Biocatalysis by immobilized lipoxygenase in a ternary micellar system

Biocatalysis by immobilized soybean lipoxygenase (LOX) (EC 1.13.11.12) in selected organic solvent systems, including monophasic, biphasic and ternary micellar systems, was investigated using linoleic acid as a model substrate. The highest specific activity for the immobilized LOX was observed in a ternary micellar system composed of Tris–HCl buffer solution containing 4% iso-octane and 10 μM Tween 40. The immobilized LOX had optimum activity at a pH of 9.5 and showed better stability than its free counterpart at high temperatures, exhibiting maximum activity at a temperature of 70 °C. The highest catalytic efficiency value for the immobilized LOX was found to be 4.20 in the monophasic reaction medium of octane, followed by 0.59 and 0.44 obtained in the biphasic systems composed of buffer and containing either 3.5% octane or 4% iso-octane, respectively. The immobilized LOX showed higher specificity toward linoleic acid, followed by arachidonic acid. Characterization of the enzymatically catalyzed end products indicated that the proportions of hydroperoxide (HPOD) isomers produced from linoleic acid were dependent on the free and immobilized states of LOXs. The immobilized LOX was recovered and recycled up to four times before a complete loss of activity.