This paper is concerned with optimization of submerged culture conditions for mycelial growth and exo-biopolymer production by Paecilomces tenuipes C240 by one-factor-at-a-time and orthogonal matrix methods. The one-factor-at-a-time method was adopted to investigate the effects of medium components (i.e. carbon, nitrogen, and mineral sources) and environmental factors (i.e. initial pH and temperature) on mycelial growth and exo-biopolymer production. Among these variables, glucose, KNO3, KHPO4, and MgSO4 were identified to be the most suitable carbon, nitrogen, and mineral sources, respectively. The optimal temperature and initial pH for mycelial growth and exo-biopolymer production were 28 degreesC and 6.0, respectively. Subsequently, the concentration of glucose, KNO3, K2HPO4, and MgSO4 were optimized using the orthogonal matrix method. The effects of media composition on the mycelial growth of P. tenuipes C240 were in the order of glucose > K2HPO4 > KNO3 > MgSO4, and those on exo-biopolymer production were in the order of glucose > K2HPO4 > MgSO4 > KNO3. The optimal concentration for enhanced production were determined as 4 g/l glucose, 0.6 g/l KNO3, 0.1 g/l K2HPO4, and 0.1 g/l MgSO(4)(.)5H(2)O for mycelial yield, and 3 g/l glucose, 0.4 g/l KNO3,0.1 g/l K2HPO4, and 0.1 g/l MgSO(4)(.)5H(2)O for exo-biopolymer production, respectively. The subsequent verification experiments confirmed the validity of the models. This optimization strategy in shake flask culture lead to a mycelial yield of 10.18 g/l, and exo-biopolymer production of 1.89 g/l, respectively, which were considerably higher than those obtained in preliminary studies. Under optimal culture conditions, the maximum exo-biopolymer concentration in a 5 1 stirred-tank bioreactor was 2.36 g/l. (C) 2002 Elsevier Science Ltd. All rights reserved.