Production of high quality biodiesel from sunflower soapstock acid oil as novel feedstock: Catalyzed by immobilized pancreatic lipase

Edible refined oils, which are utilized as raw materials in biodiesel production, have been replaced by by-products (acid oil, fatty acid, deodorized distillate, and soapstock distillates) obtained from the vegetable oil refining industry, in recent years. This study aims to investigate the production of high quality biodiesel fuel in accordance with the standards (TS EN and ASTM) from sunflower soapstock acid oil. This feedstock was donated by an oil factory in the Thrace region, Turkey. Esterification reaction was performed by immobilized enzyme. For this, immobilization was carried out by covalent binding of pancreatic lipase in glutaraldehyde activated chitosan and optimum immobilization conditions were determined. The activity of the immobilized lipase and the retained activity were found to be 65.69 U/μg and 61.8%, respectively (pH: 7.5, 37°C). The K_m (Michealis constant) and V_max (maximum velocity of an enzymatically catalyzed reaction) values of the immobilized enzyme were found to be 5.1 mmol/L and 48.6 U/min/mg protein, respectively. The immobilized enzyme was employed as a biocatalyst for esterification of sunflower soapstock acid oil. Notably, an impressive yield of 75.6% was attained under the conditions of a 1:5 molar ratio of soapstock acid oil to methanol, with 10 wt% immobilized lipase as the catalyst, and a reaction temperature of 45°C for 36 h. The resulting biodiesel exhibits fuel characteristics that meet the standards outlined in TS EN 14214:2012 + A2 and ASTM D6751-02.