Expression constructs, host cells, and methods for producing insulin

A cell for producing insulin, comprising:

• an E. coli host cell;
• and
• a polynucleotide disposed within the E. coli host cell, the polynucleotide comprising:
• a first expression construct comprising a first inducible promoter and a first coding sequence to be transcribed from the first inducible promoter, the first coding sequence encoding an insulin polypeptide;
• and
• a second expression construct comprising a second inducible promoter and a second coding sequence to be transcribed from the second inducible promoter, the second coding sequence encoding one or more of cDsbA, cDsbC, a protein disulfide isomerase, Ervlp, and a chaperone;
• and
• wherein the first inducible promoter and the second inducible promoter are selected from the group consisting of E. coli sugar-inducible promoters and propionate-inducible promoters, and the first inducible promoter and the second inducible promoter are not responsive to the same inducer, and each of the first inducible promoter and the second inducible promoter is not a lactose-inducible promoter.