Optimization of pure linoleic acid 13-HPX production by enzymatic reaction pathway: Unravelling oxygen transfer role

Abstract

This work is, to our knowledge, the first to have investigated the role of gas–liquid oxygen transfer on the determination of the kinetic parameters of an oxidase, and on oxidase reactor sizing for pure hydroperoxides production using soybean lipoxygenase-1. The addition of a small amount of ethanol (2% v/v) was found suitable for simple linoleic acid handling and probably a better dispersion of the latter in the reaction medium. Then, the kinetic parameters of the enzyme in a pH 9 buffered medium were determined and compared to the literature data. Following a simple methodology which accounts for gas–liquid oxygen transfer, the dissolved oxygen kinetics were reprocessed to correct the initial reaction rates. kLa was thus found essential to determine accurate reaction rates. The latter were found consistent with the hydroperoxide production and linoleic acid consumption rates, confirming that the data reprocessing method was necessary. This sheds new light on several literature results on lipoxygenase activity characterizations, where a discrepancy is often observed between the apparent oxygen kinetics and the hydroperoxide production rates. Based on these results and the Damköhler number (Da) in relation to oxygen uptake and transfer, a reactor sizing procedure was proposed and led to the almost full conversion of linoleic acid into pure 13-hydroperoxide.