<P><B>Background</B></P><P>Invertase Suc2 was recently identified as a key hydrolase for inulin catabolism in <I>Saccharomyces cerevisiae</I>, whereas the Suc2 activity degrading inulin varies greatly in different <I>S. cerevisiae</I> strains. The molecular mechanism causing such variation remained obscure. The aim of this study is to investigate how Suc2 activity is regulated in <I>S. cerevisiae</I>.</P><P><B>Results</B></P><P>The effect of <I>SUC2</I> expression level on inulin hydrolysis was investigated by introducing different <I>SUC2</I> genes or their corresponding promoters in <I>S. cerevisiae</I> strain BY4741 that can only weakly catabolize inulin. Both inulinase and invertase activities were increased with the rising <I>SUC2</I> expression level. Variation in the promoter sequence has an obvious effect on the transcript level of the <I>SUC2</I> gene. It was also found that the high expression level of <I>SUC2</I> was beneficial to inulin degradation and ethanol yield.</P><P><B>Conclusions</B></P><P>Suc2-mediated inulin catabolism is regulated at transcript level in <I>S. cerevisiae</I>. Our work should be valuable for engineering advanced yeast strains in application of inulin for ethanol production.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s12934-015-0243-3) contains supplementary material, which is available to authorized users.</P>