Microencapsulation of silicone oils within polyamide—polyethylenimine membranes as oxygen carriers for bioreactor oxygenation

Abstract

Silicone oils were microencapsulated within polyamide (nylon) membranes cross-linked with polyethylenimine. Solubility of oxygen within the silicones, whether encapsulated or not, was approximately 6 mmol dm⁻³, representing solubilities approximately 20-fold higher than that of oxygen in water. The response time of oxygen transfer from the microencapsulated oxygen carrier was less than 2.5 s; a more precise measurement was limited by the response time characteristics of the oxygen probe. Assuming that the bioreactor volume consists of 10–20% (v/v) microencapsulated silicone oil, this represents an enhancement of the oxygen reservoir by a factor ranging from 4 to 7 and improvement in oxygen transfer rates greater than 15-fold due to the greatly increased specific surface area in comparison to conventional bubble aeration. Circulation of oxygenated silicone oils encapsulated within inert polymeric membranes may provide an efficient alternative to bioreactor oxygenation with shear sensitive cell systems, or in fermentations with high oxygen requirements.