Immobilized lipoxygenase in a packed-bed column bioreactor: continuous oxygenation of linoleic acid

The continuous oxygenation of linoleic acid (LA) by immobilized lipoxygenase (LOX) was studied. Enzymatic oxidation was carried out in a recirculating packed column reactor using immobilized LOX as the stationary phase and LA as the substrate. The column, when packed with LOX immobilized in either a calcium alginate sol-gel matrix or a phyllosilicate sol-gel matrix, is equivalent to five continuous stirred tank reactors (CSTRs). The reactor cascade was calculated from the residence-time distribution for the reactor. Based on mass-balance calculations, a set of mathematical equations for predicting the concentration of oxygenated product generated in each CSTR was calculated. Product formation in the packed column reactor was simulated and results calculated with the model were compared with the experimental results. The data indicated that product yield (hydroperoxyoctadecadienoic acid, HPOD) increased asymptotically with reaction time. Experimentally, when the bioreactor was packed with calcium alginate sol-gel-immobilized LOX, an initial linear increase in HPOD production with time was observed, but reached a steady state. For the bioreactor packed with phyllosilicate sol-gel-immobilized LOX, initial HPOD production increased more rapidly but reached a lower steady-state concentration. From these data, a simple computer simulation model was developed to determine the process kinetics of this reactor design.