The effect of the changes of culturing environments of Aspergillus terreus on lovastatin production was investigated in the study. A relatively low supplement of dissolved 02 (DO) by the fungus almost stopped performing product formation. With the DO controlled at 20%, lovastatin production using a 5-1 fermenter enhanced by 38%, biomass production decreased by 25% and sugar utilization increased by 18%, as compared with the shaking-flask culture. Meanwhile, an average diameter 0.95 mm of compact pellets was found. We thus concluded that pellet formation with a narrow size distribution dominated lovastatin production by A. terreus, which was closely affected by the relatively saturated level of DO. Nevertheless, manipulating the broth pH at 5.5-7.5 starting from 48 h provided no benefit to product formation although biomass production was reduced largely. In the part of work, a pH/DO interaction was also confirmed. A simple temperature-shift method (28-23 degrees C) was proved surprisingly valuable to the fermentation process. Such experiments showed that the maximum of lovastatin production was further enhanced by 25% (572mg/l at day 10) in comparison with that when the fungus was cultured at 28 degrees C. The timing to initiate the temperature-shift (96 h) corresponded to that of pellet formation and the subsequent core compactness. Hence, it was found that lovastatin production by A. terreus favored sub-optimal growth conditions. (c) 2004 Elsevier Inc. All rights reserved.