Engineered Saccharomyces cerevisiae for High-Yield and Sustainable Production of α-Bisabolol via Combinatorial Genomic Integration and Pathway Amplification

α-Bisabolol is naturally occurring in many plants and has great potential in health products and pharmaceuticals. However, the current extraction method from natural plants is unsustainable and cannot fulfil the increasing requirement. This study aimed to develop a sustainable strategy to enhance the biosynthesis of α-bisabolol by metabolic engineering. Integration of ERG20 (encoding farnesyl diphosphate synthase) and tHMG1 (encoding truncated 3-hydroxy-3-methylglutaryl-CoA reductase) genes with a constitutive strong promoter into the yeast genome elevated α-bisabolol production from 20.21 mg/L to 98.30 mg/L, representing a 4.86-fold increase. Further optimization of the mevalonate pathway and amplification of ERG20, tHMG1, and OsTPS1 copy numbers enhanced α-bisabolol synthesis to 423.01 mg/L, achieving a 20.93-fold improvement relative to the baseline. This work establishes a reference strategy for high-yield α-bisabolol biosynthesis in engineered yeast.