Screening microbially produced pentyl diacetic acid lactone using an Escherichia coli biosensor workflow

Cannabinoid compounds have been approved as prescription drugs for treating various human ailments. However, the production using both microbial and plant-based sources is time-consuming and expensive because their yield is extremely low. Tetraketide synthase (TKS), the key enzyme in the biosynthesis of cannabinoid compounds, produces only 4% of the intermediate compound olivetolic acid. However, it may be possible to rearrange the carbon metabolic flux of TKS using genetic methods to increase the overall yields of cannabinoid compounds. In this context, protein engineering is an economically beneficial and viable solution to improve the catalytic activity of TKS. However, the ability to produce enzyme variants significantly exceeds the capacity to screen and identify high producers, creating a bottleneck in the enzyme engineering process. This study constructed an Escherichia coli-based biosensor workflow for detecting the byproduct pentyl diacetic acid lactone (PDAL). Rational design was used to generate E. coli strains with mutant regulatory protein AraC and an altered effector PDAL to control the transcription of gfp and kanamycin. The developed biosensor could detect PDAL at the concentrations of the operational range from microbial cell culture and cell-free catalytic system. The E. coli-based biosensor developed in this study efficiently detected PDAL with high throughput and low cost.