Genome-scale CRISPRi screen identifies pcnB repression conferring improved physiology for overproduction of free fatty acids in Escherichia coli

Microbial physiology plays a pivotal role in construction of a superior microbial cell factory for efficient production of desired products. Here we identified pcnB repression through genome-scale CRISPRi modulation combining fluorescence-activated cell sorting (FACS) and next-generation sequencing (NGS), which confers improved physiology for free fatty acids (FFAs) overproduction in Escherichia coli. The repression of pcnB could improve the stability and abundance of the transcripts involved in proton-consuming system, conferring a global improvement on cell membrane, redox state, and energy level. These physiological advantages facilitated further identification of acrD repression enhancing FFAs efflux. The engineered strain pcnBi-acrDi-fadR+ achieved 35.1?g?l-1 FFAs production in fed-batch fermentation, which is the maximum titer in E. coli reported to date. This study underscores the significance of hidden genetic determinants in microbial biosynthesis and sheds light on the role of microbial physiologies in boosting microbial biosynthesis. Overall design: In this study, we carried out genome-scale CRISPRi modulation combining fluorescence-activated cell sorting (FACS) and next-generation sequencing (NGS) to identify genetic determinants for FFAs overproduction in Escherichia coli. The pcnBi (AP) strain that repressed the expression of pcnB produced 2992 mg l FFAs, which was 4.0-fold of the CF (A) strain. To analyze the underlying mechanism of FFAs overproduction, the engineered strain pcnBi and the control strain CF were applied to the transcriptomic and proteomic analyses.