Methods for inducible expression

A method of producing a polypeptide, the method comprising:

• growing a culture of a host cell, wherein the host cell comprises at least one extrachromosomal expression construct comprising first inducible promoter selected from the group consisting of an Escherichia coli sugar-inducible promoter and a propionate-inducible promoter, and at least one polynucleotide sequence encoding a polypeptide, wherein at least one said polynucleotide sequence is to be transcribed from said first inducible promoter, wherein the polypeptide lacks a signal peptide,
• wherein the host cell comprises at least one extrachromosomal expression construct comprising a second inducible promoter, selected from the group consisting of an Escherichia coli sugar-inducible promoter and a propionate-inducible promoter, that is inducible by at least one inducer that is different than that of said first inducible promoter,
• wherein none of said inducible promoters is a lactose-inducible promoter,
• wherein the host cell has an altered gene function of at least one gene that affects the reduction/oxidation environment of the host cell cytoplasm, and
• wherein the host cell has a reduced level of gene function of at least one gene encoding a protein that metabolizes an inducer of at least one said inducible promoter;
• and
• adding an inducer of said first inducible promoter to the culture.