Process for preparing high levels of interferon beta

A process for the production of interferon beta in an Escherichia coli host cell comprising the steps of:

• a) providing the host cell that is capable of producing the said protein;
• and
• b) culturing the cell under conditions effective to induce production of the protein in a medium comprising a complex nitrogen source selected from gelatin digest, casein enzyme hydrolysate, and tryptone, either alone or in a mixture thereof, or any of said medium in combination with yeast extract, where the process is carried out at a pH at about 6.5 to 7.0 and at a temperature about 37° C.;
• and
• c) wherein the culture media further comprises thiamine at a concentration of at least 3 g/L.