Integrated lipase-catalyzed isoamyl acetate synthesis in a miniaturized system with enzyme and ionic liquid recycle

Abstract

Isoamyl acetate synthesis employing aqueous Candida antarctica lipase B (CaLB) solution was performed in a two-phase solvent system comprising hydrophilic ionic liquid 1-butyl-3-methylpyridinium dicyanamide and n-heptane. An X-junction glass microfluidic chip was used to obtain uniform microdroplets of n-heptane within a continuous phase of ionic liquid with dissolved enzyme and reactants, namely, isoamyl alcohol and acetic anhydride. A developed flow pattern resulted in a very large specific interfacial area for the reaction with amphiphilic CaLB and simultaneous extraction of isoamyl acetate in n-heptane. Biotransformation was performed within a continuously operated microfluidic system consisting of an X-junction chip and a silanized tube of a submillimeter diameter, which was further integrated with a microseparator based on a hydrophobic membrane. Efficient separation of n-heptane with product from ionic liquid phase containing enzyme and remaining substrates and products was achieved, enabling reuse of CaLB together with ionic liquid phase. More than 80% of productivity was preserved in each of the eight consecutive biotransformations within the integrated microfluidic system with reused lipase B in the ionic liquid phase. Subsequent ionic liquid regeneration accomplished by vacuum distillation enabled efficient reuse of this solvent in esterification with fresh enzyme.