The aim of this investigation was to obtain an efficiently immobilized intracellular lipase from Rhizomucor miehei and Yarrowia lipolytica. The activity of intracellular lipases from R. miehei and Y lipolytica was enhanced by the addition of waste fats (beef tallow or poultry fat) to the medium and by cell immobilization on biomass support particles (BSPs, cubic particle of polypropylene or polyurethane foams). The highest intracellular activity of lipases was obtained after adding 20 and 50 BSPs to the medium of R. miehei (130.5 U) and Y lipolytica (90.3 U), respectively. The best carrier for immobilizing intracellular lipases was polyurethane foam and the lipolytic activity of immobilized lipases was 2.1-4.3-times higher than the activity of lipases obtained from free biomass. The properties of the immobilized enzymes were very similar to the free enzymes but the immobilized intracellular lipases were more useful for the hydrolysis of waste fats. The highest reaction ratio (72%) and content of free fatty acids (68% (w/w)) in the reaction mixture was obtained after 72 h for beef tallow hydrolysis in a batch reaction with the immobilized lipases from R. miehei. (C) 2003 Elsevier Ltd. All rights reserved.