Combinatorial Engineering of Upper Pathways and Carotenoid Cleavage Dioxygenase in Escherichia coli for Pseudoionone Production.

Pseudoionone is a valuable intermediate for the flavor industry. However, few attempts have been made to synthesize pseudoionone using biotechnology. In this work, an Escherichia coli strain harboring both the isopentenol utilization pathway (IUP) and mevalonate (MVA) pathway was engineered for the production of the pseudoionone precursor lycopene, which increased the titer of lycopene to approximately 20-fold the yield obtained by the original MEP pathway. Subsequently, the crucial limiting step of carotenoid cleavage dioxygenases (CCDs) was evaluated and optimized. The most effective upstream module for pseudoionone synthesis in E. coli was determined to be MnCCD1 from Morus notabilis without a GST-tag and under the control of the tac promoter. Finally, the highest pseudoionone production achieved 20.61 mg/L under the optimum fermentation conditions in a shake flask. This study provided an efficient approach for pseudoionone production and advanced our understanding of the characteristics of the CCD family for the biosynthesis of aroma compounds.