(593q) Systems Metabolic Engineering of Polyhydroxyalkanoates

Polyhydroxyalkanoates (PHAs) form a class of natural polyesters that many organisms accumulate as intracellular granules to store carbon and reducing equivalents in response to specific environmental conditions. Thus, using microbial route to producing them may be an economically viable and sustainable alternative to current processes. Metabolic pathway analysis and flux balance analysis have been used to analyze the in silico biosynthesis of such polyesters. Using bilevel optimization we identify strategies for knocking in and knocking out genes for PHB production in common recombinant hosts- E. coli and Yeast that can be metabolically engineered in the laboratory. In E. coli, bilevel optimization returns only combination of 5 knockouts for increased production of PHA including several central metabolism genes. Concurrence with litearture related to microaerophilic conditions being better than highly aerobic conditions.  We use in parallel, elementary mode analysis, to understand the dominant modes that will allow simultaneous production of biomass and biopolyester.

Using the previously published E.coli genome-scale model iAF1260, knocking out a speciifc set of genes results in a dramatic reduction of possible modes and also removes alternate by-product formation like succinate. These modes could help rationally design a pathway that could potentially be synthetically constructed in the laboratory. Results from the experiments and simulations will be discussed.