The regulation of the synthesis of invertase in Aspergillus niger with different carbohydrates was studied. In order to investigate the mechanism of induction, we worked with conidia protoplasts and permeabilied mycelium and used actinomycin D, cycloheximide and cAMP. The synthesis of invertase in A. niger was induced by beta-fructofuranoside substrates such as raffinose, sucrose and turanose. Inulin also produced synthesis, suggesting that the beta link and the fructose located at the end of the molecule are involved in the induction mechanism. Glucose and fructose, which are products of the action of invertase, are repressors of the synthesis and act at the level of the translation of the genetic message. The induction of invertase is different from that of yeasts and other filamentous fungi. A mechanism of induction of the synthesis of invertase in A. niger with the participation of cAMP is proposed. (c) 2005 Elsevier Inc. All rights reserved.