Efficient enzymatic synthesis of D-α-tocopherol acetate by Carica papaya lipase-catalyzed acetylation of D-α-tocopherol in a solvent-free system

Enzymatic synthesis of D-α-tocopherol acetate is a promising approach for cost-effective production of liposoluble food and pharmaceutical antioxidant. In this study, we developed an efficient and environmentally friendly process that employed plant-derived Carica papaya lipase (CPL) as biocatalyst for the synthesis of D-α-tocopherol acetate in a solvent-free system. The optimum conditions were: 400 mg/mL D-α-tocopherol, 125 mg/mL CPL (44 U, aw=0.328), with acetic anhydride as acyl donor, at 60°C and 200 rpm for 30 h. Interestingly, yields of 90.7%, 77.7%, 60.3% and 48.1% of D-α-tocopherol acetate were achieved after the "naturally immobilized" CPL recycled for 4 times, indicating a novel enzyme immobilization mechanism. Moreover, the synthetic product was purified from scaled-up reaction, and confirmed by FTIR and GC-MS analysis, providing a total of 97.5% purity (91.1% D-α-tocopherol acetate plus 6.4% D-α-tocopherol). Overall, this work provided an efficient alternative method for green production of D-α-tocopherol acetate probably being applied in food and pharmaceutical industries, and this could also enhance the comprehensive utilization of Carica papaya.