An Enzyme Cascade Synthesis of [epsi]-Caprolactone and its Oligomers

Poly-[epsi]-caprolactone (PCL) is chemically produced on an industrial scale in spite of the need for hazardous peracetic acid as an oxidation reagent. Although Baeyer-Villiger monooxygenases (BVMO) in principle enable the enzymatic synthesis of [epsi]-caprolactone ([epsi]-CL) directly from cyclohexanone with molecular oxygen, current systems suffer from low productivity and are subject to substrate and product inhibition. The major limitations for such a biocatalytic route to produce this bulk chemical were overcome by combining an alcohol dehydrogenase with a BVMO to enable the efficient oxidation of cyclohexanol to [epsi]-CL. Key to success was a subsequent direct ring-opening oligomerization of in situ formed [epsi]-CL in the aqueous phase by using lipase A from Candida antarctica, thus efficiently solving the product inhibition problem and leading to the formation of oligo-[epsi]-CL at more than 20gL-1 when starting from 200mM cyclohexanol. This oligomer is easily chemically polymerized to PCL.