Hello Maisa,
you can check the medium using "model.medium".
If you are running it in python, you will see a dic with exchange reactions of metabolites like :
"{ EX_XX: 1000 , EX_compound: 1000}"
The medium is a constraints and you can insert another dict to your model as below:
medium_1 = {EX_metabolite_1: 1000 , EX_metabolite_ 2 : 1000}
medium_2 = {EX_metabolite_X: 1000 , EX_metabolite_ Y : 1000}
model.medium = medium_1, run FBA and
model.medium = medium_2, run FBA again.
I think it will help you
best regards,
Bruno