carbon-oxygen lyase activity, acting on polysaccharides inulin fructotransferase (DFA-I-forming) activity https://github.com/geneontology/go-ontology/issues/30193 MetaCyc:4.2.2.17-RXN inulin fructotransferase (DFA-I-producing) activity EC:4.2.2.17 2,1-beta-D-fructan lyase (alpha-D-fructofuranose-beta-D-fructofuranose-1,2':2,1'-dianhydride-forming) activity inulin fructotransferase (depolymerizing, difructofuranose-1,2':2',1-dianhydride-forming) activity inulin D-fructosyl-D-fructosyltransferase (1,2':1',2-dianhydride-forming) activity GO:0033997 inulin D-fructosyl-D-fructosyltransferase (forming alpha-D-fructofuranose beta-D-fructofuranose 1,2':1',2-dianhydride) activity Catalysis of the reaction: [(2->1)-beta-D-fructosyl](n) = [(2->1)-beta-D-fructosyl](n-1) + alpha-D-fructofuranose-beta-D-fructofuranose 1,2':1,2'-dianhydride. This reaction is the production of alpha-D-fructofuranose beta-D-fructofuranose 1,2':2,1'-dianhydride (DFA I) by successively eliminating the diminishing (2->1)-beta-D-fructan (inulin) chain from the terminal D-fructosyl-D-fructosyl disaccharide. molecular_function