We have been investigating temperature shifts but we haven’t seen much improvement using this technique. Any thoughts?

Answer

The answer depends on the desired outcome that you are looking to get from the temperature shift: to increase titers, to improve the quality of a given protein or both. Temp shifts are typically used for both increasing titers as well as for assisting in the expression of hard-to-express proteins, such as proteins that are aggregate prone during cellular processing. However, simply adding a temperature shift to an existing protocol without simultaneous optimization of other aspects of the protocol may provide modest gains, at best. As part of the ExpiCHO expression system, we provide three different protocols: Standard titer protocol which is performed at 37C as well as High Titer and Max Titer protocols that utilize a temperature shift to 32C. In this case, we have rigorously optimized the three protocols to ensure that the temperature shift is providing benefit to most proteins. For example, for a given IgG that expresses at 1g/L in the Standard protocol at 37C, we have seen this same antibody express at 2g/L in the High Titer protocol at 32C and at 3g/L in the Max Titer protocol at 32C. However, we, and others, have also seen that some proteins express better in the Standard protocol in the ExpiCHO system, again indicating that there is some protein dependence in which protocol/temperature works best for a given protein. The ability to choose temperature shift or no temperature shift in the ExpiCHO system provides two different options to best express your protein of interest.