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Control of Cell Growth and Glucose Uptake Rates by Controlled Expression of Phosphofructokinase (Pfk) in B. Subtilis

Zhiwei Pan1, Tao Zhu2, Richard Koepsel3, Michael M. Domach4, and Mohammad Ataai3. (1) Chemical and Petroluem Engineering, University of Pittsburgh, 300 Technology Drive, Pittsburgh, PA 15219, (2) Carnegie Mellon Univ., 5000 Forbes Ave., Pittsburgh, PA 15213, (3) Chemical and Petroleum Engineering, University of Pittsburgh, 300 Technology Drive, Pittsburgh, PA 15219, (4) Chemical Engineering, Carnegie Mellon University, Doherty Hall 3102A, 5000 Forbes Avenue, Pittsburgh, PA 15213

Recently, we have constructed a Bacillus subtilis mutant with regulated pfk expression and established a dose response relationship between IPTG concentration and pfk expression. Results of batch and continuous culture experiments that establish the effect of PFK levels on growth rate, acid production, and metabolic fluxes will be presented. In a defined glucose minimal medium, the glucose uptake and cell growth rates of the mutant are closely related to the expression of PFK. However, the intracellular concentration of glucose-6-phosphate (G6P) is inversely proportional to the pfk expression. Thus, it is likely that reduced glucose uptake rate is due to the elevated G6P pool in the mutant with reduced PFK activity. In summary, the regulated pfk expression provides an alternative way to control glucose uptake rate even in the presence of excess glucose.