The biosynthesis of glucose oxidase (GOD) by Penicillium-producing strain Z-I-C in batch and chemostat culture was studied. In a glucose-limited chemostat, the experimental results showed that the maintenance coefficient of this strain was 0.04 g glucose/g dry cell wt/h; yield factor of growth was 0.714 g dry cell wt/g glucose; maximum specific growth rate was 0.385 h and saturation constant Ks was 4.76 g/l. Theoretical optimum dilution rate was 0.260 h-1. Maximum specific enzyme activity was increased from 1.51 x 10(3) mu/mg in batch culture to 2.16 x 10(3) mu/mg in chemostat culture and to 3.11 x 10(3) mu/mg in chemostat culture supplemented in feed medium with 0.02% inducer, alpha-methyl-D-glucose, a 43% or 106% increase, respectively, compared with that of batch culture.