Fructooligosaccharides production using immobilized cells of Aspergillus japonicus

Abstract

The fructooligosaccharides (FOS) production using immobilized cells of the fungus Aspergillus japonicus ATCC 20236 was evaluated. Polyurethane foam, stainless steel sponge, vegetal fiber sponge, pumice stones, zeolites and cork were tested as immobilization carrier during the fermentation under submerged conditions. Experiments were carried out in 500 ml Erlenmeyer flasks containing 1 g of carrier and 100 ml of sucrose medium (165 g/l) enriched with nutrient sources. The flasks were agitated in an orbital shaker at 160 rpm, 28°C, for 48 h. Samples were withdrawn during the fermentation to determine the consumption of sucrose, liberation of glucose and fructose to the medium, production of FOS (1-kestose (GF2), 1-nystose (GF3) and 1-β-fructofuranosyl nystose (GF4)) and enzymatic activity of β-fructofuranosidase. At the fermentation end, the cell mass adhered to the carrier was quantified. The microorganism adhesion to the carrier varied to each tested material. Consequently, the FOS production and enzymatic activity also varied to each medium, due to the differences in the amount of free and immobilized cells present. The highest values of immobilized cells, FOS production and enzymatic activity were achieved by using vegetal fiber sponge as immobilization carrier, while cork gave the worst results.