Evaluation of the impact of lipid fouling during the chromatographic purification of virus‐like particles from Saccharomyces cerevisiae

BACKGROUND: Production of recombinant virus‐like particles (VLPs) in yeast expression systems for use as vaccines requires cell disruption and detergent‐mediated steps to liberate the product. Typically, these release high levels of cellular components such as lipids that foul chromatography columns. This study compares the impact of applying lipid‐rich and lipid‐depleted feedstocks to hydrophobic interaction chromatography columns to quantify the loss of performance caused by the presence of host lipids over a total of 40 operational cycles. RESULTS: VLP binding capacity in the lipid‐rich feed was significantly lower than for the lipid‐depleted feed, with greater than 24% of the lipids remaining in the column after each cycle. Triacylglycerol was found to be the major contaminant. The effectiveness of subsequent caustic clean‐in‐place was limited, resulting in column hydrophobicity increasing over repeated loading cycles. This improved the effective VLP binding capacity and affinity, but also made product elution more difficult, and recovery decreased by more than 70% over the 40 cycles. CONCLUSION: Host cell lipids cause major fouling problems during VLP purification. Instead of screening for better CIP conditions, priority should be given to identifying suitable upstream lipid removal strategies in order to maintain column performance and so yield more economically viable processes. Copyright © 2009 Society of Chemical Industry     

A study on dynamic rheological characterisation of electron beam crosslinked high vinyl styrene butadiene styrene block copolymer

Crosslinking of elastomers using electron beam radiation has several advantages over conventional method. It is accomplished much faster, in a more environmental friendly approach and in a much simpler manner. When fast moving electrons that are generated from electron accelerators are targeted on a polymer matrix, they primarily crosslink the polymer. However, in the process, some chain scission may also occur. In this work, a high vinyl (~50%) styrene–butadiene–styrene (S–B–S) block copolymer was used as the base polymer. Radiation doses were varied from 25 to 300 kGy. A detailed investigation was made to understand the effect of electron beam radiation on the rheological properties such as storage modulus, loss modulus, storage viscosity and complex viscosity of the block copolymer under strain and frequency sweeps performed in a Rubber Process Analyzer (RPA). Recyclability of the crosslinked S–B–S polymer was also explored by RPA and mechanical studies.     

Effect of heat pre-treatment temperature on isolation of hydrogen producing functional consortium from soil

A functional hydrogen producing consortium was isolated from soil by heat pre-treatment technique and hydrogen production at different substrate concentration was evaluated. The forest soil was heat pre-treated at 65, 80, 95, 105 and 120 °C temperature for 1 h. As revealed by PCR-DGGE analysis and hydrogen yield, the hydrogen producing microbial community changed with increase in heat pre-treatment temperatures giving potential hydrogen producing consortium at 95–105 °C soil pre-treatment. The maximum hydrogen production rate, hydrogen yield and cumulative hydrogen with 15–20 g glucose were 1390–1576 mL/L/day, 1.83–1.93 mol H₂/mol glucose, and 2966–3146 mL H₂/L, respectively. The metabolic pathways shifted from ethanol-type to acetate–formate type as soil pre-treatment temperature increased from 65 to 120 °C. The soil heat pre-treatment approach is effective for isolating hydrogen producing natural Clostridium consortium from the soil as enumerations of the functional strains need specific temperature range to florish.     

5th International Symposium on Electrochemical Impedance Spectroscopy Marilleva (Trento), Italy, June 2001

Preface

5th International Symposium on Electrochemical Impedance Spectroscopy Marilleva (Trento), Italy, June 2001     

美工常用硬件参数面面观

对于一个从事计算机图形方面工作的美术工作者来说，手中的电脑无疑是工作中的左膀右臂。而其在图形图像方面的处理能力则是美工最关注的。借本次专题企划介绍美工相关硬件之机，笔者将一些显卡、绘图板、扫描仪的相关参数向读者朋友们做一介绍，希望能对各位的日常采购有所帮助。     

浅谈图形工作站的选购

图形工作站主要被用于CAD（辅助图形设计）、DCC（数字内容创作）、虚拟仿真以及一些后期制作和特殊的研究领域（比如医学）。比起普通PC，图形工作站属于相对高端的产品．也正因为如此．它一直蒙着神秘的面纱．让普通消费者仿若隔湖观花、看不真切。     

Inducing safer oblique trees without costs

Abstract: Decision tree induction has been widely studied and applied. In safety applications, such as determining whether a chemical process is safe or whether a person has a medical condition, the cost of misclassification in one of the classes is significantly higher than in the other class. Several authors have tackled this problem by developing cost-sensitive decision tree learning algorithms or have suggested ways of changing the distribution of training examples to bias the decision tree learning process so as to take account of costs. A prerequisite for applying such algorithms is the availability of costs of misclassification. Although this may be possible for some applications, obtaining reasonable estimates of costs of misclassification is not easy in the area of safety .
This paper presents a new algorithm for applications where the cost of misclassifications cannot be quantified, although the cost of misclassification in one class is known to be significantly higher than in another class. The algorithm utilizes linear discriminant analysis to identify oblique relationships between continuous attributes and then carries out an appropriate modification to ensure that the resulting tree errs on the side of safety. The algorithm is evaluated with respect to one of the best known cost-sensitive algorithms (ICET), a well-known oblique decision tree algorithm (OC1) and an algorithm that utilizes robust linear programming.     

我来教你榨——比WinRAB还强的UHARC GUI

在日常的电脑操作中，我们常常需要将一些大文件进行压缩保存或者传送给其他人，WinRAR是我们使用最多的一个压缩工具，但是WinRAR压缩比并不高．往往压缩后的文件并没有多大改变．有没有一个工具能真正实现高倍压缩呢?这里就为大家介绍一款比WinRAR还强的“世界上压缩比最高”的软件——UHARC GUI，它能够“榨”干你文件中的“水分”，真正实现“浓缩的都是精华”！     

Performance-Based Optimization of Land and Water Resources within Irrigation Schemes. II: Application

The area and water allocation model which uses simulation–optimization technique for optimum allocation of land and water resources to different crops cultivated in different allocation units of the irrigation scheme was modified to include both productivity and equity in the process of developing the allocation plans for optimum productivity and/or maximum equity. This paper illustrates the potential of this approach with the help of a case study on Nazare medium irrigation scheme in India. The allocation plans were developed for optimization of different performance parameters (productivity and equity) for different management strategies based on irrigation amount and irrigation interval and cropping distribution strategies of free and fixed cropping. The results indicated that the two performance objectives productivity and equity conflict with each other and in this case, equitable water distribution may be preferred over free water distribution at the cost of a small loss in productivity. Though these results relate to one case study, they show the value of the approach of incorporating productivity and equity in the allocation process with the help of the simulation-optimization model described in the companion paper.