Enzymatic preparation of linoleic acid from sunflower oil: an experimental design approach

Enzymatic preparation of linoleic acid from sunflower oil was examined through a statistical approach. Initially, enzyme screening for oil hydrolysis was investigated. The results indicated that lipases from yeast and bacteria provided higher rates of hydrolysis, when compared to lipases from fungi. In particular, the utilization of Candida rugosa lipase offered the highest hydrolysis rate of 67.12%. Once the optimal lipase for oil hydrolysis was identified, an optimization of the enzymatic process was further investigated. Central composite design was employed in this experiment. The independent variables, affecting the degree of hydrolysis, were found to be buffer-to-oil and enzyme-to-oil ratios, as well as the initial pH (p < 0.05). Statistical analysis suggested that the precision of the predictive model was adequate, due to the low p-values (p < 0.01) and satisfactory levels of the coefficient of determination (R 2 = 0.89). In addition, verification of the statistical model suggested that the difference between the predicted and actual degree of hydrolysis was less than 5%. To achieve a hydrolysis degree of 76.07%, the optimal conditions were as follows: buffer-to-oil ratio of 4:1 (w/w), enzyme-to-oil ratio of 750.28 U/g and initial pH of 6.7. Subsequently, urea complex fractionation was performed to enrich the polyunsaturated fatty acids in the enzymatic hydrolysates. The results suggested that the purity of the linoleic acid could be enriched to 70% (w/w). Thus, this process could be used to effectively prepare the linoleic acid as a bio-based ingredient for nutraceutical and cosmetic products.