C - DTU Nanotech - Danmarks Tekniske Universitet

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12 1 Introduction sampling system with a reactor chamber. This thesis is organized as follows: Chapter 2 gives a short overview over commercial available and currently developed small scale cultivation systems. In Chapter 3 two polymer materials, poly (methyl methacry- late) (PMMA) and Topas R○ , which have been used successfully for a variety of microsystems [27, 35], are introduced. Additionally, the machining methods for these polymers are ex- plained. Furthermore, in Chapter 4, the basic principle of Peltier cooling and the suitability of Peltier elements for different applications is described. In Chapter 5 the freezing of PBS–buffer, LB–medium and cell samples in a sampling chamber using a Peltier element is described. The chapter also includes a description of the chosen methods, the results and the discussion of the results. In Chapter 6, the development of a bio–microreactor with an integrated sampling system using Peltier cooling and the testing of the setup with PBS–buffer is presented, and the results are discussed. Chapter 7 concludes this thesis and provides an outlook for future work.
2 Overview of Small–Scale Cultivation Systems This chapter gives a short overview of the performance of commercial available and currently developed small–scale cultivation systems. 2.1 Shaken small–scale cultivation systems Most of the initial culture experiments in biotechnology are performed in shaken small–scale systems [4]. Erlenmeyer flasks, test–tubes and microtiter plates belong to this class of shaken small–scale systems. The size of Erlenmeyer flasks is very variable, but the nominal volume normally ranges between 25 ml and 5 l. They are made of borosilicate glass (hydrophilic) or polymer (hy- drophobic) and are equipped with or without baffles. For the liquid mixing at defined temperatures orbital shaking devices in incubators are usually used. Dissolved oxygen can be measured with an integrated electrochemical O2 sensor or with a new developed opti- cal sensor system, which allows a robust and precise online measurement [45]. Hereby, an immobilized small sensor spot at the bottom of the flask is irradiated by fluorescent light and fluorescence quenching or decay time is sensed [23]. Because of the oxygen limitation in shaken flasks, various modifications like baffles and steel springs or other enhancements to improve aeration have been developed [5, 15, 42]. The pH is usually kept within acceptable range by using buffers, whereas pH excursions might occur without being observed [23]. But recently new developed shaken flasks with inserted pH probes have been described for measurement and control of pH [44, 42]. Test–tubes are primarily used for various screening applications and are useful for de- veloping inoculums for small–scale fermentations. Normally the volumes are ranging from about 2 − 25 ml and the tubes are made of glass or polymer. For maintaining the steril- ity of the culture, the opening of the tube is fitted with a cotton or a plastic foam plug. Test–tube devices are also used for anaerobic cultivation where the O2 concentration is kept below the critical values with evacuation and steel–wool plugs [37]. To use test–tubes for 13
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Page 8 and 9: 8 Contents 6 Development of a Bio-M
Page 10 and 11: 10 Nomenclature COC Cyclo-olefin co
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Page 17 and 18: 3 Theoretical Considerations of Pol
Page 19 and 20: 100µm 3.2 Topas R○ and the CNC m
Page 21 and 22: 3.2 Topas R○ and the CNC micromil
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62 6 Development of a Bio-Microreac
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64 7 Concluding Remarks Reactor cha
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Appendix Freezing experiments with
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Experiments with 20 µl PBS-buffer
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72 List of Figures 6.8 Heat wire de
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Bibliography [1] Arisawa, H.; Brill
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Bibliography 77 [26] Mark, H. F.: E
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Bibliography 79 [50] Zimmermann, H.
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C - DTU Nanotech - Danmarks Tekniske Universitet

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