Countinous Production of Gluconic Acid and Sorbitol from Jerusalem Artichoke and Glucose Using an Oxidoreductase of Zymomonas mobilis and Inulinase
Dong-Man Kim and Hak-Sung Kim
Gluconic acid and sorbitol were simultaneously produced from glucoes and Jerusalem artichoke using a glucose-fructose oxidoreductase of Zymomonas mobilis and inulinase. inulinase was immobilized on chitin by cross-linking with glutaraldehyde. Cells of Z. mobilis permeabilized with toluene were coimmobilized with chitin-immobilized inulinase in algenate beads. The optimum amounts if both chitin-immobilized inulinase and permeabilized cells for coimmobilization were determined, and operational conditions were determined. In a continous stirred tank reactor operation, the maximum productivities for gluconic acid and sorbitol were about 19.2 and 21.3g/L/h, respectively, at the dilution rate of 0.23/h and the substrate concentration of 20%, but operational stability was low because of the abrasion of beads. As an approach to increase the operational stability, a recycle packed-bed reactor(RPBR) was employed. In RPBR operation, the maximum productivities for gluconic acid and sorbitol were found to be 23.4 and 26.0g/L/h, respectively, at the dilution rate of 0.35/h and the substrate concentration of 20% when the recirculation rate was fixed at 900mL/h. Coimmobilized enzymes were stable for 250 h in a recycle packed-bed reactor without any loss of activity, while half-life in a continous stirred tank reactor(CSTR) was observed to be about 150h.