Constraining objective returns all shadow prices as 0

[Brian Parker]

Hello,

I am working in COBRApy, but I imagine this issue is not dependent on a difference between Python and MATLAB.

When I set BIOMASS_reaction as the objective in the Recon3D model without adjusting its bounds, it returns an objective value of around 700 and has nonzero values for the shadow prices. When I constrain the BIOMASS_reaction objective function to a more biologically relevant growth rate of 0.17, however, all of my shadow prices return 0. I have also noticed that the reduced cost is consistently double the value of the shadow price. Does anybody know why this might be happening and how to fix it?

Thank you.