Efficient synthesis of methyl 3-acetoxypropionate by a newly identified Baeyer-Villiger monooxygenase

ABSTRACT Baeyer-Villiger monooxygenases (BVMOs) are an emerging class of promising biocatalysts for the oxidation of ketones to prepare corresponding esters or lactones. Although many BVMOs have been reported, the development of highly efficient enzymes for use in industrial applications is desirable. In this work, we identified a BVMO from Rhodococcus pyridinivorans (BVMO Rp ) with a high affinity toward aliphatic methyl ketones ( K m k cat = 2.1 s −1 ; K m = 1.5 μM). Furthermore, BVMO Rp exhibited excellent regioselectivity toward most aliphatic ketones, preferentially forming typical (i.e., normal) products. Using the newly identified BVMO Rp as the catalyst, a high concentration (26.0 g/liter; 200 mM) of methyl levulinate was completely converted to methyl 3-acetoxypropionate after 4 h, with a space-time yield of 5.4 g liter −1  h −1 . Thus, BVMO Rp is a promising biocatalyst for the synthesis of 3-hydroxypropionate from readily available biobased levulinate to replace the conventional fermentation. IMPORTANCE BVMOs are emerging as a green alternative to traditional oxidants in the BV oxidation of ketones. Although many BVMOs are discovered and used in organic synthesis, few are really applied in industry, especially in the case of aliphatic ketones. Herein, a highly soluble and relatively stable monooxygenase from Rhodococcus pyridinivorans (BVMO Rp ) was identified with high activity and excellent regioselectivity toward most aliphatic ketones. BVMO Rp possesses unusually high substrate loading during the catalysis of the oxidation of biobased methyl levulinate to 3-hydroxypropionic acid derivatives. This study indicates that the synthesis of 3-hydroxypropionate from readily available biobased levulinate by BVMO Rp -catalyzed oxidation holds great promise to replace traditional fermentation.