Releases fructooligosaccharides and levan, a high-molecular-mass fructosyl polymer, from sucrose. It acts more as a sucrose hydrolase than as a fructan polymerase. [6)-beta-D-fructofuranosyl-(2->](n) alpha-D-glucopyranoside + sucrose = [6)-beta-D-fructofuranosyl-(2->](n+1) alpha-D-glucopyranoside + D-glucose Belongs to the glycosyl hydrolase 68 family.