Batch cultures of Penicillium variabile P16 were grown in a 3-1 benchtop bioreactor. Glucose oxidase and catalase production was followed while varying stirrer speed and adding buffering agents. Four hundred rev min(-1) appeared to be optimum to ensure good growth and best enzyme production; above this, production was reduced. Among the different chemicals (CaCO3, NaOH, and NaOH plus CaCl2) employed to counteract the pH drop in the fermentation broth, CaCO3 gave the best results. The time course of growth, enzyme activities, and gluconate production at 400 rev min(-1) and using CaCO3 as neutralizing agent is reported.