Production of 10-hydroxystearic acid from oleic acid and olive oil hydrolyzate by an oleate hydratase from Lysinibacillus fusiformis

A recombinant enzyme from Lysinibacillus fusiformis was expressed, purified, and identified as an oleate hydratase because the hydration activity of the enzyme was the highest for oleic acid (with a kcat of 850 min−1 and a Km of 540 μM), followed by palmitoleic acid, γ-linolenic acid, linoleic acid, myristoleic acid, and α-linolenic acid. The optimal reaction conditions for the enzymatic production of 10-hydroxystearic acid were pH 6.5, 35 °C, 4% (v/v) ethanol, 2,500 U ml−1 (8.3 mg ml−1) of enzyme, and 40 g l−1 oleic acid. Under these conditions, 40 g l−1 (142 mM) oleic acid was converted into 40 g l−1 (133 mM) 10-hydroxystearic acid for 150 min, with a molar yield of 94% and a productivity of 16 g l−1 h−1, and olive oil hydrolyzate containing 40 g l−1 oleic acid was converted into 40 g l−1 10-hydroxystearic acid for 300 min, with a productivity of 8 g l−1 h−1.