SIMULTANEOUS ENZYMATIC-SYNTHESIS OF GLUCONIC ACID AND SORBITOL - PRODUCTION, PURIFICATION, AND APPLICATION OF GLUCOSE-FRUCTOSE OXIDOREDUCTASE AND GLUCONOLACTONASE

With regard to the enzymatic synthesis of sorbitol and gluconic acid, a screening was carried out to identify promising producers of glucose -fructose oxidoreductase (GFOR) and gluconolactonase (GL). Zymomonas m obilis DSM 473 and Rhodotorula rubra DSM 70403 have been selected for the synthesis of GFOR and GL, respectively. Maximal enzyme production by these organisms has been achieved at D-glucose concentrations of 20 0 and 150 g/L, respectively. Both GFOR and GL were purified and charac terized with respect to some of their catalytic properties. GL showed strict specificity for 1,5-(delta)-lactones and was activated by Mg2and Mn2+ ions. The potential use of soluble GFOR is limited by its ina ctivation during substrate conversion, and the effects of reaction tem perature and pH on the ''catalytic'' stability of GFOR were evaluated. Exogenous adddition of auxiliary GL had no effect on oxidoreductase s tability and did not improve productivities.