ecYeast - oxygen exchange lower bound can't be set to -1

[alvxi]

Hi, I'm trying to use the ecYeast model, on matlab with COBRA and then I set up the model without any modifications:

model=readCbModel('ecYeast.xml');
writeCbModel(model,'format','xls');
biomassRxn = 'r_2111';
ethanolRxn = 'r_1761';
glucose = 'r_1714';
oxygen = 'r_1992';
model = changeObjective(model, biomassRxn);
changeCobraSolver('gurobi', 'all');
solution=optimizeCbModel(model);

Then, I create another model to change the lower bound of glucose to -10:

modelGlu=changeRxnBounds(model,glucose, -10, 'l');
solutionGlu=optimizeCbModel(modelGlu);
printFluxVector(modelGlu, solution.x, false, false);

And finally, I create another model, on the top of the modelGlu, with the O2 exchange lower bound at -1:

modelMix=changeRxnBounds(modelGlu,oxygen, -1, 'l');
solutionMix=optimizeCbModel(modelMix);
printFluxVector(modelMix, solution.x, false, false);

But, as you can see, on the solution vector, the O2 reaction didn't change to -1 as is supposed to (but the glucose changed to -10, though):

I also tried to create a model only with the O2 modification, and the same happened. Also tried to use the batch model, and it's the same.

So, I ask if the model is taking into account that I set the O2 to -1 or if the modification I did doesn't occur at all.

Thanks