Extracellular lipase production by Yarrowia lipolytica was increased by mutant selection from 28 U/ml to 1000 U/ml. This activity was also reached in a 500 I bioreactor. The properties of the mutant lipase were the same of those of the wild type : M(r) 38 kDa, optimum pH 7 and optimum temperature 37 degrees C.