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41.
42.
Binbing?Han Jonathan?O.?Carlson Scott?M.?Powers S.?Ranil?WickramasingheEmail author 《Biotechnology and Bioprocess Engineering》2002,7(1):6-9
In this work we have investigated the feasibility of virus clearance by flocculation and tangential flow microfiltration.
Chinese hamster ovary cell feed streams were spiked with minute virus of mice and then flocculated using cationic polyelectrolytes
prior to tangential flow microfiltration. Our results indicate that flocculation prior to microfiltration leads to more than
100 fold clearance of minute virus of mice particles in the permeate. Today, validation of virus clearance is a major concern
in the manufacture of biopharmaceutical products. Frequently new unit operations are added simply to validate virus clearance
thus increasing the manufacturing cost. The results obtained here suggest that virus clearance can be obtained during tangential
flow microfiltration. Since tangential flow microfiltration is frequently used for bioreactor harvesting this could be a low
cost method to validate virus clearance. 相似文献
43.
With flocculent cells of Zymomonas mobilis levan was produced in a continuous upflow-tower fermentation with a productivity of up to 16 gl-1h-1. A large-scale process basing on whole Zymomonas cells is thought to be economical, if levan and ethanol production can be carried out simultaneously. Levan sucrase as the enzyme responsible for levan biosynthesis was purified and partially characterized. 相似文献
44.
In-situ floc size measurements were made in suspended matter of the Elbe and Dollard estuaries. Floc size was found to be generally
smaller in the surface water than in the bottom water and varied systematically with time in relation to the tidal phase.
Maximum floc size was also related to particle concentration and, in the Dollard, probably also to flow on and off the tidal
flats. Salinity and the total organic matter content of the suspended matter played a minor or no role. Since flocs break
up into uniform size distributions during sampling and analysis, Coulter counter particle size was about constant during the
tidal cycle.
temporarily at Netherlands Institute for Sea Research, Texel, The Netherlands. 相似文献
45.
Joaquin F Christiaens Sebastiaan E Van Mulders Jorge Duitama Chris A Brown Maarten G Ghequire Luc De Meester Jan Michiels Tom Wenseleers Karin Voordeckers Kevin J Verstrepen 《EMBO reports》2012,13(12):1145-1151
Gene duplication stimulates evolutionary innovation as the resulting paralogs acquire mutations that lead to sub‐ or neofunctionalization. A comprehensive in silico analysis of paralogs in Saccharomyces cerevisiae reveals that duplicates of cell‐surface and subtelomeric genes also undergo ectopic recombination, which leads to new chimaeric alleles. Mimicking such intergenic recombination events in the FLO (flocculation) family of cell‐surface genes shows that chimaeric FLO alleles confer different adhesion phenotypes than the parental genes. Our results indicate that intergenic recombination between paralogs can generate a large set of new alleles, thereby providing the raw material for evolutionary adaptation and innovation. 相似文献
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Sílvia Bofill-Mas Ayalkibet Hundesa Byron Calgua Marta Rusi?ol Carlos Maluquer de Motes Rosina Girones 《Journal of visualized experiments : JoVE》2011,(58)
Microbial contamination of the environment represents a significant health risk. Classical bacterial fecal indicators have shown to have significant limitations, viruses are more resistant to many inactivation processes and standard fecal indicators do not inform on the source of contamination. The development of cost-effective methods for the concentration of viruses from water and molecular assays facilitates the applicability of viruses as indicators of fecal contamination and as microbial source tracking (MST) tools. Adenoviruses and polyomaviruses are DNA viruses infecting specific vertebrate species including humans and are persistently excreted in feces and/or urine in all geographical areas studied. In previous studies, we suggested the quantification of human adenoviruses (HAdV) and JC polyomaviruses (JCPyV) by quantitative PCR (qPCR) as an index of human fecal contamination. Recently, we have developed qPCR assays for the specific quantification of porcine adenoviruses (PAdV) and bovine polyomaviruses (BPyV) as animal fecal markers of contamination with sensitivities of 1-10 genome copies per test tube. In this study, we present the procedure to be followed to identify the source of contamination in water samples using these tools. As example of representative results, analysis of viruses in ground water presenting high levels of nitrates is shown.Detection of viruses in low or moderately polluted waters requires the concentration of the viruses from at least several liters of water into a much smaller volume, a procedure that usually includes two concentration steps in series. This somewhat cumbersome procedure and the variability observed in viral recoveries significantly hamper the simultaneous processing of a large number of water samples.In order to eliminate the bottleneck caused by the two-step procedures we have applied a one-step protocol developed in previous studies and applicable to a diversity of water matrices. The procedure includes: acidification of ten-liter water samples, flocculation by skimmed milk, gravity sedimentation of the flocculated materials, collection of the precipitate and centrifugation, resuspension of the precipitate in 10 ml phosphate buffer. The viral concentrate is used for the extraction of viral nucleic acids and the specific adenoviruses and polyomaviruses of interest are quantified by qPCR. High number of samples may be simultaneously analyzed using this low-cost concentration method.The procedure has been applied to the analysis of bathing waters, seawater and river water and in this study, we present results analyzing groundwater samples. This high-throughput quantitative method is reliable, straightforward, and cost-effective. 相似文献
50.
Nripen Singh Kara Pizzelli Jonathan K. Romero James Chrostowski Greg Evangelist James Hamzik Neil Soice K.S. Cheng 《Biotechnology and bioengineering》2013,110(7):1964-1972
Increasingly high cell density, high product titer cell cultures containing mammalian cells are being used for the production of recombinant proteins. These high productivity cultures are placing a larger burden on traditional downstream clarification and purification operations due to higher product and impurity levels. Controlled flocculation and precipitation of mammalian cell culture suspensions by acidification or using polymeric flocculants have been employed to enhance clarification throughput and downstream filtration operations. While flocculation is quite effective in agglomerating cell debris and process related impurities such as (host cell) proteins and DNA, the resulting suspension is generally not easily separable solely using conventional depth filtration techniques. As a result, centrifugation is often used for clarification of cells and cell debris before filtration, which can limit process configurations and flexibility due to the investment and fixed nature of a centrifuge. To address this challenge, novel depth filter designs were designed which results in improved primary and secondary direct depth filtration of flocculated high cell density mammalian cell cultures systems feeds, thereby providing single‐use clarification solution. A framework is presented here for optimizing the particle size distribution of the mammalian cell culture systems with the pore size distribution of the gradient depth filter using various pre‐treatment conditions resulting in increased depth filter media utilization and improved clarification capacity. Feed conditions were optimized either by acidification or by polymer flocculation which resulted in the increased average feed particle‐size and improvements in throughput with improved depth filters for several mammalian systems. Biotechnol. Bioeng. 2013; 110: 1964–1972. © 2013 Wiley Periodicals, Inc. 相似文献