Date

2010

Author

Taşpınar, Hatice

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In this study, the aim was to investigate the effects of exponential feeding strategy on benzaldehyde lyase (BAL) production by recombinant Escherichia coli BL21. For this purpose, the effects of medium components were investigated to optimize the initial medium composition of the fed-batch fermentations. For the batch bioreactor operations, the highest cell concentration and BAL activity were achieved in a media containing 30 g L-1 pretreated molasses, and 5 g L-1 (NH4)2HPO4 as 5.07 g L-1, and 1611 U ml-1 at t=8 h, respectively. Thereafter, in order to increase the cell growth and BAL production while avoiding acetate accumulation, fed-batch bioreactor operations were conducted with exponential feeding at different specific growth rates namely, 0.1 h-1 (mu-0.1), 0.15 h-1 (mu-0.15), and 0.2 h-1 (mu-0.2), and a combined exponential and constant feeding (mu-0.2+) strategy. In the experiments, 9 hours of batch-wise operation with the optimized production medium was followed by a fed-batch operation phase using the pre-determined exponential feeding profiles and for mu-0.2+ operation after 10 hours of exponential feeding as mu-0.2, where the feed rate was kept constant at 21.6 g h-1. Additionally, the plasmid stability was investigated using the feeding method of mu-0.2+ operation with antibiotics in the feed solution, and it was observed that the plasmid was stable. Among the three exponential feeding conditions, the highest cell concentration and BAL activity were determined in -0.15 operation as 21.7 g L−1 and 8379 U ml-1, respectively. In mu-0.2+ operation, the maximum cell concentration was achieved as 28.1 g L-1 which was higher than mu-0.15 experiment, though a lower maximum BAL activity was obtained as 6695 U ml-1.

Subject Keywords

Biotechnology.

URI

http://etd.lib.metu.edu.tr/upload/12612311/index.pdf
https://hdl.handle.net/11511/19869

Collections

Graduate School of Natural and Applied Sciences, Thesis