Dynamic response of Aspergillus niger to single pulses of glucose with high and low concentrations

Abstract

Abstract Microorganisms generally encounter a fluctuating environment in their natural habitat and similar conditions also happen in large-scale bioreactors. In this work, the dynamic response of intracellular and extracellular metabolites of Aspergillus niger was investigated after sudden exposure to high and low excess glucose concentrations in chemostats. It was found that the steady-state pathway turnover time of the carbon flux through the central carbon metabolism (CCM) was PP pathway 50 s, EMP pathway 20 s, and TCA cycle 189 s, and an upper limit for individual metabolite concentrations in the CCM was estimated. Regardless of the glucose pulse size, little changes of amino acids levels were observed except for aspartate, which showed a significant decrease. The ATP paradox, known from other organisms, was also observed in the studied A. niger strain. However, a different response of the NAD+/NADH ratio to the glucose pulses was found in A. niger compared to previously published observations on Penicillium chrysogenum and Saccharomyces cerevisiae. These findings are valuable for better understanding A. niger culture performance in large-scale bioreactors.

Keywords

• Aspergillus niger
• Substrate pulse
• Glucose excess
• Rapid sampling
• Dynamic responses
• Intracellular metabolites