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Although a number of previous studies have demonstrated that solution pH can have a dramatic effect on protein transport through ultrafiltration membranes, the exact origin of this behavior has been unclear. Experimental data were obtained for the transport of a broad range of proteins with different surface charge and molecular weight. The effective hydrodynamic size of the proteins was evaluated using size‐exclusion chromatography. The membrane charge, both before and after exposure to a given protein, was evaluated using streaming potential measurements. In most cases, the electrostatic interactions were dominated by the distortion of the electrical double layer surrounding the protein, leading to a distinct maximum in protein transmission at the protein isoelectric point. Attractive electrostatic interactions did occur when the protein and membrane had a large opposite charge, causing a second maximum in transmission at a pH between the isoelectric points of the protein and membrane. The sieving data were in good agreement with theoretical calculations based on available models for the partitioning of charged solutes in cylindrical pores. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 27–37, 1999. 相似文献
84.
以豆粕为氮源生产虫草菌丝体的研究 总被引:3,自引:0,他引:3
采用豆粕粉取代蚕蛹粉作氮源进行了虫草菌丝体的发酵试验,生产出无异臭味的虫草菌丝体,扩大了它的应用范围;对虫草菌丝体的抽提液进行超滤处理,测定了虫草多糖的含量和分子量。 相似文献
85.
Ultrafiltration of high-purity grade bovine serum albumin has been carried out under various temperature between 5 and 30 degrees C and at various cross-flow velocities, pressures, and concentrations with the aim of studying protein denaturation and its consequences on the process. Three different pump heads have been tested. Denaturation of proteins in solution has been monitored by laser light scattering and size exclusion chromatography. The rate of protein denaturation increases with temperature, cross-flow, and time. It is observed that membrane fouling is different whether denaturation has occurred or not. Under high-concentration polarization, denaturation can occur in the boundary layer if the wall concentration exceeds 400 g/L. It is shown how the residence time, operating temperature, and pressure play an important part in membrane fouling. This can provide guidelines for process design and control. 相似文献
86.
Badireddy AR Chellam S Yanina S Gassman P Rosso KM 《Biotechnology and bioengineering》2008,99(3):634-643
A 2:1 molar ratio preparation of bismuth with a lipophilic dithiol (3-dimercapto-1-propanol, BAL) significantly reduced extracellular polymeric substances (EPS) expression by Brevundimonas diminuta in suspended cultures at levels just below the minimum inhibitory concentration (MIC). Total polysaccharides and proteins secreted by B. diminuta decreased by approximately 95% over a 5-day period when exposed to the bismuth-BAL chelate (BisBAL) at near MIC (12 microM). Fourier-transform infrared spectroscopy (FTIR) suggested that a possible mechanism of biofilm disruption by BisBAL is the inhibition of carbohydrate O-acetylation. FTIR also revealed extensive homology between EPS samples with and without BisBAL treatment, with proteins, polysaccharides, and peptides varying predominantly only in the amount expressed. EPS secretion decreased following BisBAL treatment as verified by atomic force microscopy and scanning electron microscopy. Without BisBAL treatment, a slime-like EPS matrix secreted by B. diminuta resulted in biofouling and inefficient hydrodynamic backwashing of microfiltration membranes. 相似文献
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The role of phytoplankton in pollutant transfer processes in rivers. Example of River Marne (France) 总被引:2,自引:0,他引:2
The impact of the spring phytoplanktonic blooms on the partition of nutrients and metals between the dissolved and particulate phases was studied over two years in the river Marne, upstream of its confluence with the river Seine. Particular attention was devoted to copper and manganese, determined in the dissolved phase (< 0.22 m), subdivided into the colloidal phase and the 'truly dissolved' phase (< 10 KDaltons) obtained by tangential ultrafiltration. During the algal growth peaks, a sharp reduction of nutrients was observed in the dissolved phase: in 1994, consumption of 70% of silica, 50% of ammonium and 40% of soluble phosphorus present before the phytoplanktonic bloom.The water concentration peaks of suspended matter (SM) and of particulate metals, phosphorus and carbon coincide with those of chlorophyll. The highly significant correlations between pH and chlorophyll (r = 0.92, P < 0.001), pH and SM (r = 0.97, P < 0.001) and chlorophyll and SM (r = 0.93, P < 0.001) confirmed the phytoplanktonic nature of SM and the determining role of pH in the partition of metals, its increase being responsible for the coprecipitation of metal. As a corollary to the increase in the particulate phase, a decrease of 55% was observed for copper and manganese in the 'truly dissolved' phase compared to the concentrations outside bloom periods.The importance of the colloidal fraction was also shown. During the strong algal growth periods, the proportion of 'colloidal metal' in the dissolved phase (< 0.22 m) reached 60% and the increase in the colloidal fraction was 4 times stronger for copper than for manganese. While manganese seemed to be more associated with macroparticles, copper was more associated with fine colloidal biological particles intrinsic to the phytoplankton. 相似文献
89.
Bin Sun Mahsa Hadidi Jose Santiago Nuñez Benben Song Gilbert E. Tumambac Ken Wong Gregor Kalinowski James J. Hathcock 《Biotechnology progress》2024,40(1):e3400
In the production of biological therapeutics such as monoclonal antibodies (mAbs), ultrafiltration and diafiltration (UF/DF) are widely regarded as effective downstream processing steps capable of removing process equipment related leachables (PERLs) introduced upstream of the UF/DF step. However, clearance data available in the literature are limited to species with low partition coefficients (log P) such as buffer ions, hydrophilic organic compounds, and some metal ions. Additional data for a wide range of PERLs including hydrophobic compounds and elemental impurities are needed to establish meaningful, comprehensive safety risk assessments. Herein, we report the results from studies investigating the clearance of seven different organic PERLs representing a wide range of characteristics (i.e., log P (−0.3 to 18)), and four model elements with different chemical properties spiked into a mAb formulation at 10 ppm and analyzed during clearance using gas chromatography–mass spectrometry (GC–MS), liquid chromatography-photodiode-array-mass spectrometry (LC-PDA-MS), and inductively coupled plasma mass spectrometry (ICP-MS). The clearance data showed ideal clearance and sieving of spiked organic PERLs with log P < 4, partial clearance of PERLs with 4 < log P < 9, and poor clearance of highly hydrophobic PERLs (log P > 9) after nine diafiltration volumes (DVs). Supplemental clearance studies on seven additional PERLs present at much lower concentration levels (0.1–1.5 ppm) in the mAb formulation upstream of UF/DF and three PERLs associated with the tangential flow filtration (TFF) equipment also demonstrated the similar correlations between log P and % clearance. For model elements, the findings suggest that UF/DF in general provides ideal clearance for elements. Evidence showed that the UF/DF process does not only help mitigate leachables risk from PERLs introduced upstream of UF/DF, but also from the TFF operation itself as all three TFF-related PERLs were effectively cleared. Overall, the UF/DF clearance presented in this work demonstrated whereas highly hydrophobic PERLs and elements that exist as charged species, particularly transition metal ions, may not be as effectively cleared and thus warrant further risk assessment; hydrophilic and some hydrophobic PERLs (log P < 4) are indeed well-cleared and thus present a lower overall safety risk. 相似文献
90.
Kyung Hwa Chang Jong Hwa Park Chang Ho Park In Sik Chung 《Biotechnology and Bioprocess Engineering》1999,4(3):224-225
Recombinant enhanced green fluorescent protein (EGFP) fromE. coli was concentrated 1.9 times by ultrafiltration using a temperature-sensitive hydrogel. Protein recovery and separation efficiency
were 64% and 45%, respectively. Increased concentration of recombinant EGFP was confirmed by SDS-PAGE. Rotavirus was concentrated
3.2 times by ultrafiltration using a temperature-sensitive hydrogel, at 95% of virus recovery and 93% of separation efficiency.
Hydrogel ultrafiltration appears to be an attractive alternative for the concentration of rotavirus and recombinant proteins
fromE. coli. 相似文献