A method of preparing 1,5-D-anhydrofructose in large quantities includes treating .alpha.-1,4-glucan with a substantially pure .alpha.-1,4-glucan lyase, which has been isolated from algae alone, wherein 1,5-D-anhydrofructose is produced directly from the .alpha.-1,4-glucan.

Метод подготовлять 1,5-D-anhydrofructose в больших количествах вклюает обрабатывать alpha.-1.4-$$ET-alpha.-1,4-glucan с существенн чисто лиазой alpha.-1.4-$$ET-alpha.-1,4-glucan, которая была изолирована от водорослей самостоятельно, при котором 1,5-D-anhydrofructose произведено сразу от alpha.-1.4-$$ET-alpha.-1,4-glucan.