Chemoenzymatic Epoxidation of Terpenes by Lyophilized Mycelium of Psychrophilic Cladosporium cladosporioides 01

Samenvatting

Terpene epoxides constitute a group of compounds of particular importance due to their biological activity or use in the production of polymers. It is important to develop a universal, inexpensive, and sustainable method to obtain these compounds from readily available terpenes. Chemoenzymatic epoxidation by the freeze-dried mycelium of Cladosporium cladosporioides01 is an alternative to processes based on the well-known and expensive lipase B fromCandida antarctica. In the present work, we studied the kinetics of limonene epoxidation by the fungal biocatalyst and found the highest epoxidation activity in the “green” solvent ethyl acetate with a 4-fold excess of H₂O₂ relative to the substrate. Epoxidation followed a two-way sequential mechanism in which the major initial product limonene 1,2-epoxide and the minor intermediate product limonene 8,9-epoxide were further converted to limonene diepoxide. Substrate specificity studies revealed that a wide number of linear and cyclic monoterpenes, e.g., linalool, citronellene, citronellal, α-pinene, β-pinene, myrtenol, and perillyl alcohol, were efficiently converted to their respective epoxides by this biocatalyst. The biocatalyst may show activity in the direct oxidation of a double bond without the use of a peracid. The freeze-dried mycelium exhibited higher biocatalytic activity after defatting and high stability in ethyl acetate and in the presence of an oxidant. No decrease in its activity was observed after eight biocatalytic cycles. Therefore, the mycelium can be successfully used for the sustainable large-scale production of terpene epoxides.