Inulinase gene inuA1 was obtained from Aspergillus niger AF10 and amplified by the polymerase chain reaction. The isolated DNA of inuA1 was then sequenced. The results showed that the Open Reading Frame of inuA1 was 1551 bp long, encoding 516 amino acids. No intron was found in the sequence and there were four potential sites for N-linked glycosylation and a conserved sequence WMNEPN. pUC118 and E. Coli JM 109 were used as cloning vector and host strain, respectively, yielding the clones JM109/inuA1. The gene inuA1 was integrated into the genomic DNA of GS115 by inserting into a single site for recombination, yielding the recombinant GS115/inuA1. Inulinase expressed by GS115/inuA1 was induced by methanol, at an activity of 50.6 U/ml in the fermentation liquid after 72 h. It was 11 times that of the wild type A. niger AF10. (C) 2002 Elsevier Science Ltd. All rights reserved.