BIOT 82 |
| Metabolic constraints during the production of recombinant DNA protein in Escherichia coli impede the efficient utilization of resources by the cells thus reducing their production potential. In order to minimize these adverse effects we have proposed to segregate the cells into two groups, one not induced growing at a high specific growth rate and rapidly contributing cells to the system, and the other fully induced, growing slowly but using the cell machinery to express the target protein. An adequate balance between these two populations should maximize the protein expression in a given system. The segregation model is based on the “all or none” phenomenon previously described by other authors and in which at inducer sub saturated conditions the cells are either fully induced or fully un induced. Our experimental findings demonstrate that the cells used in this study exhibit such behavior. Based on this two population theory we have developed a mathematical model in which the cell culture in batch fermentations is segregated into two groups, one fully induced and the other not induced. The parameters that characterize the model were determined experimentally and used to simulate different induction strategies in which the fraction of induced cells was varied with time according to several pre-determined schemes. It was found that the linear increase of this fraction ending at maximum induction in the final fermentation time would give the best results. The slope of this line varies with the particular conditions of the fermentation and a method to determine this “best” slope is discussed. Finally these results were validated experimentally finding that the results closely match the mathematical simulation. |
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Upstream Processing: Advances in Microbial Fermentation Process Development
8:00 AM-10:15 AM, Monday, August 20, 2007 BCEC -- 106, Oral
Division of Biochemical Technology |