A metabolic model was developed to describe the degradation of thiodiglycol (TDG) by Alcaligenes xylosoxydans ssp. xylosoxydans (SH91). Experimental evidence has suggested there is a metabolic capacity constraint that limits the specific thiodiglycol utilization rate, leads to metabolic byproducts, and ultimately inhibits the overall degradation process. A global inhibition function, η, was introduced to mathematically characterize this constraint based on thiodiglycol consumption. The resulting model described well the dynamic response of cells consuming thiodiglycol in several reactor configurations (batch, repeated batch, repeated fed batch) and was used to optimize overall thiodiglycol degradation as well as define conditions for optimizing conversion to byproducts [(2-hydroxyethyl)thio]acetic acid (HETA) and thiodiglycolic acid (TDGA), which are of commercial interest.