Method for the preparation of a strain, particularly from yeast, transformed by an expression vector, that can be propagated in a complete medium, without selection pressure, and strain thus obtained.

摘要

Process for the preparation of a strain transformed by a cloning or expression vector of a gene coding for a predetermined protein which may be cultivated on a complete medium without selection pressure, characterized in that: a) a metabolite of which the absence is lethal for the strain and which is synthetized by at least two metabolic pathways is identified, b) a first pathway of said metabolic pathways is blocked by alteration of at least one of the genes implied in said pathway, c) the strain is transformed by the vector which additionally comprises the functional allele of the altered gene, and d) the other metabolic pathways are blocked.