Rational Designing and Stepwise Cascade for Efficient Biosynthesis of Raspberry Ketone

Raspberry ketone (RK) is the primary aromatic compound in raspberry fruit, which is widely utilized in perfume, cosmetics, and food additive industries. Currently, RK is predominantly produced chemically. RK biosynthesis through enzyme or whole cell has garnered significant attention due to the mild reaction conditions and the process being regarded as ‘natural’. This study proposed a ‘dual-microorganism, two-phase’ stepwise cascade strategy to produce RK from an economical precursor, 4-hydroxybenzaldehyde (4-HBD). An acetone-tolerant deoxyribose-phosphate aldolase DERAEc (S238D) mutant was obtained through a site-specific rigidification strategy for converting 4-HBD to 4-hydroxybenzylaceton (4-HBA). Then, an engineered E. coli co-expressing isocitrate dehydrogenase and raspberry ketone synthase RiRZS1 with a citrate-sodium citrate buffer to recycle nicotinamide adenine dinucleotide phosphate (NADPH) was constructed for the conversion of 4-HBA to RK. The final concentration of RK was 50.00 ± 1.92 mmol·L−1 with a yield of 86.96%. This strategy provides a scalable coenzyme self-recycling and two-phase catalysis platform for high-value phenolic compounds.