Integrierte Prozessentwicklung zur Herstellung von L-Phenylalanin mit Escherichia coli

This work gives a summary of an integrated process development for the production of Lphenylalanine by Escherichia coli. Hereby, the term integrated" describes the simultaneous development of the process and of different genetically engineered strains. Furthermore, this work summarises the results obtained by the integration of a reactive-extraction DSP unit into the fermentation process. An universal fermentation strategy was developed in order to characterise potential auxotroph production strains of L-tyrosine. Two closed loop control strategies for glucose (main carbon source) and L-tyrosine were introduced. To obtain optimal amino acid production, Ltyrosine accumulation had to be prevented by limited feeding. Nevertheless, optimal growth should be achieved. Furthermore, an glucose excess of 5g/1 was found to be positive for high production rates. This process was reproducible and a scale-up to pilot scale was successful. The L-tyrosine feed control permitted the use of feed-back sensitive DAHP-synthase (aro.F). Overexpressing the native enzyme and further identification and elimination ofbottlenecks within the aromatic amino acid pathway lead to a significant increase in L-phenylalanine production. Fermentation of the final production strain resulted in the prevention of aromatic amino acid intermediates accumulation. Genetic engineering as well as process development lead to increasing production rates. Therefore, the fermentation time to reach more then 30g/1 L-phenylalanine was reduced from 50h to 25h. The integral product yield increased from 16.2% to 24.4% and the integral space time yield from 0.8g/(1*) to 1 .2g/(1*h). The down stream operation unit was successfully integrated after scale-up to the pilot scale (300L bioreactor). L-phenylalanine was extracted simultaneously from the fermentation process and concentrated up to over 98% using only one purification step. Furthermore, the decreasing amino acid concentration during the fermentation lead to an increase in product yield from 15% to more than 20%. By recirculating the fermentation medium back into the bioreactor, a so-called hybrid process was established which proved its function for the first time in pilot scale