Continuous production of high-purity fructooligosaccharides and ethanol by immobilized Aspergillus japonicus and Pichia heimii

High-purity fructooligosaccharides (FOS) were produced from sucrose by an innovative process incorpo- rating immobilized Aspergillus japonicus and Pichia he- imii cells. Intracellular FTase of A. japonicus converted sucrose into FOS and glucose, and P. heimii fermented glucose mainly into ethanol. The continuous production of FOS was carried out using a tanks-in-series bioreactor consisting of three stirred tanks. When a solution composed of 1 gL -1 yeast extract and 300 g L -1 sucrose was fed continuously to the bioreactor at a dilution rate of 0.1 h -1 , FOS at a purity of up to 98.2 % could be achieved and the value-added byproduct ethanol at 79.6 g L -1 was also obtained. One gram of sucrose yielded 0.62 g FOS and 0.27 g ethanol. This immobilized dual-cell system was effective for continuous production of high-purity FOS and ethanol for as long as 10 days.