Aspergillus niger is an important filamentous fungus used for the in- dustrial 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
essen- tial 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.
