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     

Hydrophobically modified poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate): synthesis and viscosity of aqueous solution

BACKGROUND: Hydrophobically modified polyelectrolytes are widely used polymers due to their good water solubility, stretched configuration in water and strong hydrophobic association. The study reported here aimed at researching the double action of hydrophobic association and electrostatic effect of novel hydrophobically modified polyelectrolytes in solution. RESULTS: A series of novel hydrophobically modified polyelectrolytes were synthesized by micellar copolymerization with various feed ratios of sodium 2‐acrylamido‐2‐methylpropanesulfonate, N‐n‐dodecylamine and sodium dodecylsulfonate. Their structure was characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance and gel permeation chromatography, and the viscosities of their aqueous and salt solutions were studied. CONCLUSION: The results show that the addition of the hydrophobic comonomer results in a decrease in molecular weight (M_w). The smaller the initial number of hydrophobes in one micelle, the higher is M_w of the resulting copolymer. The viscosity of PAD‐1.73 polyelectrolyte is less sensitive to salt than those of the others. According to the zero shear viscosity and corresponding concentration, the critical cluster‐forming concentration, critical overlap concentration and critical entanglement concentration of these polymer solutions were determined. Moreover, in the dilute regime the viscosity decreases with increasing salinity, while in the semi‐dilute regime the viscosity decreases first and then increases. It is suggested that in dilute and semi‐dilute regimes, hydrophobic intramolecular association and intermolecular association dominate, respectively. Copyright © 2009 Society of Chemical Industry     

水解蛋白的苦味及消除方法

经酶法制备的水解蛋白往往带有苦味,其主要原因是蛋白质本身的一些疏水基团的作用:水解过程中影响苦味程度的主要因素是疏水基团的位置、水解度、pH用酸、原料的品质等.本文介绍了通过流水性吸附、掩蔽、专一性酶的应用以及选择性沉淀的方法消除或减轻水解蛋白的苦味.     

氨酯型疏水缔合水溶性聚合物的合成

采用自由基胶束聚合的方法合成了侧链上含有两个苯坏和长链烷基的氨酯型疏水缔合水溶性聚合物，探讨了不同侧链链长的疏水聚合物及不同表面活性剂下共聚物溶液的增粘效果，当侧链上烷基碳原子数n=8及用十二烷基苯磺酸钠作表面活性剂量，共聚物具有较好的增粘性能。对聚合物的合成条件进行了研究，结果表明合成聚合物的最佳实验条件为：引发剂浓度0.2%，疏水单体摩尔用量0.5%，丙烯酰胺（AM）浓度10％－15％，表面活性剂用量0.75%。     

α-Sulfonated fatty acid esters: I. Structural effects of sodium α-sulfonated fatty acid higher alcohol esters on surface-active properties and emulsification ability

The surface-active properties and emulsification ability of sodium α-sulfonated fatty acid esters, C_mH_2m+1CH-(SO₃Na)COOC_nH_2n+1, were studied as a function of the hydrophobic alkyl chainlength in the fatty acid (m=8−16) and the alcohol (n=8−18). As a result, it was discovered that sodium α-sulfonated fatty acid esters have a structural effect on the Krafft point different from that of amphiphiles with short alkyl chains. Moreover, some of the α-sulfonated fatty acid esters have quite low interfacial tensions, as well as non-foaming properties, which depend upon the total (m+n) number of carbon atoms in the alkyl chains.     

New modifications of poly(vinyl alcohol)s and their applications

Poly(vinyl alcohol) (PV-OH), prepared from poly(viny) acetate), is used widely in many industries. Various grades have been produced, with different degree of polymerization and degree of hydrolysis. Recently, novel modified (PV-OH)s with anion, cation, silanol or hydrophobic groups have been studied and developed. They have new properties in addition to those of ordinary PV-OH and have new applications. The methods of modification and the characteristics and some applications of the modified polymers are described.     

三种疏水催化剂耐氚辐照稳定性初步研究

为考察3种疏水催化剂Pt-SDB(SDB为苯乙烯-二乙烯苯共聚物)，Pt-PTFE（PTFE为聚四氟乙烯），Pt-C-PTFE 的耐氚辐照稳定性，将其置于1.26×10¹²Bq/L的氚水中静态辐照210 d后，对其催化交换性能及催化剂中残存氚进行分析。结果表明，3种催化剂在氚的β辐照下未发生裂解，催化剂中氚的残存量随催化剂比表面积的增加而增加，基本没有发生结构上的氚取代反应；但在氚水辐照后，3种疏水催化剂的交换性能出现了不同程度的变化，按单位质量Pt粒子计算，在测试不确定度范围内Pt-PTFE和Pt-C-PTFE的转化率没有发生明显变化，Pt-SDB(1)的转化率下降了11.2％，Pt-SDB(2)的转化率下降了16.9％。     

疏水性涂层的制备及防结霜性能

基于聚偏氟乙烯(PVDF)、纳米碳酸钙和十七氟癸基三甲氧基硅烷(FAS-17)制备了一种疏水性涂层。采用扫描电镜(SEM)分析,表明少量的FAS-17可改善CaCO3在PVDF中的分散状况和提高涂层表面与水滴的接触角,同时对涂层的力学性能没有影响。该疏水涂层可显著改善铜表面的防结霜性能。     

热氧化法制备透明超疏水ZnO薄膜

高透明性的无机超疏水薄膜材料具有广阔的应用前景，采用磁控溅射法制备出表面具有纳米结构的金属Zn前驱体薄膜，并利用在低气压5Pa，温度350℃热氧化方法对其采取了处理，获得了接触角为151°，可见光透过率达80％以上的超疏水ZnO薄膜。SEM表明薄膜由100nm短棒状的ZnO堆积而成，通过XRD，IR的测量与分析，进一步讨论了沉积条件及热氧化处理对超疏水透明ZnO薄膜形成机理。     

疏水网覆盖的开放微管道中的液体输运

考虑完全开放的微管道中液体输运不稳定,不利于生物气溶胶采样和监测的自动化集成,本文提出了用覆盖有疏水网的开放微管道来实现液体的可靠输运.通过理论分析得到了该微管道液体输运特性的估计公式,并用水作为试验介质对其输运特性进行了实验分析.分析实验显示,开放微管道中液体输运的稳定性依赖于栅网特性、液体性质和流动速度、管道尺寸和表面特性.栅网表面疏水性越好,孔径越小,微管道中液体的最大许可压强就越大,液体输运就会越稳定.对于孔径50 μm、表面涂覆有Teflon的栅网,最大许可压强可达2000 Pa.管道中的最大许可流速取决于管道尺寸和最大许可压强；对于较浅、较长的管道,最大许可流速较小.当液体流过干的疏水管道时,液体的表面张力会阻碍流动,管道截面尺寸越小,表面张力的阻碍效果越明显.