Assessment of Zymomonas mobilis biotechnological potential in ethanol production by flux variability analysis

Metabolic engineering of microorganisms is a promising direction in industrial biotechnology. Engineering approach requests finding the best possible alternative of metabolic pathway fluxes, with preset limitations for productivity, yield, set of by- products, robustness and other features. In case of industrial applications the steady state precondition has to be taken into ac- count, thus enabling application of stoichiometric modeling. Spectrum of solutions maximizing ethanol or succinate production from glucose or xylose is analyzed at fixed maximal production rate of products and for 80-100% range of maximal production rate to assess the robustness of yield to disturbances in the performance of reactions. Maximal production of desired components from glucose and xylose turned out to be very similar by the flux distribution with very limited ability to compensate throughput limitations of important reactions thus causing reduction of yield. Requesting the network performance at 80-100% of yield leads to increase of robustness, and majority of reactions can be compensated by others to maintain the steady state at the desired yield level.