When the transketolase-defective and D-ribose-producing Bacillus subtilis strain ATCC 21951 was cultured in a medium provided with certain organic acids, a significantly enhanced D-ribose titre was obtained, while the production of acetoin and 2,3-butanediol drastically decreased. Although the biochemical background of this phenomenon is not completely understood, it makes D-ribose synthesis more efficient and cheaper, the latter due to an easier recovery of D-ribose from the fermentation medium.