Production and Recovery of Limonene-1,2-Diol and Simultaneous Resolution of a Diastereomeric Mixture of Limonene-1,2-Epoxide with whole Cells of Rhodococcus Erythropolis DCL14

Abstract

Cells of Rhodococcus erythropolis DCL14 present a limonene epoxide hydrolase activity when grown on terpenes, which enables them to convert cis-limonene-1,2-epoxide to limonene-1, 2-diol. Trans-limonene-1,2-epoxide is only converted when no cis is present. An organic/aqueous system was developed to overcome the low solubility and instability of limonene-1,2-epoxide in the aqueous phase. The presence of the organic solvent allowed high epoxide concentrations to be used which resulted in high limonene-1,2-diol production rates. Relatively cheap solvents were tested without any significant loss of epoxide hydrolase activity. Using a 500 ml fed-batch mechanically stirred reactor it was possible to produce 197.2 g of diol per g of protein and to obtain a yield of 98.2% and 67.9% for the trans-epoxide and the diol, respectively. Production of 72.4 g of diol per g of protein was obtained using a magnetically stirred reactor with an external loop for product separation. In this case, trans-epoxide and diol yields were 98.5% and 94.1%, respectively.

A downstream process, based both on the preference of the substrate for organic solvents and that of the product for the aqueous phase, allowed the recovery of limonene- 1,2-diol, as well as of the trans-epoxide, with a purity higher than 99%.

Key Words:

• Organic/aqueous system
• Rhodococcus erythropolis
• Epoxide hydrolase
• Limonene epoxide
• Limonene-1,2-diol