EN
The screening methods used for improvement of industrial strains are presented.Two general categories of methods have been distinguished: random screening and rational screening.Major techniques employed in rational screening are based on the selection of auxotropic mutants, reverants of non-producers, strain resistant to some factors like toxic analogues of metabolism intermediates, induction and catabolite regression or end-product inhibition, mutants with modified cell wall permeability and microorganisms tolerating somenutrients and precursors of secondary metabolites.