Some biochemical changes during growth of Pleurotus sajor-caju, an edible mushroom in deproteinized whey supplemented with diammonium hydrogen phosphate and indole-3-acetic acid were determined. Growth of P. sajor-caju in whey medium is a slow process. There was a time lag of 24 h for the onset of growth; however, logarithmic growth phase started after 120 h and maximum growth was obtained at 240 h. The protein content of mycelial material harvested at different growth phases was variable. The maximum protein could be harvested between 216 and 264 h of fermentation. (C) 2002 Elsevier Science Ltd. All rights reserved.