The metabolism of Aspergillus niger A10 growing on agar plates is analyzed using a structured model that includes the pathways for glicolysis (EMP), pentose-phosphate (PP), the Krebs cycle (TCA), and mycelial biosynthesis; and takes into account enzyme regulation in EMP and TCA either due to low or high levels of citrate and ATP in cytosol. Model predictions are supported by a series of experiments measuring mycelial growth under different glucose concentrations in the agar plates, as well as the use of a two-carbon sources mixtures. Besides measurements of biomass, CO₂ production and O₂ consumption were also continuously measured in the gas-phase of a modified Petri dish. Atkinson's energy charge (1969) concept is used to analyze the growth efficiency under increasing glucose concentration in the agar plates in the range: 25 to 250 gL^-1.