Methods for Producing Recombinant Proteins

The present invention provides a method for controlling the partitioning of a recombinant protein between the supernatant and the periplasm in E.coli host cell cultures wherein expression of the recombinant protein by said cells is under the control of an inducible system, which method comprises: a) providing an E. coli host cell culture b) changing the growth rate of theE.coli host cells c) inducing expression of the recombinant protein wherein steps (b) and (c) can be performed in any order or simultaneously; and subsequently d) determining the yield of recombinant protein in the culture supernatant and the E.coli host cell periplasm e) comparing the yield determined in step (d) with the yield determined when at least one other growth rate has been used in step (b) f) selecting a growth rate from the comparison made in step (e) in which the partitioning of the recombinant protein between the supernatant and the periplasm is most suited to the primary recovery of the recombinant protein.