Hi Kristy,
To convert your keys to objects you can simple use {model.metabolites.glu__L_c:-1.0, model.metabolites.h2o_c:-1.0, etc, ect.}
Then you refer to the objects in your model, if you called it model at least. If you called it ecoli then use ecoli.metabolites.glu__L_c .
One warning: If your metabolite has a name which is illegal according to python use .get_by_id("string with name"), f.i. objects can not start with a number, so 4abz_c is not a valid name.
Then you do: model.metabolites.get_by_id('4abz_c'):-1.0 and it will work fine.
Good luck with your modeling,
Dennis