Soapstock from refining plant oils was processed by biotechnol. and chem. methods to recover long-chain fatty acids. The biotechnoL fed-batch method was based on fermentation of soapstock in presence of Yarrowia lipolytica yeast culture, glycerol and peptone and carried out at 28 degrees C for 48 h. The chem. method was based on treatment of soapstock with H2SO4, HCI or H3PO3 at 90 degrees C for 1 h. Welds of long-chain fatty acids in biotechnoL method was 28 cm(3)/100 g of soapstock and 31 cm(3), 30 m(3) and 28 cm3/100 g, resp., in the chem. method. Oleic acid was the main component of the product (more than 53%). The product contained also P, N and S.