Chemoenzymatic Epoxidation of Methyl Oleate in a Solvent-Free System Using Rhizopus Oryzae CGMCC 3.5040 Freeze-Dried Mycelium as Biocatalyst

Freeze-dried Rhizopus oryzae mycelium efficiently catalyzed chemoenzymatic epoxidation of methyl oleate • Solvent-free system improved conversion and epoxide yield. • Epoxy methyl oleate showed excellent plasticizing performance. Unsaturated fatty acid epoxidation reactants are widely regarded as a new generation of bio-based plasticizers with the potential to replace traditional plasticizers. Herein, a chemoenzymatic epoxidation process using methyl oleate (MO) as a model substrate was established based on the perhydrolytic activity of freeze-dried Rhizopus oryzae CGMCC 3.5040 mycelium. Moreover, better epoxy conversion and yield were achieved by adopting a solvent-free system compared to the solvent system. It was found that high concentrations of hydrogen peroxide favored the perhydrolysis reaction over hydrolysis, thereby increasing the purity of the product. After 16   hours of reaction, a conversion of methyl oleate of 94.37% was achieved, the total epoxide yield reached 88.93%, and epoxy methyl oleate (EME) was quantified at 63.54%. The reaction process was described more accurately using the Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic model, which suggested that a peroxycarboxylic acid was generated at the lipase on the mycelia surface and then transferred to the oil phase to catalyze the epoxidation reaction. When the purified methyl oleate epoxide was used as a plasticizer in polyvinyl chloride (PVC), the elongation at break ( ε b ) was significantly increased from 189.88% to 406.23%, demonstrating excellent plasticizing properties. This study provides a feasible and green catalytic process for the epoxidation of unsaturated fatty acids. Download: Download high-res image (205KB) Download: Download full-size image