A formal framework of bioprocesses enables accurate prediction of reaction outcomes, thereby optimizing resource allocation and reducing production costs. This study aimed to establish an approximate stoichiometric equation and determine the bioenergetics growth parameters of the pink oyster mushroom (Pleurotus djamor) using a “black box” modeling approach. A commercial strain was cultivated in polypropylene bags at 28 °C and 75% relative humidity. The harvested mushroom biomass was dried and analyzed for C, H, and N content, with O determined by difference. The resulting empirical formulas were CH_1.33O_0.36N_0.02 for the dry wheat straw substrate and CH_1.81O_0.41N_0.09 for the fungal biomass. The bioprocess exhibited a primordia initiation period of 20.5 days, a total harvest window of 50.0 days, a maximum biological efficiency of 16.77%, a model yield (Y) of 0.90%, and a productivity of 20.5 g/100 g substrate. In conclusion, this biotechnological framework provides a robust predictive tool for industrial scaling, enabling mass and energy balance optimization in real time without reliance on costly intracellular measurements. Thus, it establishes a reliable and sustainable pathway to convert low-cost agricultural residues into high-value bioproducts, supporting the goals of a circular economy.