OPTIMIZED BIOCATALYTIC REACTIONS ON MONOCYCLIC MONOTERPENE EPOXIDATION BY IMMOBILIZED COMMERCIAL LIPASES

Terpene epoxidation has an important industrial application, as its epoxides are used as intermediates for the synthesis of flavors and fragrances. The interest in monoterpene epoxidation is due to the high reactivity of the oxirane ring, allowing the reaction with different nucleophiles (DA SILVA; BIRTH, 2007). Currently, there is in the literature the synthesis of epoxides using enzymatic biocatalysts. Among the advantages of this biocatalyst, the following stand out high yields, possibility of enzyme reuse, reactive means under milder conditions. The objective of this work is to perform the epoxidation of monoterpenes using immobilized commercial lipases, such as Candida antarctica (Novozyme 435) and Rhizomucor mieheir. The epoxidation reaction was conducted with 2 mmol of β-pinene, 2 mmol of octanoic acid, 1 mmol of urea-hydrogen peroxide complex (UHP) and 10% of Novozyme 435 enzyme (1422 U / mL), relative to mass of monoterpene and octanoic acid in 3 mL of solvent in a 4 mL vial. Reactions were conducted with different solvents: cyclohexane, dichloromethane, and acetonitrile at 40 ° C under stirring in an orbital shaker (250 rpm) for 24 to 72 h. Ethyl acetate was also used as a solvent, however, in this reaction medium, no octanoic acid was added (AKUNDEY et al, 2007). Aliquots of 50 µL were taken every 24 hours and analyzed by Gas Chromatography coupled with Mass Spectrometry (GC-MS) to determine the conversion rate through the relative percentage area (%) of the formed product. The reaction with the best conversion rate was ethyl acetate as solvent, yielding approximately 40% of the product (Spiro [bicyclo [3.1.1] heptane-2,2'-oxirane) in 24h. In subsequent reactions, the reaction time was reduced to decrease the degradation of the product and reaction kinetics were performed at times 0, 2, 4, 6 and 24 h. To optimize the reaction conditions, ethyl acetate was solvent and some parameters were changed. First, the UHP concentration was increased to 2 mmol, so that the ratio of monoterpene and urea was 1: 1. In the second change, the ratio discussed above was maintained at 1: 1, and the amount of enzyme of 10% about the mass of UHP and monoterpene. The kinetics of each reaction were performed at reaction times of 0, 1, 2, 3, 4 and 24 hours. From these described changes, it was observed that with the increase of UHP concentration, it was obtained about 90% of the product conversion, while with the change of the proportion of added enzyme, the conversion was around 80%. Therefore, because of these results, it is planned to outline an experimental design and after establishing the best-achieved condition, a reaction recycle study and also conduct the reactions. With perspective we will also use other reactors such as the microwave reactor and continuous flow as well as use other monoterpenes as substrates and thus further evaluate the biological activity of the product formed against different pathogenic fungi.