We report the production of the functional trisaccharide 1-kestose, O-beta-d-fructofuranosyl-(2 -> 1)-beta-d-fructofuranosyl alpha-d-glucopyranoside, by beta-fructofuranosidase from Aspergillus japonicus using sugar cane molasses as substrate. Sucrose in cane sugar molasses acted as a fructosyl donor and acceptor for the enzyme. The tetrasaccharide nystose, O-beta-d-fructofuranosyl-(2 -> 1)-beta-d-fructofuranosyl-(2 -> 1)-beta-d-fructofuranosyl alpha-d-glucopyranoside, was produced from 1-kestose. Cane sugar molasses mixed with water provided a better substrate solution for beta-fructofuranosidase compared to undiluted molasses due to the high concentration of product inhibitors such as glucose and fructose in molasses. The maximum concentration of 1-kestose obtained was 84.9 mg/ml and the maximum production efficiency was 32.3% after 24 h reaction at 40 A degrees C. The maximum efficiency of combined fructo-oligosaccharide (1-kestose and nystose) production was 40.6%. 1-Kestose was therefore produced via a fructosyl-transfer reaction catalyzed by beta-fructofuranosidase from A. japonicus.