Aspergillus niger whole-cell catalyzed synthesis of caffeic acid phenethyl ester in ionic liquids

Synthesis of caffeic acid ester essentially requires an efficient esterification process to produce various kinds of medicinally important ester derivatives. In the present study, a comprehensive and comparative analysis of whole-cell catalyzed caffeic acid esters production in ionic liquids (ILs) media was performed. Olive oil induced mycelial mass of halotolerant Aspergillus niger (A.niger) EXF 4321 was freeze dried and used as a catalyst. To ensure maximum solubilization of caffeic acid for highest substrate loading several ILs were screened and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][Tf₂N]) was found to have the maximum solubility and favoured for enzymatic activity of freeze dried mycelia. The whole-cell catalyzed synthesis of caffeic acid phenethyl ester (CAPE) conditions were optimized and bioconversion up to 84% was achieved at a substrate molar ratio of 1:20 (caffeic acid:2-phenyl ethanol), 30°C for 12h. Results obtained during this study were encouraging and helpful to design a bioreactor system to produce caffeic acid derived esters.