Biocatalytic hydroxylation of linoleic acid in a double-fed batch system with lipoxygenase and cysteine

The enzymatic large-scale preparation of unsaturated fatty acid hydroperoxides is the first step in the preparation of the corresponding fatty acid hydroxides. Since hydroxides are more suitable than hydroperoxides as precursors of fine chemicals like certain flavour compounds, a convenient and effective reduction step of hydroperoxides is required. In this paper a double-fed batch procedure for the enzymatic preparation of fatty acid hydroperoxides including the application of cysteine as a mild reducing agent is described. A crude extract from defatted soybean flour was used as the source of lipoxygenase, while the primary substrate was linoleic acid from hydrolyzed safflower oil. Enzyme and substrate were fed synchronously into the bioreactor that already contained buffer solution and cysteine. Typically, reactions with 40 g/l substrate in a 7 l reactor were done on a 2 l scale. Without any intermediate work-up, a final product yield of 90% could be achieved consisting for nearly 96% of 13(S)-hydroxy-(9Z,11E)-octadeca-9,11-dienoic acid