Rapid Gene Target Tracking for Enhancing β-Carotene Production Using Flow Cytometry-Based High-Throughput Screening...

β-Carotene is a provitamin A precursor and an important antioxidant that is used widely in the aquaculture, food, cosmetic, and pharmaceutical industries. Oleaginous Yarrowia lipolytica has been demonstrated as a competitive producer microorganism for the production of hydrophobic β-carotene through rational engineering strategies. However, the limited understanding of the complexity of the metabolic network between carotenoid biosynthesis and other cellular processes has hampered further advancement. Genome-scale mutagenesis and high-throughput screening of mutagenesis libraries have been extensively employed in gene mining or in the identification of key targets associated with particular phenotypes. In this study, we developed a fluorescence-activated cell-sorting approach for the effective high-throughput screening of high-β-carotene-producing strains. Using this approach, millions of mutants were screened rapidly, and new gene targets involved in lipid metabolism, sterol metabolism, signal transduction, and stress response were identified. The disruption of the genes affecting fatty acid oxidation, lipid composition, and sterol transcriptional regulation (4CL-8, GCS, and YIsterTF) increased β-carotene significantly. By engineering these targets in a high-β-carotene production, a strain that produced 9.4 g/L β-carotene was constructed. Here, we used a flow cytometry approach to improve screening efficiency and eliminate the interference of intermediate metabolites. The targets obtained in this study can be used in studies focusing on metabolic engineering in the future for improving carotenoid production. IMPORTANCE β-Carotene is a high-value-added product that is widely used in the aquaculture, food, cosmetic, and pharmaceutical industries. In our previous study, Yarrowia lipolytica has been engineered extensively to produce β-carotene. To further improve its production, high-throughput screening and the identification of new beneficial gene targets are required. Herein, we developed a fluorescence-activated cell-sorting approach for the effective high-throughput screening of high-β-carotene-producing strains. Using this approach, millions of mutants were screened rapidly, and new gene targets involved in lipid metabolism, sterol metabolism, signal transduction, and stress response were identified. The disruption of the genes affecting fatty acid oxidation, lipid composition, and sterol transcriptional regulation (4CL-8, GCS, and YIsterTF) increased β-carotene significantly. By engineering these targets in a high-β-carotene production, a strain that produced 9.4 g/L β-carotene was constructed.