d-Glucose does not catabolite repress a transketolase-deficientd-ribose-producingBacillus subtilis mutant strain

Abstract

WhenBacillus subtilis strain ATCC 21951, a transketolase-deficientd-ribose-producing mutant, was grown ond-glucose plus a second substrate which is metabolized via the oxidative pentose phosphate cycle (d-gluconic acid,d-xylose,l-arabinose ord-xylitol),d-glucose did not catabolite repress metabolism of the second carbon source. Thed-ribose yield obtained with the simultaneously converted carbon substrates, significantly exceeded that when onlyd-glucose was used. In addition, the concentration of glycolytic by-products and the fermentation time significantly decreased. Based on these findings, a fermentation process was developed withB. subtilis strain ATCC 21951 in whichd-glucose (100 g L⁻¹) andd-gluconic acid (50 g L⁻¹) were converted into 45 g L⁻¹ ofd-ribose and 7.5 g L⁻¹ of acetoin. A second process, based ond-glucose andd-xylose (100 g L⁻¹ each), yielded 60 g L⁻¹ ofd-ribose and 4 g L⁻¹ of acetoin plus 2,3-butanediol. Both mixed carbon source fermentations provide excellent alternatives to the less efficientd-glucose-based processes used so far.