Date

2010

Author

İnankur, Bahar

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In this study, the aim was to achieve high concentration of recombinant human growth hormone (rhGH) production by recombinant Pichia pastoris by investigating the effects of various operation parameters and to determine the suitable peptide ligand sequence that shows affinity and specificity to hGH. In this context, firstly the effect of temperature and Tween-20/80 addition on production and cell growth were investigated. While at T=30 and 32°C, there was no difference, at 27 and 25°C cell growth slowed down and production decreased significantly. The addition of Tween-20/80 in existence of co-substrate sorbitol did not affect the bioprocess while in absence of sorbitol Tween alone did not show the same positive effect on product formation and cell growth. Thereafter at T=30°C, without addition of Tween, three sets of pilot scale bioreactor experiments were performed. In the first set, the effect of methanol feeding rate on bioprocess characteristics were investigated at the specific growth rates of μ=0.02, 0.03 and 0.04 h-1. While the highest cell concentration was achieved at μ=0.04 h-1, the highest rhGH concentration was achieved at μ=0.03 h-1. Secondly, conducting methanol feeding at μ=0.03 h-1, pH=5.5 experiment was conducted. The highest cell concentration, 45 g L-1 and maximum rhGH concentration 0.25 g L-1 were achieved at t=18 h of the process. Finally, the effect of batch sorbitol feeding on bioprocess was observed by the addition of 50 g L-1 sorbitol at t=0, 14 and 31 h of the production phase. It was shown that sorbitol addition to the medium increased process duration; hence cells enter stationary phase after a longer production phase. However, the protease concentration continued increasing with respect to time and at the end of the process reached twice the concentration it was obtained with single sorbitol addition case decreasing the rhGH concentration. In selection of the peptide sequence that shows affinity towards hGH, phage display method was conducted. Additionally the sequences from literature and computational design were used as alternatives. The interaction between these peptides and hGH was investigated by isothermal titration calorimetry and surface plasmon resonance.

Subject Keywords

Chemical engineering., Feeding strategy.

URI

http://etd.lib.metu.edu.tr/upload/12612197/index.pdf
https://hdl.handle.net/11511/19748

Collections

Graduate School of Natural and Applied Sciences, Thesis