In this paper, we describe an easy approach for the production of low sugar fruit juices by the use of invertase (EC 3.2.1.26) and glucose–fructose oxidoreductase (GFOR) as water soluble, cell and carrier-free enzymes.
GFOR (EC 1.1.99.28), a periplasmic enzyme of Zymomonas mobilis [14], oxidizes glucose to gluconolactone, which is rapidly hydrolyzed to gluconic acid, and simultaneously reduces fructose to sorbitol as shown in the reaction scheme (Fig. 1).
The native enzyme contains the small coenzyme molecule NADP(H) tightly bound (“macromolecularized”) to the active site of GFOR and is regenerated during the reaction cycle.
The great advantage of this fact is that no additional technological steps for coenzyme retention or regeneration are required.
Both enzymes (invertase and GFOR) together would allow to establish a (semi) continuous ultrafiltration membrane reactor for the production of calorie (sugar) reduced “dietetic” pineapple juice.