Optimization of D-ribose production with a transketolase-affected Bacillussubtilis mutant strain in glucose and gluconic acid-based media |
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Authors: | P De Wulf W Soetaert D Schwengers & EJ Vandamme |
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Institution: | Laboratory of Industrial Microbiology and Biocatalysis, Faculty of Agricultural and Applied Biological Sciences, University of Gent, Gent, Belgium,;Pfeifer und Langen, Dormagen, Germany |
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Abstract: | When the transketolase-deficient and D -ribose-producing Bacillus subtilis strain ATCC 21951 was grown in a glucose (200 g l−1)-based medium (Kintaka et al. 1986), only 11 g l−1 D -ribose was synthesized, in addition to acetic acid (12 g l−1) and acetoin plus 2,3-butanediol (24 g l−1), within 1 week of fermentation. After optimizing the process conditions at 2 l fermentor scale (simplified medium composition, pH 5·0 or 6·0, highly oxidative (1000 rev min−1, 3 vvm)), 40 g l−1 D -ribose was obtained from 200 g l−1 D -glucose, in addition to 14·5 g l−1 acetoin, during 1 week of fermentation. By partially substituting D -glucose with D -gluconic acid (100 g l−1 D -glucose plus 50 g l−1 D -gluconic acid) under highly oxidative (1000 rev min−1, 3 vvm) and pH-controlled (pH 6·5) conditions, D -ribose productivity increased (45 g l−1) and acetoin formation (7·5 g l−1) dropped, as did the fermentation time (3·5 d). The mixed carbon substrate procedure here developed provides an excellent alternative to the less efficient glucose-based processes described so far. |
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