A 1.7 kb DNA fragment encoding beta-D-fructofuranosidase in a strain of Aspergillus niger was amplified by PCR, inserted into a 4.4 kb cloning vector and sequenced. Comparison of this sequence with suc1 (GenBank) showed that this invertase gene had suffered a single base deletion followed by a single base insertion 49bp further down-stream with the result that 16 amino acids are coded by a different reading frame.