Caproyl and cholesteryl derivatives of native dahlia inulin were prepared from the respective chloride donors, and the light derivatization was monitored by C-13-NMR and by FTIR. These inulin derivatives were employed as carbon sources and as inulinase inducers using different strains of the inulinolytic yeast Kluyveromyces marxianus. A low but consistent basal inulinase activity (constitutive) was expressed in control cultures grown in carbon source-free and yeast extract-based media, independently of the salt supplement. A higher enzyme activity resulted from induction with native inulin. The highest inulinase activity, in U/mL of cell-free medium, was attained with the lipophilic inulin derivatives. Caproylated inulin was superior as an inulinase inducer compared to the cholesteryl derivative. The native inulin-based medium was used as reference for the induction of inulinase in the IZ-275 yeast strain at 28 degrees C and 100 rpm for 70 h. With caproyl-inulin, a 6.8-or 4.9-fold increase of the units of inulinase/mL of cell-free medium was observed, respectively, in the absence or presence of ammonium phosphate supplement. The corresponding values for the IZ-619 yeast strain were 4.9 and 1.8. Cholesteryl-inulin did not induce the IZ-265 strain, but IZ-619 inulinase activity experienced a 4.1-fold increase in the ammonium phosphate supplemented medium. Thus, the induction/secretion process of inulinase is affected by the presence of ammonium phosphate, depending on the yeast strain and the modified inducer.