Sucrose Biotransformation to Fructooligosaccharides by Aspergillus sp. N74 Free Cells

Fructooligosaccharide production with the fructosyltransferase from free cells of the native strain Aspergillus sp. N74 at laboratory level was evaluated. The biomass of the native strain Aspergillus sp. N74 was produced in a sucrose fermentation medium and was employed in the enzymatic reaction in solutions of sucrose and phosphate buffer, where pH, temperature, and initial sucrose concentration effect were evaluated. Fructooligosaccharides and reaction subproducts were identified and quantified by high-performance liquid chromatography. The enzyme produced by the strain Aspergillus sp. N74 possessed hydrolytic and transfructosylating activities that changed with process conditions. The best transfructosylating condition was obtained at 80 min reaction time at pH 5.5, 60 °C, and initial sucrose concentrations higher than 550 g L−1, with fructooligosaccharide production of about 50% w/w (based on initial sucrose concentration) and conversion selectivity higher than 90%. In addition, the transfructosylating and hydrolytic activities ratio was of 20. The high transfructosylating activity showed by the fructosyltransferase produced from the native strain Aspergillus sp. N74 suggest considering it as an alternative for the scale-up production of fructooligosaccharides by means of the whole microorganism at bench and pilot plant levels.