Zymomonas mobilis As Catalyst for the Biotechnological Production of Sorbitol and Gluconic Acid

摘要

The conversion of glucose and fructose into gluconic acid (GA) and sorbitol (SOR) was conducted in a batch reactor with free (CTAB-treated or not) or immobilized cells of Zymomonas mobilis. High yields (more than 90%) of gluconic acid and sorbitol were attained at initial substrate concentration of 600 g/L (glucose plus fructose at 1:1 ratio), using cells with glucose-fructose-oxidoreductase activity of 75 U/L. The concentration of the products varied hyperbolically with time according to the equations (GA) = t (GA)_(max) / (W_(GA) + t), (SOR) = t (SOR)_(max) / (W_(SOR) + t), v_(GA) = [W_(GA) (GA)_(max)] / (W_(GA) + t)~2 and v_(SOR) = [W_(SOR) (SOR)_(max)] / (W_(SOR) + t)~2. Taking the test carried out with free CTAB-treated cells as an example, the constant parameters were (GA)_(max) = 541 g/L, (SOR)_(max) = 552 g/L, W_(GA) = 4.8 h, W_(SOR) = 4.9 h, v_(GA) = 112.7 g/L·h and v_(SOR)= 112.7 g/L·h.