Fructosyltransferase that catalyzes the polymerization of the fructose moiety of sucrose to produce levan polymer and the fructo-oligosaccharide (FOS) 1-kestose. Also displays sucrose hydrolase activity. [6)-beta-D-fructofuranosyl-(2->](n) alpha-D-glucopyranoside + sucrose = [6)-beta-D-fructofuranosyl-(2->](n+1) alpha-D-glucopyranoside + D-glucose Optimum pH is 5.4. Displays 50% of the optimal activity between pH values 4.0 and 6.2. A pH above 7 leads to a complete inhibition of the enzyme. Optimum temperature is 35-45 degrees Celsius. The wild-type strain metabolizes sucrose with formation of acetate, mannitol, glucose, kestose and levan while cells lacking this gene do not metabolize sucrose, do not liberate glucose from sucrose, and do not form mannitol, acetate, kestose or levan. Growth and acidification are lower in wheat doughs prepared with the deletion mutant than in those employing the wild-type. Belongs to the glycosyl hydrolase 68 family.