process in the larger scale fermentor was developed. The final titer of rapamycin was 812 mg/L in the 120 L fermentor and 783 mg/L in the 20,000 L fermentor. This work highlights a high rapamycin producing strain derived by mutagenesis and subsequent screening, fermentation optimization of which has now made it feasible to produce rapamycin on an industrial scale by fermentation. The strategies developed here should also be applicable to titer improvement of other important microbial natural products on an industrial scale. Biotechnol. Bioeng. 2010;107: 506–515. © 2010 Wiley Periodicals, Inc.     

Large scale transient expression with COS cells

We demonstrate here that transient expression with COS cells can be performed at the one litre scale for a period of more than 10 days. Cells grown in T225 flasks were transfected by electroporation, transferred into spinners, and then grown either in suspension or on microcarriers. A daily medium change significantly extented culture life and production time, compared with standard protocols.Concentrations of the product, the secreted fusion protein CD40-Fc, were comparable in microcarrier and suspension culture. Cultures were started in fetal calf serum containing medium and the subsequent production process was performed in a low protein serum free medium which allowed easy downstream processing. 10 litres of supernatant, collected from one transfected batch of cells, yielded 30 mg of purified and biologically active protein.In addition to developing a simplified protocol for generation of cells we also reduced the material (DNA, cuvettes) required for electroporation. Our results show that scale up of transient expression to the litre scale can be successfully acieved. This provides a new tool to generate milligram quantities of protein within weeks of gene cloning.     

喉返神经对大鼠甲状腺激素分泌的影响

观察了喉返神经对大鼠血清甲状腺素水平和甲状腺摄碘功能的影响：（１）切断大鼠单侧喉返神经后血清甲状腺素（Ｔ４）水平升高,如于切断后立即电刺激其外周端,在３０ｍｉｎ内血清Ｔ４水平甚至降至对照值之下,事先给以阿托品,可阻断电刺激引起的效应。（２）切断单侧喉返神经后该侧甲状腺摄碘增多,以上结果表明,喉返神经抑制甲状腺素的分泌,这作用可能是由Ｍ受体介导调节的。     

西江坪常绿阔叶林地表径流的研究

本文采用固定小区径流法,对常绿阔叶林及其皆伐迹地草坡地表径流进行了对比研究,结果表明:常绿阔叶林年径流量为9.79毫米,占大气降水量0.5％;较迹地草坡减少径流56.3％。径流的季节变化以夏、春、秋、冬依次递减;其中4—8月为径流高峰期,径流量占全年62.4—96.5％。常绿阔叶林对暴雨以下雨量级的削减作用显著;而对持续性大暴雨以上雨量级的削减作用不明显。     

Determination of aflatoxins in medicinal herbs by HPLC. An efficient method for routine analysis

A fast and easy to perform method for the routine determination of aflatoxins in medicinal herbs was developed. The described method involves a single-step extraction with a non-chlorinated solvent, an immunoaffinity clean-up and HPLC with fluorescence detection. Whilst assays with naturally contaminated and with spiked samples of several herbs showed that the recoveries were somewhat low and dependent on the kind of sample and the degree of grinding, the intra-batch reproducibility was good, allowing a reliable quantitation by the standard-addition method. Good linearity, repeatability and accuracy were demonstrated in assays involving several medicinal herbs. The limit of quantitation was of the order of 0.05-0.1 ng/g, being dependent of the species analysed, and the method required no tedious concentration or back-extraction steps.     

Robust scale-up of dead end filtration: impact of filter fouling mechanisms and flow distribution

Robust design of a dead end filtration step and the resulting performance at manufacturing scale relies on laboratory data collected with small filter units. During process development it is important to characterize and understand the filter fouling mechanisms of the process streams so that an accurate assessment can be made of the filter area required at manufacturing scale. Successful scale-up also requires integration of the lab-scale filtration data with an understanding of flow characteristics in the full-scale filtration equipment. A case study is presented on the development and scale-up of a depth filtration step used in a 2nd generation polysaccharide vaccine manufacturing process. The effect of operating parameters on filter performance was experimentally characterized for a diverse set of process streams. Filter capacity was significantly reduced when operating at low fluxes, caused by both low filtration pressure and high stream viscosity. The effect of flux on filter capacity could be explained for a variety of diverse streams by a single mechanistic model of filter fouling. To complement the laboratory filtration data, the fluid flow and distribution characteristics in manufacturing-scale filtration equipment were carefully evaluated. This analysis identified the need for additional scale-up factors to account for non-uniform filter area usage in large-scale filter housings. This understanding proved critical to the final equipment design and depth filtration step definition, resulting in robust process performance at manufacturing scale.     

Oxygen transport and cell viability in an annular flow bioreactor: comparison of laminar Couette and Taylor-vortex flow regimes

Rotating wall vessel bioreactors have been proposed as a means of controlling the fluid dynamic environment during long-term culture of mammalian cells and engineered tissues. In this study, we show how the delivery of oxygen to cells in an annular flow bioreactor is enhanced by the forced convective transport afforded by Taylor vortex flows. A fiberoptic oxygen probe with negligible lag time was used to measure the dissolved oxygen concentration in real time and under carefully controlled aeration conditions. From these data, the overall mass transfer coefficients were calculated and mass transport correlations determined under laminar Couette flow conditions and discrete Taylor vortex flow regimes, including laminar, wavy, and turbulent flows. While oxygen transport in Taylor vortex flows was significantly greater, and the available oxygen exceeded that consumed by murine fibroblasts in free suspension, the proportion of cells that remained viable decreased with increasing Reynolds number (101.8 < Rei < 1018), which we attribute to the action of fluid shear stresses on the cells as opposed to any limitation in mass transport. Nevertheless, the results of this study suggest that laminar Taylor-vortex flow regimes provide an effective means of maintaining the levels of oxygen transport required for long-term cell culture.