Recovery and properties of a fructooligosaccharides-producing beta-fructofuranosidase from Aspergillus japonicus CCRC 38011

The fungus (Aspergillus japonicus CCRC 38011) was found to be able to produce beta-fructofuranosidase with high transfructosylating activity (Ut), a key enzyme involved in synthesis of fructooligosaccharides from sucrose. The Ut productivities of this microorganism were 191.5 units/ml broth in a 6-L jar-fermentor and 256.1 units/ml broth in a 1000-L pilot-fermentor in a modified medium containing 8% sucrose as a carbon source. Most of the Ut of this microorganism was found to be bound with mycelia. Incubation and sonication treatment extracted this enzyme from mycelia with maximum efficiencies of 66.3% and 44.3%, respectively. On the other hand, homogenization and freeze-thawing treatment had only a small effect on enzyme extraction. The soluble enzyme extracted from mycelia by incubation at pH 5.0 and 40 degrees C for 3 hours could be easily recovered and purified by acetone precipitation. The recovery of Ut from the crude enzyme solution was 99.5% by mixing the solution with an equal volume of acetone at 4 degrees C, followed by centrifugation. The purification factor of acetone precipitation was 15.8. The optimum pH and temperature of Ut was 5.0 and 65-70 degrees C, respectively. The enzyme was stable at a pH between 4.0 and 5.0 and at a temperature below 60 degrees C.

Production of beta-fructofuranosidase with transfructosylating activity for fructooligosaccharides synthesis by Aspergillus japonicus NTU-1249

Microbial beta-fructofuranosidases with transfructosylating activity can catalyze the transfructosylation of sucrose and synthesize fructooligosaccharides. Aspergillus japonicus NTU-1249 isolated from natural habitat was found to produce a significant amount of beta-fructofuranosidase with high transfructosylating activity and to have the potential for industrial production of fructooligosaccharides. In order to improve it's enzyme productivity, the medium composition and the cultivation conditions for A. japonicus NTU-1249 were studied. A. japonicus NTU-1249 can produce 83.5 units of transfructosylating activity per ml broth when cultivated in a shaking flask at 28 degrees C for 72 hours with a modified medium containing 80 g/l sucrose, 15 g/l soybean flour, 5 g/l yeast extract and 5 g/l NaCl at an initial pH of 6.0. The enzyme productivity was also optimized by submerged cultivation in a 5-litre jar fermentor with aeration at 1.5 vvm and agitation at 500 rpm. Under these operating conditions, the productivity of transfructosylating activity increased to 185.6 U/ml. Furthermore, the transfructosylating activity was improved to 256.1 U/ml in 1,000-litre pilot-scale fermentor. Enzymatic synthesis of fructooligosaccharides by beta-fructofuranosidase from A. japonicus NTU-1249 was performed in batch type by adding 5.6 units of transfructosylating activity per gram of sucrose to a 50% (w/v) sucrose solution at pH 5.0 and 50 degrees C. The yield of fructooligosaccharides was about 60% after reaction for 24 hours, and the syrup produced contained 29.8% (w/v) fructooligosaccharides, 15.2% (w/v) glucose and 5.0% (w/v) sucrose.