抄録
Escherichia coli JM105 harboring an expression plasmid which bears the xylose isomerase gene controlled by tac promoter was cultivated under different conditions in order to find an optimal fermentation condition. By shake-flask cultures it was found that low concentration of organic nitrogen sources such as yeast extract or casamino acids was essential for efficient production of xylose isomerase. By fed-batch culture in a jar-fermentor, we obtained very high cell concentration. Glucose did not hamper gene expression as much as glycerol. Excess addition of yeast extract lowered the specific activity of the gene product. Although the specific activity of the enzyme in high-concentration culture was a half that in batch culture, the amount of enzyme produced by unit volume in a representative high-concentration culture was more than 33-fold that by batch culture.
