Orthogonal Optogenetic Circuits for Optimizing Microbial Chemical Production

Microbial chemical production offers a sustainable alternative to traditional petrochemical processing. To circumvent metabolic burden resulting from expression of heterogeneous pathways, metabolic engineers implement dynamic control: accumulating sufficient amounts of biocatalyst in a growth phase, then activating metabolic pathways in a production phase. Optogenetic control of metabolic pathways presents an advantageous method for dynamic regulation of microbial metabolism: light is cheap, reversible, and tunable via pulsing in different duty cycles.

Our group has developed various optogenetic circuits that allow for flexible switching between cellular growth and chemical production. By optogenetically regulating the abundances of transcriptional activators and repressors, these circuits are able to induce gene expression in either blue light or darkness. Moreover, by implementing protein pairs that do not interfere with each others activities, we have allowed for simultaneous signal amplification and inversion. Our circuits display high expression levels, rapid activation kinetics, and minimal cross-talk. Through co-utilization of these optogenetic amplifier and inverter circuits, we are able to optimize production titers as well as tunably produce chemicals in different ratios. We believe that our results validate the potential of optogenetics for sustainable and economically feasible production of valuable chemicals.