A significant difference was observed in the production pattern of exo-biopolymer and broth rheology during submerged culture of Paecilomyces japonica when two efficient carbon sources (maltose and sucrose) were employed. The maximum concentration of biopolymers in maltose medium (30 g/l) was higher than that in sucrose medium (25 g/l), whereas maximum mycelial concentration displayed an inverse result (i.e., 25 g/l in sucrose medium and 20 g/l in maltose medium). The broth rheology and morphology of P. japonica were also markedly different between the two culture media.