In this study, the effects of bioprocess operation parameters on benzaldehyde lyase production were systematically investigated. For this purpose, the research program was carried out in mainly four parts. In the first part of the study, Escherichia coli K12 (ATCC 10798), having the highest benzaldehyde lyase production capacity, was selected as the host microorganism. Next, using the selected microorganism, the production medium was designed in terms of its carbon and nitrogen sources. Among the investigated media, the highest cell concentration and benzaldehyde lyase activity were obtained as 1.8 kg m-3 and 745 U cm-3, respectively, in the medium containing 8.0 kg m-3 glucose, 5.0 kg m-3 (NH4)2HPO4 and the salt solution. Thereafter, by using the designed medium, the effects of bioreactor operation parameters, i.e., oxygen transfer and pH, were investigated in pilot scale bioreactor. Oxygen transfer effects on benzaldehyde lyase production were investigated at QO/VR=0.5 vvm / N=250, 375, 500, 625, 750 min-1 and at QO/VR=0.7 vvm, N=750 min-1 conditions. The highest cell concentration and benzaldehyde lyase activity were obtained at 0.5 vvm, 500 min-1 condition as 2.3 kg m-3 and 860 U cm-3, respectively.
Finally, the effect of pH was investigated for benzaldehyde lyase production process at Qo/VR=0.5 vvm, N=500 min-1 condition, at pHC=5.0, 6.4, 6.7, 7.0, 7.2 and 7.8 values. Among the investigated pH values, the highest cell concentration and enzyme activity were obtained at pHC=7.0 condition as 2.1 kg m-3 / 775 U cm-3. However, the values obtained at this condition, were lower than the values obtained at pHUC=7.2 uncontrolled pH operation. Hence, medium oxygen transfer condition and uncontrolled pH operation are found to be favorable for benzaldehyde lyase production.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/3/12605242/index.pdf |
| Date | 01 August 2004 |
| Creators | Yilgor, Pinar |
| Contributors | Calik, Pinar |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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