Hydroperoxide formation from linoleate and linolenate esters using enzymatic and non-enzymatic approaches

Abstract

Fatty acid hydroperoxides can be used as intermediates in many chemical reactions, but we were particularly interested in reducing the hydroperoxides to alcohols as a potential substitute for castor oil, which currently is used for numerous industrial applications. Two innovative approaches were tried to achieve acceptable hydroperoxide formation. The first approach was to utilize the enzyme lipoxygenase-2 (LOX-2), since LOX-2 has been reported to work on triglycerides. The second approach used the photosensitizers, rose bengal, and chlorophyllin along with light to accelerate the oxidation. The use of LOX-2 was frustrated by the instability of the enzyme. We varied reaction conditions and immobilized the enzyme in various ways to increase enzyme stability and yield, but none were very successful. The yield was increased significantly by removing tocopherols from the substrate. For the photooxidation approach, we optimized the effect of reaction time, sensitizer concentration, pumping rate, and light exposure. With distilled soybean methyl ester as a substrate, the non-enzymatic method could reach 7% conversion in 5 h, whereas, the enzymatic method could only reach 1% conversion before the enzyme became inactive.