A bioprocess with a high conversion rate of limonene to alpha-terpineol was described. The enzyme hydratase involved in this process was found as being cofactor independent, non-inducible and able to perform the transformation of both R-(+) and S-(-)-limonene. The system used consisted of a biphasic medium in which the aqueous phase contained a concentrated resting cells of Sphingobium sp. and the organic phase was sunflower oil. After 30 h at 30 degrees C ca. 25 g of R-(+)-alpha-terpineol per liter of organic phase were obtained from R-(+)-limonene in Erlenmeyer flasks. Performance of the bioconversion in a bioreactor increased the production rate with no changes in yield and maximal R-(+)-alpha-terpineol concentration, which demonstrated that experiments in flasks were limited by liquid-liquid transport phenomena. A mathematical model able to explain the fact that the reaction always stopped before the precursor became exhausted has also been proposed and validated. Finally, the process reported was the most promising alternative for the biotechnological production of natural R-(+)-alpha-terpineol published so far and up to ca. 130 g L(-1) metabolite could finally be obtained. (C) 2009 Elsevier Ltd. All rights reserved.