A process for the improved separation of a hydrophobic organic solution from an aqueous culture medium is provided. The process includes preparing an aqueous culture medium of a metabolically active cell having a decreased activity; contacting of the aqueous culture medium with a hydrophobic organic solution comprising a substrate for biotransformation; conducting a biotransformation of the substrate; and separating the hydrophobic organic solution comprising a biotransformed substrate from the aqueous culture medium. The decreased activity of the metabolically active cell is in comparison to a wild-type of the active cell and the decreased activity is of at least of one enzyme that catalyzes one reaction of β-oxidation of fatty acids. The invention further provides a metabolically active cell that has a decreased activity, compared to its wild-type, of an enzyme that catalyzes one of the reactions of the β-oxidation of fatty acids, including an enzyme selected from FadA, FadB, FadD, FadL and FadE as well as variants thereof.