The influence of culturing environments on lovastatin production by Aspergillus terreus in submerged cultures

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 O2 (DO) by the fungus almost stopped performing product formation. With the DO controlled at 20%, lovastatin production using a 5-l 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 °C) was proved surprisingly valuable to the fermentation process. Such experiments showed that the maximum of lovastatin production was further enhanced by 25% (572 mg/l at day 10) in comparison with that when the fungus was cultured at 28 °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.