APPLICATION OF MATHEMATICAL TOOLS FOR METABOLIC DESIGN OF MICROBIAL ETHANOL-PRODUCTION

Many attempts to engineer cellular metabolism have failed: due to the complexity of cellular functions. Mathematical and computational metho ds are needed that can organize the available experimental information , and provide insight and guidance for successful metabolic engineerin g. Two such methods are reviewed here. Both methods employ a (log)line ar kinetic model of metabolism that is constructed based on enzyme kin etics characteristics;The first method allows the description of the d ynamic responses of metabolic systems subject to spatiotemporal variat ions in their parameters. The second method considers the product-orie nted, constrained optimization of metabolic reaction networks using mi xed-integer linear programming methods. The optimization framework is used in order to identify the combinations of the metabolic characteri stics of the glycolytic enzymes from yeast and bacteria that will maxi mize ethanol production. The methods are also applied to the design of microbial ethanol production metabolism, The results of the calculati ons are in qualitative agreement with experimental data presented here . Experiments and calculations suggest that, in resting Escherichia co li cells, ethanol production and glucose uptake rates can be increased by 30% and 20%, respectively, by overexpression of a deregulated pyru vate kinase, while increase in phosphofructokinase expression levels h as no effect on ethanol production and glucose uptake rates. (C) 1998 John Wiley & Sons, Inc.