The aldA gene of Aspergillus niger encodes an aldehyde dehydrogenase. Chromosomal deletion of this gene using gene replacement techniques has defined several growth conditions, thought to involve aldehyde and semialdehyde intermediates, that require this enzyme. Reintroduction of aldA clones carrying in vitro-generated deletions in the promoter region into the aldA deletion strain has been used to identify three elements controlling aldA expression: an enhancer required for high-level expression, an ethanol induction-responsive element, and a fructose induction-responsive element.