Efficient Transformation of Linoleic Acid into 13(S)-Hydroxy-9,11-(Z,E)-octadecadienoic Acid Using Putative Lipoxygenases from Cyanobacteria

Enzymatic dioxygenation of unsaturated fatty acids by lipoxygenases (LOXs) represents a useful method in the transformation of bioresources for hydroperoxy and hydroxy fatty acids production. Difficulties in screening for optimal enzymes and in producing LOXs in sufficient quantity limit the large-scale application of LOXs. In this work, we identified three putative LOXs from Cyanobacteria, i.e., Ca-LOX from Calothrix sp. HK-06, Ri-LOX from Rivularia sp. PCC 7116, and Tb-LOX from Tolypothrix bouteillei VB521301. After heterologous expression in Escherichia coli and purification by HisTrap affinity chromatography, these LOXs showed high specific activities toward linoleic acid (73.1, 68.8, and 10.1 U mg–1 protein, respectively). All three enzymes were identified as linoleate 13S-lipoxygenases. Ca-LOX and Ri-LOX are the highest-activity LOXs yet reported, and Ri-LOX gave a high titer of 38.3 U/mL on heterologous expression in E. coli. Consequently, by using Ri-LOX as an efficient biocatalyst with a subsequent reduction step, the renewable material linoleic acid was efficiently transformed into a value-added chemical, 13(S)-hydroxy-9,11-(Z,E)-octadecadienoic acid (13S-HODE), with an unprecedented space–time yield of 1008 g L–1 d–1, indicating great potential of this LOX for sustainable production of 13-HODE and its derivatives.