A repeat-batch membrane bioreactor with a phase inversion for the desaturation of isopropyl palmitate by a mutant Rhodococcus strain

A repeat-batch membrane bioreactor was constructed for the novel bioconvers ion of isopropyl hexadecanoate to isopropyl cis-6-hexadecenoate by a Rhodoc occus mutant. The addition of glutamate, thiamine, and MgSO4 was very effec tive in improving not only the rate and yield of the bioconversion but also the maintenance of desaturation activity during cell. recycling. An oil-in -water (O/W) type emulsion of the reaction medium was inverted to a water-i n-oil (W/O) type by discharging the water phase from the reaction mixture. The continuous oil phase containing the product could effectively be recove red through a hydrophobic hollow-fiber module. By decreasing the oil-to-wat er ratio upon addition of fresh medium, the medium was spontaneously invert ed again to an O/W type emulsion to proceed with the next conversion. The b atch reaction coupled with the phase inversion could be repeated more than 13 times for over about 300 h operation. Finally, a highly purified product was obtained with high yield by the urea adduct procedure. (C) 2000 Elsevi er Science B.V. All rights reserved.