Optogenetic regulation of engineered cellular metabolism for microbial chemical production

Abstract

The optimization of engineered metabolic pathways requires careful control over the levels and timing of metabolic enzyme expression1-4. Optogenetic tools are ideal for achieving such precise control, as light can be applied and removed instantly without complex media changes. Here we show that light-controlled transcription can be used to enhance the biosynthesis of valuable products in engineered Saccharomyces cerevisiae. We introduce new optogenetic circuits to shift cells from a light-induced growth phase to a darkness-induced production phase, which allows us to control fermentation purely with light. Furthermore, optogenetic control of engineered pathways enables a new mode of bioreactor operation using periodic light pulses to tune enzyme expression during the production phase of fermentation to increase yields. Using these advances, we control the mitochondrial isobutanol pathway to produce up to 8.49 ± 0.31 g/L of isobutanol and 2.38 ± 0.06 g/L of 2-methyl-1-butanol micro-aerobically from glucose. These results make a compelling case for the application of optogenetics to metabolic engineering for valuable products.

Xylose assimilation enhances the production of isobutanol in engineered Saccharomyces cerevisiae

“…However, the simultaneous deletion of PDC1, PDC5 , and PDC6 substantially decrease strain fitness, complicating isobutanol production (Milne, Wahl, van Maris, Pronk, & Daran, ). A more effective strategy to draw metabolic flux from ethanol to isobutanol has been used to dynamically control the expression of PDC1 and ILV2 in a triple‐ PDC deletion strain background (Zhao et al, ), which would likely help to further improve isobutanol production from xylose in SR8‐Iso.…”

“…triple-PDC deletion strain background (Zhao et al, 2018), which would likely help to further improve isobutanol production from xylose in SR8-Iso.…”

A yeast optogenetic toolkit (yOTK) for gene expression control in Saccharomyces cerevisiae

“…Optogenetic approaches for controlling natural and synthetic biological networks are garnering attention as the toolkit expands and more powerful applications are demonstrated (Harrigan et al, ; Melendez et al, ; Ng et al, ; Rullan et al, ; Zhao et al, ). Here we report an orthogonal light‐inducible transcriptional activator for gene expression control in S. cerevisiae .…”

The renaissance of yeasts as microbial factories in the modern age of biomanufacturing

“…Zhao et al () created novel optogenetic circuits by fusing a light‐sensitive transcription factor from Erythrobacter litoralis (EL222) to the VP16 transcriptional activation domain and its cognate C120 promoter (P C120 ). The OptoEXP circuit enabled strong, titratable, and light‐inducible gene expression and could shift cells from a light‐induced growth phase to a darkness‐induced production phase, allowing fermentation to be controlled using only light The researchers constructed a light‐repressible gene circuit by inverting the response of the OptoEXP system to create a “NOT” logic gate like those used in digital circuits.…”