Ketoisophorone Synthesis with an Immobilized Alcohol Dehydrogenase

The monoterpenoid alpha-isophorone is sourced from the available and renewable plant dry matter, as well as a waste recovery operation from acetone. This compound, can be hydroxylated to 4-hydroxy-isophorone which is the main precursor for the synthesis of ketoisophorone. On its turn, ketoisophorone is a key intermediate for the production of carotenoids and Vitamin E. Here, the enzymatic oxidation of 4-hydroxy-isophorone to ketoisophorone is demonstrated employing an alcohol dehydrogenase (ADHaa) from Artemisia annua and a NADPH oxidase (NOX), as a cofactor regeneration enzyme. After 24 h of reaction and an initial substrate concentration of 50 mM, 95.7 % yield and a space time yield of 6.52 g L-1 day(-1) could be obtained. Furthermore, the immobilization of the alcohol dehydrogenase was studied on 17 different supports. An epoxy-functionalized agarose resulted in the highest metrics, 100 +/- 0% immobilization yield and 58.2 +/- 3.5 % retained activity. Finally, the immobilized ADHaa was successfully implemented in 4 reaction cycles (96 h operation) presenting a biocatalyst yield of 23.4 g product g(-1) of enzyme. It represents a 2.5-fold increase compared with the reaction with soluble enzymes.