Fructose Production from Dahlia Tuber Inulin by Immobilized Whole Yeast Cells in a Packed Bed Bioreactor

Abstract

At present, fructose is commonly produced from starch by the multi -step processes including hydrolysis into glucose followed by the treatment with isomerase and the chromatographic separation of fructose and glucose. In the present work, an alternative process for producing fructose from inulin was investigated. An immobilized biocatalyst with inulinase activity prepared by immobilization of non growing whole yeast cells was tested in a packed-bed bioreactor for continuous fructose production from dahlia tuber inulin. The free whole cells was used for batch inulin conversion in a 2.0 L stirred reactor at substrate concentration of 25-200 g.L·1, pH 5.0 and temperature 50°C for 10 h. The maximum conversion of 72.4 % was obtained from a cultivation containing 125 g.L·1substrate after 6 h. In the second study, the whole yeast cells was immobilized in calcium alginate heads and used for the production at 50°C and pH 5.0. The optimal gel concentration and cell !oad were determined The dilution rate of inulin solution ( 125 g.L·1) was varied from 0.08 to 0.30 h -I. The reactor performance was found to be highest at a dilution rate of O. 20 h .1. In this process, the yield of 109.12 g.L-1fructose, conversion degree of 87.3 % and reactor productivity of 21.83 g.L·1.h·1were obtained, respectively.This bioreactor productivity is noticeably higher than that previously reported. The continuous process was then operated a period of 200 h. However, a good stability of process was achieved during the first 100 h