The present invention provides a method for producing a desired protein (such as a desired heterologous protein) comprising: (a) providing a host cell comprising a first recombinant gene encoding a protein comprising the sequence of a first chaperone protein, a second recombinant gene encoding a protein comprising the sequence of a second chaperone protein and a third gene, such as a third recombinant gene, encoding a desired protein (such as a desired heterologous protein), wherein the first and second chaperones are different; and (b) culturing the host cell in a culture medium to obtain expression of the first, second and third genes.