Date

2016

Author

Hoxha, Bebeta

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The objective of this study is to investigate different feeding strategies leading to higher recombinant human growth hormone (rhGH) production by Pichia pastoris, driven under constitutive promoter of the glyceraldehyde-3-phosphate dehydrogenase gene. rhGH production took place in a pilot bioreactor where glucose and molasses were examined as carbon sources. For batch phase, which is the first production phase of the reactor, all experiments share the same characteristics where glycerol was utilized as the carbon source. For semi-batch phase, exponential and consecutive strategies, were designed by using predetermined specific growth rates as μo =0.07, 0.10, and 0.15 h-1. Consecutive feeding consisted of designed cyclic repetitions of 1.5h exponential feeding as semi-batch operation followed by a 0.5h of interruption period where bioreactor operates batch-wise. The cells were more responsive to feeding + starvation strategies, when glucose was utilized as carbon source by obtaining cell concentrations up to 135 g L-1 . For consecutive feeding strategy with glucose based continuous feed stream designed with μo = 0.10 h-1, the maximum CrhGH was obtained as 611 mg L-1 and rhGH production increased by 1.37-fold compared to continuous exponential feeding profile with the same μo = 0.10 h-1. On the other hand, molasses was a more effective carbon source, when was exponentially fed to the production medium with μo =0.07 h -1 and resulted in higher production yields on the cell and substrate. Among all the strategies, this strategy produced the highest rhGH concentration as CrhGH = 650 mg L-1 at t =17 h where the cell concentration was CX =71.2 g L-1. The overall product and cell yield on total substrate were obtained as Y’P/S = 10.7 mg g-1 and Y’X/S=0.434 g g-1, respectively

Subject Keywords

Somatotropin., Molasses., Pichia pastoris., Recombinant human somatotropin.

URI

http://etd.lib.metu.edu.tr/upload/12620270/index.pdf
https://hdl.handle.net/11511/25882

Collections

Graduate School of Natural and Applied Sciences, Thesis