Efficient Whole‑Cell Biosynthesis of Curcumin Monoacetate by Rhizopus arrhizus With Improved Stability and Tyrosinase Inhibitory Activity

Curcumin, a natural food colorant and functional ingredient, suffers from poor stability, low lipophilicity, and limited oral bioavailability. This study, for the first time, employs a whole‐cell catalyst (Rhizopus arrhizus MQ1 isolated from lipid‐rich soil) to achieve green acylation of curcumin in a non‐aqueous system, aiming at efficient synthesis of curcumin monoacetate (CA). Using vinyl acetate as the acyl donor, the reaction conditions were optimized (DMSO, 40 mg/mL whole‐cell catalyst, substrate ratio 1:62.5, 60°C), reaching a conversion >90%. To investigate the substrate specificity of the whole‑cell catalyst towards acyl donors of different chain lengths, vinyl butyrate and vinyl octanoate were also tested, yielding the corresponding monoacylated derivatives—curcumin monobutyrate (CB) and curcumin monooctanoate (CO). All three derivatives showed increased Log P relative to curcumin; CA (3.32) fell within the optimal range and exhibited the highest aqueous solubility (Log S = ‐4.11) among the series. All three derivatives exhibited improved photothermal stability, stability in simulated body fluids, and tyrosinase inhibitory activity compared to curcumin. Among them, CA showed superior overall performance: >75% retention after 6 h at 100°C and an IC 50 of 125.94 µmol/L (23.8% higher potency than curcumin), making it a promising candidate for functional food ingredients, anti‑browning agents, and natural colorant improvement. This study provides a green whole‐cell acylation strategy that not only achieves high conversion of CA but also demonstrates substrate specificity towards acyl donors of different chain lengths.