Production of fructooligosaccharides by beta-fructofuranosidases from Aspergillus oryzae KB.

Aspergillus oryzae KB produces two types of beta-fructofuranosidases: F1 and F2. F1 produces the fructooligosaccharides (FOSs) 1-kestose, nystose, and fructosyl nystose from sucrose through a transfructosylation action, whereas F2 mainly hydrolyzes sucrose to glucose and fructose. F1 and F2 enzymes were more selectively produced from the KB strain in liquid media with a sucrose concentration>2% and <2%, respectively. Immobilization using an anion-exchange resin (WA-30; polystyrene with tertiary amine) and cross-linking with glutaraldehyde depressed the hydrolysis reaction of F2 (high hydrolyzing enzyme) alone and enhanced the thermal stability of F1 (high transferring enzyme). F1 enzyme produced in the high sucrose medium was immobilized, cross-linked, and packed in a tubular reactor for continuous production of FOSs (24.6% 1-kestose, 21.6% nystose, 5.7% and fructosyl nystose). In a long-term operation in which 60% sucrose was imputed at 55 degrees C, the composition of FOSs produced was 51.9% (transfer ratio: 92%), and production by the immobilized enzyme was maintained for 984 h.