Abstract: The present invention relates to a method for producing a recombinant polypeptide of interest in a microbial host cell, comprising (a) introducing a polynucleotide encoding the polypeptide of interest into a microbial host cell which has been modified such that an enzymatic activity selected from the group consisting of ketol-acid reductoisomerase (NADP(+)) activity (EC 1.1.1.86), acetohydroxyacid synthase activity (EC 2.2.1.6), aspartate kinase activity (EC 2.7.2.4), homoserine dehydrogenase activity (EC 1.1.1.3), and L-threonine dehydratase activity (EC 4.3.1.19) is modulated in said microbial host cell as compared to the enzymatic activity in an unmodified microbial host cell, and (b) expressing said polypeptide of interest in said microbial host cell. Moreover, the present invention relates to a method for reducing misincorporation of at least one non-canonical branched-chain amino acid into a recombinant polypeptide of interest expressed in a microbial host cell.