Manganese and its regulatory role on the citrate exporter CexA - exploring the citric acid production mechanism of Aspergillus niger

Abstract

Aspergillus niger is an important filamentous fungus used for the industrial production of citric acid. One of the main contributors to high citric acid accumulation by the fungus is the citrate transporter CexA. It belongs to the major faciliatory superfamily subclass DHA1 which act as drug-H+ antiporters1. Since cexA and its regulators are essential within the citric acid production process, it is crucial to study their regulatory mechanism, which is the focus of this work. The amount of manganese present in the culture broth has a major impact on the production process. Observations showed that the fungus develops a certain pellet-like morphology under manganese limitation conditions and that this limitation is decisive for high citric acid accumulation by A. niger2,3. However, the exact mode of action of manganese in the cell was not clear until now. Thus, in this work, we show the regulatory role of manganese on the citrate transporter CexA.