Possibly a higher cell death rate and carotenoid extraction rate could have been achieved by increasing the dodecane sparging rate. However, the sparging rate applied (0.286 Ldod LRV −1 min−1 ) resulted in the formation of a dodecane emulsion in the aqueous phase after 6 days of operation, as shown in Fig. 4. Dead cell material such as amphipolar membrane components will have acted as surfactants and have lead to strong emulsification of the two-phase system. Consequently, the small dodecane droplets were stabilized and hardly coalesced anymore [8]. These droplets interfered with the turbidity measurements of the system and resulted in an appar- ent increase of the turbidity, causing an increased dilution rate. Consequently cells were washed out (data not shown). Moreover, due to increasing emulsion formation it was not possible to sepa- rate the aqueous and organic phase anymore (Fig. 4d).