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S. Schaepe A. Kuprijanov C. Sieblist M. Jenzsch R. Simutis A. Lübbert 《Journal of biotechnology》2013
By means of improved feedback control kLa measurements become possible at a precision and reproducibility that now allow a closer look at the influences of power input and aeration rate on the oxygen mass transfer. These measurements are performed online during running fermentations without a notable impact on the biochemical conversion processes. A closer inspection of the mass transfer during cultivations showed that at least the number of impellers influences mass transfer and mixing: On the laboratory scale, two hollow blade impellers clearly showed a larger kLa than the usually employed three impeller versions when operated at the same agitation power and aeration rate. Hollow blade impellers are preferable under most operational conditions because of their perfect gas handling capacity. Mixing time studies showed that these two impeller systems are also preferable with respect to mixing. Furthermore the widths of the baffle bars depict a significant influence on the kLa. All this clearly supports the fact that it is not only the integral power density that finally determines kLa. 相似文献
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Hybrid models aim to describe different components of a process in different ways. This makes sense when the corresponding knowledge to be represented is different as well. In this way, the most efficient representations can be chosen and, thus, the model performance can be increased significantly. From the various possible variants of hybrid model, three are selected which were applied for important biotechnical processes, two of them from existing production processes. The examples show that hybrid models are powerful tools for process optimisation, monitoring and control. 相似文献
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Kuprijanov A Schaepe S Aehle M Simutis R Lübbert A 《Bioprocess and biosystems engineering》2012,35(3):333-340
An new cascade control system is presented that reproducibly keeps the cultivation part of recombinant protein production
processes on its predetermined track. While the system directly controls carbon dioxide production mass and carbon dioxide
production rates along their setpoint profiles in fed-batch cultivation, it simultaneously keeps the specific biomass growth
rates and the biomass profiles on their desired paths. The control scheme was designed and tuned using a virtual plant environment
based on the industrial process control system SIMATIC PCS 7 (Siemens AG). It is shown by means of validation experiments
that the simulations in this straightforward approach directly reflect the experimentally observed controller behaviour. Within
the virtual plant environment, it was shown that the cascade control is considerably better than previously used control approaches.
The controller significantly improved the batch-to-batch reproducibility of the fermentations. Experimental tests confirmed
that it is particularly suited for cultivation processes suffering from long response times and delays. The performance of
the new controller is demonstrated during its application in Escherichia coli fed-batch cultivations as well as in animal cell cultures with CHO cells. The technique is a simple and reliable alternative
to more sophisticate model-supported controllers. 相似文献
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The metalloprotease PrtV from Vibrio cholerae 总被引:2,自引:0,他引:2
Vaitkevicius K Rompikuntal PK Lindmark B Vaitkevicius R Song T Wai SN 《The FEBS journal》2008,275(12):3167-3177
The Vibrio metalloprotease PrtV was purified from the culture supernatant of a Vibrio cholerae derivative that is deficient in several other secreted peptidases, including the otherwise abundant hemagglutinin/protease HapA. The PrtV is synthesized as a 102 kDa protein, but undergoes several N- and C-terminal processing steps during V. cholerae envelope translocation and prolonged incubation. Purified V. cholerae PrtV protease forms of 81 or 73 kDa were stabilized by calcium ions. Removal of calcium resulted in further rapid autoproteolysis. The two major products of autoproteolysis of the PrtV protease were approximately 37 and 18 kDa and could not be separated under non-denaturing conditions, indicating they are interacting domains. In an assay using cultured cells of the human intestinal cell line HCT8, the PrtV protein showed a cytotoxic effect leading to cell death. Using human blood plasma as a source of potential substrates of mammalian origin for the PrtV protease, we found that the extracellular matrix components fibronectin and fibrinogen were degraded by the enzyme. Additional tests with individual protein substrates revealed that plasminogen was also a possible target for the PrtV protease. 相似文献
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Barbro Lindmark Pramod Kumar Rompikuntal Karolis Vaitkevicius Tianyan Song Yoshimitsu Mizunoe Bernt Eric Uhlin Patricia Guerry Sun Nyunt Wai 《BMC microbiology》2009,9(1):220
Background
Background: Cytolethal distending toxin (CDT) is one of the well-characterized virulence factors of Campylobacter jejuni, but it is unknown how CDT becomes surface-exposed or is released from the bacterium to the surrounding environment. 相似文献7.
Gangwei Ou Pramod Kumar Rompikuntal Aziz Bitar Barbro Lindmark Karolis Vaitkevicius Sun Nyunt Wai Marie-Louise Hammarstr?m 《PloS one》2009,4(11)
Background
Vibrio cholerae is the causal intestinal pathogen of the diarrheal disease cholera. It secretes the protease PrtV, which protects the bacterium from invertebrate predators but reduces the ability of Vibrio-secreted factor(s) to induce interleukin-8 (IL-8) production by human intestinal epithelial cells. The aim was to identify the secreted component(s) of V. cholerae that induces an epithelial inflammatory response and to define whether it is a substrate for PrtV.Methodology/Principal Findings
Culture supernatants of wild type V. cholerae O1 strain C6706, its derivatives and pure V. cholerae cytolysin (VCC) were analyzed for the capacity to induce changes in cytokine mRNA expression levels, IL-8 and tumor necrosis factor-α (TNF-α) secretion, permeability and cell viability when added to the apical side of polarized tight monolayer T84 cells used as an in vitro model for human intestinal epithelium. Culture supernatants were also analyzed for hemolytic activity and for the presence of PrtV and VCC by immunoblot analysis.Conclusions/Significance
We suggest that VCC is capable of causing an inflammatory response characterized by increased permeability and production of IL-8 and TNF-α in tight monolayers. Pure VCC at a concentration of 160 ng/ml caused an inflammatory response that reached the magnitude of that caused by Vibrio-secreted factors, while higher concentrations caused epithelial cell death. The inflammatory response was totally abolished by treatment with PrtV. The findings suggest that low doses of VCC initiate a local immune defense reaction while high doses lead to intestinal epithelial lesions. Furthermore, VCC is indeed a substrate for PrtV and PrtV seems to execute an environment-dependent modulation of the activity of VCC that may be the cause of V. cholerae reactogenicity. 相似文献8.
Reyes-Sandoval A Wyllie DH Bauza K Milicic A Forbes EK Rollier CS Hill AV 《Journal of immunology (Baltimore, Md. : 1950)》2011,187(3):1347-1357
Identification of correlates of protection for infectious diseases including malaria is a major challenge and has become one of the main obstacles in developing effective vaccines. We investigated protection against liver-stage malaria conferred by vaccination with adenoviral (Ad) and modified vaccinia Ankara (MVA) vectors expressing pre-erythrocytic malaria Ags. By classifying CD8(+) T cells into effector, effector memory (T(EM)), and central memory subsets using CD62L and CD127 markers, we found striking differences in T cell memory generation. Although MVA induced accelerated central memory T cell generation, which could be efficiently boosted by subsequent Ad administration, it failed to protect against malaria. In contrast, Ad vectors, which permit persistent Ag delivery, elicit a prolonged effector T cell and T(EM) response that requires long intervals for an efficient boost. A preferential T(EM) phenotype was maintained in liver, blood, and spleen after Ad/MVA prime-boost regimens, and animals were protected against malaria sporozoite challenge. Blood CD8(+) T(EM) cells correlated with protection against malaria liver-stage infection, assessed by estimation of number of parasites emerging from the liver into the blood. The protective ability of Ag-specific T(EM) cells was confirmed by transfer experiments into naive recipient mice. Thus, we identify persistent CD8 T(EM) populations as essential for vaccine-induced pre-erythrocytic protection against malaria, a finding that has important implications for vaccine design. 相似文献
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A. V. Deryugina G. A. Boyarinov I. S. Simutis V. O. Nikolskiy A. B. Kuznetsov T. S. Efimova 《Cell and Tissue Biology》2018,12(3):207-212
The early posttransfusion period after acute blood loss using erythromass without ozone was characterized by decreased electrophoretic mobility of erythrocytes (EPME), ATP, 2,3-diphosphoglycerate (2,3- DPG) concentration, Na+-K+-ATPase activity, and increased concentration of malonic dialdehyde (MDA) and catalase activity in erythrocytes. Most parameters gradually were restored over 5 days, but a reduced concentration of 2,3-DPG was observed throughout the entire experiment with transfusion of erythromass without ozone. Transfusion of the ozonized erythrocyte mass 1 h after its administration caused an increase in 2,3- DPG concentration in erythrocytes circulating in the vascular bed. Twenty-four hours later, increased catalase activity, EPPE, and ATP concentration were registered, and, after 5 days, enhanced Na+-K+-ATPase activity was registered. Their values were maintained until the end of the experiment at a higher level than in animals that had undergone transfusion of the nonozonized erythromass. Ozonized erythrocyte mass improves the functional metabolic state of erythrocytes, promotes an earlier recovery of the oxygen transport in blood, and limits the damage to the microcirculatory bed of the myocardium and cardiomyocytes during blood loss. 相似文献