(599ad) Simple Improvements to Dynamic Control Schemes Improve Product Yield

Authors: 
Blenner, M. A., Harvard Medical School & Children's Hospital Boston
Wilson, A. N., Clemson University
Guiseppi-Elie, A., Clemson University

Dynamic control is an advanced metabolic engineering strategy to improve production of a bioproduct by employing metabolite responsive feedback of gene expression. This type of regulatory network is frequently employed in nature to optimally utilize valuable substrates – a goal shared by nature and engineers alike. The dynamic nature of these feedback control schemes requires the both a sensor, which detects metabolite concentration in real-time, and an actuator, which regulates gene expression based on the sensor measurements. Bacterial transcription factors have been used for this purpose, as they are sensor-regulators by design. This approach has been implemented for the production of fatty acid ethyl ester (FAEE) biodiesel producing in E. coli, with great success. Based on a tractable nonsteady model of this pathway, we describe a few simple changes that result in FAEE production improvement and experimental evidence to support these strategies, which include altering the enzymes for more balanced pathway flux, and improving the dynamics of the regulator. These changes result in better carbon distribution and bring the pathway into better balance, allowing the dynamic nature of dynamic control schemes to be utilized. The strategies employed here are likely to be generally applicable to metabolic pathways rather than merely specific to this one.