Production of High Quality Biodiesel from Sunflower Acid Oil Obtained by Acidulation of Soapstock from Refining Process: Immobilized Pancreatic Lipase for Biodiesel Production

Abstract

Abstract Edible refined oils, which are utilized as raw materials in biodiesel production, have been replaced by by-products (acid oil, fatty acid, deodorized distillate and soapstock distillates) obtained from the vegetable oil refining industry, in recent years.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 soapstock acid oil. Waste sunflower soapstock acid oil used in the study was donated by an oil factory in the Thrace region. The acid oil, which comprises predominantly of FFA (≥ 95 wt%), is obtained through the liberation of soapstock from the refining process employed for edible sunflower oil via acidulation. Transesterification reaction was performed by immobilized pancreatic lipase. For this, the immobilization by covalent binding of pancreatic lipase in glutaraldehyde activated chitosan was optimized. The activity of the immobilized lipase and the retained activity were found to be 35.69 U/µg and 61.8%, respectively (pH: 7.5, 37°C). The Km and Vmax values of the immobilized enzyme were found to be 5.1 mmol/L and 486 U/mg, respectively. Following immobilization, the enzyme was employed as a biocatalyst for transesterification, converting 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% immobilized lipase as the catalyst, and a reaction temperature of 45°C for 36 hours. The resulting biodiesel exhibits fuel characteristics that meet the standards outlined in TS EN 14214:2012 + A2 and ASTM D6751.