Metabolic Engineering of Rhodotorula toruloides for Biosynthesis of Retinal

Rapid advancements in biotechnology have enabled biomanufacturing to emerge as a feasible approach for industrial chemical production. By harnessing synthetic biology and metabolic engineering, engineered microbial cell factories can convert renewable resources into valuable chemicals, providing a sustainable alternative to traditional chemical methods. This study focuses on the microbial production of retinal, an important retinoid used in pharmaceuticals, food, and cosmetics. The oleaginous yeast Rhodotorula toruloides NP11 was genetically modified to synthesize retinal by incorporating and optimizing three β-carotene 15,15'-dioxygenase genes from various sources. Several genetic modifications were made to enhance retinal yield, including the overexpression of isopentenyl-diphosphate isomerase (IDI1), geranylgeranyl diphosphate synthase (BTS1), phytoene synthase (CARRP), and phytoene dehydrogenase (CARB), which led to increased β-carotene levels and boosted retinal production. Furthermore, fermentation conditions such as temperature, antioxidants, and extractants were fine-tuned. The engineered strain Rt13 ultimately achieved a maximum retinal concentration of 20.38 mg/L through fed-batch fermentation. This study highlights the potential of R. toruloides as a cell factory for terpenoid biosynthesis, providing valuable insights for future metabolic engineering endeavors.