LAUSR

Abstract Motivated by the search for inexpensive biocatalysts, this study aimed to investigate the potential of lipase from castor bean seeds for hydrolysis of high-acidity oils. Biochemical properties, kinetics, and thermal stability were investigated in reactions with vegetable (macaw pulp and kernel) and microalgal (Dunaliella salina, Nannochloropsis gaditana, and Chlorella minutissima) oils. Enzyme performance was optimal at pH 4.5 and 35 °C. Thermal stability tests revealed a half-life of 9.6 h at 35 °C and apparent Vmax and Km values of 181.82 U g−1 and 215.15 mmol L−1, respectively. The rate of hydrolysis was influenced by oil type, fatty acid composition, and oil concentration in the reaction medium. Castor bean lipase showed higher specificity toward vegetable oils rich in polyunsaturated fatty acids. The highest hydrolysis percentage of macaw pulp oil (53.55 ± 2.03%) was obtained at an oil/water weight ratio of 1:4 after 3 h of reaction. Lower performances were achieved with microalgal oils (31–43%), attributed to the presence of pigments, particularly chlorophyll, which has a negative effect on biocatalyst activity. The highest hydrolysis percentage was obtained using D. salina oil (43%) in 4 h of reaction. N. gaditana and C. minutissima oils had a hydrolysis percentage of 34 and 31%, respectively. D. salina oil had a similar fatty acid composition to macaw pulp oil, with 37.5% oleic acid and 15.4% linoleic acid. Nevertheless, the hydrolysis percentage of N. salina oil was 10% lower than that of macaw pulp oil. The low-cost solid preparation of castor bean lipase showed satisfactory performance in catalyzing the hydrolysis of vegetable oils. This economically attractive strategy can be used to obtain free fatty acids from non-edible oils for the production of biodiesel by hydroesterification.