Optimization of esterification reactions of perillyl alcohol with different fatty acids catalyzed by Novozym® 435...

Perillyl alcohol is a monoterpene known for its potent antitumor activity. In this study, we focused on esterification reactions of perillyl alcohol catalyzed by the immobilized enzyme Novozym 435 from Pseudozyma antarctica. Initially, the reaction conditions using a molar ratio of 1:4 (2:5 mmol of monoterpene: 10 mmol of octanoic acid), 40 mg of Novozym 435, 30 °C, and 150 rpm, 10 mL of cyclohexane, resulted in conversions up to 90% by 24 h. To explore the impact of different fatty acid carbon chain lengths on conversion, we conducted reactions with fatty acids containing chain lengths with 3, 6, 8, 12, and 18 carbons, evaluating the impact of the molar ratio of monoterpene:fatty acid. The observed impacts on conversion led to the categorization of fatty acids into two groups: the first group (C₃ and C₆) showed a positive impact with an increased molar ratio, while the second group (C₈-C₁₈) exhibited the opposite behavior. Based on these findings, we performed an experimental design (CCRD-Central Composite Rotatable Design) using octanoic acid (representing fatty acids with chains equal to or greater than eight carbons) and propionic acid (representing acids with chains lower than six carbons). The optimized conditions in CCRD resulted in conversions of 95.22% ± 0.61% with octanoic acid (substrate: acid, 2.5 mmol: 3.87 mM, enzyme: 48 mg) and 90.38% ± 0.99% with propionic acid (substrate: acid, 2.5 mmol: 3.10 mM, enzyme: 66.6 mg), at 30 °C and 150 rpm for 24 h. Finally, we assessed the reusability of Novozym 435 (48 mg) in the esterification reaction of (S)-(-)-perillyl alcohol (2.5 mmol) with octanoic acid (3.87 mM) for 24 h at 30 °C and 150 rpm. Remarkably, even after 10 cycles of 24 h, no loss of enzyme activity was detected, suggesting the potential for industrial applications.