| 초록 |
D-Ribose is a five-carbon sugar used for commercial syntheses of riboflavin, antiviral agents and flavor enhancers. Mechanisms of D-ribose biosynthesis from xylose were investigated by genetically engineered Bacillus subtilis JY200 showing the transketolase deficiency. The transketolase disruption cassette in plasmid pUNKC was introduced into the chromosomal transketolase gene in the wild type of B. subtilis 168. In batch fermentation of B. subtilis JY200, the tktA gene disruption caused loss of cell viability after glucose depletion, and hence prevented further accumulation of D-ribose. Fed-batch fermentation by feeding 400 g/l glucose solution was carried out to supply ATP to the xylose metabolism and to maintain cell viability throughout cultivation. Fed-batch fermentation of B. subtilis JY200 in MY medium containing 11 g/l xylose and 5 g/l glucose initially gave the best result of 10.1 g/l D-ribose concentration, yield of 0.24 g ribose/g sugar and 0.29 g/l-hr productivity, corresponding to 40-, 5- and 12-fold increases compared with those in the batch culture. A kinetic study of D-ribose production in fed-batch fermentations of B. subtilis JY200 suggested that xylose uptake might be a key factor for maximizing D-ribose biosynthesis from xylose. |
