Bacterial FadR and synthetic promoters function as modular fatty acid sensor- regulators in Saccharomyces cerevisiae

Fatty acid derivatives have ideal properties for use as drop-in biofuels. An effective strategy in engineering microbial cells to maximize productivity and yield involves dynamic control of protein production in response to concentrations of key intermediates. In Saccharomyces cerevisiae, the activities of the native transcription factors responsive to fatty acids are repressed in the presence of a glucose carbon source. In order to develop a modular fatty acid regulation system in S. cerevisiae, we constructed fatty acid/fatty acyl-CoA biosensors in S. cerevisiae using bacterial FadR transcriptional repressors and yeast synthetic promoters containing DNA-binding operators. We demonstrated the functionality of FadR repressors in S. cerevisiae, and tuned the sensing system by varying the promoter strength upstream to the FadR-coding sequence by varying the number of operator sites in the synthetic promoter and by using FadR from two bacterial sources (Escherichia coli and Vibrio cholerae) with different ligand sensitivities. We envision that our fatty acid/fatty acyl-CoA biosensors can be used for regulation of protein expression based on the availability of fatty acid intermediates, which will assist in balancing of cellular metabolism during fatty acid derivatives production in yeast.