Demuth C.,Institute For Biotechnologie
Chemie in Unserer Zeit | Year: 2014
Measurement and control of the pH value and the dissolved oxygen concentration are crucial tasks in every bioprocess. For many years electrochemical sensors have been used to manage these chemical parameters. Only recently, new measurement principles have gained ground in bioprocess analytics. These include optical chemical sensors, which are especially suited to use in single-use bioreactors. It is clear that robustness, reliability, ease of use and low maintenance costs will all be key considerations if these sensors are to be applied to process control.
Stirling C.H.,University of Otago |
Stirling C.H.,ETH Zurich |
Andersen M.B.,ETH Zurich |
Warthmann R.,ETH Zurich |
And 3 more authors.
Geochimica et Cosmochimica Acta | Year: 2015
A series of laboratory-controlled microbial experiments using gram-negative sulphate-reducing bacteria (Desulfovibrio brasiliensis) inoculated with natural uranium were performed to investigate 238U/235U fractionation during bacterially-mediated U reduction. Control experiments, without bacteria to drive U reduction, were conducted in parallel. Paired measurements of 238U/235U and U concentration for both the residual growth medium solution and the accumulated biologically-mediated precipitate were obtained using multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS). The control experiments show that only minor (<0.1‰), if any 238U/235U fractionation occurs during co-precipitation with calcite. This implies that carbonate sediments are capable of faithfully recording the signature of the global ocean during Earth's major climatic events, including oxygenation and de-oxygenation transitions in the marine environment. The results for the microbial experiments demonstrate that the 238U/235U composition of the unreacted growth medium containing U(VI) is isotopically lighter than the composition of the U(IV)-bearing precipitate as U(VI) is consumed, in agreement with field-based observations of microbially-mediated U reduction. Uranium isotopic shifts of up to 0.8‰ were observed between the liquid and solid phases. These observations can be modelled using a Rayleigh distillation approach describing kinetic uptake in a closed system, which yields a fractionation factor α of 0.99923±0.00004 (ε=-0.77±04‰) for U(VI)-U(IV) reduction mediated by the D. brasiliensis microbe. This fractionation behaviour is consistent with that observed in field-based redox environments, which give rise to similar α values. Competing processes such as U co-precipitation (e.g. adsorption) may act to lower the apparent value for α and possibly play a secondary role both in the microbial experiments of this study and in natural U reduction settings where variable α values are found. These results may suggest that microbes adept at inducing U(VI) reduction play a crucial role in facilitating significant 238U/235U isotope fractionation in nature. © 2015 Elsevier Ltd.
Werner S.,Institute For Biotechnologie |
Eibl R.,Institute For Biotechnologie |
Lettenbauer C.,Sartorius Stedim Switzerland AG |
Roll M.,Sartorius Stedim Switzerland AG |
And 13 more authors.
Chimia | Year: 2010
Innovative mixing principles in bioreactors, for example using the rocking of a platform to induce a backwards and forwards 'wave', or using orbital shaking to generate a 'wave' that runs round in a cylindrical container, have proved to be successful for the suspension cultures of cells, especially when combined with disposable materials. This article presents an overview of the engineering characteristics when these new principles are applied in bioreactors, and case studies covering scales of operation from milliliters to 1000 liters. © Schweizerische Chemische Gesellschaft.
Werner S.,Institute For Biotechnologie |
Olownia J.,Infors AG |
Egger D.,Infors AG |
Eibl D.,Institute For Biotechnologie
Chemie-Ingenieur-Technik | Year: 2013
An initial approach for scaling up geometrically dissimilar orbitally shaken bioreactors is presented. A novel ShakerBag Option for Multitron Cell shaking incubators allows a rapid increase in working volume from small TubeSpin bioreactors or shake flasks up to 10 L, thus offering a simple and cost-efficient alternative to present systems for scale-up. The engineering parameters for scale-up of the orbitally shaken single-use bags were determined using traditional methods. Modern computational fluid dynamics based methods were used to gain a deeper insight into the fluid flow behavior. Furthermore, mass propagation of plant cell suspensions (Nicotiana tabacum and Vitis vinifera), as well as cell expansion and production of protein complexes using insect cells (Sf-9), show the potential of orbitally shaken single-use bags. Copyright © 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.