A novel approach to utilize deproteinated cheese whey by cultivating mycelia of the edible mushroom Ganoderma lucidum is described. A central composite in cube design for the experiments was used to develop empirical models providing a quantitative interpretation of the relationships between the two variables studied, which were pH and temperature. The designed intervals were 3.3 < pH < 4.7, 23 degreesC < temperature < 37 degreesC, respectively. Response surface methodology was successfully applied to determine the optimum condition where the maximum mycelial production occurred, which was pH 4.2 at 28.3 degreesC. The soluble chemical oxygen demand (SCOD) removal ranged from 80.7 to 93.1% within the design boundary, where the condition for maximum SCOD removal was pH 4.6 and 27.1 degreesC soluble chemical oxygen demand (COD). The condition for a maximum mycelial yield, 0.35 mg mycelial weight per mg SCODremoved, was calculated as pH 4.2, and 28.5 degreesC soluble COD; which was almost the same as optimum condition for mycelial production. The high extract ratio of 10.7% (i.e. 1820 mg extract/17 057 mg mycelium) as well as high content of polysaccharide (i.e. 1.12 g/l) indicated that the deproteinated whey could be an alternative substrate for mycelial production. Therefore, cultivation of G. lucidum mycelia can offer a potential cost-effective solution for an alternative utilization of the deproteinated cheese whey. (C) 2002 Elsevier Science Ltd. All rights reserved.