Alkyl Formate Ester Synthesis by a Fungal Baeyer-Villiger Monooxygenase

Abstract

We investigated Baeyer-Villiger monooxygenase (BVMO)-mediated synthesis of alkyl formate esters, which are important flavor and fragrance products. A recombinant fungal BVMO from Aspergillus flavus was found to transform a selection of aliphatic aldehydes into alkyl formates with high regioselectivity. Near complete conversion of 10 mm octanal was achieved within 8 h with a regiomeric excess of ∼80 %. Substrate concentration was found to affect specific activity and regioselectivity of the BVMO, as well as the rate of product autohydrolysis to the primary alcohol. More than 80 % conversion of 50 mm octanal was reached after 72 h (TTN nearly 20 000). Biotransformation on a 200 mL scale under unoptimized conditions gave a space-time yield (STY) of 4.2 g L^-1 d^-1 (3.4 g L^-1 d^-1 extracted product).

Keywords: Baeyer-Villiger monooxygenase; aldehydes; alkyl formate; biocatalysis; formate ester.