The conventional biodiesel production process has some disadvantages. It is necessary to use refined vegetable oils with low free fatty acids (FFAs) content. An alternative route is to use low-cost acid oils in an enzymatic process. The use of lipases allows simultaneous esterification of FFAs and transesterification of triglycerides present in raw material forming alkyl esters. The aim of this work was to study the production of biodiesel using soybean oils with different acid contents (Acid Value of 8.5, 50, 90) and ethanol catalyzed by commercial immobilized lipases (Novozym 435, Lipozyme RM IM and Lipozyme TL IM). A significant decrease of acid value was observed mainly with Novozym 435 and Lipozyme RM IM. The use of a mixture of two immobilized lipases was also investigated to decrease catalyst cost and increase the amount of ester produced. The three commercial immobilized lipases were mixed in a dual system and tested for biodiesel synthesis from acid oil (AV of 8.5, 50 and 90). A positive synergistic effect occurred mainly for Lipozyme TL IM (1,3-specific lipase) and Novozym 435 (non-specific lipase) blend. The ester content doubled when this lipase mixture was used in ethanolysis of acid oil with AV of 90.