Epoxidation of propylene utilizing Nocardia corallina immobilized by gel entrapment or adsorption

Nocardia corallina B-276 cells are capable of catalysing the direct epoxidation of propylene to propylene oxide, through a monooxygenase enzyme system. The present work was undertaken to see how immobilization of the whole cells by adsorption or entrapment on solid supports would influence the rate and duration of the epoxidation activity. With immobilization by adsorption, the propylene oxide forming activity was highest on hydrophobic supports, such as polypropylene or polyethylene. Under certain conditions the activity was three times that of the free control cells. However, the duration of epoxidation activity was considerably less for the adsorbed cells. The cell loading by adsorption, determined with¹⁴C-labelled cells was 1.0–2.8 mg dry cell weight g^?1of support. The cells, whether immobilized or not (controls), were tested using a continuous gas flow packed-bed or bubble-type reactor. Immobilization of the cells by entrapment in calcium alginate beads gave about the same propylene oxide forming activity and stability as with control cells, provided the reactor was operated at low temperature (30°C) and low oxygen content (20%) of the feed stream. The results suggest that entrapment in a hydrophobic matrix might be a more favourable system; although additional investigation of the rate limiting steps as well as the cause of the activity loss with time is needed.