help with robustness analysis

[dtusso]

Hello everyone 

I did a robustness analysis of a genomic scale metabolic model on a yeast. I performed this analysis under two conditions: The first included fixing the lower boundary of the glucose exchange reaction while varying the oxygen consumption rate, and in the second, the lower boundary of the oxygen exchange reaction was fixed while the glucose consumption rate was varying.

When the rate of oxygen consumption increases, the growth rate exhibits a linear behavior in the first condition (Figure1), and it provides a constant behavior for the second condition (Figure2).

I have concerns about the first condition because there doesn't seem to be any difference in the growth rate when I change the lower boundary of the oxygen exchange reaction to 0 and perform an FBA with the biomass maximization, and in the second condition, it seems that the glucose limits the grown rate. If anyone has any suggestion, I would be eternally grateful.

 Thank you so much.