The object of the present invention is a method of recombinant protein production in vitro with cultivated non pathogenic Kinetoplastidae parasites (Leishmania tarentolae, Crithidia fasciculata, Wallaceina inconstans) (former Proteomonas inconstans), (Leptomonas collos, Leptomonas sp. Cfm, Leptomonas sp. Nfm or Leptomonas seymouri). This includes description of cultivation conditions for several species that allow large scale growth of these organisms on cheap media. The method of the invention includes strategies and construct description for generation of stably transfected organisms capable of expression of recombinant proteins.