A method for improving the quality and homogeneity of recombinant expression of a peptide of interest encoded by a first nucleotide sequence, said method comprises the steps of: - putting into contact a host cell with a cassette sequence or a vector comprising said cassette, the cassette comprising: - a first nucleotide sequence encoding said peptide of interest to be produced by said host cell, said nucleotide sequence being upstream of and linked to - a second nucleotide sequence either providing a resistance to a toxin (11,12, 15) that is toxic for said host cell or encoding an antitoxin peptide to a toxin (11, 12, 15), wherein said first nucleotide sequence and second nucleotide sequence are linked to encode their corresponding peptides (7, 9) as a fusion protein and - between the first nucleotide sequence and the second nucleotide sequence, a third nucleotide sequence encoding a linker peptide producing two peptides after cleavage and having a length comprised between 2 and 500 amino acids and wherein said first, second and third nucleotide sequences (3, 5, 4) are organized in such a way that production of the antitoxin peptide encoded by the second nucleotide sequence(s) is translationally coupled to production of the peptide of interest encoded by the first nucleotide sequence as a fusion protein, with either the host cell comprising in its genome, preferably under the control of a promoter/operator sequence, one or more copies of a fourth nucleotide sequence encoding a toxin (12, 15) which is toxic for said host cell and/or with said host cell being present in a culture medium comprising said toxin and/or comprising a cell different from the host cell secreting in said culture medium, said toxin, and - recovering from said host cell medium, either the fusion protein or the peptide of interest, possibly after a cleavage of the linker peptide. - putting into contact a host cell with a cassette sequence or a vector comprising said cassette, the cassette comprising: - a first nucleotide sequence encoding said peptide of interest to be produced by said host cell, said nucleotide sequence being upstream of and linked to - a second nucleotide sequence either providing a resistance to a toxin (11,12, 15) that is toxic for said host cell or encoding an antitoxin peptide to a toxin (11, 12, 15), wherein said first nucleotide sequence and second nucleotide sequence are linked to encode their corresponding peptides (7, 9) as a fusion protein and - between the first nucleotide sequence and the second nucleotide sequence, a third nucleotide sequence encoding a linker peptide producing two peptides after cleavage and having a length comprised between 2 and 500 amino acids and wherein said first, second and third nucleotide sequences (3, 5, 4) are organized in such a way that production of the antitoxin peptide encoded by the second nucleotide sequence(s) is translationally coupled to production of the peptide of interest encoded by the first nucleotide sequence as a fusion protein, with either the host cell comprising in its genome, preferably under the control of a promoter/operator sequence, one or more copies of a fourth nucleotide sequence encoding a toxin (12, 15) which is toxic for said host cell and/or with said host cell being present in a culture medium comprising said toxin and/or comprising a cell different from the host cell secreting in said culture medium, said toxin, and - recovering from said host cell medium, either the fusion protein or the peptide of interest, possibly after a cleavage of the linker peptide.